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HP Pascal for OpenVMS Language Reference Manual

1. file variable The name of the file variable associated with the file whose component is to be unlocked error recovery The action to be taken if an error occurs during execution of the routine 9 64 Input and Output Processing 9 8 24 The file must be in inspection mode before UNLOCK is called it remains in inspection mode after UNLOCK has executed If the component at which the file pointer is positioned has been locked the UNLOCK procedure releases it Consider the following example UNLOCK Sales File The UNLOCK procedure releases the contents of the current component For More Information On the error processing parameter Section 9 7 UPDATE Procedure The UPDATE procedure writes the contents of the file buffer into the current component UPDATE file variable ERROR error recovery file variable The name of the file variable associated with the file whose component is to be updated error recovery The action to be taken if an error occurs during execution of the routine The file must be in inspection mode before UPDATE is called it remains in that mode after the procedure s execution The UPDATE procedure is legal for files that have been opened for random access direct or keyed The current component must already have been locked by a successful FIND FINDK GET RESET or RESETK procedure before the contents of the file buffer can be rewritten into it After the update has taken pla
2. OpenVMS 164 format 7 decimal digits Double precision VAX D floating point 1 part 2 OpenVMS VAX DOUBLE 16 decimal digits types VAX G_floating point 1 part in 22 OpenVMS Alpha format 15 decimal digits IEEE T floating point 1 part in 27 OpenVMS 164 format 15 decimal digits QUADRUPLE VAX H_floating point 1 part in 21 OpenVMS VAX format 33 decimal digits IEEE X_floating point 1 part in 21 OpenVMS 164 format 33 decimal digits OpenVMS Alpha 1Use the FLOAT qualifier to specify the default floating point format The IEEE data types are not supported on VAX systems 2On OpenVMS Alpha systems D floating is not a fully supported data type no D floating arithmetic operations are provided in the architecture For backward compatibility D floating binary data can be processed but without the last three bits of precision by automatically converting to G floating format performing G floating operations and converting back to D floating format 30n OpenVMS I64 systems F floating D floating and G floating formats are implemented by transparently converting them to an appropriate IEEE floating format before performing any necessary operation and then transparently converting them back This conversion to from IEEE format might result in slightly different answers and precision than on OpenVMS Alpha and OpenVMS VAX systems HP Pascal also provides data types to allow the selection of floating types indepe
3. See the HP Pascal for OpenVMS User Manual for information on how to enable disable the message VOLATILE accesses of items larger than 64 bits strings entire records entire arrays and other such items have never been atomic in nature and are not flagged by the compiler The VOLATILE attribute ensures atomic access for all objects 32 bits or less Table 10 6 Allowed Combinations of Volatile and Nonvolatile Parameters Formal Parameter Actual Parameter VAR VAR VOLATILE VOLATILE Volatile No Yes Yes Nonvolatile Yes Yes Yes Consider the following example VAR x CHAR a VOLATILE RECORD CASE BOOLEAN OF FALSE i INTEGER TRUE c CHAR END In the executable section 8 0 t Als TRUE becomes the current variant a i 66 Assignment makes FALSE the current variant x s 3 0 TRUE is again the current variant X is assigned the value B which has an ordinal value of 66 As the comments in this example show a reference to one field identifier causes the corresponding variant to become the current variant In addition each reference immediately causes the other variant to become undefined So when the assignment a i 66 is made the reference to a i causes FALSE to become the current variant and a c to become undefined As a result of the statement x a c the value last assigned to the variant is assigned to x 10 48 Attributes Ordinarily the compiler could assume that a c had
4. To force an INTEGER64 constant to become UNSIGNED64 you can use the UINT64 predeclared routine For More Information e On unary operators Section 4 2 e On built in routines Chapter 8 2 1 1 4 INTEGER ADDRESS Type The INTEGER_ADDRESS data type has the same underlying size as a pointer INTEGER_ADDRESS is equivalent to the INTEGER data type For More Information e On INTEGER notations Section 2 1 1 1 e On the IADDRESS function Chapter 8 2 6 Data Types and Values 2 1 2 CHAR Type The CHAR data type consists of single character values from the ASCII character set The largest possible value of the CHAR type is the predefined constant MAXCHAR To specify a character constant enclose a printable ASCII character in single quotation marks To specify the single quote character enclose two single quotation marks in single quotation marks Each of the following is a valid character constant zv ips eg This is the character 0 not the integer value 0 tage d The apostrophe or single quotation mark 151 You can also specify a character constant by enclosing printable ASCII characters in double quotation marks To specify the double quote character when using double quotation marks as delimiters use the V escape sequence Each of the following is a valid character constant AU n z The double quotation mark wou The ORD function accepts parameters of type CHAR The function return value is the or
5. 0 THEN WRITELN Index bounds are legal and element contained 0 The precedence of AND THEN and OR ELSE is the same as AND and OR respectively Because the Pascal language associates parameters of operands at the same precedence level from left to right you might not get the answer you expect For example in this code you might expect the AND THEN to guard all the expressions to its right IF PTR NIL AND THEN P DATA1 0 AND P DATA2 1 THEN However AND THEN is at the same precedence level as AND so the previous expression is equivalent to IF PTR NIL AND THEN P DATA1 0 AND P DATA2 1 THEN Given this assocation and the fact that the two operands of the AND operator can be evaluated in any order the compiler might evaluate P DATA2 1 without it being guarded by the PTR lt gt NIL test To guard both dereferences to P you must use parentheses as shown in this example IF PTR lt gt NIL AND THEN P DATA1 0 AND P DATA2 1 THEN Expressions and Operators 4 7 Alternatively you can replace all the occurrences of AND and OR with AND_ THEN and OR_ELSE repectively For example IF PTR lt gt NIL AND THEN P DATA1 0 AND THEN P DATA2 1 THEN For More Information e On precedence of operators Section 4 2 7 e On the BOOLEAN data type Section 2 1 3 4 2 4 String Operators A string operator concatenates or compares character string expressions Th
6. 2 4 2 5 Data Types for Integer Constants for OpenVMS I64 and OpenVMS Alpha Systems lees 2 6 2 6 Data Types for Integer Constants for OpenVMS VAX uci u PT n TP 2 6 2 7 Supported Floating Point Formats 000 2 12 2 8 Floating Data Types 1 0 eee 2 13 2 9 Precision in Exponential Notation 0 2 14 2 10 Predefined Identifiers for Real Data Types 2 14 2 11 Assignment Compatibility 0 0 0 0 0c 2 52 4 1 Arithmetic Operators is ciara ead eee a ee a a eR Ux 4 3 4 2 Results of Negative Exponents 0000 ee eee 4 3 4 3 Result Types of Arithmetic Operators 4 5 4 4 Relational Operators 0 eee eee eee eee 4 6 4 5 Logical Operators cv e Re Ow SER Ve ew ee Reo 4 6 4 6 String Operators 0 0 eee ees 4 8 4 7 Set Operators obese a dah aoe a bo ae Shee Ga oar 4 10 4 8 Precedence of Operators 0 0 0 eee 4 12 6 1 Formal Parameter Semantics llle 6 7 6 2 Parameter Passing Mechanisms sss 6 7 6 3 Specifiers and Attributes for Passing Mechanisms 6 15 6 4 Default Values on Formal Parameters 6 26 8 1 Predeclared Routine Categories 00000eeee 8 1 xiv 8 2 8 3 9 2 9 4 Return Values of Alignment Predeclared Routines Value of ZERO eee Characteristics of the KEY Attribute File Organization Support for Component F
7. Unlike other declaration sections the VALUE section can appear only in a program or module declaration section You cannot use the VALUE declaration section in procedures or functions If you wish to initialize variables in procedures and functions use an initial state specifier by using the VALUE reserved word in either the TYPE or VAR section You can assign values to complete structured variables or to a single component of that variable For More Information e On data types Chapter 2 e On expressions Section 4 1 3 7 VAR Section The VAR section declares variables and associates each variable with an identifier a type and an optional initial value It has the following form var attribute list VAR variable identifier attribute list type denoter Declaration Section 3 9 THe j initial state specifier var attribute list One or more attributes that apply to the entire VAR section Only the ALIGN ENUMERATION SIZE or HIDDEN attributes can be specified here variable identifier The identifier of the variable being declared attribute list One or more identifiers that provide additional information about the variable type denoter Any legal Pascal type syntax initial state specifier Any constant expression that is assignment compatible with the variable identifier The variable is initialized to this expression You can combine several identifiers in the same variable decl
8. Wombat X CHAR In the executable section x Stringl 9 Generates an error X Stringl BODY 9 Provides whatever is in memory there x Stringl 5 Is legal Stringl 9 X Generates an error For More Information e On schema types Section 2 5 e On arrays Section 2 4 1 e On the SIZE predeclared function Section 8 83 2 7 Null Terminated Strings HP Pascal includes routines and a built in type to better coexist with null terminated strings in the C language The C STR T datatype is equivalent to C STR T ARRAY 0 0 OF CHAR C STR T is a pointer to an ARRAY OF CHARs It does not allocate memory for any character data C STR T behaves like a normal pointer type in that you can assign NIL into it and the optional pointer checking code will check for dereferencing of a NIL pointer The individual characters can be used by dereferencing the pointer and using an array index In these cases no bounds checking will be performed even if array bounds checking is enabled However you cannot dereference a C STR T pointer without also indexing a single character If you want to access an entire null terminated string see the PAS STR function For More Information e On the MALLOC C STR function Section 8 54 e On the C_STR function Section 8 16 On the PAS_STRCPY function Section 8 68 e On the PAS_STR function Section 8 69 Data Types and Values 2 47 2 8 TIMESTAMP Type The TIMESTA
9. e On attributes and parameter compatibility Chapter 10 e On type conversions Section 4 4 6 3 3 Routine Parameters To write a routine that invokes another routine whose effect is not determined until the program is executed use routine parameters To declare a procedure or a function as a formal parameter to another routine you must include a complete routine heading in the formal parameter list You can also associate a foreign mechanism specifier and a default value with a formal procedure or function parameter 6 12 Procedures and Functions The following examples show formal routine parameter sections in procedure and function declarations PROCEDURE Apply FUNCTION Operation Left Right REAL REAL VAR Result REAL FUNCTION Copy PROCEDURE Get Char VAR c CHAR PROCEDURE Put Char i CHAR BOOLEAN The identifiers listed as formal parameters to a formal procedure or function parameter are not accessible outside the routine declaration they indicate the number and kind of actual parameters necessary You refer to these identifiers only when you use nonpositional syntax to call a routine parameter In the previous example the formal parameter list of Get Char informs the compiler that Copy must pass one character parameter to Get Char using variable semantics Copy does not refer explicitly to the formal parameter c unless it calls Get Char using nonpositional syntax To pass a routine as an actual
10. e On the UNSIGNED type Section 2 1 1 2 e On the subrange type Section 2 1 5 e On attributes Chapter 10 e On schema discriminants in sets Section 2 5 2 4 3 4 Set Constructors Set constructors are lists of values that you can use to initialize a set they have the following form data type component value data type The data type of the constructor This identifier is optional when used in the CONST and executable sections do not use this identifier in the TYPE and VAR sections or in nested constructors component value Specifies values within the range of the defined data type Component values can be subranges to indicate consecutive values that appear in the set definition These values are compile time values if you use the constructor in the executable section you can also use run time values Data Types and Values 2 31 A set having no elements is called an empty set and is written as empty brackets A possible constructor for a variable of type SET OF 35 115 is the following VAR Numbers SET OF 35 115 VALUE 39 67 110 115 In the executable section run time expressions are legal Numbers 39 67 x 95 110 115 The set constructors contain up to nine values 39 67 x 95 in the executable section only and all the integers between 110 and 115 inclusive If the expression x 95 evaluates to an integer outside of the range 35 115 then Pascal includes no set ele
11. A label can appear only once within the scope of the label declaration It can precede any executable statement in the program Use a colon to separate the label from the statement it precedes Labels can be accessed only by GOTO statements Consider the following example LABEL marker 5 In the executable section IF a lt 150 THEN GOTO 5 ELSE GOTO marker marker WHILE x lt 20 DO Statement For More Information e For information on the GOTO statement see Section 5 8 3 3 TO BEGIN DO Section The TO BEGIN DO section allows you to specify a statement in a module that is to be executed before the executable section of the main program it has the following form TO BEGIN DO statement statement A Pascal statement The TO BEGIN DO section can only appear in modules can only appear once in a module and must appear as the last section in the declaration section If appearing together the TO BEGIN DO section must precede the TO END DO section at the end of the declaration section Declaration Section 3 3 Consider the following example MODULE x INPUT OUTPUT VAR Debug BOOLEAN PROCEDURE Test Executable section TO BEGIN DO BEGIN WRITE Debug Module x ys READLN Debug END END As a general rule if a program or module inherits an environment file the compiler executes the initialization section in the inherited module before the initialization section in the program or
12. MAIN ST 19724 SMITH HOLT RD 11733 WYMAN MAIN ST 2254 V Data Records P In Figure 9 3 the components are logically stored in an order that is determined by the primary index The actual physical location of components is transparent to your program Figure 9 4 shows the presence of a first alternate index determined by the presence of first alternate keys in the components that points to components stored in order by the primary key ZK 1835A GE Input and Output Processing 9 5 Figure 9 4 A First Alternate Key KEY DEFINITION Primary Key woe 2254 woe 11733 see 19724 eee 21000 see 24379 see 35112 and Pointers ADAMS PINE ST 35112 eee CLARK ELMAVE 24379 eee JONES MAINST 19724 eee SMITH HOLTRD 11733 eee WYMAN MAINST 2254 iN DATA J 9 6 ZK 1336A GE For More Information e On component formats in indexed files Section 9 2 e On access methods for indexed files Section 9 3 e On the KEY attribute Section 10 2 23 In an indexed file each component includes one or more key fields or simply keys that HP Pascal uses to build the specified indexes Each key is identified by its location within the component its length and its data type A key
13. TYPE Array Typel Array Template 10 PROCEDURE Example Param Array Typel Procedure body For any undiscriminated schema there is a range of possible data types that you can form by discrimination A schema family is the undiscriminated schema type and the range of data types that can be formed from it Also two separate discriminations that provide the same actual discriminant value specify the same data type Consider the following TYPE My Subrange a b INTEGER a b Sub A My Subrange 1 5 Sub B My Subrange 1 5 Sub C My Subrange 50 50 The types Sub A Sub B and Sub C are all of the My Subrange schema type family Sub A and Sub B are of the same data type Consider the following Wo I TYPE My Subrange a b INTEGER a b My Array Upper INTEGER ARRAY 1 Upper OF INTEGER VAR i My Array 10 j My Array 10 k My Array 15 l ARRAY My Subrange 1 10 OF INTEGER m ARRAY My Subrange 1 10 OF INTEGER Data Types and Values 2 39 In the executable section ges Legal same schema family same actual discriminant il i2 kj Illegal same schema family different actual i s 1 Illegal different types l 2m Illegal different types Types 1 and m are not assignment compatible despite having the same subrange values specified by the same schema type the two distinct type declarations create two distinct types regardless of the ranges of
14. The WEAK EXTERNAL attribute specifies that a variable or routine is not critical to the linking operation To resolve a weak reference the linker searches only the named input modules You can specify an identifier with this attribute to indicate the name by which the corresponding object is known to the linker WEAK EXTERNAL t e Du string literal identifier Identifier passed to the linker If you omit the identifier the name of the variable is used as the name of the common block string literal Passes the specified string literal to the linker unmodified Compilation units cannot have the EXTERNAL or WEAK_EXTERNAL attribute For More Information e On the EXTERNAL attribute Section 10 2 15 On linking HP Pascal for OpenVMS User Manual 10 50 Attributes 10 2 44 WEAK_GLOBAL The WEAK_GLOBAL attribute specifies that an object is linked only when it is specifically included in the linking operation To resolve a weak reference the linker searches only the named input modules You can specify an identifier to indicate the name by which the corresponding object is known to the linker WEAK GLOBAL I eerie D string literal identifier Identifier passed to the linker If you omit the identifier the name of the variable is used as the name of the common block string literal Passes the specified string literal to the linker unmodified For More Information e On the GLOBAL attribute Secti
15. UNSIGNED type is 0 The largest possible value of the UNSIGNED64 type is represented by the predefined constant MAXUNSIGNED64 The smallest possible value of the UNSIGNED64 type is 0 Table 2 4 lists the sizes and the corresponding values of MAXUNSIGNED and MAXUNSIGNED64 Table 2 4 Values of MAXUNSIGNED and MAXUNSIGNED64 Constant Size Value MAXUNSIGNED 32 bits 22 1 16 FFFFFFFF MAXUNSIGNED64 64 bits 264 1 1648FFFFFFFFFFFFFFFF 2 1 1 3 Integer Literals Literal values of the INTEGER type have the following form decimal number base number extended digit Ii FI b P 0 extended digitf X 2 4 Data Types and Values decimal number Specifies an integer in conventional Pascal integer notation You cannot specify commas or decimal points Examples of decimal notation are as follows 17 0 89324 base number Specifies the base or radix of the number HP Pascal accepts numbers in bases 2 through 36 extended digit Specifies the notation that is appropriate for the specified base b Oo x Specifies an integer in either binary base 2 octal base 8 or hexadecimal base 16 notation In HP Pascal you can use either uppercase or lowercase letters to specify the extended digit notation You can use extended digit notation in the same way you use the conventional integer notation The one restriction is that you cannot use extended digit values as labels HP Pasc
16. e Section 7 4 Modules and Programs e Section 7 5 Compilation Units and Data Sharing 7 1 Blocks A block is a declaration section and an executable section Programs modules and routines are structured in blocks A declaration section can contain routine blocks nested within the outer program or module block routine blocks can also be nested within other routines The declaration section contains data definitions and declarations and nested routine declarations that are local to the enclosing block The executable section contains the statements that specify the block s actions You can cause an exit from a block with the last executable statement of the block which causes normal termination or with a GOTO statement which transfers control to an outer block For More Information e On declaration sections Chapter 3 e On routine declarations Section 6 1 e On the GOTO statement Section 5 8 Program Structure and Scope 7 1 7 2 Scope of Identifiers The scope of an identifier is the part of the program in which the identifier has a particular meaning In Pascal the scope of an identifier is the block in which it is defined or declared including nested blocks but excluding any nested blocks that redeclare the same identifier Outside its scope and assuming that it is not declared elsewhere an identifier has no meaning in this case attempts to use the identifier generate an error All Pascal identifiers observe the fo
17. 0 Subrange 0 REAL 0 0 DOUBLE 0 0 QUADRUPLE 0 0 ARRAY ZERO applied to each component RECORD ZERO applied to each field VARYING OF CHAR STRING The null string SET The empty set Pointer NIL 1 Note that an ordinal target with a subrange type can be initialized outside of the subrange The compiler treats this as an error if used in a compile time expression The ZERO function is used in two ways You can use it as a compile time expression to initialize a variable in the TYPE VAR CONST or VALUE sections You can also use it on the right side of an assignment statement that appears in the executable section where the target is either a variable or within the body of a function the function identifier Predeclared Functions and Procedures 8 53 This example shows both uses TYPE Pre Zeroed Record RECORD A INTEGER B Array 1 3 of Real END VALUE ZERO VAR An Array Array 1 10 of Real Pre Zeroed Pre Zeroed Record BEGIN An Array ZERO Initializes all of An Array to zeroes For More Information e On data initialization Chapter 2 e Using the ZERO function with records Section 2 4 2 2 8 54 Predeclared Functions and Procedures 9 Input and Output Processing The HP Pascal I O model provides an extensive set of predeclared routines When programming with I O remember that the routines and their effects depend on the capabilities available in your environment not all routines or organiz
18. 8 106 8 107 8 108 8 109 8 110 8 111 PRESENT Fuhc uon zeekuerewbe t ORE E PRPERPIEEPREES QUAD Function ssas casse naa vensa taa ee hh RANDOM Func n PE oe tome Mae ete Gene aa toch a E READV Procedure 0 0 0 cece eee ee eens RENAME FILE Procedure 0 00000 eee eee REVERT Procedure 0 0 0 0 cece eee eens ROUND Punict Otis odes eV E X Roe we ae ROUND64 Function llle RSHIET E rnchon 24222290 padre gc qur ce dere Soeur 4 SEED Function SET INTERLOCKED Function eee SIN Function SIZE Function SNGL Function SQR Function SQRT Function STATUSV Func Gon 3 ae ETCOCREEESTTSRERINS TERCER SUBSTR Function 000 0000 eee ee eee SUCC Function SYSCLOCK Function oc seti socio we ores wp e eee wwe we ee TIME Procedures norice crouer t EDELA eee ERR ee Re E TRUNC Function 0 0 0 cc ec cc hm hts TRUNCG64 Function sese 64655 0054 682 kea EE b44804 663 3 WAND Function u a S RES VUE RUE S EAS x UDEG Punction gt ice e odie eee kOe REESE PEIUS RE RES UINT Function UINT64 Function ese dua dur ober bose P obo robur b toned UNDEFINED Function eeee eA UNOT Function s 5o gcn ree a oe Nee EO C alte e UNPACK Procedure 0 cc ccc ec ee eee eee eee UOR Function UPPER Function 34 25 44 06 954 55 044 Hb bad PUR RES ES Fusdobus UROUND Func DIODE S onsite avo ee E ee ee ee ee UROUND64 Function reciso rercia retten ECN ees UTR
19. 8 56 MFPR Function OpenVMS VAX systems only The MFPR function returns an unsigned value that is the value of a VAX internal processor register MFPR ipr register expression Predeclared Functions and Procedures 8 27 The ipr register expression parameter is an expression compatible with the UNSIGNED type When you call this function the value of the internal processor register is retrieved with the MFPR privileged VAX instruction Note The HP Pascal compiler generates user mode code HP Pascal does not explicitly support the running of HP Pascal generated code in kernel mode However if the following rules are observed then the generated code has a good chance of working as expected in elevated access modes e All code must be compiled with the NOCHECK qualifier or CHECK NONE attribute The HP Pascal run time signaling method relies on trying to execute the HALT instruction In user mode this causes an exception that is a signal to the HP Pascal Run Time Library In kernel mode this HALTs the machine e Avoid all routine calls that translate into run time library calls These include all I O routines several arithmetic routines several string routines and so forth 8 57 MIN Function The MIN function returns a value of the same type as that of the parameters that is the minimum value of a specified list of parameters MIN x1 xn The parameters can be any arithmetic type but must all be of
20. 8 71 PRESENT Function The PRESENT function returns a Boolean value that indicates whether the actual argument list of a routine contains an argument that corresponds to a formal parameter This function is usually used to supply a default value or to take a default action when the argument for a parameter is omitted PRESENT parameter name Predeclared Functions and Procedures 8 35 The parameter name parameter is the name of a formal parameter with the TRUNCATE attribute The parameter name must be the name of a formal parameter of the function from which PRESENT is called or from a subroutine of that function The function result indicates whether the argument list of the containing routine specifies an actual argument corresponding to an optional parameter Parameters that do not have the TRUNCATE attribute and also do not follow a parameter with the TRUNCATE attribute in the formal parameter list are allowed in their case the PRESENT function always returns TRUE Default parameters are considered to be present in the argument list and the PRESENT function returns TRUE when passed the name of a parameter with a default value For More Information e On examples using PRESENT and TRUNCATE Section 10 2 37 e On parameters Section 6 3 8 72 QUAD Function The QUAD function converts the parameter and returns its QUADRUPLE equivalent QUAD x The parameter x must be an arithmetic type For More Information e
21. A 2 3 A 2 4 A 2 5 A 2 6 A 2 7 A 3 A 3 1 A 3 2 A 3 2 1 A 3 2 2 A 3 2 3 A 3 2 4 A 3 2 5 A 3 2 6 A 3 2 7 A 3 3 A 3 3 1 A 3 3 2 A 3 3 3 Program Sections verse es Pa ea ee RR eS aeRO Establishing Program Sections 0000 ee eee Establishing Program Section Properties Storage Allocation 2 0 0 40 dede s odere ana dh aon gaa duet Allocation of Variables iile Allocation of Symbolic Constants and Executable Blocks Allocation Example 0 0 0 cece eee ee eee Allocation Sizes of Variables llle Storage Allocation of Types 0 00 eee eee Allocation Size Examples 0 0 0 0 cee eee eee Alignment Boundaries llle Internal Representation of Data Types sss Representation of Varying Data llle Representation of Floating Point Data F floating Point Numbers 0000000 S floating Point Numbers 0000 0s eee D floating Point Numbers 0000005 G floating Point Numbers 00000 T floating Point Numbers 0000000 H floating Point Numbers 0000 eee X floating Point Numbers 0000000 Representation of Nonstatic Types and Variables Representation of Nonstatic Types 04 Representation of Variables of Nonstatic Types Representation of Nonstatic Record Fields B
22. Adding 1 to the field containing the exponent gives the same result as multiplying A by 2 0 For More Information e On data types Chapter 2 e On the VOLATILE attribute Section 10 2 42 e On conformant array parameters Section 6 3 7 1 4 2 7 Precedence of Operators The operators in an expression establish the order in which HP Pascal combines the operands The compiler performs operations with higher precedence operators before operations with lower precedence operators Table 4 8 lists the order of operator precedence from highest to lowest operators on the same line are of equal precedence Table 4 8 Precedence of Operators Operators Precedence i Highest NOT dek DIV REM MOD AND AND THEN continued on next page 4 12 Expressions and Operators Table 4 8 Cont Precedence of Operators Operators Precedence OR OR ELSE unary unary lt gt lt lt gt gt IN Lowest In Pascal operators of equal precedence such as plus and minus are combined from left to right within the expression You must use parentheses for correct evaluation of an expression that combines relational operators Consider the following expression a lt x AND b lt y Without parentheses this expression is interpreted as A lt X AND B lt Y The logical operator AND requires its operands X and B to be Boolean expressions and returns a Boolean result which is then used as
23. Also pointer types clearly define the type of an object but you can create or eliminate objects during program execution The syntax of a pointer type is as follows attribute list attribute list base type identifier attribute list One or more identifiers that provide additional information about the base type base type identifier The type identifier of the dynamic variable to which the pointer refers The base type can be any type name or schema name If the base type is an undiscriminated schema type you need to supply actual discriminants when you call the NEW function Unlike other variables dynamic variables do not have identifiers You can access them indirectly with pointers When you use pointers you call the procedure NEW to allocate storage for dynamic variables You call the procedure DISPOSE to deallocate this storage A variable of a pointer type refers to a dynamic variable of the base type and is said to be associated with that type In the following example the variable Ptr is associated with a record of type My Rec TYPE My Rec RECORD Name STRING 30 Age INTEGER END VALUE Name Chris Lee Age 29 Initialized VAR Ptr My Rec In executable section NEW Ptr To reference the dynamic variable to which a pointer refers write the pointer variable name followed by a circumflex The following example assigns values to the record variable Ptr A
24. END In this example the last field in this record will be one of the following e The integer field Capital if the range A Z is the variant most recently referred to e The integer field Number if the range 0 9 is the variant most recently referred to e The Boolean field Misc if the character value falls outside the previous two variants You can refer only to the fields in the current variant You should not change the variant while a reference exists to any field in the current variant 2 26 Data Types and Values You can include an OTHERWISE clause as the last case label list OTHERWISE is equivalent to a case label list that contains tag values if any not previously used in the record The variant labeled with OTHERWISE is the current variant when the tag identifier has a value that does not occur in any of the case label lists The variant can contain a nested variant as follows VAR Hospital RECORD Patient Name Birthdate Date Age INTEGER CASE Pat Sex Sex OF Male 05 Female CASE Births BOOLEAN OF FALSE TRUE Num Kids INTEGER END This record includes a variant field for each woman based on whether she has children A second variant which contains the number of children is defined for women who have children For More Information On the syntax of a field list Section 2 4 2 e On conditions that establish a variable reference Section 3 7 e On attributes Chapte
25. END VAR An order Orders 2358 FALSE 10 293 99 For More Information e On standard record constructors Section 2 4 2 2 e On record variants Section 2 4 2 1 2 5 Schema Types A schema type is a user defined construct that provides a template for a family of distinct data types A schema type definition contains one or more formal discriminants that take the place of specific boundary values or variant record selectors By specifying boundary or selector values to a schema type you form a valid data type the provided boundary or selector values are called actual discriminants Schema types have the following form schema identifier discriminant identifier attribute list ordinal type name attribute list type denoter schema identifier The name of the schema discriminant identifier The name of a formal discriminant attribute list One or more identifiers that provide additional information about the type denoter ordinal type name The type of the formal discriminant which must be an ordinal type except those types that have INTEGER64 or UNSIGNED64 base types type denoter The type definition of the components of the schema This must define a new record array set or subrange type Data Types and Values 2 37 Each schema type definition requires at least one discriminant identifier A discriminant identifier does not have to be used in the type denoter definition but Pasca
26. For example you can use the POINTER type in the following ways e To assign to or from any other type of pointer including function result variables e To compare equality with any other type of pointer e To pass actual parameters of type POINTER to VAR and value parameters of any other type of pointer e To accept parameters of any other type of pointer with formal parameters of type POINTER 2 4 Structured Types The structured data types are user defined and consist of components Each component of a structured data type has its own data type components can be any type 2 18 Data Types and Values To express values of structured objects arrays records and sets you can use a list of values called constructors Constructors are valid in the TYPE CONST VAR and executable sections of your program Examples of valid constructors are provided throughout the following sections The following sections also contain examples that show how to assign values to individual components of structured objects To save storage space you can specify PACKED before any structured type identifier except VARYING OF CHAR for example PACKED ARRAY PACKED RECORD and PACKED SET Defining PACKED structured types causes the compiler to economize storage by storing the structure in as few bits as possible Keep in mind however that a packed data item is not compatible with a data item that is not packed Also accessing components of some packed
27. Lexical and syntactical extensions Reserved words BREAK CONTINUE ERR EXIT NEXT REM RETURN VARYING DESCR STDESCR IMMED REF INCLUDE TITLE SUBTITLE DICTIONARY DICTIONARY IF ELIF ENDIF DEFINED ERROR WARN INFO MESSAGE ARCH_NAME SYSTEM_ NAME SYSTEM_VERSION DATE TIME COMPILER_ VERSION LINE FILE ROUTINE MODULE IDENT REM operator NOT IN operator Type cast operator for variables and expressions Ooradix specifier number form for binary hexadecimal and octal notation for integers Alphanumeric strings for labels Double and quadruple precision real numbers Identifiers can contain the dollar sign character Identifiers can begin with the dollar sign character and the underscore character Double quotation marks as string and character delimiters Escape sequences within double quotation marks Labels can be alphanumeric strings Extended syntax for inclusion of nonprinting characters in single quoted character strings Parenthetical form constructor for constructors of structured types used anywhere in place of a constant of the structured type Attributes Relaxed rules for assignment compatibility Structural compatibility enforced between actual and formal parameters for end of line comments continued on next page Summary of HP Pascal Extensions B 5 Table B 2 Cont HP Pascal Extensions to Extended Pascal Category Extension
28. MOD returns the remainder of A MODULO B The result of the operation A MOD B is defined only when B is a positive integer This result is always an integer between 0 and B 1 The modulus of A with respect to B is computed as follows e If A is greater than B then B is subtracted repeatedly from A until the result is a nonnegative integer less than B e If Ais less than B and not negative the result is A e If Ais less than zero B is added repeatedly to A until the result is a nonnegative integer less than B For example 5 MOD 3 equals 2 4 MOD 3 equals 2 and 2 MOD 5 equals 2 When both operands are positive the REM and MOD operators return the same result For example 28 REM 5 equals 3 and 28 MOD 5 equals 3 However when the first operand is negative REM produces a negative or zero result while MOD produces a positive or zero result For example 42 REM 8 equals 2 and 42 MOD 8 equals 6 Enabling subrange checking ensures that a MOD operation is legal by verifying at run time that B is a positive integer Note that the use of negative integer and real number constants as operands in MOD and exponentiation operations can not produce the results you expect because the minus sign is actually a negation operator For example the expression 2 0 2 is equivalent to the expression 2 0 2 and produces the result 4 0 Therefore you should enclose a negative constant in parentheses 4 4 Expressions and Ope
29. READLN and WRITELN 9 18 Input and Output Processing 9 5 1 Carriage Control Some devices such as printers and terminals are carriage control devices and require characters to provide information regarding output HP Pascal supports the following carriage control options OPEN Parameter Option Description LIST Single spacing between components This is the default carriage control option for all TEXT files including OUTPUT and VARYING OF CHAR files CARRIAGE FORTRAN The first character of every output line is a carriage control character NONE NOCARRIAGE No carriage control This is the default for all files other than TEXT and VARYING OF CHAR files For FORTRAN carriage control if output is directed to devices that do not use carriage control characters the character is written into the file as a component and is read back when the file is opened for input If output is directed to devices that do use carriage control then the OPEN parameter options described previously determine the action taken by HP Pascal Table 9 5 summarizes carriage control characters and their effects For purposes of carriage control HP Pascal ignores any characters other than those listed in the table Table 9 5 Carriage Control Characters Character Meaning 4 Overprinting starts output at the beginning of the current line uf Single spacing starts output at the beginning of the next line 0 Double spacing ski
30. RECORD TEST VAR COMMON EXAMPLE VAR VAR ITEM 10 VAR ITEM NAME 0123456789 END Data Storage and Representation A 5 The HP Pascal program initializes the common record Myrec to zero then calls the HP Fortran routine Call_Fort to assign the desired values to the elements within the common record The HP Pascal program then writes the assigned values to your terminal Only one variable can be allocated in a particular HP Pascal common block To share more than one data item in the same common block the record variable containing all shareable items is declared and used For More Information e On the PSECT and COMMON attributes Chapter 10 A 1 2 Establishing Program Section Properties Whether the compiler establishes a program section or you create one the program section is assigned one property from each class listed in Table A 1 These properties are assigned to satisfy the requirements of the types variables and executable blocks that have been allocated in the same program section Table A 5 lists the minimal properties required by various objects Table A 5 Required Program Section Properties Object Properties EXE RD WRT NOSHR Read only variable X Write only variable X X xi Read write variable X X xi Executable block OpenVMS I64 X and OpenVMS Alpha systems only Executable block OpenVMS X X VAX systems only lThis property is not assigned on OpenVMS VAX systems if the variabl
31. ROUND64 SIN continued on next page Table 1 5 Cont Predeclared Identifiers SINGLE SIZE SNGL SQR SQRT STATUS STATUSV STRING SUBSTR SUCC SYSCLOCK T_FLOAT TEXT TIME TIMESTAMP TRUE TRUNC TRUNC64 TRUNCATE UAND UDEC UFB UINT UNDEFINED UNLOCK UNOT UNPACK UNSIGNED UNSIGNED8 UNSIGNED16 UNSIGNED32 UNSIGNED64 UOR UPDATE UPPER UROUND UROUND64 UTRUNC UTRUNC64 UXOR WALLCLOCK WRITE WRITELN WRITEV X_FLOAT XOR ZERO Note This table does not include predefined identifiers that are only provided by HP Pascal for compatibility with other Pascal compilers For More Information e On attributes Chapter 10 1 3 Comments Comments document the actions or elements of a program The text of a comment can contain any ASCII character except a nonprinting control character such as an ESCAPE character You can place comments anywhere in a program that white space can appear You signify a comment with braces or with a parenthesis and asterisk pair as follows This is a comment This ig a comment too Language Elements 1 9 HP Pascal allows you to mix the two symbol pairs in one comment as follows The delimiters of this comment do not match HP Pascal allows you to mix delimiters in this way HP Pascal does not allow you to nest comments The following example causes a compile time error because the comment ends at the first closing delimiter Cannot nest comments inside of comments
32. Suppose you declare a file variable Math_Scores of type FILE OF INTEGER You might call a procedure to move the file position to the first component of this file At this point the file buffer variable Math_Scores equals the value of the first component here 90 If you then called a procedure to advance the file position by two components Math_Scores would equal the value of the third component here 70 Consider the following example VAR f FILE OF INTEGER In the executable section OPEN File Variable f File Name sample dat History OLD Organization Sequential Access Method Direct EXTEND f F 20 PUT f Input and Output Processing The OPEN procedure opens the existing file sample dat The EXTEND procedure positions the file after its last component The assignment statement places the value 20 into the file buffer variable F The PUT procedure writes the value of the file buffer variable at the end of the file f When you declare a variable of type FILE you indicate the type of all of its components For example TYPE DataRecord RECORD Fieldl INTEGER Field2 REAL END RECORD VAR DataFile FILE OF DataRecord VAR gains access to the file After calling RESET REWRITE or EXTEND you use file variables to refer to the selected component The following code continues the previous example A DataRecord is a component of this file each component contains an i
33. Table 10 3 lists the keywords for the ENUMERATION SIZE attributes Table 10 3 ENUMERATION SIZE Attribute Keywords Keyword Description Default on BYTE Allocates unpacked enumerated types with OpenVMS VAX systems fewer than 255 elements and Booleans in a 8 bit byte Otherwise the enumerated types are allocated in a 16 bit word LONG Allocates all unpacked enumerated types OpenVMS 164 and and Booleans in a 32 bit longword OpenVMS Alpha systems 10 2 14 ENVIRONMENT You can apply the ENVIRONMENT attribute to compilation units which causes the unit s program or module level declarations and definitions to be saved ENVIRONMENT name string If the name string is omitted the name of the source file is used as the environment file name 10 16 Attributes The declarations and definitions made at the outermost level of the compilation unit provided they do not have the AUTOMATIC or HIDDEN attribute are saved in a newly created environment file If the name string is specified you must include a legal file specification Usage and Default Information There is a default file type of PEN for environment files if a file name is specified If you do not specify a file name with the ENVIRONMENT attribute then the file name of the source file is used with a PEN extension for the name of the environment file For example Module share data pas ENVIRONMENT Module Share Data CONST Rate For Q1 0 1211
34. The STATUSV function returns an integer value that specifies the status of the last READV or WRITEV procedure completed STATUSV does not have any parameters This example shows the use of the STATUSV function VAR Vary Src VARYING 20 OF CHAR Int Result INTEGER In the executable section Vary Src 255 READV Vary Src Int Result ERROR CONTINUE IF STATUSV lt gt 0 THEN 0 means READV executed successfully WRITELN Error in READV If however you have an asynchronous system trap AST routine condition handler in your program that uses READV and WRITEV the call of STATUSV in your main program may not return the results you expected if an AST occurred between the READV WRITEV procedure and the STATUSV procedure For More Information e On the READV procedure Section 8 74 e On the WRITEV procedure Section 8 109 e On character strings Section 2 6 8 42 Predeclared Functions and Procedures 8 88 SUBSTR Function The SUBSTR function returns a substring from a string specified as a parameter that is of the specified starting point and length The return value is compatible with all other string types SUBSTR str start length The parameter str is a character string value the parameter start is an integer value indicating the starting position of the substring The parameter length is an integer value that indicates the length of the substring The following rules apply to the use of
35. e On component format Section 9 2 Random Access by Relative Component Numbers Direct Access HP Pascal supports random access by relative component numbers for relative files and for sequential files with fixed length components on disk To access the desired component you need to specify the relative component number of the corresponding cell relative component numbers are relative to the beginning of the file Figure 9 9 shows the process of randomly accessing cells in a file For random access of sequential files the cells must be of a fixed length Input and Output Processing Figure 9 9 Using Random Access on Sequential and Relative Files Start of File System software User Program 1 Read sixth cell 2 Read second cell ZK 1354A GE 9 3 2 2 Random Access to Indexed Files Keyed Access HP Pascal supports random access to indexed files To retrieve a component you must specify an index primary index first alternate index second alternate index and so forth and a key value To store a component HP Pascal determines existing keys from the file organization and stores the record and alternate key information according to information as it exists in the data portion of the component Your program can use several methods to randomly access a record by key e Exact match of key values e Approximate match of key values When accessing an index in ascending sort order HP Pascal returns the compon
36. error recovery code if specified For More Information e On error recovery codes HP Pascal for OpenVMS User Manual 8 23 DATE and TIME Functions The DATE and TIME functions provide a standard way of returning a character string value that indicates the calendar date and time The return value is compatible with all string types DATE t TIME t The parameter t is a variable of the predeclared type TIMESTAMP You can either call the GETTIMESTAMP procedure to initialize parameter t before you pass t to either DATE or TIME or you can construct your own TIMESTAMP object 8 12 Predeclared Functions and Procedures The size of the function s return value depends on the string length that is normally returned by your system for either date or time data Consider the following example VAR Time Var TIMESTAMP The Time The Date STRING 23 In the executable section GETTIMESTAMP Time Var The Date DATE Time Var The Time TIME Time Var WRITELN The Date The Time Writes 15 JUL 1992 14 20 25 98 For More Information e On the GETTIMESTAMP predeclared procedure Section 8 38 e On the layout of the TIMESTAMP type Section 2 8 8 24 DATE and TIME Procedures The DATE and TIME procedures write the date and the time to their parameters DATE str TIME str The parameter str must be of type PACKED ARRAY 1 11 OF CHAR After execution of the procedure the parameter str contains either the da
37. form feed 1 10 nonprinting 2 7 of type CHAR 2 7 ordinal value of 2 7 page break 1 10 Character set See ASCII character set Character string 2 43 comparing for equality 8 16 8 19 8 24 comparing for inequality 8 19 8 20 8 24 8 26 8 29 comparing with predeclared routines 4 9 comparing with relational operators 4 9 default field width of 9 23 extracting substring from 8 43 finding length of 8 25 fixed length 2 43 locating pattern in 8 23 nonpadded for comparison 4 9 operators 4 8 padding 8 34 padding for comparison 4 9 reading from 8 37 reading from text file 9 53 varying length 2 44 writing to 8 51 CHAR type 2 7 allocation size of A 11 default field width of 9 23 reading from text file 9 53 CHECK attribute 10 11 summary of options 10 11 CHR function 8 11 Classes of attributes 10 52 to 10 54 CLASS A attribute 10 13 used to specify descriptor in parameter 6 16 CLASS NCA attribute 10 13 used to specify descriptor in parameter 6 16 CLASS S attribute 10 14 used to specify descriptor in parameter 6 16 Index 3 CLEAR INTERLOCKED function 8 11 CLOCK function 8 12 CLOSE procedure 9 31 CODE and CODE program section A 2 CODE program section A 10 Comments 1 9 nested 1 10 COMMON attribute 10 15 effect on allocation of variables A 7 program section properties A 6 use in allocating storage A 8 use when defining prog
38. function returns a pointer an array or a record you can directly dereference index or select the returned value For example WRITELN Make Node 10 Data 1 WRITELN Make Vector 15 2 Make Node 10 Data 1 42 4 4 Type Conversions Because HP Pascal is a strongly typed language you cannot normally treat a value of one type as though it were of a different type as you can in many languages For example you cannot assign the character 1 to a variable of type INTEGER because 1 is not an integer constant but a character constant However there are times when it makes sense to combine values of two different types because the values have some aspect in common For example suppose you wish to add a value of type REAL to a value of type INTEGER This operation is legal because the value of type INTEGER is converted to its equivalent value of type REAL before the operation is performed The result of the operation is of type REAL In HP Pascal values are converted from one type to another when the conversion is required for an operation an assignment or a formal actual parameter association Before any type conversion the arithmetic types are ranked as follows from lowest to highest e INTEGER e UNSIGNED e INTEGER64 e UNSIGNED64 e REAL or SINGLE e DOUBLE e QUADRUPLE Expressions and Operators 4 15 Similarly the character types are also ranked as follows from lowest to highest e CHAR e PACK
39. spaces are assigned to the remaining components You can also read TEXT file characters into a variable of types STRING or VARYING OF CHAR Characters are assigned to a STRING or VARYING OF CHAR variable in a manner similar to that in which they are assigned to a packed array However if the end of line marker is encountered before the STRING or VARYING OF CHAR variable has been filled to its maximum length the STRING or VARYING OF CHAR value is not padded with spaces Instead its current length is set equal to the number of characters that have been read into it If you call the READ procedure with a parameter of type STRING or VARYING OF CHAR and EOLN returns TRUE no characters are read into the STRING or VARYING OF CHAR variable its current length is set to zero Every nonempty TEXT file ends with an end of line marker and an end of file marker Therefore EOF never becomes TRUE when you are reading strings with the READ procedure To test EOF when reading strings use a READLN procedure to advance the file beyond the end of line marker Consider the following example READ Temp Age Weight Assume that Temp Age and Weight are real variables and that the following values have been entered at the terminal 98 6 11 75 The variable Temp is assigned the value 98 6 Age is assigned the value 11 0 and Weight is assigned the value 75 0 You need not type all three values on the same line 9 54 Input and Output Processing C
40. specify an integer subrange in the data type definition unless you are using a conformant array parameter You can use an array component anywhere in a program that a variable of the component type is allowed Also the only operation defined for entire array objects is the assignment operation unless your array components are of a FILE type 2 4 1 1 ARRAY Components To refer to an array component you specify the name of the array variable or the name of an object whose result when used as an expression is of an array type followed by an index value enclosed in brackets Consider the following TYPE Count ARRAY 1 10 OF INTEGER Array type of 10 integers VAR Numbers Count Array variable In the executable section Numbers 5 18 Assigns the value 18 to the fifth element HP Pascal also allows array components to be arrays These types of arrays are called multidimensional arrays The following example shows two ways of declaring the same multidimensional array 2 20 Data Types and Values VAR Tic Tac Toe ARRAY 1 3 OF ARRAY a c OF CHAR Or equivalently Tic Tac Toe ARRAY 1 3 a c OF CHAR 3x3 matrix In the executable section Tic Tac Toe 1 a X Or equivalently Tic Tac Toe 1 a X For More Information e On character string types Section 2 6 e On conformant array parameters Section 6 3 7 1 e On attributes Chapter 10 e On the TEX
41. the relationship holds the result is TRUE otherwise the result is FALSE Table 4 4 lists the relational operators that you can apply to arithmetic operands You can also apply some of the relational operators to string operands and to set operands Expressions and Operators 4 5 Table 4 4 Relational Operators Operator Example Result A B TRUE if A is equal to B lt gt A lt gt B TRUE if A is not equal to B lt A lt B TRUE if A is less than B lt A lt B TRUE if A is less than or equal to B gt A gt B TRUE if A is greater than B gt A gt B TRUE if A is greater than or equal to B Note that operators designated with two characters must appear in the order specified and cannot be separated by a space For More Information e On relational operators in string expressions Section 4 2 4 e On relational operators in set expressions Section 4 2 5 e On the BOOLEAN data type Section 2 1 3 4 2 3 Logical Operators A logical operator evaluates one or more Boolean expressions and returns a Boolean value The logical operators are listed in Table 4 5 Table 4 5 Logical Operators Operator Example Result AND A AND B TRUE if both A and B are TRUE OR AORB TRUE if either A or B is TRUE or if both are TRUE NOT NOTA TRUE if A is FALSE and FALSE if A is TRUE AND THEN A AND THEN B OR ELSE A OR ELSE B TRUE if both A and B are TRUE forces left to right evaluation order with short circuiting
42. 1 4 OCT function 8 32 in output procedure 9 26 ODD function 8 32 OPEN procedure 9 44 carriage control parameter 9 19 syntax 9 44 Operator assignment 5 2 negation 2 14 Operators 4 2 to 4 14 arithmetic 4 2 to 4 5 logical 4 6 precedence of 4 12 relational 4 5 set 4 10 string 4 8 type cast 4 11 Optimization effect of VOLATILE 10 47 OPTIMIZE attribute 10 29 Oracle CDD Repository See CDD ORD function 8 33 Ordinal types 2 2 to 2 11 Ordinal value 2 2 of Boolean values 2 8 of case label 5 3 of characters 2 7 of characters in comparisons 4 8 of enumerated type 2 8 of parameter 8 33 of subrange type 2 9 Index 13 OR operator 4 6 OR ATOMIC function 8 32 OR ELSE operator 4 6 OTHERWISE clause in array constructor 2 21 in CASE statement 5 4 in record constructor 2 28 in records 2 27 Output of enumerated types 9 28 of REAL numbers 9 25 specifying field width in 9 25 9 26 specifying fraction size 9 24 specifying radix 9 24 specifying the base in 9 26 OUTPUT file variable definition of PASSOUTPUT C 4 definition of SYS OUTPUT C 4 description of 9 18 OUTPUT identifier 7 6 Overflow detecting at execution time 4 3 output field 9 25 P Packed array copying from unpacked array 8 33 PACKED ARRAY OF CHAR 2 43 reading from text file 9 54 Packed variable allocation size of A 10 Packing multidimensional a
43. 31 characters generates a warning message The compiler ignores characters beyond the thirty first character e The Pascal standard dictates that an identifier cannot start or end with an underscore nor can two adjacent underscores be used within an identifier However HP Pascal allows both cases of underscore use and generates an informational message if you compile with the standard switch On OpenVMS systems HP Pascal uses uppercase characters for all external user symbols 1 6 Language Elements You can provide a string argument to the GLOBAL WEAK_GLOBAL EXTERNAL and WEAK_EXTERNAL attributes to override this case usage HP Pascal passes the string unmodified to the linker This manual shows predeclared identifiers in uppercase letters If you choose you can express them in mixed case or lowercase in your programs The following examples show valid and invalid identifiers Valid For2n8 MAX WORDS upto LOGICAL NAME TABLE Logical Name Scanner SYSSCREMBX Invalid 4Awhile up amp to YEAR END 87 MASTER FILE TOTAL DISCOUNT Year End 87 Master File Total Dollars Unique in first 31 characters Starts with a digit Contains an ampersand Not unique in first 31 characters Table 1 5 presents the HP Pascal predeclared identifiers that name data types symbolic constants file variables procedures and functions You can redefine a predeclared identifier but if you do the original declaration be
44. 9 18 INPUT identifier 7 6 Inspection file mode description of 9 29 Inspection mode definition Glossary 7 INT64 function 8 24 INTEGER16 2 2 INTEGERS32 2 2 INTEGER64 2 2 INTEGER8 2 2 Integers decimal notation for 2 2 negative 2 2 radix notation for 2 2 unsigned 2 3 INTEGER type 2 2 allocation size of A 11 default field width of 9 23 reading from text file 9 53 specifying the base 9 26 specifying the radix 9 24 INTEGER ADDRESS 2 6 Interface module definition Glossary 7 Internal file definition 9 2 Glossary 7 INT function 8 24 IN RANGE function 8 23 ISO standard 1 1 Item list definition Glossary 7 K Kernel mode code use in HP Pascal 8 28 Key alternate and primary 9 4 characteristics defined with KEY attribute 9 6 definition Glossary 7 fields 9 6 KEY attribute 9 4 10 23 Keyed access definition Glossary 7 Key field alignment of 10 24 allocation of 10 24 defining in record 10 23 description of 9 6 type of 10 24 Key of reference definition Glossary 8 L Label accessing 3 3 case 5 3 definition 3 2 Glossary 8 in GOTO statement 5 7 LABEL section 3 2 Language extensions summary of B 1 to B 7 Language standard violation of D 1 to D 7 Language standards Extended Pascal 1 2 Pascal 1 1 unextended Pascal 1 1 Lazy lookahead access to TEXT files 9 20 definition Glossary 8 LE function 8 24 Index 11
45. 9 17 9 10 File Position After GET Procedure 0005 9 41 11 1 INCLUDE File Levels 0 000 eee 11 4 A 1 Storage of Varying Data llle A 20 A 2 F_floating Point Data Representation A 21 A 3 S_floating Point Data Representation A 22 A 4 D floating Point Data Representation A 22 A 5 G_floating Point Data Representation A 23 A 6 T floating Point Data Representation A 24 A 7 H_floating Point Data Representation A 25 A 8 X_floating Point Data Representation A 26 A 9 Storage of Nonstatic Data Types llle A 27 xiii A 10 Storage of Variables of Nonstatic Types A 29 A 11 Storage of Pointer Variables to Undiscriminated Schema Types sande ded c km etek chee etadvad ee tbadtesets A 29 Tables 1 1 Special Symbols 2 oss oe ret Roe eh e gos 1 4 1 2 Embedded String Constants llle eee eee 1 5 1 3 Reserved Words llle 1 5 1 4 Redefinable Reserved Words 0000e eee eee 1 6 1 5 Predeclared Identifiers cc cece eee eee 1 7 2 1 Range of Values of Integer Ordinal Types 2 2 2 2 Values of MAXINT and MAXINT64 Predeclared Constants x2 cis de edie xm eed edad hes eee a ded Deu RUD 2 3 2 3 Range of Values of Unsigned Ordinal Types 2 4 2 4 Values of MAXUNSIGNED and MAXUNSIGNED64
46. A GLOBAL INTEGER B UNALIGNED INTEGER VAR Al GLOBAL A Illegal duplicates GLOBAL attribute of type A A2 EXTERNAL A Illegal conflicts with GLOBAL attribute of type A Illegal pointer base type cannot be UNALIGNED Legal B1 B C A Attributes 10 3 The first three variable declarations are illegal for the reasons shown in the comments The declaration of C is legal C is declared as a global INTEGER because of the characteristics of its type The compiler supplies defaults for all other classes applicable to the variable C Attributes associated with data items usually modify type compatibility rules These modifications are explained in the sections describing individual attributes For More Information e On extended string syntax Section 2 6 e On program elements and attribute properties Section 10 3 e On type compatibility Section 2 10 10 2 Attributes The following sections describe each attribute in alphabetical order 10 2 1 ALIGN The ALIGN attribute controls the default alignment packing and allocation rules in a compilation unit TYPE section or VAR section For example ALIGN keyword The ALIGN attribute takes a single keyword parameter that has the same name and meaning as the keywords for the ALIGN qualifier However specifying the ALIGN attribute overrides any value that you previously specified using the ALIGN qualifier The ALIGN attribute can
47. A program is a set of instructions that can be compiled and executed by itself Program blocks contain a declaration and an executable section A compilation unit is a unit of HP Pascal code that can be compiled independently the term compilation unit refers to either a program or a module Each module and program must be in a separate file you cannot place multiple modules or a module and a program in the same file You can compile modules and a program together or separately the syntax of compilation depends on the operating system you are using The formats for compilation units are as follows attribute list PROGRAM comp unit identifier file identifier declaration section BEGIN statement END attribute list MODULE comp unit identifier file identifier declaration section TO BEGIN DO statement TO END DO statement END The module syntax of HP Pascal is slightly different than that of Extended Pascal However the concepts in both languages are the same attribute list One or more identifiers that provide additional information about the compilation unit Program Structure and Scope 7 5 comp unit identifier Specifies the name of the program or module The identifier appears only in the heading and has no other purpose within the compilation unit file identifier Specifies the names of any file variables associated with the external files used by the compilation uni
48. ACCESS Sus eet hk Goa pare Ced pane adus dba d es Random Access to Indexed Files Keyed Access File Locking ues 2sacceqe eoa wee Stk RA acu QU dunes MD UM E Dm Carriage Control 1 0 0c ees Prompting on a Terminal llle Delayed Device Access to Text Files 000 Writing Partial Lines to Terminals Formatting Outputs jc x race eso o Eur a V oe bue eoe Specifying the Field Width 0 000000 cence Writing Real Numbers 00000 Explicitly Specifying the Base lille sess Specifying the Base with Predeclared Conversion Functions scers Rt RR EE CHES GEESE EES TS Writing Nonnumeric Types l l Error Processing Parameter llle en VO Routines so os ree eh ee heey heed E E es CLOSE Procedure 0 0 0 0 cece eee ee ees DELETE Procedure 0 cece eee ee eee EOF Function 2212 24 2 42 c 4e bre tiita P eR E duobus EOLDN Function i432 RR ERGO ARS reias EXTEND Procedure 2 oec e ee ee FIND Proced re eroici ep Smead cue Rupe ed eR As FINDK Procedure i Res ee naa ee eae eens GET Procedure scese s b440 cho 0 beh ches ERREUR EY ETE LINELIMIT Procedure 0 0 0 0 cee eee eee 9 1 9 2 9 3 9 4 9 7 9 10 9 10 9 10 9 11 9 12 9 13 9 13 9 15 9 15 9 16 9 17 9 17 9 18 9 19 9 20 9 20 9 23 9 23 9 24 9 25 9 26 9 26 9 28 9 29 9 29 9 31 9 32 9 33 9 34 9 35 9 36 9 37 9 3
49. Default Information e This attribute can be applied to routines and compilation units e If not specified on a routine or compilation unit the CHECK qualifier or switch value is used as the default If you specify options for CHECK HP Pascal enables only the specified options Consider the following example CHECK is equivalent to CHECK ALL CHECK option is equivalent to CHECK NONE option Consider the following example 10 12 Attributes PROGRAM Check Features CHECK POINTERS CASE SELECTORS PROCEDURE Linked List VAR Client Info Rec Body of the procedure CHECK OVERFLOW FUNCTION Integer Compute VAR Intl Int2 Int3 INTEGER INTEGER Body of the function PROCEDURE Bounds Check VAR A String VARYING 30 OF CHAR VAR Char Array ARRAY 1 25 OF CHAR VAR Half Alpha A W Body For the routines Linked List and Integer Compute HP Pascal enables only the specified options The procedure Bounds Check has only the BOUNDS and DECLARATIONS options enabled by default unless you use a compilation switch to override the default For More Information On type compatibility Section 2 10 10 2 9 CLASS A The CLASS A attribute causes a formal parameter to be passed by an array descriptor that describes contiguous arrays of atomic data types or contiguous arrays of fixed length strings This attribute is illegal on parameters of schema types Consider the follo
50. Double precision real number All double precision numbers in your program must appear in this exponential format otherwise the compiler reverts to single precision representation Qorq Quadruple precision real number All quadruple precision numbers in your program must appear in this exponential format otherwise the compiler reverts to single precision format On systems that do not support the quadruple data type the letters Q and q are treated as double precision numbers D To express negative real numbers in exponential notation use the negation operator Remember that a negative real number such as 4 5E 3 is not a constant but is actually an expression consisting of the negation operator and the real number 4 5E 3 Use caution when expressing negative real numbers in complex expressions Table 2 10 presents the identifiers that are predefined by HP Pascal for use with the real data types Table 2 10 Predefined Identifiers for Real Data Types Identifier Value Single Precision F floating MINREAL 2 938736E 39 MAXREAL 1 701412E438 EPSREAL 1 192093E 07 IEEE Single Precision S floating MINREAL 1 175494E 38 MAXREAL 3 402823E 38 EPSREAL 1 192093E 07 1Smallest value of the REAL DOUBLE and QUADRUPLE data types such that 1 0 EPSREAL gt 1 0 1 0D0 EPSDOUBLE gt 1 0D and 1 0Q0 EPSQUADRUPLE gt 1 0Q0 continued on next page 2 14 Data Types and Values Tabl
51. END 2 22 Data Types and Values If field list is not specified an empty record is created The syntax of field list is as follows field identifier attribute list type variant clause variant clause j field identifier The name of a field attribute list One or more identifiers that provide additional information about the field type The type of the corresponding field A field can be of any type variant clause The variant part of the record The names of the fields must be unique within one record type but can be repeated in different record types You can specify the fields by specifying the record variable name or the name of an object whose result when used as an expression is of a record type followed by a period and followed by the field name If the record is unpacked you can use a field anywhere in a program that a variable of the field type is allowed This manual flags circumstances in which components of packed records cannot appear where a variable of the field type is allowed The only operation defined for entire records is the assignment operation The following example shows how to assign a value to a record component TYPE Player Rec RECORD Wins INTEGER Losses INTEGER Percentage REAL END VAR Playerl Player2 Player Rec In the executable section Playerl Wins 18 Assigns the value 18 to the Wins field You can partially in
52. F floating point data representation of A 21 G GE function 8 19 Generation file mode description of 9 29 Generation mode definition Glossary 6 GET procedure 9 39 file position after 9 40 GETTIMESTAMP procedure 8 19 GLOBAL attribute 10 19 Global identifiers sharing of 7 9 GOTO statement 5 7 as alternative to CONTINUE 5 5 terminating a FOR loop 5 7 using to access labels 3 3 GT function 8 20 G_FLOAT 2 13 G_floating double precision representation of A 23 H HALT procedure 8 21 Heading definition Glossary 6 of function 6 1 of procedure 6 1 Index 9 Hexadecimal nondecimal output of WRITE WRITELN and WRITE 9 26 Hexadecimal notation 2 2 in output procedure 9 26 Hexadecimal number representation 1 4 HEX function 8 21 in output procedure 9 26 HIDDEN attribute 10 20 Horizontal tab character 1 4 H FLOAT 2 13 H_floating point data representation of A 24 I O procedures additional error recovery parameter 9 29 T O processing 9 1 to 9 69 file modes during 9 29 I O routines 9 29 to 9 69 random access 9 16 sequential access 9 12 used with TEXT files 9 18 IADDRESS64 function 8 23 IADDRESS function 8 22 IDENT attribute 10 20 IDENT directive 11 10 Identifier constant 2 8 3 2 description of 1 6 external 7 9 global 7 9 predeclared 1 7 scope of 7 2 to 7 5 type 3 7 IF directive 11 6 IF statement 5 8 examples 5 8 with EL
53. If you do not specify values for the optional parameters a default length and a default minimum number of significant digits is used If the size of x is greater than 32 the defaults are 20 characters for the length and 19 characters for the minimum number of digits Otherwise the defaults are 11 characters for the length and 10 characters for the minimum number of digits Because the default length is 1 greater than the number of significant digits positive numbers will be preceded by a blank and negative numbers will be preceded by a minus sign Consider the following example VAR Account INTEGER In the executable section Account 16 F WRITELN DEC Account 8 7 The value of the integer variable Account is converted to its decimal equivalent 15 and in this example printed in eight columns seven digits and one leading blank 0000015 For More Information e On character strings Section 2 6 e On conformant parameters Section 6 3 7 8 14 Predeclared Functions and Procedures 8 27 DELETE_FILE Procedure The DELETE_FILE procedure deletes one or more files DELETE FILE file name error return The file name specification can contain an explicit device and directory name plus it must contain a file name a file type or extension and a version number If you omit either the directory or device name HP Pascal uses the directory you are working in at the time of program execution The error return par
54. LENGTH function 8 25 LENGTH predeclared identifier example 4 9 Lexical elements 1 2 definition Glossary 8 identifiers 1 6 reserved words 1 5 special symbols 1 4 LIB INITIALIZE program section A 2 LINE directive 11 10 Line feed character 1 4 LINELIMIT procedure 9 42 Line number 11 10 LINK program section A 2 Linker allocation of memory for executable image A 1 LIST attribute 10 25 on external definitions 10 26 on formal parameter 6 13 LIST qualifier use with DICTIONARY directive 11 5 use with INCLUDE directive 11 2 LITERAL program section A 2 LN function 8 25 LOCAL attribute 10 27 LOCAL program section A 2 A 10 LOCATE procedure 9 43 Lock definition Glossary 8 Logarithm of parameter 8 25 Logical operators 4 6 evaluating 4 7 LONG attribute 10 28 Loop in FOR statement 5 6 in REPEAT statement 5 10 in WHILE statement 5 12 LOWER function 8 25 example of 8 49 LSHIFT function 8 26 LT function 8 26 Index 12 M MALLOC C STR function 8 27 MAXCHAR 2 7 MAXDOUBLE 2 14 MAX function 8 27 MAXINT 2 2 MAXINT64 2 2 MAXQUADRUPLE 2 15 MAXREAL 2 14 MAXUNSIGNED 2 3 MAXUNSIGNED64 predeclared constant 2 4 MAXUNSIGNED predeclared constant 2 4 Mechanism specifier on actual parameter 6 17 on formal parameter 6 15 MESSAGE directive 11 8 MESSAGE procedure 9 44 Messages See Error messages MFPR function 8 27 MINDOUBLE 2 14 MIN
55. Memory allocated only for Fish variant DISPOSE To Var Record Fish Specify Fish to DISPOSE NEW To Var Record Beef Oz 32 Allocates more memory this time DISPOSE To Var Record Beef Oz 32 NEW To Schema Bound Allocation for undisc schema object DISPOSE To Schema For More Information On variant records Section 2 4 2 1 e On schema types Section 2 5 e On the DISPOSE procedure Section 8 28 8 61 NEXT Function The NEXT function returns an integer value that indicates the number of bytes that would be allocated for one component of the specified type in an unpacked array or if the specified variable appeared as the cell in an unpacked array NEXT x The parameter x can be a type identifier or variable Cells in an unpacked array are affected by alignment attributes and by default are byte aligned Therefore the size returned includes the actual size of the type or variable in addition to trailing space required to ensure proper alignment If a variable that is not allocated to an integral number of bytes is passed to NEXT the number of bits are rounded down to the nearest byte and then the number of bytes are returned For More Information e On examples of return values for this function Section 8 83 e On arrays Section 2 4 1 Predeclared Functions and Procedures 8 31 8 62 OCT Function The OCT function returns a character string value that is the octal equivalent of the
56. On precision and support for the QUADRUPLE data type Chapter 2 8 73 RANDOM Function The RANDOM function returns a randomly computed real value in the range 0 0 1 0 based on a seed that is initially set to the value 7774755 The seed used by the RANDOM function can be modified with the SEED function RANDOMI expression If present the optional expression parameter is ignored For More Information e On the SEED function Section 8 80 8 36 Predeclared Functions and Procedures 8 74 READV Procedure The READV procedure reads characters from a character string expression and assigns them to parameters in the READV call The behavior of READV is similar to that of READLN the character string is similar to a one line file READV str variable identifier radix specifier ERROR error recovery str The str parameter is the string to be read variable identifier The variable identifier is the name of the variable to be assigned a value from str radix specifier The radix specifier parameter is one of the format values BIN OCT or HEX These values when used on a variable identifier read the variable in binary octal or hexadecimal respectively You can read a variable of any type by using a radix specifier except a type that contains a file component error recovery The error recovery parameter is the action to be taken if an error occurs during execution of the routine An error occurs at run
57. QUADRUPLE The value of x must not be too large to be represented by an integer 8 93 TRUNC64 Function The TRUNC64 function converts the value of the parameter by truncating the fractional part of the value and returns its INTEGER64 equivalent TRUNC64 x The parameter x must be of type REAL SINGLE DOUBLE or QUADRUPLE The value of x must not be too large to be represented by an INTEGER64 8 94 UAND Function The UAND function returns an unsigned value that represents a binary logical AND operation on each corresponding pair of bits of the specified parameters UAND ut u2 8 44 Predeclared Functions and Procedures The parameters ul and u2 must be of type UNSIGNED Consider the following example Result UAND 16 FF9 16 703 Returns 1793 which is 16 701 For More Information e On specifying extended digit notation Section 2 1 1 1 8 95 UDEC Function The UDEC function returns a character string value that is the unsigned decimal equivalent of the specified parameter The return value is compatible with all other string types UDEC x length digits The parameter x is the expression to be converted The UDEC function can take a parameter of any type except VARYING of CHAR conformant parameters or schema types This function requires the size of the parameter x to be less than or equal to the size of INTEGER64 if supported on your system If your system does not support INTEGER64 then the
58. RE UR Rx FS ao REECE ee dq OR 10 2 13 ENUMERATION SIZE eee 10 2 14 ENVIRONMENT 3 6 4 6 64 0 84 20 PREISEN WEE XE Eee 10 2 15 EXTERNAL 25 et shes hace xor Woah s WAS ae S rs 10 2 16 ELCOAT osea eon tt Ieee op OR Ve de Vo OR as ee Sh oe en 10 2 17 GLOBALE 4565565245 dnan uide taO DERE Coma ea ae Sas 10 2 18 HIDDEN 22259 e n eU Uer bee ee eee a 10 2 19 IVEN ET r 10 2 20 IMMEDIATE XE xe WE we oe wie wT ae 10 2 21 INHER 0 UR ated a RE RU UR Up E MP 9 43 9 44 9 44 9 49 9 50 9 52 9 56 9 58 9 59 9 60 9 61 9 63 9 63 9 64 9 65 9 66 9 67 10 1 10 4 10 4 10 5 10 7 10 8 10 9 10 10 10 11 10 11 10 13 10 13 10 14 10 15 10 16 10 16 10 18 10 19 10 19 10 20 10 20 10 21 10 21 11 10 2 22 INITIALE sessar abe ae death e Oak ChE ob Pe ee as 10 22 10 2 23 KEY L2 045 a du a Os op eum uc u Gon 10 23 10 2 24 TIS oe oe ace ase aie ee ete ce fa RE es ee en DET 10 25 10 2 25 TOCA cee 2 yates ach eek a hee hae uS 10 27 10 2 26 LONG Sua Ue PRESE PEN ey Egone qe queo 10 28 10 2 27 NOOPTIMIZHE amp 4 2 55 09 meo sum Sce oat Ss a eee 10 28 10 2 28 OCTA yes tes ari cca Sak ee ee eee ee a Sees MR MS 10 29 10 2 29 OPTIMIZE nekani ta hinti kan bed Be He be EK RP SE 10 29 10 2 30 PEN CHECKING STYLE Attribute 10 31 10 2 31 POS LT ee os hee ee ahs aah Gates Ste te wea ons 10 32 10 2 32 PO Oana setae dg ok Awe ass es arie cds 10 33 10 2 33 QUIAT coca en Ee adita to Sit toh auter
59. Rate For Q2 0 1156 END The above module when compiled would result in the creation of an environment file named share_data pen The ENVIRONMENT attribute can not be specified on a program that declares nonstatic types or variables of nonstatic types at the outermost level The ENVIRONMENT attribute can be specified on a module that declares nonstatic types or variables of nonstatic types at the outermost level Programs and modules can access definitions and declarations in a created environment file by using the INHERIT attribute For More Information On name string syntax Section 10 1 On static and nonstatic types Section 2 9 On programs and modules Section 7 4 On examples of separate compilation HP Pascal for OpenVMS User Manual Attributes 10 17 10 2 15 EXTERNAL The EXTERNAL attribute indicates a variable or routine that is assumed to be global in another independently compiled unit EXTERNAL identifier j TI string literal identifier Identifier passed to the linker It is passed in uppercase If you omit the identifier the name of the variable is used as the name of the common block string literal Passes the specified string literal to the linker unmodified If you specify an identifier with EXTERNAL HP Pascal supplies that name rather than the identifier being declared to the linker Usage and Default Information e The names available to the linker for corresponding glo
60. SUBTITLE TITLE AND ARRAY BEGIN CASE CONST DIV DO DOWNTO ELSE END FILE FOR FUNCTION GOTO IF IN LABEL MOD NIL NOT OF OR PACKED PROCEDURE PROGRAM RECORD REPEAT SET THEN TO TYPE UNTIL VAR WHILE WITH Language Elements 1 5 The manuals in the HP Pascal documentation set show these reserved words in uppercase letters If you choose you can express them in mixed case or lowercase in your programs Table 1 4 presents the redefinable reserved words that are used to name operators and identifiers You can redeclare these words but if you do the language feature becomes unavailable within the block in which you redeclare the word Table 1 4 Redefinable Reserved Words AND THEN BREAK CONTINUE MODULE OR ELSE OTHERWISE REM RETURN VALUE VARYING Note This table does not include statements that are only provided by HP Pascal for compatibility with other Pascal compilers This manual shows redefinable reserved words in uppercase letters If you choose you can express them in mixed case or lowercase in your programs 1 2 6 Identifiers An identifier is a combination of letters digits dollar signs and underscores that conforms to the following restrictions e An identifier cannot start with a digit e An identifier cannot contain spaces or special symbols The first 31 characters of an identifier must denote a unique name within the block in which the identifier is declared An identifier longer than
61. String Daisy Real Var 7 3 PRED Bouquet Write String contains DAISY232 705 LILY WRITEV Write String Daisy Real Var 7 3 PRED Bouquet Bouquet Error there is no more room in the string parameter For More Information e On VARYING OF CHAR strings Section 2 6 2 e On formatting output Section 9 6 e On error recovery codes HP Pascal for OpenVMS User Manual XOR Function The XOR function returns a value of the same type as the parameters of a binary logical exclusive OR operation on two specified parameters XOR p1 p2 The pl and p2 parameters must be of the same type and must be of either the BOOLEAN or SET types Result XOR A B C B C D Returns A D For More Information e On Boolean types Section 2 1 3 e On SET types Section 2 4 3 8 52 Predeclared Functions and Procedures 8 111 ZERO Function The ZERO function returns data whose type depends on the context of the function call that sets any variable except a file variable to its binary zero ZERO If you attempt to use the ZERO function to initialize a file variable an error occurs Do not specify a parameter list when you call the ZERO function Table 8 3 shows the value that ZERO assigns for each data type Table 8 3 Value of ZERO Data Type Value All INTEGER types 0 All UNSIGNED types 0 CHAR The character NUL BOOLEAN FALSE Enumerated The enumerated element with ORD element
62. TRUE if either A or B is TRUE or if both are TRUE forces left to right evaluation order with short circuiting The AND AND_THEN OR and OR_ELSE operators combine two conditions to form a compound condition The NOT operator reverses the value of a single condition so that if A is TRUE NOT A is FALSE and vice versa 4 6 Expressions and Operators The following examples show logical expressions and their Boolean results Expressions Results 4 gt 3 AND 18 3 6 TRUE 3 gt 4 OR 18 3 6 n NOT 4 lt gt 5 FALSE i lt 11 AND THEN Array A i 0 Not known p NIL OR ELSE p 0 Not known You can use Boolean variables and functions as operands in logical expressions Consider the following example Flag AND ODD i Suppose that Flag is a Boolean variable and ODD i is a function that returns TRUE if the value of the integer variable i is odd and FALSE if the value of i is even Both operands Flag and ODD i must be TRUE for the expression to be TRUE Normally the compiler does not guarantee the evaluation order for logical operations The AND THEN and OR ELSE operators force the compiler to evaluate an expression from left to right stopping when the overall result can be determined also called short circuiting The following example forces the compiler to verify that an array element is within index bounds before evaluating the element s contents IF i lt 11 AND THEN Array A i
63. a comma Consider the following example 6 26 Procedures and Functions FUNCTION Net Pay Hours INTEGER Tax REAL 0 05 Rate REAL Fica REAL 0 07 Overtime INTEGER REAL Body In the executable section Nonpositional syntax Take Home Year Take Home Year Net Pay Overtime Overtime Week Rate Pay Rate Hours Hours Week Positional syntax Take Home Year Take Home Year Net Pay Hours Week Pay Rate Overtime Week The formal parameters Tax and Fica are given the default values 0 05 and 0 07 respectively You can override a formal parameter s default value by associating the formal parameter with an actual parameter in a routine call For example if you want to replace the default value of the formal parameter Tax in the previous example for one call you can call Net Pay as follows Take Home Year Take Home Year Net Pay Hours Week 0 06 Pay Rate Overtime Week As a result of this routine call the default value of Tax will be replaced by the value 0 06 supplied in the actual parameter list For More Information e On specifying passing mechanisms Section 6 3 5 e On positional and nonpositional syntax of parameters Section 6 3 8 Procedures and Functions 6 27 7 Program Structure and Scope This chapter describes the following topics e Section 7 1 Blocks e Section 7 2 Scope of Identifiers e Section 7 3 Redeclaring Routine Names
64. a label A GOTO statement has the following form GOTO label label An unsigned decimal integer or symbolic name that represents a statement label The GOTO statement must be within the scope of the label declaration A GOTO statement that is outside a structured statement cannot jump to a label within that structured statement A GOTO statement within a routine can branch to a labeled statement in an enclosing block only if the labeled Statements 5 7 statement appears in the block s outermost level Consider the following example FOR I 1 TO 10 DO BEGIN IF Real Array I 0 0 THEN BEGIN Result 0 0 GOTO 10 Use GOTO to exit from loop END Result Result 1 0 Real Array I Compute sum of inverses END 10 Invertsum Result For More Information e On label declarations Section 3 2 e On exiting FOR loops using GOTO Section 5 7 5 9 IF Statement The IF statement tests a Boolean expression and performs a specified action if the result of the test is TRUE The ELSE clause when it appears executes only if the test condition results to FALSE An IF statement has the following form IF boolean expression THEN statement ELSE statement2 boolean expression Any Boolean expression statement The statement to be executed if the value of the Boolean expression is TRUE statement2 The statement to be executed if the value of the Boolean expression is FALSE If an IF statement contains an ELSE clau
65. a varying length string that has more components than the packed array a run time error occurs For More Information e On data types Chapter 2 4 16 Expressions and Operators 5 Statements HP Pascal statements specify actions to be performed and appear in executable sections This chapter discusses the following statements Assignment statement Section 5 1 BREAK statement Section 5 2 CASE statement Section 5 3 Compound statement Section 5 4 CONTINUE statement Section 5 5 Empty statement Section 5 6 FOR statement Section 5 7 GOTO statement Section 5 8 IF statement Section 5 9 Procedure call Section 5 10 REPEAT statement Section 5 11 RETURN statement Section 5 12 WHILE statement Section 5 13 WITH statement Section 5 14 When coding separate statements with a semicolon The semicolon is not syntactically part of a statement so it is not included in the syntax examples in this chapter Statements 5 1 5 1 Assignment Statement The assignment statement uses an assignment operator to assign a value to a variable or to a function identifier An assignment statement has the following form variable access expression variable access An identifier array component record component pointer dereference pointer function dereference or file buffer expression A run time expression whose type is assignment compatible with the type of the variable The value of the expression is the
66. an object of a structured type prohibits the object from having values assigned to it e You can only pass a read only actual VAR parameter to a read only formal VAR parameter e A pointer expression whose base type is read only is assignment compatible only with a pointer variable whose base type is also read only Consider the following example TYPE t RECORD i INTEGER END P Read Only READONLY t VAR Pro P Read Only Prw T PROCEDURE q p P Read Only VAR X INTEGER BEGIN X i p i More statements END In the executable section NEW Pro NEW Prw Q Pro Q Prw Prw I 0 This example shows the declaration of two pointer variables Pro and Prw and the calls to NEW that create the dynamic variables Pro and Prw The type of the formal parameter p requires that a corresponding actual parameter have read access therefore both Pro and Prw can legally be passed to Q as actual parameters Because P is a READONLY parameter the value of the dynamic variable P which corresponds to either Pro or Prw can be assigned to a Attributes 10 35 variable as shown in the assignment statement in the body of Q However only Prw can have values assigned to it as shown in the last statement For More Information e On the NEW procedure Section 8 60 e On parameters Section 6 3 e On type compatibility Section 2 10 10 2 35 REFERENCE The REFERENCE attribute causes the for
67. an operand in evaluating one of the relational operators lt This operation causes an error because you cannot use relational operators with Boolean operands You can modify the expression with parentheses as follows a lt x AND b lt y In the rewritten expression the compiler combines the Boolean values of the two relational expressions with the AND operator You can use parentheses in an expression to force a particular order for combining the operands For example Expression Result 8 5 DIV 2 4 16 8 5 DIV 2 4 20 The compiler evaluates the first expression according to normal precedence rules First 8 is multiplied by 5 and the result 40 is divided by 2 Then 4 is subtracted to get 16 The parentheses in the second expression however force the subtraction of 4 from 2 yielding 2 to be performed before the division of 40 by 2 The result is 20 Parentheses can help to clarify an expression For instance you could write the first example as follows 8 5 DIV2 4 Expressions and Operators 4 13 The parentheses eliminate any confusion about how the compiler associates the operands in the expression The desired results of your program should not depend on the order of subexpression evaluation Unless you use the AND_THEN or OR_ELSE operators the compiler does not guarantee the order in which subexpressions and complex expressions are evaluated In fact if the result of an
68. and primary key keyed access Random file access by key value See also random access Glossary 7 key of reference A key used by HP Pascal to determine the index to use when sequentially accessing components of an indexed file See also key indexed file organization and sequential access method label A tag declared in the LABEL declarations section that makes an executable statement accessible to a GOTO statement language extensions See HP Pascal extension lazy lookahead See delayed device access lexical elements Characters and identifiers that have meaning to a compiler such as the legal character set special symbols predeclared identifiers and reserved words lock Action taken by HP Pascal that prevents other programs from accessing a file component while your program reads or writes that same component module A set of instructions that can be compiled but not executed by itself Module blocks contain only a declaration section which can include an initialization TO BEGIN DO and a finalization TO END DO section module heading See module multidimensional array An array whose components are also arrays name string A special form of constant expression required by some attributes The name string is equivalent to a Pascal character string constant with one exception name strings cannot use the extended string syntax See also attribute and extended string format Glossary 8 natura
69. atomic fashion Because operations on structured objects can require many more instructions the use of the VOLATILE attribute on an object of a structured type can not produce the expected results if the data is accessed asynchronously e A volatile variable is structurally compatible only with a formal variable parameter that is volatile The compiler does not allow a volatile variable to be passed to a nonvolatile formal VAR parameter because the called routine did not guarantee that it could handle volatile parameters e Formal VAR parameters with the VOLATILE attribute can accept both volatile and nonvolatile actual parameters treating a nonvolatile variable as volatile never produces the wrong answer e A pointer expression whose base type is volatile is assignment compatible only with a pointer variable whose base type is volatile e Two pointer types are structurally compatible only if their base types have identical volatility Attributes 10 47 e On OpenVMS I64 and OpenVMS Alpha systems the VOLATILE attribute ensures true atomic accesses for bytes aligned words aligned longwords and aligned quadwords For unaligned words unaligned longwords or unaligned quadwords that are marked VOLATILE the compiler will issue a warning message indicating that the resulting code sequence is not an atomic sequence and contains a timing window where incorrect results can occur if an asychronous thread writes to the unaligned volatile storage
70. bounds If both types are VARYING OF CHAR types their maximum lengths must be equal The lengths of the current values of the VARYING OF CHAR strings do not affect structural compatibility If two components of packed structured types are set types their base types must have identical upper and lower bounds If both types are set types file types or pointer types their base types must be structurally compatible Because of the possibility that a pointer type can be defined in terms of itself the HP Pascal compiler begins the test for the structural compatibility of two pointer types by assuming that they are compatible Next the compiler tests the two base types for structural compatibility If within the base type the compiler encounters the same pointer types it is testing it still follows the original assumption that the pointer types are compatible If the base types prove to be structurally compatible then the two pointer types are judged to be structurally compatible 2 50 Data Types and Values 2 10 2 For More Information On attributes that affect size and structure ALIGNED POS READONLY UNALIGNED UNSAFE VOLATILE and WRITEONLY Chapter 10 On ordinal types Section 2 1 On real types Section 2 2 On pointer types Section 2 3 On structured types Section 2 4 On allocation sizes of objects Section A 2 4 Assignment Compatibility Assignment compatibility rules apply to the types of values used to ini
71. characters and Salary is printed with 12 characters The output values preceded by two initial blanks could look like this 000031F2 000058AB Consider the following example WRITELN OCT Social Security 14 BIN Survey 8 The value of the variable Social Security is converted to its octal equivalent and printed with 14 characters The value of the variable Survey is then converted to its binary equivalent and printed with eight characters A sample line of output preceded by three blanks could look like this 0271137762500101110 Consider the following example WRITEV Final Balance OCT Debits 16 OCT Credits 16 Input and Output Processing 9 27 The values of the variables Debits and Credits are converted to their octal equivalents and written to the string variable Final_Balance with 16 characters each The output string preceded by five blanks could look like this d 777771770342 00000033766 9 6 5 Writing Nonnumeric Types For an expression of an enumerated type the constant identifier denoting the expression s value is written Consider the following example VAR Color Blue Yellow Black Fire Engine Green In the executable section WRITE My favorite color is Color 15 When the value of Color is Yellow the following is written My favorite color is YELLOW When the value of Color is Fire Engine Green the following appears My favorite color is FIRE ENGINE GRE
72. characters can improve the legibility of your programs e Extended unspecified characters with numeric codes from 128 to 255 Each ASCII character corresponds to a numeric value Each element of the character set is a constant of the predefined HP Pascal type CHAR An ASCII decimal number is the same as the ordinal value as returned by the Pascal ORD function of the associated character in the type CHAR HP Pascal allows full use of eight bit characters The HP Pascal compiler does not distinguish between uppercase and lowercase characters except when they appear inside single or double quotation marks For example the word PROGRAM has the same meaning when written as any of the following PROGRAM PRogrAm program The characters in each pair of characters however represent different values h IB o wan Language Elements 1 3 1 2 2 Special Symbols Special symbols represent operators delimiters and other syntactic elements Some symbols are composed of more than one character you cannot place a space between the characters of these special symbols Table 1 1 lists the HP Pascal special symbols Table 1 1 Special Symbols Symbol Name Symbol Name d Apostrophe lt Less than or equal to Assignment operator Minus sign or Brackets m Multiplication Colon lt gt Not equal Comma Parentheses or Comments Percent Division Period Double quote Plus sign i Equal sign
73. component fixed length component format A component format that specifies that all file components are the same length See also component and component format formal discriminant An identifier in a schema type declaration that takes the place of specific boundary values or variant record selectors See also schema type formal parameter A name in the routine header that specifies information about the type size and passing mechanism of data that is expected to be passed to the routine as an actual parameter This term is synonymous with the term argument function A subprogram that contains one or more statements to be executed once the function is called and that returns a single value generation mode A file state that indicates when output is being written to a file See also inspection mode and undefined mode heading A part of a program module or routine that includes an identifier a list of external files used for programs and modules a list of formal parameters for routines and a return value for functions See also declaration section executable section and formal parameter implementation module A module that contains data to which you want to restrict access and that inherits an environment file from an interface module See also environment file and interface module index A internal data structure that provides pointers based on key values to file components in an indexed file Glossary 6 in
74. conformant parameters e Calls to user defined functions e Calls to EOF and EOLN predeclared functions e Constructors of schema types or of types containing schema components Run time expressions result in a value at the time you execute your program These expressions can contain variables predeclared functions user declared functions and everything that a constant expression cannot contain Expressions and Operators 4 1 When you form an expression the operands must be of the same data type Under some circumstances the compiler performs data type conversions and allows you to form an expression with operands of different types Pascal does not evaluate expressions contained within a single statement in a predictable order Also the compiler does not always evaluate all expressions in a single statement if the correct execution of the statement can be determined by evaluation of fewer expressions For example some IF statement conditions can be determined TRUE or FALSE by only evaluating one of the Boolean expressions in the condition Do not write code that depends on the evaluation order of expressions and in some cases on the evaluation of all expressions in a single statement If you require a predictable order of evaluation you can use the AND_THEN and OR_ELSE operators For More Information e On data type conversion Section 4 4 e On data types Chapter 2 e On evaluation of IF statement conditions Section 5 9
75. d abyd e Ifa parameter is positioned after the TRUNCATE parameter in the formal parameter list and is present explicitly with a null actual parameter or by being skipped over by a nonpositional actual parameter then the list is not truncated at the TRUNCATE parameter Any parameters after the TRUNCATE parameter must be present or have a default value 10 38 Attributes In Example 10 1 each call to procedure p in the main body of the program has a comment that shows the expected parameter list behavior and the expected output The parameter list is truncated at either parameter a or parameter c If parameters b and d did not have default values the call p w or p w x y would be illegal because the list cannot be truncated at the second or fourth positions Attributes 10 39 Example 10 1 Using the TRUNCATE Attribute PROGRAM Trunc OUTPUT VAR wW CHAR VALUE w X CHAR VALUE x y CHAR VALUE y Z CHAR VALUE z PROCEDURE p a TRUNCATE CHAR a b CHAR b C TRUNCATE CHAR c d CHAR d BEGIN IF PRESENT a THEN WRITE a IF PRESENT b THEN WRITE b IF PRESENT c THEN WRITE c IF PRESENT d THEN WRITE d WRITELN END In the executable section CALL LIST RESULT ps NO PARAMETERS TRUNCATE AT a uM pO DEFAULT a AND b TRUNCATE AT c ab pl DEFAULT a AND b TRUNCATE AT c ab p i DEFAULT a b c AND d abcd p DEFAULT a b c AND d abcd p w D
76. declared to begin on bit position 0 and is 3 bits long Due to the use of the UNALIGNED attribute on Field2 Field2 begins on bit position 3 and is 32 bits long You can obtain the same behavior by packing record X A 18 Data Storage and Representation Without using the UNALIGNED attribute or without X being a PACKED record Field2 would have been longword aligned that is it would have started on bit position 32 You cannot use the UNALIGNED attribute with INTEGER64 because of the 32 bit rules which states that variables greater than 32 bits must be at least byte aligned For More Information e On ranges and precision of integer and real types Chapter 2 e On the representation of data types Section A 3 e On the 32 bit rules Section A 2 4 e On the ALIGNED and UNALIGNED attributes Chapter 10 A 3 Internal Representation of Data Types The following sections summarize the internal representation of the HP Pascal data types A 3 1 Representation of Varying Data This section summarizes the internal representation of VARYING OF CHAR types A variable of type VARYING OF CHAR is stored as though it were an HP Pascal record type of the following form RECORD Length WORD 0 Maxlength Body PACKED ARRAY 1 Maxlength OF CHAR END Figure A 1 shows the storage allocated for a variable of type VARYINGI 8 OF CHAR Data Storage and Representation A 19 Figure A 1 Storage of Varying Data 15 0 LENGTH Co s 7
77. default as described in in Section 9 6 1 Section 9 6 2 and Section 9 6 3 Table 9 6 lists the default field widths Input and Output Processing 9 23 Table 9 6 Default Field Widths Type of ltem Printed Number of Characters INTEGER 10 UNSIGNED 10 INTEGER64 19 UNSIGNED64 20 CHAR 1 BOOLEAN 6 Enumerated Size of the longest identifier plus 1 up to 32 REAL 12 DOUBLE 20 QUADRUPLE 40 Character string Length of string 9 6 1 Specifying the Field Width When you write any value you can specify a field width to override the default The format is identical for the WRITE WRITELN and WRITEV procedures The formats are REAL format output minimum fraction INTEGER format output minimum radix String Boolean and enumeration format output minimum output The expression to be written as you would write it without specifying the field width minimum A nonnegative integer expression for the minimum number of characters to be written for the value Pascal uses a greater field width if required by the magnitude of the number to be printed fraction The fraction which is permitted only for values of real types indicates the number of digits to be written to the right of the decimal point 9 24 Input and Output Processing radix The radix which is permitted only for values of integer types specifies the use of a base notation other than decimal If you try to write a number is too larg
78. end of file added to the file Although each character of a TEXT file is one file component the end of line marker allows you to process the file line by line using READLN WRITELN or EOLN if you choose The predeclared file variables INPUT OUTPUT and ERR are files of type TEXT They refer to the standard input output and error files When executing programs at a terminal INPUT OUTPUT and ERR default to the terminal you are using The file type FILE OF CHAR differs from TEXT files in that FILE OF CHAR allows a single character to be the unit of transfer between a program and its associated I O devices and that FILE OF CHAR files do not include special markers FILE OF CHAR components are always read with the READ procedure and must be read exclusively into variables of type CHAR including CHAR components of structured variables You cannot use the EOLN READLN and WRITELN routines on FILE OF CHAR files Default Information e Anew file of type TEXT or FILE OF VARYING OF CHAR is a sequential file with variable length components e All TEXT file routines use the predefined files INPUT and OUTPUT by default e HP Pascal performs an implicit call to RESET on the predeclared file INPUT and an implicit call to REWRITE on the predeclared file OUTPUT e The default size for the output buffer is 255 characters for TEXT files The following are the HP Pascal I O routines that are used only with TEXT files EOLN LINELIMIT PAGE
79. executable image the OpenVMS Linker divides the image into sections Each image section contains program sections that have the same properties The linker controls memory allocation by arranging image sections according to program section properties You can use special linker options to change program section properties and to influence the memory allocation in the image You include these options in a linker options file which is input to the linker The OpenVMS Linker refers to the various characteristics of program sections as attributes This chapter uses the term properties to avoid confusion with the HP Pascal attribute classes Table A 1 lists the possible program section properties on OpenVMS systems Data Storage and Representation A 1 Table A 1 Program Section Properties Property Description PIC NOPIC Position independent or position dependent CON OVR Concatenated or overlaid REL ABS Relocatable or absolute GBL LCL Global or local scope EXE NOEXE Executable or nonexecutable RD NORD Readable or nonreadable WRT NOWRT Writable or nonwritable SHR NOSHR Shareable or nonshareable For More Information e On program sections and linker options HP OpenVMS Linker Utility Manual A 1 1 Establishing Program Sections Table A 2 Table A 3 and Table A 4 list the program sections that HP Pascal can establish if necessary on OpenVMS I64 OpenVMS Alpha and OpenVMS VAX systems respectively A 2 Data Storage and
80. executable section Digits 8 NEW p Result HEX p 10 Digits In this example the HEX function returns a string of 10 characters containing the hexadecimal equivalent of the value of the pointer variable p The string has eight significant digits as specified by the value of the actual parameter Digits Predeclared Functions and Procedures 8 21 8 42 IADDRESS Function The IADDRESS function returns an INTEGER_ADDRESS value that refers to the address of either a constant or VOLATILE variable or parameter or a routine IADDRESS does not generate compile time warnings about volatility as does the ADDRESS function The IADDRESS function is commonly used for constructing arguments for system services of the OpenVMS operating system IADDRESS x The parameter x can be of any type except a component of a packed structured type Note The HP Pascal compiler automatically assumes that all pointers refer either to dynamic variables allocated by the NEW procedure or to variables that have the VOLATILE attribute You therefore should use utmost caution when using the IADDRESS function This function does not generate compile time warnings about volatility Consider the following example VAR Real Addr INTEGER ADDRESS Real Var VOLATILE REAL In the executable section Real Addr IADDRESS Real Var Returns address of Real Var WRITELN The address of Real Var is Real Addr For Mor
81. have been done if the value of x is positive or zero then 0 lt x TRUNC x lt 1 otherwise 1 lt x TRUNC x lt 0 Explanation Detected at run time if overflow checking was enabled during compilation The resulting value of ROUND x does not exist after the following calculations have been done if the value of x is positive or zero then ROUND x is equivalent to TRUNC x 0 5 otherwise ROUND x is equivalent to TRUNC x 0 5 Explanation Detected at run time if overflow checking was enabled during compilation The resulting value of CHR x does not exist Explanation Detected at run time if subrange checking was enabled during compilation The resulting value of SUCC x does not exist Explanation Detected at run time if subrange checking was enabled during compilation The resulting value of PRED x does not exist Explanation Detected at run time if subrange checking was enabled during compilation The function EOF f is called when the file f is undefined Explanation Not detected The function EOLN f is called when the file f is undefined Explanation Not detected The function EOLN f is called when the result of EOF f is TRUE Explanation Not detected A variable is not initialized before it is first used Explanation Not detected In the expression x y the value of y is zero Explanation Detected at run time Compiler and Run Time System Error Detection
82. it e When it is passed as a writable VAR parameter e When it is read into by a READ READLN or READV procedure e When it is used as the control variable of a FOR loop 10 46 Attributes In addition the compiler expects to evaluate the object only when it appears in an expression The value of a volatile object can change as the result of an action not directly specified in the program Thus the compiler assumes that the value of a volatile object can be changed or evaluated at any time during program execution Consequently a volatile object does not participate in any optimization based on assumptions about its value The behavior of many device registers and modifications by asynchronous processes and exception handlers are two examples that demonstrate volatile behavior Usage and Default Information See Table 10 6 which also summarizes combinations of volatile and nonvolatile parameters and variables accepted by the compiler e You can apply this attribute to variables formal parameters the base types of pointer variables components of structured variables and function results e By default objects are not volatile e An object of a structured type that has a volatile component is volatile as a whole However the presence of a volatile component does not make other components of the same variable volatile e The presence of the VOLATILE attribute guarantees that operations are performed on scalar objects in an
83. legal for testing character strings of different lengths as well as for testing character strings of the same lengths The shorter of the two character strings is padded with blanks for the comparison The following two strings for instance result in a value of TRUE John lt Johnny abc abc d The EQ NE GE GT LE and LT predeclared routines make string comparisons that are similar to the relational operators but these routines do not pad strings of unequal length with blanks Instead they halt string comparison when they detect unequal lengths If you are comparing the equality or inequality of very large strings it is sometimes more efficient to use the EQ and NE functions instead of the and operators When using the operators HP Pascal compares each string character by character until detecting either a difference or the end of one string When you use the functions HP Pascal sometimes detects different string lengths without comparing the strings character by character When trying to determine the length of a string you can use either the LENGTH function or the LENGTH component of a STRING or VARYING OF CHAB type The LENGTH routine and LENGTHprovide the same value Consider the following example VAR One String STRING 25 VALUE Harvey Fierstein In the executable section WRITELN One String LENGTH LENGTH One String The WRITELN call writes 16 and 16 to the predeclared fil
84. length of the string an error occurs For More Information e On arrays Section 2 4 1 e On attributes Chapter 10 e On the SIZE predeclared function Section 8 83 e On the LENGTH predeclared function Section 8 49 2 6 3 STRING Schema Type The STRING predefined schema provides a way of declaring variable length character strings The compiler stores STRING data as though it were stored in the following schema definition TYPE STRING capacity INTEGER VARYING capacity OF CHAR The syntax of the discriminated schema is as follows STRING capacity capacity An integer in the range 1 65 535 that indicates the length of the longest possible string Data Types and Values 2 45 To use the predefined STRING schema you provide an upper bound as the actual discriminant as in the following example VAR Short String STRING 5 Maximum length of 5 characters Long String STRING 100 Maximum length of 100 characters You can assign string constants to STRING variables from length 0 to the specified upper bound The compiler allocates enough storage space to hold a string of the maximum length A STRING variable with length 0 is the empty string To provide values for variables of this type you must use character string constants or expressions that evaluate to character strings you cannot use array constructors Also you can initialize a character string to the empty string as follows
85. level block because Levella contains no nested routine e Formal parameter identifiers v u and t are declared at the same level Levellb They cannot be redeclared within this block They can be redeclared as local identifiers in the nested block of FUNCTION Level2 e Procedure identifier Levella is declared in the outermost block of the example This identifier can be redeclared within its own declaration section e Function identifier Level2 is declared in the next highest level Levellb It cannot be declared within this block Level2 can be redeclared as a local identifier within a nested block Program Structure and Scope 7 3 Figure 7 1 Scope of Identifiers PROGRAM Scope INPUT OUTPUT VAR a b INTEGER PROCEDURE Levella z y INTEGER TYPE c ARRAY 1 35 OF CHAR End procedure Levella PROCEDURE Level 1b v u CHAR VAR t INTEGER FUNCTION Level2 CHAR VAR b BOOLEAN END End function Level2 END End procedure Level1b Executable section of program Scope ZK 1112A GE 7 4 Program Structure and Scope For More Information e On scope of routine identifiers Section 6 1 e On scope of formal parameters Section 6 3 e On scope of labels and GOTO statements Section 5 8 7 4 Modules and Programs A module is a set of instructions that can be compiled but not executed by itself Module blocks contain only a declaration section and TO BEGIN DO and TO END DO sections
86. like this The IF directive can be used to essentially comment out large sections of code as follows IF FALSE STHEN code to disable SENDIF For more information on IF see Section 11 4 HP Pascal allows for an end of line comment using an exclamation point If an exclamation point is encountered on a line in the source program the remainder of that line will be treated as a comment This comment syntax is not recognized by SCA for report generation 1 4 Page Breaks and Form Feeds in Programs A page break or form feed character can appear anywhere in your program except on a line with text surrounding the form feed For example the following lines are legal FF TITLE Variable Declarations end FF FF FF VAR FF However the following line generates an error BEGIN FF END The page break does not affect the meaning of the program but causes a page to eject at the corresponding line in a listing file 1 10 Language Elements 2 Data Types and Values Every piece of data that is created or manipulated by an HP Pascal program has a data type The data type determines the range of values set of valid operations and maximum storage allocation for each piece of data This chapter describes the following topics e Section 2 1 Ordinal Types e Section 2 2 Real Types e Section 2 3 Pointer Types e Section 2 4 Structured Types e Sectio
87. may be one of the following data types e A single contiguous character string e A 2 or 4 byte unsigned binary number e A 1 2 or 4 byte signed integer You can use the KEY attribute to specify certain characteristics about the index and about the keys themselves Table 9 1 describes these characteristics Input and Output Processing Table 9 1 Characteristics of the KEY Attribute Keys Description Sort order This characteristic determines how HP Pascal creates an index and determines the order in which HP Pascal accesses components The order can either be ascending or descending If you specify ascending order HP Pascal considers the component with an equal or greater key value to be the next component for access If you specify descending order HP Pascal considers the component with an equal or lesser key value to be the next component for access Using different indexes and both ascending or descending order you can use different collating sequences for a file s components according to the needs of your application Duplicate keys This characteristic permits you to use the key value in more than one component However only the first component having the key value can be accessed randomly other components having the same key value can only be accessed sequentially Changeable keys This characteristic applies to alternate keys only When you specify changeable keys you can change the alternate keys in a component
88. of CHAR PACKED ARRAY OF CHAR VARYING STRING string whose current value does not exceed the maximum length of the variable or parameter Pointer to a structurally compatible type Two record types or two array types are assignment compatible if they are structurally compatible When you assign one record variable to another or one array variable to another the HP Pascal compiler does not check for out of range assignments to record fields or array components such assignments do not result in an error message even if subrange checking is enabled at compile time A set expression is assignment compatible with a set variable if the set s base types are compatible In addition all elements of the set expression must be included in the range of the variable s base type Note that assignment operations are not allowed on objects of file types or structured types that have file components Data Types and Values Two discriminated schema types are assignment compatible if they are of the same type family and if their actual discriminant values are identical A dereferenced pointer to an undiscriminated schema type is actually referencing a discriminated schema object whose discriminants were specified in a call to the NEW function Although STRING is a schema the rules in Table 2 11 take precedence For More Information e On ordinal types Section 2 1 e On real types Section 2 2 e On pointer types Section 2 3 e On str
89. on a sequentially organized file works differently than sequential access on an indexed file Default Information e The default is the sequential access method e You can always process a file using sequential access even when the currently specified access method is one of the direct access methods e By default HP Pascal does not designate a component as a starting point for access you must do this explicitly using one of the RESET REWRITE or REWIND procedures or using an access specific procedure to locate a specified component Input and Output Processing 9 11 Table 9 4 shows which file organizations support which component access modes Table 9 4 File Organization Support for Component Access Modes Sequential Relative Indexed Access Mode Organization Organization Organization Sequential Yes Yes Yes Random by relative Yes Yes No component number direct access Random by key No No Yes value keyed access 1This access is permitted with a fixed length component format on disk only For More Information e On file organizations Section 9 1 e On component formats Section 9 2 9 3 1 Sequential Access Using the sequential access method storage or retrieval begins at a designated position in the file and continues through the file according to the component s position in storage You can specify two starting points for sequential access the beginning of the file using REWRITE or RESET or th
90. or Pointer ae Exponentiation Semicolon gt Greater than E Subrange operator gt Greater than or equal to Type cast operator lt Less than 1 2 3 String Delimiters HP Pascal accepts single quote and double quote characters as string and character delimiters 1 2 4 Embedded String Constants Within double quotation marks HP Pascal supports constant characters specified with a backslash in a syntax similar to that of the C programming language Table 1 2 lists the constants supported by HP Pascal 1 4 Language Elements Table 1 2 Embedded String Constants Constant Definition ASCII Value a Bell character 16 7 b Backspace character 16 8 f Form feed character 16 C n Line feed character 16 A r Carriage return character 16 D t Horizontal tab character 16 9 v Vertical character 16 B Backslash character 16 5C i Double quotation character 163422 T Single quotation character 163227 nnn Character whose value is nnn nnn is an octal number from 000 to 377 Leading zeros can be omitted xnn Character whose value is nn nn is a hexadecimal number from 00 to FF Leading zeros can be omitted 1 2 5 Reserved Words Reserved words are used to designate data types directives identifiers specifiers statements and operators You cannot redefine these identifiers Table 1 3 presents the HP Pascal reserved words Table 1 3 Reserved Words DESCR DICTIONARY IMMED INCLUDE REF STDESCR
91. order The effect of reading a text file for which the PAGE procedure was called Treatment Reads a line containing only the form feed character ASCII value 12 Description of Implementation Features C 3 The binding of a nonfile variable whose name is listed in the program heading to entities that are external to the program Treatment Reported as an error at compile time The binding of a file variable whose name is listed in the program heading Explanation The file name unless it is INPUT or OUTPUT is equated to a logical name if a translation for the file name exists If there is no corresponding translation the file type DAT is appended to the name listed in the heading as in INFILE DAT If the file name is INPUT the file is equated to PAS INPUT if PASSINPUT is defined otherwise the file is equated to SYS INPUT Similarly if the file name is OUTPUT the file is equated to PASSOUTPUT if PAS OUTPUT is defined otherwise the file is equated to SYS OUTPUT C 4 Description of Implementation Features D Compiler and Run Time System Error Detection This appendix describes how the HP Pascal compiler and run time system detect violations of the Pascal language standards Errors detected at run time cause a program to terminate and return appropriate error messages Errors described here as not detected cause a program to produce unexpected results For More Information e On Pascal standards Section 1 1 e On HP Pas
92. parameter the formal parameter list of the routine being passed and the routine specified as the formal parameter must be congruent Two formal parameter lists are congruent if they have the same number of sections and if the sections in corresponding positions meet any of the following conditions e Both are value parameter sections containing the same number of parameters The types of parameters must either be compatible or be equivalent conformant parameters e Both are variable parameter sections containing the same number of parameters The types of the parameters must either be compatible or be equivalent conformant parameters Any attributes associated with a formal variable parameter affect the kinds of actual parameters that can be passed to it e Both are procedure parameter sections having either congruent formal parameter lists or no formal parameters e Both are function parameter sections having either congruent formal parameter lists or no formal parameters and having compatible result types e Both are foreign parameter sections having the same mechanism specifier and the same number of parameters and whose types must be compatible e If one formal parameter list has a LIST attribute on its last parameter section the other formal parameter list must also have this attribute Procedures and Functions 6 13 The following example shows a function declaration that includes two functions as formal parameters VAR Cos
93. return an integer value that indicates the number of bytes that would be allocated for a variable or record field of type x If x is a variable then the functions return an integer value that indicates the number of bytes that are allocated for that variable In the case where the parameter x is a variant record variable or variant type identifier SIZE returns an integer value that indicates the number of bytes that are allocated for a variant record variable or would be allocated for a variant type identifier for both the fixed portion of the record and the largest variant In addition you can supply additional parameters t1 through tn that correspond to the case labels of the record The function returns an integer value that indicates the number of bytes that would be allocated by the NEW procedure for a dynamic variable of the specified variant If a variable that is not allocated to an integral number of bytes is passed to SIZE the number of bits will be rounded up to the nearest byte and then the number of bytes will be returned 8 40 Predeclared Functions and Procedures Table 8 2 presents values returned by the alignment routines if the routines accepted objects of the specified data types Table 8 2 Return Values of Alignment Predeclared Routines Type or Variable Size in Bits Size in Bytes BITNEXT BITSIZE NEXT SIZE BIT 1 BOOLEAN 1 1 1 I 0 25 subrange 5 5 44 44 BYTE 0 255 8 8 1 1 byte BYTE A
94. set expression DO statement control variable The name of a previously declared variable of an ordinal type initial value final value Expressions that form a range and whose type is assignment compatible with the type of the control variable Set expression An expression resulting in a value of SET type The base type of the set must be assignment compatible with the control variable statement Any Pascal statement that does not change the value of the control variable At run time the initial and final values or the set expression is evaluated before the loop body is executed Execution or termination of the statement occurs in the following cases n the TO form Pascal checks to see if the value of the control variable is less than or equal to the final value If this condition is met the control variable takes on the value of the initial value for the first loop iteration During iterations the control variable increments according to its data type Looping ceases when the control variable is greater than the final value e In the DOWNTO form Pascal checks to see if the value of the control variable is greater than or equal to the final value If this condition is met the control variable takes on the value of the initial value for the first loop iteration During iterations the control variable decrements according to its data type Looping ceases when the control variable is less than the final value 5 6 Statem
95. structural compatibility of the base types when a pointer expression is assigned to a pointer variable Structural compatibility does not apply to nonstatic types schema types and types derived from schema types Two ordinal types are structurally compatible only if they have the same base type and the same allocation size Data Types and Values 2 49 If two ordinal types are components of packed structured types they are structurally compatible only if the ranges of values they describe have identical upper and lower bounds In general each real type is structurally compatible only with itself However because REAL and SINGLE are synonymous they are structurally compatible with each other For two structured types to be structurally compatible they must have the same allocation size and both must be packed or both unpacked The following conditions also affect structural compatibility If both types are record types they must have the same number of fields and the types of corresponding fields must be structurally compatible and identically positioned If the record types have variant parts the corresponding variants must have identical case labels written in the same order The types of the fields within corresponding variants must be structurally compatible If both types are array types the types of their components must be structurally compatible The index types must have identical base types and identical upper and lower
96. structures can be slower than accessing components of unpacked structures HP Pascal also provides the predefined structured type TIMESTAMP for more easily manipulating date and time information For More Information e On string data types Section 2 6 On VARYING OF CHAR Section 2 6 2 e On array constructors Section 2 4 1 2 e On record constructors Section 2 4 2 2 e On set constructors Section 2 4 3 1 e On the TIMESTAMP type Section 2 8 2 4 1 ARRAY Types An array is a group of components called elements that all have the same data type and share a common identifier An individual element of an array is referred to by an ordinal index or subscript that designates the element s position or order in the array An array type has the following form PACKED ARRAY attribute list index type OF attribute list component type Data Types and Values 2 19 attribute list One or more identifiers that provide additional information about the component type index type The type of the index which can be any ordinal type or discriminated ordinal schema type component type The type of the array components which can be any type The components of an array can be another array The indexes of an array must be of an ordinal type However specifying large types such as INTEGER as the index type can cause the memory request to exceed available memory space To use integer values as indexes you must
97. tag field can be a discriminant identifier or can be specified in one of the following ways e tag identifier attribute list tag type identifier The tag identifier and tag type identifier define the name and type of the tag field The tag type identifier must denote an ordinal type You refer to the tag field in the same way that you refer to any other field in the record with the record field identifier syntax Data Types and Values 2 25 The following example shows the use of the tag identifier form TYPE Orders RECORD Part 1 9999 CASE On Order BOOLEAN OF TRUE Order Quantity INTEGER Price READ FALSE Rec Quantity INTEGER Cost REAL END In this example the last two fields in the record vary depending on whether the part is on order Records for which the value of the tag identifier On_ Order is TRUE will contain information about the current order those for which it is FALSE about the previous shipment e attribute list tag type identifier In the second form there is no tag identifier you can evaluate to determine the current variant If you use this form you must keep track of the current variant yourself The tag type identifier must denote an ordinal type The following example shows the specification of a tag field without a tag identifier TYPE Characters RECORD CASE CHAR OF A Z Capital INTEGER 0 9 Number INTEGER OTHERWISE Misc BOOLEAN
98. that points to the object data type A property of data that determines the range of values set of valid operations and maximum storage allocation for the data object HP Pascal extension A language element that is not part of the unextended Pascal standard or the Extended Pascal standard In the HP Pascal for OpenVMS Language Reference Manual the term extension refers to language elements that are not part of the Extended Pascal standard See also Extended Pascal standard and unextended Pascal standard declaration section A part of a program module or routine that includes constant label type variable and routine declarations A module can also contain an initialization TO BEGIN DO and a finalization TO END DO section See also executable section heading and module delayed device access An HP Pascal technique used to fill the file buffer HP Pascal reads and inserts a file component into the file buffer only when the program is ready to process it when the program makes the next reference to the file direct access A component access method that locates a file component according to either the random access number or the key value See also random access and key discriminated schema type The data type resulting from applying actual discriminants to a schema type element A component of an array See also array Glossary 4 environment file A file created using the ENVIRONMENT attribute that contain
99. the WHILE statement When the test is performed HP Pascal attempts to read a line of input from the TEXT file Therefore it is very important to prompt for the integer or empty line before testing for EOLN Suppose you respond to the first prompt by supplying an integer as input Access to the input device is delayed until the EOLN function makes the first reference to the file INPUT The EOLN function causes a line of text to be read into the internal line buffer The subsequent READLN procedure reads the input value from the line of text and assigns it to the variable i The WRITELN procedure writes the input value to the text file OUTPUT The final statement in the WHILE loop is the request for another input value The loop terminates when EOLN detects the end of line marker Input and Output Processing 9 21 9 22 A sample run of a program containing this loop might be as follows Enter an integer or an empty line 10 The integer was 10 Enter an integer or an empty line 99 The integer was 99 Enter an integer or an empty line Retum Done The following program fragment shows a method of writing the same loop that does not take into account delayed device access so it produces incorrect results WHILE NOT EOLN DO BEGIN WRITE Enter an integer or an empty line READLN i WRITELN The integer was i 1 END The EOLN test at the beginning of the loop causes the file buffer to be filled However beca
100. the calling block For More Information e On ordinal types Section 2 1 e On arrays Section 2 4 1 e On attributes Chapter 10 6 3 7 2 Conformant VARYING Parameter The syntax for a conformant VARYING string has the following form VARYING upper bound identifier OF attribute list CHAR attribute list One or more identifiers that provide additional information about the conformant VARYING string 6 22 Procedures and Functions upper bound identifier An identifier that represents the upper bound of the conformant VARYING OF CHAR string s index The type of the upper bound identifier is always an integer The upper bound identifier specifies the maximum length of the VARYING OF CHAR string and must denote an integer The upper bound identifier that represents the maximum length can be thought of as a READONLY value parameter implicitly declared in the procedure declaration When you pass a string expression to a value conformant varying length parameter the length of the actual parameter s current value parameter not its declared maximum length becomes both the current length and the maximum length of the formal parameter When you pass either a conformant VARYING OF CHAR string variable or a discriminated STRING variable to a VAR conformant varying length parameter the declared maximum length of the actual parameter becomes the maximum length of the formal parameter The following example shows how to declare an
101. the file for sequential access 9 48 Input and Output Processing 9 8 13 Consider the following example OPEN Journal Accounts JOURNAL DAT HISTORY UNKNOWN ACCESS METHOD KEYED ORGANIZATION INDEXED If the file JOURNAL DAT already exists this procedure opens it otherwise HP Pascal creates a new file named JOURNAL DAT with the specified characteristics If the file does exist it must have the same characteristics as those in the parameter list of the OPEN procedure HP Pascal opens the file with indexed organization for keyed access For More Information e On positional and nonpositional syntax Section 6 3 8 e On file organizations Section 9 1 e On component format Section 9 2 e On component access Section 9 3 e On carriage control Section 9 5 1 e On the error processing parameter Section 9 7 PAGE Procedure The PAGE procedure skips from the current page to the next page of a TEXT file PAGE file variable ERROR error recovery file_variable The name of the file variable associated with a TEXT file error recovery The action to be taken if an error occurs during execution of the routine The file must be in generation mode before the PAGE procedure is called the mode does not change as a result of the procedure s execution Execution of the PAGE procedure clears the record buffer if it contains data by performing a WRITELN procedure and then advances the outpu
102. the integer unsigned and real types In some sections of this manual reference is made to entire categories of routines Table 8 1 lists the routines in each category Table 8 1 Predeclared Routine Categories Category Category Description and Routines Allocation size Routines that provide information about the amount of storage allocated for variables and for components of various types BITNEXT BITSIZE NEXT and SIZE Arithmetic Routines that perform mathematical computations ABS ARCTAN CARD COS EXP EXPO LN LSHIFT RSHIFT MAX MIN RANDOM SEED SIN SQR SQRT UNDEFINED UAND UNOT UOR UXOR and XOR Character string Routines that manipulate character strings BIN DEC EQ FIND MEMBER FIND NONMEMBER GE GT HEX INDEX LE LENGTH LT NE OCT PAD READV STATUSV SUBSTR UDEC and WRITEV Component position Routines that provide information about the offset of record components BIT OFFSET and BYTE OFFSET Condition handling ASSERT ESTABLISH HALT REVERT continued on next page Predeclared Functions and Procedures 8 1 Table 8 1 Cont Predeclared Routine Categories Category Category Description and Routines Date time Dynamic allocation File operations Input and Output Low level Null terminated strings Ordinal Parameter Privileged OpenVMS VAX systems only Type conversion Miscellaneous Routines that provide information on the calendar date and time CLOCK
103. the two types Once you create a discriminated schema you can access the value of an actual discriminant Consider the following example VAR Arrayl Array Template 10 In the executable section WRITELN Arrayl Upper Bound Writes 10 to the default device Discriminant values can appear in all expressions except constant expressions The following example shows a valid use of the discriminant value expression FOR i 1 TO Arrayl Upper Bound DO Arrayl i i You can use discriminated schema in the type denoter of a schema definition You can also discriminate a schema in the type denoter of a schema definition but the actual discriminants must be expressions whose values are nonvarying the actual discriminants cannot be variables or function calls Consider the following valid schema definitions TYPE Legal schema types Rangel a b INTEGER SET OF a b 1 Run time bounds checking My Record Number Size Status Size INTEGER RECORD Part Number PACKED ARRAY 1 Number Size OF INTEGER Status STRING Status Size Nested schema END Range2 Low Span INTEGER Low Low Span My Integer Dummy INTEGER MAXINT 1 MAXINT Matrix Bound INTEGER ARRAY 1 Bound 1 Bound OF REAL Illegal schema types they do not form new types My String Len INTEGER VARYING Len OF CHAR My Integer Dummy INTEGER INTEGER 2 40 Data Types and Values 2 6 String Types Yo
104. time if values have not been assigned to all the parameters listed in the READV procedure call before the end of the character string is reached as shown in this example TYPE Color Yellow Red Blue VAR Paint Paint2 Color Month VARYING 5 OF CHAR Real Var REAL Read String VARYING 17 OF CHAR In the executable section Read String Red July 26 33805 READV Read String Paint Month Real Var Paint contains Red Month contains July and Real Var contains 26 33805 READV Read String Paint Month Real Var Paint2 Error end of string reached after assigning to Real Var READV Read String Paint Month Legal 26 33805 is not used READV Read String Real Var Paint Month Error Red is not REAL Predeclared Functions and Procedures 8 37 For More Information e On input and output Chapter 9 e On character strings Section 2 6 e On error recovery codes HP Pascal for OpenVMS User Manual 8 75 RENAME FILE Procedure The RENAME FILE procedure renames a file RENAME FILE old file name new file name error return The parameter old file name specifies the names of one or more files whose specifications are to be changed The new file name parameter provides the new file specification to be applied The error return parameter contains an error recovery code if specified For More Information On error processing HP Pascal for OpenVMS User Manual 8 76 R
105. to 255 For More Information e On the ASCII character set Section 1 2 1 8 19 CLEAR_INTERLOCKED Function The CLEAR_INTERLOCKED function assigns the value FALSE to the parameter and returns the original Boolean value of the parameter CLEAR INTERLOCKED b The parameter b must be a variable of type BOOLEAN The variable does not have to be aligned therefore it can be a field of a packed record This function is used to access data that is shared between two or more threads of execution For More Information e On atomic operations HP Pascal for OpenVMS User Manual Predeclared Functions and Procedures 8 11 8 20 CLOCK Function The CLOCK function returns an integer value indicating the amount of central processor time in milliseconds used by the current process This function does not have a parameter list The result of CLOCK includes the amount of central processor time allocated to all previously executed images 8 21 COS Function The COS function returns a real value that represents the cosine of the specified parameter COS x The parameter x can be an integer or REAL type and is expressed in radians 8 22 CREATE DIRECTORY Procedure The CREATE DIRECTORY procedure creates a new directory or subdirectory CREATE DIRECTORY file name error return The file name parameter must be a directory name and optionally can contain a device name The error return parameter is optional and will return an
106. two standards and a subset of programs that comply with a third HP Pascal also provides features called extensions that are not part of any standard For portable code limit your use of these extensions or isolate the extensions in separate modules 1 1 1 Unextended Pascal Standards The unextended Pascal standards are as follows e American National Standard ANSI IEEE770X3 97 1989 ANSI e International Standard ISO 7185 1989 ISO HP Pascal accepts programs that comply to either standard In the HP Pascal documentation set the term unextended Pascal applies to both the ANSI and ISO standards HP Pascal contains FIPS 109 Federal Information Processing Standard validation support The standards are divided into two levels of standardization Level 0 and Level 1 An example of a technical difference between the Level 0 standard and the Level 1 standard is that Level 0 does not include conformant arrays while Level 1 does Language Elements 1 1 HP Pascal has passed the validation suite for Pascal compilers It received a CLASS A certificate for both levels of the ISO standard as well as the ANSI standard CLASS A certificates are given to compilers with a fully conforming implementation For More Information e On HP Pascal extensions to unextended Pascal Appendix B e On HP Pascal implementation dependent features Appendix C e On HP Pascal error processing as defined by the standards Appendix D e On flagging nons
107. type semantics See parameter passing semantics Glossary 11 sequential access method A component access method in which storage or retrieval begins at a designated position in the file and continues through the file according to the component s position in storage sequential file organization A file organization in which file components are stored one after the other in the order in which they were written to the file set A collection of data items of the same ordinal type See also base type short circuiting Compiler evaluation of an expression from left to right that stops as soon as the overall result can be determined See also expression static type A type whose object can be fully described at compile time a type that is not derived from a schema type static variable allocation Allocation for a variable that occurs only once and that exists for the duration of the executable image s execution stream component format A component format that is a continuous stream of bytes and that is delimited by a character called a terminator subscript An ordinal index or subscript that designates an individual array element s position in the array See also array terminator A delimiting character for a stream component that HP Pascal also recognizes as a valid part of the component data TIE See Translated Image Environment Glossary 12 translated code OpenVMS Alpha code created by the VAX Enviro
108. type It has the following form lower bound upper bound lower bound A constant expression or a formal discriminant identifier that establishes the lower limit of the subrange upper bound A constant expression or formal discriminant identifier that establishes the upper limit of the subrange The value of the upper bound must be greater than or equal to the value of the lower bound The base type can be any enumerated or predefined ordinal type The values in the subrange type appear in the same order as they are in the base type For example the result of the ORD function applied to a value of a subrange type is the ordinal value that is associated with the relative position of the value in the base type not in the subrange type You can use a subrange type anywhere in a program that its base type is legal A value of a subrange type is converted to a value of its base type before it is used in an operation All rules that govern the operations performed on an ordinal type pertain to subranges of that type Data Types and Values 2 9 Consider the following TYPE Day Mon Tues Wed Thur Fri Sat Sun Weekday Mon Fri subrange of base type Day Weekend Sat Sun subrange of base type Day Digit 70 9 subrange of base type CHAR Month 1 31 subrange of base type INTEGER National Debt 1 92233720368 subrange of base type INTEGER64 5477580 Using size attributes with subrange types might lead to confusi
109. unless those variables are statically allocated Procedure p can access the variable i which is declared with the STATIC attribute but it cannot access the variable b that is automatically allocated Because the formal parameter Count is unbound only other unbound routines such as p can be passed to function f as actual parameters Count must be declared UNBOUND because it is passed by immediate value For More Information e On the AUTOMATIC attribute Section 10 2 5 e On parameters Section 6 3 10 2 40 UNSAFE The UNSAFE attribute indicates that an object can accept values of any type without type checking The exact properties of an unsafe object depend on the object s machine representation 10 42 Attributes Usage and Default Information You can apply this attribute to variables formal parameters formal discriminants the base types of pointer variables components of structured variables function results and the types of other data items listed in Table 10 9 A conformant VARYING parameter or a formal schema parameter cannot be declared UNSAFE UNSAFE is the only attribute allowed on schema formal discriminants An expression of any type is assignment compatible with an unsafe object However neither the expression nor the object can contain a file component If the machine representations of the expression and the unsafe object differ the compiler forces them to have the same number of bits by modifying the
110. value On OpenVMS I64 and OpenVMS Alpha systems the parameter must be 64 bits or smaller On OpenVMS VAX systems the parameter must be 32 bits or smaller Note The IMMEDIATE attribute is not allowed on formal parameters of schema types For More Information e On default parameter passing Section 6 3 e On an example of IMMEDIATE and on the REFERENCE attribute Section 10 2 35 10 2 21 INHERIT The INHERIT attribute indicates the environment file or files to be inherited by a compilation unit The environment files specified by the INHERIT attribute must already have been created in compilation units by either the ENVIRONMENT attribute or a compilation switch The compilation unit inherits one or more environment files named by the file specifications in the name strings INHERIT name string Attributes 10 21 Usage and Default Information There is a default file type of PEN for inherited environment files For example Program inherit example pas INHERIT share data Program inherit example output CONST My Rate Rate For Q1 2 0 BEGIN Writeln My Rate END When the preceding program is compiled the compiler first attempts to open the file share data as an environment file If share data is not found the compiler attempts to open share data pen as an environment file If share data pen is not found an error message is issued and the compilation is stopped For More Infor
111. value assigned to the variable You cannot assign values to a variable of a record type with variants if you allocated this variable using the NEW procedure You can assign values to a field of such a record variable Consider the following example VAR X INTEGER y z RECORD fl real f2 integer END In the executable section x 1 type of expression is same type as the variable y z variables are assignment compatible Func Return Ptr To Integer 3 19 For More Information e On the NEW procedure Section 8 60 e On assigning constructor values to structured variables Section 2 4 e On assignment compatibility Section 2 10 2 5 2 BREAK Statement The BREAK statement immediately transfers control to the first statement past the end of the FOR WHILE or REPEAT statement that contains the BREAK statement The BREAK statement appears as a single word BREAK 5 2 Statements BREAK is equivalent to a GOTO to a label placed just past the end of the closest FOR WHILE or REPEAT statement The following example shows the usage of the BREAK statement REPEAT name GetInput Your name IF ExitKeyPressed THEN BREAK address GetInput Your address IF ExitKeyPressed THEN BREAK Person Num Name name Person Num Addr address Num SUCC Num UNTIL Num 50 In the example a user defined function GetInput interacts with the user and sets a global Boolean variable ExitKeyP
112. value of the expression as follows Assignment to a variable with the UNSAFE attribute causes the value of the right hand side to be truncated or zero extended to the bit size of the left hand variable Note this can not always be its natural bit size for example if the variable you are assigning a value to was declared with an explicit size attribute If that value is the legal value of the left hand type then the assignment occurs otherwise the variable is undefined The UNSAFE attribute has no effect on variable fetches Consider the following example v LONG UNSAFE aa bb cc As an enumeration of less than 256 elements its natural size can be less than a longword Because of the LONG attribute it is allocated a longword in memory However fetches from the variable might be smaller because the explicit size attribute has no effect on any fetches Assignments correctly assign the natural size portion of V but the contents of the extra bits are zero extended at the assignment A pointer expression is assignment compatible with a pointer variable whose base type is unsafe only if the base types have the same allocation size and if they have compatible alignment READONLY VOLATILE and WRITEONLY attributes You can pass an actual parameter variable to an unsafe formal VAR parameter if the types have the same allocation size and if they have compatible alignment READONLY VOLATILE and WRITEONLY attributes
113. when control returns to the calling block Foreign value semantics differs from value semantics in that the calling block not the called routine makes the copy The passing of a variable to a foreign mechanism parameter except a parameter with the IMMED or IMMEDIATE specifier implies foreign variable semantics the variable itself is passed A compile time warning occurs if the compiler must convert the value of an actual parameter variable to make it match the type of a foreign mechanism parameter In that case the compiler passes a copy of the converted value by foreign value semantics using the specified mechanism You can eliminate this warning by enclosing the actual parameter variable in parentheses by doing so you prevent the compiler from interpreting the actual parameter as a variable The compiler takes the same action whether or not it produces a warning message 6 16 Procedures and Functions Mechanism specifiers on formal parameters produce the following results e A REF or REFERENCE formal parameter requires actual parameters to be passed by reference REF or REFERENCE implies variable semantics unless the actual parameter is an expression in that case it implies foreign value semantics e An IMMED or IMMEDIATE formal parameter requires actual parameters to be passed with the by immediate value mechanism and always implies value semantics IMMED or IMMEDIATE cannot be used on formal parameters of type
114. when defining program sections A 5 PUT procedure 9 50 Q QUAD attribute 10 34 QUAD function 8 36 Quadruple precision data representation of A 11 A 24 A 26 Quadruple precision real number 2 11 QUADRUPLE type 2 11 default field width of 9 23 Index 15 R Radix specifying in output 9 26 Random access 9 15 definition Glossary 10 to indexed files 9 17 using relative component numbers 9 16 RANDOM function 8 36 READLN procedure 9 56 READONLY attribute 10 34 effect on storage allocation A 8 on formal parameter 6 11 READ procedure 9 52 READV procedure 8 37 status of 8 42 Real number double precision 2 11 floating point formats 2 11 negative 2 14 quadruple precision 2 11 single precision 2 11 REAL type 2 11 allocation size of A 11 default field width of 9 23 reading from text file 9 53 representation of A 21 specifying fraction size 9 24 Record definition Glossary 10 packing example of A 16 selecting when returned from a function 4 15 Record constructor 2 27 RECORD type 2 22 to 2 30 allocation size of A 11 constructor with variant for 2 29 field of 2 22 nested 2 28 OTHERWISE clause in 2 27 packing A 17 position of fields in 10 32 representation nonstatic fields of A 30 Index 16 RECORD type cont d using WITH statement 5 13 variant clause in 2 24 Recursion definition Glossary 10 Redeclaring routine names 7 2 Redefinable re
115. when you update the component When an alternate key value changes HP Pascal automatically adjusts the appropriate index to reflect the new key value If you do not allow duplicate keys HP Pascal rejects any attempt to place a component into a file if it contains a key value that is a duplicate of an existing component If you do not explicitly create the file to accept alternate key values then attempts to change key values generate an error For More Information e On the KEY attribute Section 10 2 23 e On additional key characteristics HP Pascal for OpenVMS User Manual 9 2 Component Formats When you declare a file variable in your program HP Pascal automatically creates a file buffer variable of the component type This variable takes on the value of one file component at a time You can access only one file component called the current component at a given time You cannot perform operations on a file while a reference to the file buffer variable exists To dereference the file buffer variable write the name of the file buffer variable followed by a circumflex the dereferencing character Input and Output Processing 9 7 9 8 Predeclared I O procedures move the file position As the file position changes the variable in the file buffer changes Figure 9 5 shows how this change occurs Figure 9 5 File Buffer Contents one file component i PEE file position File buffer Math_Scores ZK 0101 GE
116. with the I O functions EOF UFB and EOLN nor with any reference to the file buffer 9 8 I O Routines HP Pascal provides predeclared procedures and functions to perform input and output operations on file variables These routines may operate differently depending on a file s organization and the currently defined access method The I O routines in the following sections appear in alphabetical order At any time during the execution of a process a file variable is considered to be in one of three modes inspection generation or undefined When a file is reading input it is in inspection mode When output is being written to a file the file is in generation mode A file in an undefined state of processing is in undefined mode The mode often determines the valid operations for the file Table 9 7 shows the mode required before execution of each I O routine and shows the mode in which the file is left after each routine has executed Input and Output Processing 9 29 Table 9 7 File Mode During I O Processing Mode Before Mode After Mode Before Mode After I O Routine Execution Execution I O Routine Execution Execution CLOSE Any Undefined READ Inspection Inspection DELETE Inspection Inspection READLN Inspection Inspection EOF Inspection or No change RESET Any Inspection generation EOLN Inspection Inspection RESETK Any Inspection EXTEND Any Generation REWRITE Any Generation FIND Any Inspection if STATUS Any No change succes
117. 1 2 22 2 24 2 27 2 30 2 31 2 32 2 33 2 34 2 34 2 35 2 37 2 41 2 43 2 44 2 45 2 47 2 48 2 48 2 49 2 49 2 51 3 2 3 2 3 3 3 6 3 7 3 9 3 9 4 1 4 2 4 2 4 5 4 6 4 8 4 2 5 4 2 6 4 2 7 4 3 4 4 Set Operators Type Cast Operator Precedence of Operators Structured Function Return Values lessen Type Conversions 5 Statements 5 11 5 12 5 13 5 14 Assignment Statement BREAK Statement CASE Statement Compound Statement CONTINUE Statement Empty Statement FOR Statement GOTO Statement IF Statement Procedure Call REPEAT Statement RETURN Statement WHILE Statement WITH Statement 6 Procedures and Functions 6 1 6 2 6 3 6 3 1 6 3 2 6 3 3 6 3 4 6 3 5 6 3 6 6 3 7 6 3 7 1 6 3 7 2 6 3 7 3 6 3 8 6 3 9 Routine Declarations Routine Calls Parameters Value Parameters Variable Parameters Routine Parameters Passing Predeclared Functions to Formal Function Parameters Foreign Parameters Schema Parameters Conformant Parameters Conformant Array Parameters lessen Conformant VARYING Parameter 0 Conformant Parameter Sections sss Parameter Association Defau
118. 1 TO 10 DO BEGIN WITH New Book DO BEGIN WRITE Title READLN Title WRITE Author READLN Author END Books New Book PUT Books END CLOSE Books This program writes the first 10 components read from the terminal into the file Books The component data items are typed at the terminal and assigned to the record variable New Book They consist of two 40 character strings denoting a book s author and title The FOR loop accepts 10 values for New Book assigning each new record to the file buffer variable Books The PUT statement writes the value of Books into the file for each input record For More Information e On component access Section 9 3 e On the UFB function Section 9 8 22 e On the error processing parameter Section 9 7 Input and Output Processing 9 51 9 8 15 READ Procedure 9 52 The READ procedure reads one or more file components into a variable READY file_variable variable identifier radix specifier ERROR error recovery file_variable The name of the file variable associated with the input file If you omit the name of the file the default is INPUT variable identifier The name of the variable into which a file component will be read multiple identifiers must be separated with commas radix specifier One of the format values BIN OCT or HEX These values when used on a variable identifier will read the variable in binary octal or hex
119. 11 10 TIME directive 11 10 TIME function 8 12 TIME procedure 8 13 TIMESTAMP type 2 48 TITLE directive 11 6 TO BEGIN DO section 3 3 See also TO END DO section execution order of 3 5 TO END DO section 3 6 See also TO BEGIN DO section execution order of 3 5 translated code definition Glossary 13 Translated Image Environment discriminant definition Glossary 13 TRUNC64 function 8 44 TRUNCATE attribute 10 37 TRUNCATE procedure 9 63 Truncating numbers of parameter 8 44 TRUNC function 8 44 Type See also Data type cast operator 4 11 definitions example of 3 8 definitions of 3 7 storage allocation of A 11 Type compatibility 2 49 assignment 2 51 based on actual discriminants example 2 39 of schema families example 2 39 structural 2 49 Type conversion 4 15 of actual parameter 6 9 to packed array 4 16 TYPE section 3 7 T_FLOAT 2 13 Index 19 T floating point data representation of A 24 c c a cacc c U U U U U U qogqqgc U U Undefined mode U U JAND function 8 44 DEC function 8 45 FB function 9 63 INT64 function 8 46 INT function 8 46 NALIGNED attribute 10 41 effect on alignment boundary A 16 NBOUND attribute 10 41 with IMMED routine parameter 6 17 ndefined file mode description of 9 29 NDEFINED function 8 46 definition Glossary 13 ndiscriminated schema 2 38 definition Glossary 13 nextended Pasc
120. 17 Actual discriminant 2 37 definition Glossary 1 Actual parameter associated with formal 6 25 definition Glossary 1 description of 6 8 effect of UNSAFE attribute 6 9 foreign mechanism 6 17 function 6 13 passing mechanisms 6 8 procedure 6 13 routine 6 13 value semantics 6 1 6 8 variable semantics 6 1 6 10 Addition operator 4 3 ADDRESS function 8 4 ADD ATOMIC function 8 3 ADD INTERLOCKED function 8 4 ALIGN attribute 10 4 ALIGNED attribute 10 5 effect on alignment boundary A 16 Alignment conditions determining boundary A 16 of key fields 10 24 of variables A 16 Index Alignment attributes A 16 Alignment boundary A 16 examples of A 17 Alignment routines return values of 8 41 Allocation automatic 10 9 example of A 9 in common block 10 15 in program section 10 33 A 2 of executable blocks A 9 of symbolic constants A 9 of variables automatic and static A 7 size examples of A 15 size of variable A 10 static 10 36 Allocation attributes determining for variables A 7 Alternate key default options for 10 24 definition Glossary 1 in indexed file 9 4 AND operator 4 6 AND ATOMIC function 8 5 AND THEN operator 4 6 ANSI standard 1 1 Architecture detection 11 9 ARCH_NAME directive 11 9 ARCTAN function 8 5 Arctangent of parameter 8 5 Index 1 Argument definition Glossary 1 ARGUMENT function 8 6 Argument in pa
121. 2 INTEGER32 UNSIGNED UNSIGNED32 INTEGER64 8 64 UNSIGNED64 continued on next page Data Storage and Representation A 11 Table A 6 Cont Storage Allocation of Types Unpacked Packed Data Type Size in Bytes Size in Bits CHAR 1 8 BOOLEAN lor 4 1 Enumerated 1 if 256 elements or log2 number of elements 1 fewer 2 if more than 256 elements or 4 Subrange The size of the base type If either the upper or lower REAL or SINGLE DOUBLE QUADRUPLE Pointer OpenVMS 164 and OpenVMS Alpha systems only Pointer OpenVMS VAX systems only Unpacked ARRAY 16 4 or 8 4 The sum of the unpacked sizes in bytes of all bounds contain a reference to a formal discriminant then the size of the base type otherwise the minimum number in which the upper and lower bounds can be expressed 32 64 128 32 or 64 32 Unpacked size in bytes 8 components plus the sum of the sizes in bytes of any holes created to meet alignment requirements 1Tt depends on the value specified for the ENUMERATION_SIZE qualifier 2The maximum number of elements is 65 535 3This is known as the ceiling function where the smallest integer is greater than or equal to X 4Sets of type INTEGER and UNSIGNED are limited to 256 bits 5By default pointers on OpenVMS I64 and OpenVMS Alpha systems are 32 bits in size However the QUAD attribute can be used on pointer declarations to specify 64 bit pointers See the HP Pa
122. 2 types which are used as synonyms for subranges of the INTEGER type The range of the integer values consists of positive and negative integer values and of the value 0 The range boundaries depend on the architecture of the machine you are using Table 2 1 lists the storage sizes and ranges of values for these signed ordinal types Table 2 1 Range of Values of Integer Ordinal Types Data Type Size Range INTEGERS8 8 bits 128 127 16 80 16 7F INTEGERI16 16 bits 32768 32767 16 8000 16 7FFF INTEGER32 32 bits 2147483648 2147483647 16 80000000 16 7FFFFFFF INTEGERG64 64 bits 9223372036854775808 9223372036854775807 16 8000000000000000 16 7FFFFFFFFFFFFFFF 2 2 Data Types and Values The largest possible value of the INTEGER64 type is represented by the predefined constant MAXINT64 The smallest possible value of the INTEGER64 type is represented by the value of the expression MAXINT64 While the value of MAXINT64 1 can also be represented correct results may not be produced in certain expressions The largest possible value of the INTEGER type is represented by the predefined constant MAXINT The smallest possible value of the INTEGER type is represented by the value of the expression MAXINT While the value MAXINT 1 can also be represented it may not produce correct results in certain expressions Table 2 2 lists the sizes and the corresponding values of MAXINT and MAXINT64 Table 2 2 Values of M
123. 3 10 26 Constant definition 3 2 expressions 4 1 identifier 2 8 symbolic 3 2 Constant expression definition Glossary 3 Constants allocation of A 9 Constructor array 2 21 definition Glossary 3 nonstandard array 2 34 nonstandard record 2 35 pointer 2 17 record 2 27 set 2 31 to decimal value 8 14 variant record 2 29 CONST section 3 2 CONTINUE statement 5 5 Control part definition Glossary 3 in a nonstatic type A 27 Control variable 5 6 Conversion of actual parameter type 6 9 of type 4 15 to ASCII binary value 8 8 to ASCII decimal value 8 14 to ASCII hexadecimal value 8 21 to ASCII octal value 8 32 to double precision 8 13 to integer 8 24 by rounding 8 38 by truncation 8 44 to INTEGER64 by rounding 8 39 by truncation 8 44 to quadruple precision 8 36 to single precision 8 41 to UNSIGNED64 by rounding 8 50 by truncation 8 50 to unsigned ASCII decimal value 8 45 to unsigned integer 8 46 by rounding 8 49 by truncation 8 50 COS function 8 12 Cosine of parameter 8 12 Count controlled loop See FOR statement CREATE DIRECTORY procedure 8 12 Current compilation 11 10 Current component 9 7 definition Glossary 3 Current module 11 10 Current routine 11 10 C STR function 8 10 C STR T type 2 47 D DATA A 10 DATA program section A 2 Data part definition Glossary 4 of a nonstatic type A 28 Data type 2 1 to A 30
124. 3 effect of VOLATILE 10 47 effect of WRITEONLY 10 52 POINTER type description of 2 18 Pointer variable 8 15 8 29 POS attribute 10 32 effect on compatibility 10 33 Positional syntax 6 25 definition Glossary 9 Precedence of operators 4 12 Predecessor of parameter 8 35 Predeclared identifier definition Glossary 10 EPSDOUBLE 2 14 EPSQUADRUPLE 2 15 EPSREAL 2 14 IEEE Quadruple 2 15 MAXDOUBLE 2 14 MAXQUADRUPLE 2 15 MAXREAL 2 14 MINDOUBLE 2 14 MINQUADRUPLE 2 14 MINREAL 2 14 real data types 2 14 Predeclared identifiers 1 7 Predeclared routines See also individual routines by name categories of 8 1 I O processing 9 29 to 9 69 PRED function 8 35 PRESENT function 8 35 Primary key default options for 10 24 definition Glossary 10 in indexed file 9 4 Procedure 6 1 calling of 5 9 6 4 declaration of 6 1 definition Glossary 10 heading 6 1 predeclared See Predeclared routines or individual procedures by name used as actual parameter 6 13 used as formal parameter 6 12 Procedure call 5 9 6 4 effect when calling a function 5 9 Program definition 7 5 definition of Glossary 10 heading 7 6 Program heading definition Glossary 10 Program section A 1 to A 7 allocation in 10 33 default data A 2 example of A 5 properties of A 1 required properties of A 6 Property definition Glossary 10 PSECT attribute 10 33 use in allocating storage A 8 use
125. 39 Run time error from ASSERT 8 7 Run time expression definition Glossary 11 Run time expressions 4 1 S Schema family definition Glossary 11 Schema parameters 6 19 Schema type definition Glossary 11 representation of A 27 representation of variables of A 28 Schema types 2 37 to 2 40 STRING 2 45 using the NEW procedure 8 29 Scope of identifiers 7 2 to 7 5 example 7 3 example of 7 3 in a routine 6 5 rules for 7 2 SDATA A 10 SEED function 8 39 Semantics value 6 8 variable 6 10 Sequential access 9 12 to indexed file 9 15 to relative file 9 13 to sequential file 9 13 Sequential access method definition Glossary 12 Sequential file organization 9 2 sequential access to 9 13 Sequential file organization definition Glossary 12 Set definition Glossary 12 Set constructor 2 31 Set operators 4 10 SET type 2 30 allocation size of A 11 bounds checking 10 11 cardinality of 8 11 constructor for 2 31 examples of 2 32 operators 4 10 SET INTERLOCKED function 8 40 Short circuiting definition Glossary 12 Side effects of volatile objects 10 47 with function designators 4 14 Signaling run time errors 8 7 Sine of parameter 8 40 SIN function 8 40 Single precision data representation of A 21 Index 17 Single precision real number 2 11 Single quotation character 1 4 SINGLE type 2 11 allocation size of A 11 default field wid
126. 4 Declaration Section 3 1 3 1 CONST Section The CONST section defines symbolic constants by associating identifiers with compile time expressions it has the following form CONST constant identifier constant expression constant identifier The identifier of the symbolic constant being defined constant expression Any legal compile time expression Once a constant identifier is associated with an expression the identifier retains the value of that expression throughout the scope in which it was declared You can change the value only by changing the definition in the CONST section Consider the following example TYPE array typel ARRAY 1 10 OF INTEGER CONST Year 1984 Tiny 1 7253 Month November Initial P Lie FALSE Untruth Lie Almost Pi 22 0 7 0 array_const array _typel 1 3 5 1 4 6 2 7 9 3 10 7 For More Information e On expressions Section 4 1 e On constructors Section 2 4 3 2 LABEL Section A label is a tag that makes an executable statement accessible to a GOTO statement The LABEL section declares labels and has the following form LABEL label 3 2 Declaration Section label A decimal integer between 0 and 9999 as an extension between 0 and MAXINT or a symbolic name When declaring several labels you can specify them in any order The declaration and the occurrence of the label must be at the same level in the program
127. 6 through 31 and from 0 through 6 For More Information e On F floating point range and precision Section 2 2 A 3 2 2 S floating Point Numbers An S floating point value is represented by four contiguous bytes The bits are numbered from the right 0 through 31 as shown in Figure A 3 Data Storage and Representation A 21 Figure A 3 S floating Point Data Representation 5 0 FRACTION A EXPONENT FRACTION 31 30 23 22 16 ZK 4977A GE 1 An S floating point value is specified by its address A the address of the byte containing bit 0 The form of this value is sign magnitude as follows e Bit 31 is the sign bit 0 for positive numbers 1 for negative numbers e Bits 30 through 23 are an excess 127 exponent e Bits 22 through 0 are a normalized 24 bit fraction with the redundant most significant fraction bit not represented For More Information e On S floating point range and precision Section 2 2 A 3 2 3 D floating Point Numbers A D_floating point value is represented by eight contiguous bytes The bits are numbered from the right 0 through 63 as shown in Figure A 4 Figure A 4 D floating Point Data Representation 15 14 76 0 63 48 ZK 1040 GE A 22 Data Storage and Representation A D_floating point value is specified by its address A the address of the byte containing bit 0 The form of this value is identical to that of a F_floating point value except for an additional 32 low significance fr
128. 9 8 13 BITNEXT Function 0 0 000 ccc eee ee 8 9 814 BITSIZE Function 54339 Rer RESI det eubdndecan dean 8 9 8 15 BYTE OFFSET Function 0 0 eee 8 10 816 C SER E nctionzvs aut RE RUP Y RIED LEES 8 10 817 CARD Function eese eer hh ts 8 11 848 CHR E ncti n Leste 2440064 ELiSeqeWPStRBSPC LPS es 8 11 8 19 CLEAR INTERLOCKED Function 8 11 820 CLOCK F nclon 2232 9 ER RE PIU RE RES 8 12 8 21 COS Function esra die nm RE REUS E end 8 12 822 CREATE DIRECTORY Procedure 00 8 12 823 DATE and TIME Functions 0 00000 e 8 12 824 DATE and TIME Procedures 00000 c cece eee 8 13 8 25 DBLE Function 22 5 e006 0d ee eed een ber RAE YAGETAS 8 13 8 200 DEC PUNCHON 2e ce den oo dew ee mb y Hee owe Dee d 8 14 827 DELETE FILE Procedure 0 0 00 e ees 8 15 828 DISPOSE Procedure 0 00 eee ees 8 15 vi 8 29 8 30 8 31 8 32 8 33 8 34 8 35 8 36 8 37 8 38 8 39 8 40 8 41 8 42 8 43 8 44 8 45 8 46 8 47 8 48 8 49 8 50 8 51 8 52 8 53 8 54 8 55 8 56 8 57 8 58 8 59 8 60 8 61 8 62 8 63 8 64 8 65 8 66 8 67 8 68 8 69 8 70 EQ Function ESTABLISH Procedure 0 0 0 0 ccc cee eens EXP Function EXPO Function FIND FIRST BIT CLEAR Function FIND FIRST BIT SET Function lees FIND MEMBER Function 0 0 0 0 000 eee FIND NONMEMBER Function lees GE Func
129. 9 9 42 10 9 8 10 LOCATE Procedure 0 000 cece cece eee eae 9 8 11 MESSAGE Procedure 000 cece eee 9 8 12 OPEN Procedure 0 00 ccc cee eee eens 9 8 13 PAGE Procedure 0 cece nent eens 9 8 14 PUT Procedure essem ee DG ae dee ere Hah 9 dors 9 8 15 READ Procedure eee ht nn 9 8 16 READLN Procedure see ee eee htt 9 8 17 RESET Procedure eee 9 8 18 RESETK Procedure 0 0 0 0 cece cece eA 9 8 19 REWRITE Procedure secet nn 9 8 20 STATUS Function egre RUE TR a e RR RU E 9 8 21 TRUNCATE Procedure 0 00 c eee eee eae 9 8 22 WEB Function 3 22st ans 92 8 pd dedu ee wa d 9 8 23 UNLOCK Procedure elle 9 8 24 UPDATE Procedure leen 9 8 25 WRITE Procedure cere e800 pu RU ae v Ro 9 8 26 WRITELN Procedure 0 0 00 cece cece eh Attributes 10 4 Attribute Syntax 2 eee 10 2 Attributes llle hs 10 2 1 ALIGN operer ir aere Pek Gb Ree SS 10 2 2 ALIGNED MODEL 10 2 3 ASYNCHRONOUS 24 2 C EERUR CR ED e XR RUE kS 10 2 4 AT I ESOS DENN EN OST EE ee a ea ee 10 2 5 AUTOMATIC 5 sea tiere ooeG beet dive boaw ede 10 2 6 iji 10 2 7 BY DB m vsum ume avv s donde Sete le aad ease OCA 10 2 8 CHECK vrenobe ed Papae bud edP Caa eaea 10 2 9 CLASS A aac ene amp oldie wean bI EENE beue ie nob do e durs 10 2 10 CLASS NOA o edtu Abdo ed ie be bee SDR e ERS 10 2 11 IZASS S uero os ed eg aaa e tus eg aes 10 2 12 COMMON utr
130. 9 64 ZK 1038 GE The predefined schema type STRING uses VARYING OF CHAR as its underlying data type so Figure A 1 also represents the STRING type For More Information On HP Pascal varying data types Section 2 6 2 e On the UNALIGNED attribute Section 10 2 38 On HP Pascal string data types Section 2 6 A 3 2 Representation of Floating Point Data The following sections summarize the internal representation of single precision F floating and S floating double precision D floating G floating and T floating and quadruple precision H floating and X floating floating point numbers For More Information e On HP Pascal floating point data types Section 2 2 A 20 Data Storage and Representation A 3 2 1 F floating Point Numbers An F floating point value is represented by four contiguous bytes The bits are numbered from the right 0 through 31 as shown in Figure A 2 Figure A 2 F floating Point Data Representation 15 14 76 0 EXPONENT FRACTION A FRACTION 31 16 ZK 1039 GE An F floating point value is specified by its address A the address of the byte containing bit 0 The form of this value is sign magnitude as follows e Bit 15 is the sign bit e Bits 14 through 7 are an excess 128 binary exponent e Bits 6 through 0 and 31 through 16 are a normalized 24 bit fraction with the redundant most significant fraction bit not represented Within the fraction bits of increasing significance go from 1
131. ACKED ARRAY OF BOOLEAN with an integer index type The optional start index parameter must be an integer expression that indexes the element at the point at which the search starts The starting index must be greater than or equal to the vector s lower bound and less than or equal to 1 plus the vector s upper bound otherwise a range violation occurs If omitted the starting index defaults to the vector s first element This function returns a value indexing the first element containing the value 0 If no bit is 0 the result is 1 plus the vector s upper bound If the vector or the indexed part of the vector has a size of 0 the result is start index 8 34 FIND_FIRST_BIT_SET Function The FIND_FIRST_BIT_SET function locates the first bit in a Boolean array whose value is 1 and returns an integer value that specifies the index into the array FIND_FIRST_BIT_SET vector start index The vector parameter is a variable of type PACKED ARRAY OF BOOLEAN with an integer index type The optional start index parameter must be an expression of an integer type that indexes the element at the point at which the search starts The starting index must be greater than or equal to the vector s lower bound and less than or equal to 1 plus the vector s upper bound Predeclared Functions and Procedures 8 17 otherwise a range violation occurs If omitted the starting index defaults to the vector s first element The FIND_FIRST_BIT_SET f
132. AX RANDOM RSHFT RSHIFT SEED UAND UNOT UOR UXOR XOR Allocation size functions SIZE SIZEOF NEXT BITSIZE BITNEXT Ordered sequence of values functions FIRST FIRSTOF HBOUND IN RANGE LAST LASTOF LBOUND Low level interlocked functions ADD ATOMIC ADD INTERLOCKED AND ATOMIC CLEAR INTERLOCKED FIND FIRST BIT CLEAR FIND FIRST BIT SET FIND MEMBER FIND NONMEMBER OR ATOMIC SET INTERLOCKED Null terminated string functions C STR MALLOC C STR PAS STR PAS STRCPY I O functions STATUS UFB Field position functions BIT OFFSET BYTE OFFSET Additional functions ARGC CARD CLOCK EXPO UNDEFINED ZERO DATE TIME UPPER LOWER SYSCLOCK WALLCLOCK Parameters of character string and enumerated types for READ and READLN Parameters of enumerated types for WRITE and WRITELN Prompting at the terminal with a WRITE READ or WRITE READLN sequence Optional carriage control specification for text files with WRITE and WRITELN Optional radix specification for READ and READLN Optional radix specification for WRITE and WRITELN continued on next page Summary of HP Pascal Extensions B 3 Table B 1 Cont HP Pascal Extensions to Unextended Pascal Category Extension Extended I O capabilities Declarations Statements Procedures and functions Compilation Direct access and relative file organization Keyed access and indexed file organization Optional second parameter to RESET REWRITE and EXTE
133. AXINT and MAXINT64 Predeclared Constants Constant Size Value MAXINT 32 bits 21 1 16 7FFFFFFF MAXINT64 64 bits 288 1 16 7FFFFFFFFFFFFFFF 2 1 1 2 UNSIGNED and UNSIGNED64 Types HP Pascal provides the UNSIGNED and UNSIGNED64 types not available on all systems Also provided are the UNSIGNED32 CARDINAL CARDINAL16 and CARDINAL32 types which are used as synonyms for subranges of the UNSIGNED type UNSIGNED8 and UNSIGNED16 are provided as synonyms for subranges of INTEGER with positive values that correspond to an UNSIGNED subrange of the same size The range of unsigned values consists of nonnegative integer values The unsigned data types are HP Pascal extensions that are provided to facilitate systems programming using certain operating systems Given that these data types are not standard you should not use them for every application involving nonnegative integers Table 2 3 lists the range of values for unsigned numbers Data Types and Values 2 3 Table 2 3 Range of Values of Unsigned Ordinal Types Data Type Size Range UNSIGNEDS8 8 bits 0 255 0 164FF UNSIGNED16 16 bits 0 65535 219 1 CARDINAL16 0 16 F FFF UNSIGNED32 32 bits 0 4294967295 2 1 CARDINAL32 0 168FFFFFFFF UNSIGNED64 64 bits 0 18446744073709551615 294 1 0 168FFFFFFFFFFFFFFFF The largest possible value of the UNSIGNED type is represented by the predefined constant MAXUNSIGNED The smallest possible value of the
134. Attributes 10 43 e When a formal parameter is an unsafe conformant array the HP Pascal compiler must be able to establish bounds for the corresponding actual parameter that exactly describe the amount of storage the parameter occupies If the conformant array is one dimensional the actual parameter need not be an array The compiler constructs the bounds of the formal array so that the actual parameter and the formal array have the same Size For this construction to be possible the size of the actual parameter must be an exact multiple of the size of the formal array component The compiler chooses the low bound of the formal parameter s index to be the smallest possible value of the index type If the formal conformant parameter is a multidimensional array with n dimensions the actual parameter must be an array having no fewer than n 1 dimensions The first n 1 dimensions of the two arrays will have identical array bounds The compiler chooses bounds for the last dimension of the conformant array so that the conformant as a whole describes the exact size of the actual parameter HP Pascal allows you to pass an actual parameter of a schema type to the an unsafe conformant array however because HP Pascal cannot determine the size of the actual parameter until run time you must be sure that the actual parameter is an exact multiple of the size of the formal array component Consider the following example PROGRAM Output Buffer D
135. Because the field width specified in these cases is not wide enough for all 17 characters in the identifier the identifier is truncated after the field is filled For More Information e On the WRITE procedure Section 9 8 25 e On the WRITELN procedure Section 9 8 26 e On the WRITEV procedure Section 8 109 e On the BIN function Section 8 11 e On the DEC function Section 8 26 e On the UDEC function Section 8 95 e On the HEX function Section 8 41 e On the OCT function Section 8 62 9 28 Input and Output Processing 9 7 Error Processing Parameter For I O procedures the last parameter which is optional specifies the action to be taken should the procedure fail to execute successfully You must use nonpositional syntax in order to pass the error recovery parameter to the called procedure This parameter is called ERROR and can accept two values CONTINUE and MESSAGE If you specify ERROR CONTINUE the program continues to execute regardless of any error conditions encountered during execution of the procedure If you specify this value you should use the STATUS function to be certain that the I O routine worked as expected If you specify ERROR MESSAGE and if an error occurs HP Pascal generates an appropriate error message and program execution stops By default HP Pascal displays an error message and program execution stops after the first error in an I O operation You cannot use the error recovery parameter
136. CKED ARRAY 1 5 OF Internal Arr Each component of an array of type Internal Arr is stored in a longword Each component of Sampl1 Arr in turn requires five longwords which is enough storage space for five components of type Internal Arr The entire array Sampl Arr occupies 25 longwords 800 bits Example 2 VAR Sampl Arr ARRAY 1 5 OF PACKED ARRAY 1 5 OF 0 6 Each PACKED ARRAY 1 5 of 0 6 requires 15 bits the range 0 6 requires 3 bits five 3 bit components requires 15 bits Because the packed arrays are components of an unpacked array their size is rounded up to an even 16 bits The total size of Samp1_Arr is 80 bits Example 3 TYPE Internal Arr PACKED ARRAY 1 5 OF 0 6 VAR Samp2 Arr PACKED ARRAY 1 5 OF Internal Arr Samp3 Arr PACKED ARRAY 1 5 1 5 OF 0 6 Data Storage and Representation A 15 In this example every component of Internal_Arr requires only three bits because the array is packed Each component of Samp2_Arr and Samp3_Arr can be stored in 15 bits and each array occupies 75 bits The specification of PACKED for an array with multiple indexes results in packing at every level The two arrays in this example are equivalent Example 4 VAR Sample PACKED ARRAY 1 5 1 5 1 5 OF 0 6 This example shows space savings for arrays of more than two dimensions when PACKED is specified at every level The subrange 0 6 requires 3 bits five 3 bit components require 15 bits This size de
137. CKED array parameter of type CHAR or to a conformant VARYING OF CHAR e Indexes that are equivalent and of the same ordinal type the same number of dimensions and components that are compatible in the case of passing a static or nonstatic array to a conformant array parameter Consider the following example VAR Actual 1 Actual 2 ARRAY 1 10 OF INTEGER Actual 3 ARRAY 5 10 OF INTEGER PROCEDURE TestArr One Two ARRAY L1 U1 INTEGER OF INTEGER Procedure body PROCEDURE TestStr One Two PACKED L2 U2 INTEGER OF CHAR Procedure body In the executable section TestArr Actual_1 Actual_2 Legal TestArr Actual 2 Actual 3 Illegal TestStr ABC XYZ Legal TestStr HELLO GOODBYE Illegal When using variable semantics if you specify more than one formal parameter separated by commas of a single user defined conformant parameter the corresponding actual variable parameters must be of the same type For More Information e On ordinal types Section 2 1 e On static and nonstatic types Section 2 9 6 24 Procedures and Functions 6 3 8 Parameter Association In most cases a routine call must pass exactly one actual parameter for each formal parameter The actual parameter is either listed explicitly in the routine call or supplied by means of a default value in the routine declaration One way of establishing the correspondence between actual and formal parame
138. CTION Random INTEGER VAR X STATIC INTEGER VALUE 15 BEGIN x 9 x 7 MOD 11 Random x END In the executable section FOR i 1 TO 20 DO WRITELN Random END The program Print_Random includes a function that generates a random integer Because the variable x is declared STATIC its value is preserved from one activation of the function to the next By default the storage for x would have been deallocated when control returned to the main program Because x is static it retains the value it had when Random ended and assumes this value the next time Random is called In the program Print_Random the program level variable i is declared AUTOMATIC For More Information e On the AUTOMATIC attribute Section 10 2 5 e On allocation attributes Section 10 3 e On default storage of objects Section A 3 10 2 37 TRUNCATE The TRUNCATE attribute indicates that an actual parameter list for a routine can be truncated at the point that the attribute was specified You can use TRUNCATE with the PRESENT function Attributes 10 37 Usage and Default Information The examples in this list are based on this PROCEDURE declaration from Example 10 1 which shows the use of the TRUNCATE attribute with default values PROCEDURE p a TRUNCATE CHAR a b CHAR b c TRUNCATE CHAR c d CHAR d e You can specify the TRUNCATE attribute on a formal parameter in a routine declara
139. Corporation or its subsidiaries in the United States and other countries Printed in the US ZK6083 This manual is available on CD ROM This document was prepared using DECdocument Version 3 3 1b Contents Preface ree aaee oe Bs ee ea hes Boe a ee eS e ertt 1 Language Elements 1 2 6 1 3 1 4 Pascal Language Standards sib 6 045 466 RES RS RE RE Unextended Pascal Standards 00 0000 eae Extended Pascal Standard 0 0 00 eee eee eae Lexical Elements 0 0 00 ccc eee eens Character Seb uou 2554 bu dere gore d poe ete Adee Special Symbols llle eee String Delimiters zie wv oes x or m e OW Rue s Embedded String Constants llle Reserved Words 0 cece ee eee ee eae Identifiers Comments Page Breaks and Form Feeds in Programs 2 Data Types and Values 2 1 2 1 1 2 1 1 1 2 11 2 2 1 1 3 2 1 1 4 2 1 2 2 1 3 2 1 4 2 1 5 2 2 2 3 2 3 1 2 4 Ordinal Types Integer Types iuicec ga RE AW ER eA P PEE INTEGER and INTEGER64 Types UNSIGNED and UNSIGNED64 Types Integer Literals sese rewire pered e oer gems INTEGER ADDRESS Type sseeeeeeesens CHAR Type BOOLEAN Type cseezkake a errien RR RR ER EEG E Enumerated Types peresen 0 0c cece eA Subrange Types 0 0 ccc ee ee ees Real Types Pointer Types POINTER Type veterum aca oa tors m S sues Structured Type
140. D 5 In the expression i DIV j the value ofj is zero Explanation Detected at run time In the expression i MOD j the value of j is zero or negative Explanation Detected at run time if subrange checking was enabled during compilation An operation or function involving integers does not conform to the mathematical rules for integer arithmetic Explanation Detected at run time if overflow checking was enabled during compilation A function result is undefined when the function returns control to the calling block Explanation Not detected The ordinal type of an expression is not assignment compatible with the type of the variable or function identifier to which it is assigned Explanation Detected at run time if subrange checking was enabled during compilation The set type of an expression is not assignment compatible with the type of the variable or function identifier to which it is assigned Explanation Detected at run time if subrange checking was enabled during compilation None of the case labels is equal in value to the case selector in a CASE statement Explanation Detected at run time if case selector checking was enabled during compilation In a FOR statement the type of the initial value is not assignment compatible with the type of the control variable and the statement in the loop body is executed Explanation Detected at run time if subrange checking was enabled during compilation Assignment
141. DATE GETTIMESTAMP SYSCLOCK TIME and WALLCLOCK Routines that provide for the creation and use of pointer variables ADDRESS DISPOSE IADDRESS IADDRESS64 and NEW Routines that create rename and remove files and directories CREATE_DIRECTORY DELETE_FILE RENAME_FILE Routines that you use for I O these routines are not described in this chapter Routines that allow for parallel processes and for asynchronous routines to operate in a real time or multitasking environment ADD_ ATOMIC AND_ATOMIC ADD_INTERLOCKED BARRIER CLEAR_ INTERLOCKED OR_ATOMIC and SET_INTERLOCKED Routines that operate on null terminated strings C STR MALLOC_ C STR PAS STRCPY PAS STR Routines that provide information on the ordered sequence of values PRED SUCC LOWER and UPPER ODD Routines that give information about parameter lists ARGC ARGV ARGUMENT ARGUMENT LIST LENGTH and PRESENT Routines that manipulate privileged hardware registers MFPR and MTPR Routines that convert an actual parameter to data of another type CHR DBLE INT INT64 ORD PACK QUAD ROUND ROUND64 SNGL TRUNC TRUNC64 UINT UINT64 UNPACK UROUND UROUND64 UTRUNC and UTRUNC64 FIND FIRST BIT CLEAR FIND FIRST BIT SET UNDEFINED and ZERO Note Not all routines are supported on all operating system and machine architecture environments If a routine is not supported on all environments the routine description includes any limitations 8 2 Pre
142. DEN attribute prevents information concerning a constant definition or a type variable procedure or function declaration from being included in a generated environment file You can only use the HIDDEN attribute on objects at the outermost level of the compilation unit It is possible to prevent all declarations within a declaration section from being included in the environment file by preceding the reserved word CONST TYPE or VAR with the HIDDEN attribute For More Information e On environment files Section 10 2 14 10 2 19 IDENT You can use the IDENT attribute to qualify the name of a compilation unit In the absence of an IDENT attribute the string 01 is supplied to the linker IDENT name string The name string can contain additional information whose use is implementation specific The HP Pascal compiler uses this string to supply identification information to the linker 10 20 Attributes Consider the following example IDENT 100 5 ENVIRONMENT sample pen MODULE SAMPLE In this example the IDENT string 100 5 is supplied to the linker For More Information e On name string syntax Section 10 1 e On compiling and linking HP Pascal for OpenVMS User Manual 10 2 20 IMMEDIATE The IMMEDIATE attribute causes a formal parameter value in a routine declaration to be passed by immediate value This attribute can be used on scalar and floating point parameters that are passed by immediate
143. E MODULE and IDENT LINE returns an integer that denotes the current line number in the source file FILE returns a string containing the file name that is currently being compiled The string contains a full OpenVMS file specification including the disk directory file name file type and version fields 7 ROUTINE returns a string with the name of the routine that is currently being compiled If used in the executable portion of a program the program s name is returned If used in the declaration section of a MODULE PROGRAM the name of the MODULE PROGRAM is returned MODULE returns a string containing the name of the module program that is currently being compiled IDENT returns a string that contains the ident string of the compilation that is set with the IDENT attribute 11 10 Directives A Data Storage and Representation This chapter describes how the HP Pascal compiler allocates and represents program components It discusses the following topics e Program sections Section A 1 e Storage allocation and alignment for variables Section A 2 e Internal representation of data types Section A 3 A 1 Program Sections This chapter describes how to establish program sections and program section properties The HP Pascal compiler uses contiguous areas of memory called program sections to store information about a program The compiler writes these program sections to the object file When constructing an
144. ED ARRAY OF CHAR e STRING or VARYING OF CHAR strings When values of two different arithmetic or character types are combined in an expression the lower ranked operand is converted to its equivalent in the higher ranked type The result of an operation in which conversion occurs is always of the higher ranked type All conversions or assignments to values of type UNSIGNED or UNSIGNED64 are never checked for overflow When combined with other unsigned values negative integer values are converted to large unsigned values by the calculation of the modulus with respect to 2 32 or 2 64 Conversions or assignments to values of type INTEGER or INTEGER64 can overflow Overflow will be detected at runtime if overflow checking is enabled Overflow will occur if the value is outside the range MAXINT to MAXINT for converting to INTEGER or outside the range MAXINT64 to MAXINT64 for converting to INTEGER64 A special case of conversion can occur when you attempt to assign an expression of type VARYING OF CHAR or STRING strings to a variable of type PACKED ARRAY OF CHAR or if you try to pass a string expression to a formal value parameter of type PACKED ARRAY OF CHAR If the varying length string has less than or exactly the same number of components as the packed array the varying length string is converted to a packed array of characters before the assignment is made and padded with blanks as necessary If you attempt to perform this assignment with
145. EFAULT b TRUNCATE AT c wp p w x TRUNCATE AT c wx p w x y DEFAULT d wxyd p w xX y z NO DEFAULTS wxyz pl a w DEFAULT b TRUNCATE AT c wp pt bits 5 DEFAULT a TRUNCATE AT c ax p c y i DEFAULT a b AND d abyd p d 2z DEFAULT a b AND C abcz For More Information e On the PRESENT function Section 8 71 e On parameters Section 6 3 10 40 Attributes 10 2 38 UNALIGNED The UNALIGNED attribute specifies that an object can be aligned on any bit boundary Usage and Default Information Alignment attributes are illegal on nonstatic types components of files and on VARYING OF CHAR strings An unaligned variable must have an allocation size that conforms to the rules for the platform A formal parameter cannot be unaligned so an unaligned variable cannot be passed to a formal variable parameter The base type of a pointer variable passed to the NEW procedure cannot have alignment greater than a quadword nor can it be unaligned For More Information On allocation size attributes Section 10 3 On HP Pascal alignment rules Section A 2 7 On allocation sizes of objects Section A 2 4 10 2 39 UNBOUND The UNBOUND attribute specifies that a routine does not access automatic variables outside the scope in which it is declared That is the bound procedure value of an unbound routine does not include the static scope pointer Usage and Default Information You ca
146. ET UPPER returns the upper bound of the SET base type Consider the following example TYPE A Schema a b INTEGER a atb VAR X A Schema 5 10 In the executable section WRITELN UPPER BOOLEAN Writes TRUE WRITELN LOWER x Writes 5 WRITELN UPPER x Writes 15 UROUND Function The UROUND function converts the value of the parameter by rounding the fractional part of the value and returns its unsigned equivalent UROUND x The parameter x must be of type REAL SINGLE DOUBLE or QUADRUPLE No error results if the value of x is negative or greater than 4 294 967 295 In that case the unsigned result is the rounded parameter value MOD 4 294 967 296 For More Information e On range and support of the UNSIGNED data type Chapter 2 Predeclared Functions and Procedures 8 49 8 104 8 105 8 106 UROUND64 Function The UROUND64 function converts the value of the parameter by rounding the fractional part of the value and returns its UNSIGNED64 equivalent UROUND64 x The parameter x must be of type REAL SINGLE DOUBLE or QUADRUPLE No error results if the value of x is negative or greater than MAXUNSIGNED64 In that case the UNSIGNED64 result is the rounded parameter value MOD MAXUNSIGNED64 For More Information e On range and support of the UNSIGNED64 data type Chapter 2 UTRUNC Function The UTRUNC function converts the value of the parameter by truncating the fraction
147. EVERT Procedure The REVERT procedure cancels a condition handler activated by the ESTABLISH procedure This procedure does not have a parameter list For More Information e On error processing HP Pascal for OpenVMS User Manual 8 77 ROUND Function The ROUND function converts the value of the parameter by rounding the fractional part of the value and returns its integer equivalent ROUND x The parameter x must be of type REAL SINGLE DOUBLE or QUADRUPLE The value of x must not be too large to be represented by an integer 8 38 Predeclared Functions and Procedures 8 78 ROUND64 Function The ROUND64 function converts the value of the parameter by rounding the fractional part of the value and returns its INTEGER64 equivalent ROUND64 x The parameter x must be of type REAL SINGLE DOUBLE or QUADRUPLE The value of x must not be too large to be represented by an INTEGERG64 8 79 RSHIFT Function The RSHIFT predeclared function returns a value of the same type as its first parameter The value represents the value of the first parameter after the bits have been shifted to the right RSHIFT expression expression The expression parameters are two integer or unsigned values The first parameter represents a value to shift the second represents the number of bits to shift the first value The RSHIFT function inserts zero bits on the left as the bits shift right Note that shifting integers is not equivalent to
148. F directives can be nested up to 32 deep Note that skipped sections of source code must still be valid HP Pascal tokens The skipped tokens are not processed semantically by the compiler except for control expressions of nested IF directives All control expressions are semantically processed to ensure they result in a Boolean result INCLUDE and DICTIONARY directives encountered while skipping tokens do not attempt to open the file name or access the dictionary path Instead they return the token TRUE In the following example the state of a flag Debug Flag is checked for true or false The value of an integer variable I will then be set to either 12 or 1 depending on the state of the flag CONST Debug Flag true or false VAR I integer I IF Debug Flag STHEN 12 ELSE 1 ENDIF SIF Debug Flag STHEN writeln Debug the value of I is i 2 SENDIF In the following example selected code will be compiled only if the specific configuration is selected TYPE Configs Configl Config2 Config3 CONST Config Configl or Config2 or Config3 Directives 11 7 IF Config Configl STHEN Code for Configl ELIF Config Config2 Code for Config2 oo ELSE Config Config3 Code for Config3 SENDIF Note that the compile time expression for the IF statement is the same compile time expression that can be used anywhere in HP Pascal You can use any operator or builtin rou
149. FOR WHILE or REPEAT loop can include the CONTINUE statement The CONTINUE statement is equivalent to a GOTO to a label placed at the end of the statements in the body of the FOR WHILE or REPEAT statement The CONTINUE statement appears as a single word CONTINUE In a loop that processes a series of data items you can use the CONTINUE statement to indicate that the rest of the loop does not apply to the current item and that the program should continue to the next statement Use caution when using the CONTINUE statement because future additions to the code can result in the CONTINUE statement continuing with a different loop than was originally intended 5 6 Empty Statement The empty statement causes no other action to occur than the advancement of program flow to the next statement To use the empty statement place a semicolon where the language syntax calls for a statement Consider the following example CASE Alphabetic OF Oe RE gL OOV DO 3 Alpha Flag Vowel Y Empty statement as selector no action OTHERWISE Alpha Flag Consonant END Statements 5 5 5 7 FOR Statement The FOR statement is a looping statement that repeats execution of a statement according to the value of a control variable The control variable assumes a value within a specified range or set A FOR statement has one of the following forms j final value DO FOR control variable initial value m statement FOR control variable IN
150. HP Pascal for OpenVMS Language Reference Manual Order Number AA PWVSD TK January 2005 This manual contains the complete description of the HP Pascal programming language Revision Update Information Operating System Software Version Hewlett Packard Company Palo Alto California This revised manual supersedes the Compaq Pascal Language Reference Manual Version 5 7 OpenVMS I64 Version 8 2 or higher OpenVMS Alpha Version 6 1 or higher OpenVMS VAX Version 5 5 or higher HP Pascal for OpenVMS I64 Systems Version 5 9 HP Pascal for OpenVMS Alpha Systems Version 5 9 HP Pascal for OpenVMS VAX Systems Version 5 8 Copyright 2005 Hewlett Packard Development Company L P Confidential computer software Valid license from HP required for possession use or copying Consistent with FAR 12 211 and 12 212 Commercial Computer Software Computer Software Documentation and Technical Data for Commercial Items are licensed to the U S Government under vendor s standard commercial license The information contained herein is subject to change without notice The only warranties for HP products and services are set forth in the express warranty statements accompanying such products and services Nothing herein should be construed as constituting an additional warranty HP shall not be liable for technical or editorial errors or omissions contained herein Intel and Itanium are trademarks or registered trademarks of Intel
151. ITLE directive If the TITLE directive does not appear on the first line of a page then the title area is not set until the next page The ZSUBTITLE directive affects only the subtitle area in the source listing section If a SUBTITLE directive appears on the first or second line of a page then the subtitle area is set for the current page If the SUBTITLE directive does not appear in the first two lines of a page then the subtitle area is not set until the next page On OpenVMS VAX systems if either of these directives is used and if a listing is being generated HP Pascal generates a table of contents page by default It appears first in the listing preceding the source listing section To disable the table of contents option you must use a compilation switch For More Information e On creating listings and on using compilation switches HP Pascal for OpenVMS User Manual 11 4 IF ELSE ELIF and ENDIF The IF family of directives is used to conditionally compile specified sections of source code These directives are useful if you need to compile the same source code for various configurations or environments 11 6 Directives The IF directive family has the following syntax elF compile time expression THEN Pascal tokens ELIF compile time expression YoTHEN Pascal tokens ELSE Pascal tokens ENDIF A IF directive can have zero or more ELIF parts and zero or one PELSE parts I
152. Input and Output Processing 9 8 18 The OPEN call opens the file variable f for direct access The RESET call positions the file at the first component and is necessary whether the file is new or old After execution of the OPEN and RESET procedures you can use the FIND procedure for direct access to the components of the file For example RESET Weights If the file variable Weights is already open this procedure call prepares it for reading and assigns the value of the first file component to Weights If the file is not open RESET causes HP Pascal to open the file by default If Weights is an external file its file history will be OLD If Weights does not exist an error occurs For More Information e On component access Section 9 3 e On the default parameter values for OPEN Section 9 8 12 e On the error processing parameter Section 9 7 RESETK Procedure The RESETK procedure puts an indexed file into inspection mode in which it can be read RESETK can be applied only to indexed files opened for random access by key RESETK file variable key number ERROR error recovery file variable The name of the file variable associated with the input file key number A nonnegative integer expression that indicates the key position error recovery The action to be taken if an error occurs during execution of the routine The file can be in any mode before RESETK is called to set the mode to inspection
153. KED FIND FIRST BIT CLEAR FIND FIRST BIT SET FIND MEMBER FIND NONMEMBER OR ATOMIC SET INTERLOCKED Privileged routines MTPR MFPR I O functions STATUS UFB continued on next page B 6 Summary of HP Pascal Extensions Table B 2 Cont HP Pascal Extensions to Extended Pascal Category Extension Null terminated string functions C STR MALLOC C STR PAS_ STR PAS STRCPY Field position functions BIT OFFSET BYTE OFFSET Additional predeclared functions ARGC CLOCK EXPO LOWER SYSCLOCK UNDEFINED UPPER WALLCLOCK ZERO READ Parameters of enumerated types for READ and READLN E Parameters of enumerated types for WRITE and WRITELN WRITELN Prompting at the terminal with a WRITE READ or extensions WRITE READLN sequence Extended I O capabilities Declarations Statements Procedures and functions Compilation Optional carriage control specification for text files with WRITE and WRITELN Optional radix specification for READ and READLN Optional radix specification for WRITE and WRITELN Direct access and relative file organization Keyed access and indexed file organization Optional second parameter to RESET REWRITE and EXTEND for specifying a file name VALUE initialization section BREAK CONTINUE EXIT NEXT and RETURN statements Functions called as procedures External procedure and function declarations Default values for formal parameters Nonpositional parameter passing Extended mechanism specifie
154. LETE FILE procedure 8 15 Dereferencing file buffers 9 9 DESCR foreign mechanism on actual parameter 6 17 Descriptor mechanism 6 7 for strings 6 17 DICTIONARY directive 11 5 Direct access definition Glossary 4 Directive ARCH_NAME 11 9 COMPILER VERSION 11 10 DATE 11 10 DEFINED 11 8 DICTIONARY 11 5 ELIF 11 6 ELSE 11 6 ENDIF 11 6 ERROR 11 8 FILE 11 10 IDENT 11 10 IF 11 6 INCLUDE 11 1 INFO 11 8 LINE 11 10 MESSAGE 11 8 MODULE 11 10 ROUTINE 11 10 SUBTITLE 11 6 SYSTEM_NAME 11 9 SYSTEM_VERSION 11 9 TIME 11 10 TITLE 11 6 WARN 11 8 Discriminants actual and formal 2 37 Discriminated schema 2 39 definition Glossary 4 DISPOSE procedure 8 15 Division operator 4 4 DIV operator 4 4 Double precision data representation of A 22 A 23 A 24 Double precision real number 2 11 Double quotation character 1 4 DOUBLE type 2 11 allocation size of A 11 default field width of 9 23 representation of A 22 Dynamic variable 2 16 allocating 8 29 disposing of 8 15 D FLOAT 2 13 D floating point data representation of A 22 E Element definition Glossary 4 ELIF directive 11 6 ELSE clause in IF statement 5 8 ELSE directive 11 6 Embedded string values 1 4 Empty set 2 32 Empty statement 5 5 END compound statement 5 4 ENDIF directive 11 6 End of file condition 9 33 End of line condition 9 34 Enume
155. LIGNED 2 0 225 32 8 45 1 First element of 5 5 0 1 PACKED ARRAY 1 10 OF 0 25 PACKED ARRAY 1 10 OF 56 56 7 7 0 25 1 By default the variable is unaligned in a packed context By default the variable is byte aligned in an unpacked context 3 SIZE rounds up to the nearest byte for the bit sized objects Subranges assume the size of their base types in an unpacked context 5 Extra space is needed to fulfill alignment requirements NEXT rounds down to the nearest byte for bit sized objects 7 Items larger than 32 bits must be allocated in an integral number of bytes For More Information e On storage allocation and alignment for data types Appendix A 8 84 SNGL Function The SNGL function converts the parameter and returns its real equivalent SNGL x The parameter x must be an arithmetic type The value of x must not be too large to be represented by a single precision number Predeclared Functions and Procedures 8 41 8 85 SQR Function The SQR function returns a value of the same type of the parameter that represents the square of the specified parameter SQR x The parameter x can be any arithmetic type 8 86 SQRT Function The SQRT function returns a real value that represents the square root of the specified parameter SQRT x The parameter x can be an INTEGER UNSIGNED or REAL type If the value of x is less than zero an error occurs 8 87 STATUSV Function
156. MP predefined type is used in conjunction with the GETTIMESTAMP procedure and with the DATE or TIME functions GETTIMESTAMP initializes a variable of type TIMESTAMP DATE and TIME function parameters are of type TIMESTAMP The TIMESTAMP data type is similar to the following record definition TIMESTAMP PACKED RECORD DATEVALID TIMEVALID BOOLEAN YEAR INTEGER MONTH 1 12 DAY 1 31 HOUR 0 23 MINUTE 0 59 SECOND 0 59 The last 3 fields are OpenVMS systems only HUNDREDTH 0 99 BINARY TIME QUAD RECORD L1 L2 INTEGER END 64 bit VMS binary time DAY OF WEEK 1 7 1 is Monday and 7 is Sunday END For More Information e On the GETTIMESTAMP procedure Section 8 38 e On the DATE and TIME functions Section 8 23 2 9 Static and Nonstatic Types Static types are types whose objects can be fully described at compile time For example the variables a and b are derived from static types in the following example VAR a INTEGER b ARRAY 1 10 OF INTEGER Nonstatic types are types whose objects potentially cannot be fully described at compile time the type has a component that can be a run time value Nonstatic types include the following types e Discriminated and undiscriminated schema types e Any type that contains a nonstatic component or index type 2 48 Data Types and Values Nonstatic types require storage allocation to hold information about the type at run time This sto
157. ND for specifying a file name Declaration and definition sections that can appear more than once and in any order Initialization of variables types and record fields in VAR and TYPE sections of any program module procedure or function Schema types VALUE initialization section OTHERWISE clause in variant records Ranges in variant label lists OTHERWISE clause in CASE statement Ranges in CASE label lists BREAK CONTINUE EXIT NEXT and RETURN statements FOR statement with SET iterations Functions that return values of structured types other than file types Functions called as procedures External procedure and function declarations Default values for formal parameters Nonpositional parameter passing Extended mechanism specifiers and parameter passing attributes for passing parameters to external procedures and functions IMMED REF DESCR STDESCR IMMEDIATE REFERENCE CLASS S CLASS A CLASS NCA MODULE capability for combining declarations and definitions to be compiled independently from the main program ENVIRONMENT and INHERIT attributes to control independent compilation Module initialization and finalization B 4 Summary of HP Pascal Extensions B 2 HP Pascal Extensions to Extended Pascal Table B 2 summarizes the language features provided in HP Pascal that are not part of the Extended Pascal language definitions Table B 2 HP Pascal Extensions to Extended Pascal Category Extension
158. O BEGIN DO section if TO BEGIN DO wasn t used or by augmenting an existing TO BEGIN DO section with a call to the Pascal Run Time Library to register the finalization routine Here is an example using both TO BEGIN DO and TO END DO MODULE File Output VAR i Out File TEXT t TIMESTAMP PROCEDURE Test Executable section TO BEGIN DO OPEN Out File foo dat TO END DO BEGIN GETTIMESTAMP t WRITELN foo dat closed at TIME t CLOSE Out File END END 3 6 Declaration Section For More Information e On modules Section 7 4 e On environment files Section 7 5 1 3 5 TYPE Section The TYPE section introduces the name and set of values for a user defined type or schema declaration It has the following form type attribute list TYPE type identifier attribute list type denoter j schema declaration VALUE initial state specifier type attribute list One or more attributes that apply to the entire TYPE section Only the ALIGN ENUMERATION SIZE or HIDDEN attributes can be specified here type identifier The identifier of the type being defined attribute list One or more identifiers that provide additional information about the type denoter type denoter Any legal Pascal type syntax schema declaration The declaration of a schema type initial state specifier A compile time expression that is assignment compatible with a variable of the TYPE ident
159. OBAL and VALUE attributes BSS Zeroed static storage CODE Machine instructions DATA Nonexternal static types writable variables declared with the STATIC attribute writable variables that use default allocation and are declared at program or module level of a nonoverlaid compilation unit LIB INITIALIZE Addresses of routines declared with the INITIALIZE attribute and compiler generated routines to perform module initialization LINK Procedure descriptors and small literals LITERAL Constants needing storage nonvolatile readonly static variables lExecutable code and read only data are compiled into two separate program sections Table A 4 Program Section Data on OpenVMS VAX Systems Program Section Data ABS No data is allocated in this program section It is used for defining global literals variables declared with the GLOBAL and VALUE attributes CODE Machine instructions constants needing storage nonvolatile readonly static variables LIB INITIALIZE Addresses of routines declared with the INITIALIZE attribute and compiler generated routines to perform module initialization LOCAL Nonexternal static types writable variables declared with the STATIC attribute writable variables that use default allocation and are declared at program or module level of a nonoverlaid compilation unit PAS GLOBAL Writable variables that use default allocation and are declared at program or module le
160. On size allocation restriction Section 10 2 6 e ACCURATE Default e FAST 10 2 27 NOOPTIMIZE The NOOPTIMIZE attribute prohibits the compiler from optimizing code for the compilation unit or routine The NOOPTIMIZE attribute can only be applied to routines on OpenVMS VAX systems On OpenVMS VAX systems the NOOPTIMIZE attribute guarantees left to right evaluation order with full evaluation of both operands of the AND and OR Boolean operators to aid in diagnosing all potential programming errors On OpenVMS I64 and OpenVMS Alpha systems NOOPTIMIZE only guarantees full evaluation If you wish to have short circuit evaluation even with the NOOPTIMIZE attribute then use the AND THEN and OR ELSE Boolean operators 10 28 Attributes For More Information e On the OPTIMIZE attribute Section 10 2 29 e On the AND THEN and OR ELSE logical operators Section 4 2 3 10 2 28 OCTA The OCTA attribute specifies the amount of storage in octawords to be received by the object OCTA f n JI The optional constant n indicates the number of octaword storage units For More Information e On allocation sizes of objects Section A 2 4 e On size allocation restriction Section 10 2 6 10 2 29 OPTIMIZE The OPTIMIZE attribute specifies optimization options that are to be enabled during compilation of a compilation unit or routine OPTIMIZE identifier The options listed with the OPTIMIZE attribute are enabled The negation
161. P Pascal for OpenVMS User Manual 8 6 ARCTAN Function The ARCTAN function returns a real value that expresses in radians the arctangent of the specified parameter ARCTAN x The parameter x can be an integer or REAL type Predeclared Functions and Procedures 8 5 8 7 ARGUMENT Function The ARGUMENT function specifies an argument in a variable length parameter list that was created using the LIST attribute ARGUMENT parameter name n The parameter name argument specifies the name of a parameter declared with the LIST attribute The parameter n specifies a positive integer value that identifies the argument The first argument in a list is always 1 An error occurs if the value supplied for n is less than 1 or exceeds the ARGUMENT LIST LENGTH parameter which indicates the total number of arguments If the LIST parameter is a value parameter ARGUMENT indicates the corresponding value in the argument list If the LIST parameter is a VAR parameter ARGUMENT is a reference to the corresponding variable in the argument list Also you can use the IADDRESS function with the ARGUMENT function to return the address of a selected argument For More Information On variable length parameter lists the example in Section 8 8 e On parameters Section 6 3 e On the LIST attribute Section 10 2 24 e On the IADDRESS function Section 8 42 8 8 ARGUMENT_LIST_LENGTH Function The ARGUMENT_LIST_LENGTH function returns an integer
162. PUT or OUTPUT HP Pascal implicitly opens them just before their first use HP Pascal implicitly opens INPUT with a history of READONLY If you choose you can explicitly open INPUT or OUTPUT To do this call the OPEN procedure at any point in your compilation unit before you use the first I O routine on that file Because the RESET REWRITE and EXTEND procedures implicitly open files you need not always use the OPEN procedure RESET REWRITE and EXTEND impose the same defaults as OPEN except where noted in the HISTORY parameter You must use the OPEN procedure to do the following e Create a TEXT file with fixed length components e Create a file with relative or indexed organization e Open a file for direct or keyed access e Specify a line length other than the default for a line in a TEXT file Consider the following example PROGRAM Main User Guide VAR User Guide TEXT In the executable section OPEN User Guide When the OPEN procedure is executed the system first attempts to find an environment specific translation for User_Guide If no such translation happens the file USER_GUIDE DAT is created in the default device and directory on the local computer If User_Guide had not been specified as an external file in the program header the OPEN procedure would have created an internal file By default the file is created with a record length of 255 bytes and components of variable length The system then opens
163. Pascal does not inline routines that have formal parameters of nonstatic types or that declare or access objects of nonstatic types For More Information e On the NOOPTIMIZE attribute Section 10 2 27 e On the rules for routine inlining HP Pascal for OpenVMS User Manual 10 2 30 PEN CHECKING STYLE Attribute HP Pascal in cooperation with the OpenVMS Linker performs compile time and link time checks to ensure that all compilations that inherit environment files actually used the same environment file definition Information is placed in the object file such that the OpenVMS Linker will perform the same check between each object file that inherited environment files By default compilation units that inherit an environment file compare the embedded compilation time inside the environment file against uses found in any other environment files that are also inherited If the times are different a compile time message is displayed This happens on all systems This checking can be disabled or modified by using the PEN CHECKING STYLE attribute in the Pascal source file that created the environment file Once the environment file exists its selected checking style will be performed at each use Attributes 10 31 The PEN_CHECKING_STYLE attribute is valid at the beginning of a MODULE that creates an environment The syntax is PEN CHECKING STYLE keyword In this syntax keyword is e COMPILATION TIME Uses the compilation time of t
164. Predefined types ALFA C STR T CARDINAL CARDINAL16 CARDINAL32 INTEGERS8 INTEGER16 INTEGER32 INTEGER64 INTSET POINTER UNIV PTR UNSIGNED8 UNSIGNED16 UNSIGNED32 UNSIGNED64 SINGLE F floating and S floating DOUBLE D floating G floating and T floating QUADRUPLE H floating and X floating VARYING OF CHAR structured type and concatenation operator for all strings Predeclared ARGV ASSERT BARRIER CLOSE CREATE DIRECTORY procedures DATE DELETE DELETE FILE ESTABLISH FIND FINDK LINELIMIT LOCATE MESSAGE NULL OPEN READV REMOVE RENAME FILE RESETK REVERT STLIMIT TIME TRUNCATE UNLOCK UPDATE WRITEV Predeclared Transfer functions DBLE INT INT64 QUAD ROUND64 SNGL functions TRUNC TRUNC64 UINT UINT64 UROUND UROUND64 UTRUNC UTRUNC64 Implicitly declared type conversion and type casting routines for predefined data types Dynamic allocation function ADDR ADDRESS IADDRESS IADDRESS64 Character string functions BIN DEC HEX OCT PAD STATUSV UDEC Parameter functions ARGUMENT ARGUMENT LIST LENGTH PRESENT Arithmetic functions BITAND BITNOT BITOR BITXOR LSHFT LSHIFT RANDOM RSHFT RSHIFT SEED UAND UNOT UOR UXOR XOR MIN MAX Allocation size functions SIZE SIZEOF NEXT BITSIZE BITNEXT Ordered sequence of values functions FIRST FIRSTOF HBOUND IN RANGE LAST LASTOF LBOUND Low level interlocked functions ADD ATOMIC ADD INTERLOCKED AND ATOMIC CLEAR INTERLOC
165. Ptr My Rec Name Kim Jones age 65 2 16 Data Types and Values Pointers assume values through initialization assignment and the READ and NEW procedures The value of a pointer is either the storage address of a dynamic variable or the predeclared identifier NIL NIL indicates that the pointer does not currently refer to a dynamic variable A file referenced by a pointer is not closed until the execution of the program terminates or until the dynamic variable is deallocated with the DISPOSE procedure If you do not want the file to remain open throughout program execution you must use the CLOSE procedure to close it The following example declares the pointer variable Ptr as a pointer to an integer and initializes Ptr to NIL VAR Ptr INTEGER VALUE NIL For performance reasons on OpenVMS I64 systems the HP Pascal compiler assumes that all pointers point to objects that are aligned on at least octaword boundaries The NEW predeclared routine always returns memory that is aligned on octaword boundaries For performance reasons on OpenVMS Alpha systems the HP Pascal compiler assumes that all pointers point to objects that are aligned on at least quadword boundaries The NEW predeclared routine always returns memory that is aligned on quadword boundaries For pointers holding addresses which are not quadword aligned you can explicitly specify the expected alignment of the pointer base type For example var p al
166. Representation Table A 2 Program Section Data on OpenVMS 164 Systems Program Section Data ABS BSS CODE DATA LIB INITIALIZE LINK LITERAL SDATA No data is allocated in this program section It is used for defining global literals variables declared with the GLOBAL and VALUE attributes Zeroed static storage Machine instructions Nonexternal static types writable variables declared with the STATIC attribute writable variables that use default allocation and are declared at program or module level of a nonoverlaid compilation unit All such variables must be larger than 64 bits in size Addresses of routines declared with the INITIALIZE attribute and compiler generated routines to perform module initialization Small literals Constants needing storage nonvolatile readonly static variables Nonexternal static types writable variables declared with the STATIC attribute writable variables that use default allocation and are declared at program or module level of a nonoverlaid compilation unit All such variables must be 64 bits or smaller in size lExecutable code and read only data are compiled into two separate program sections Data Storage and Representation A 3 Table A 3 Program Section Data on OpenVMS Alpha Systems Program Section Data ABS No data is allocated in this program section It is used for defining global literals variables declared with the GL
167. SE clause 5 8 IMMED foreign mechanism on actual parameter 6 17 with UNBOUND attribute 6 17 Index 10 IMMEDIATE attribute 10 21 Immediate value mechanism 6 7 Implementation features C 1 to C 4 Implementation module definition of Glossary 6 9 INCLUDE directive 11 1 example of 11 2 nesting file levels 11 3 Index definition Glossary 6 of array 2 19 Indexed file index structure of 9 5 key fields 9 6 organization 9 4 random access to 9 17 sequential access to 9 15 Indexed file organization definition Glossary 7 INDEX function 8 23 Index structure characteristics defined with KEY attribute 9 6 key fields 9 6 of indexed file 9 5 96 INFO directive 11 8 INHERIT attribute 10 21 Initialization in VALUE section 3 9 of variable 3 7 3 10 INITIALIZE attribute 10 22 Initial state specifier definition Glossary 7 example for a record field 2 23 example for arrays 2 22 example for enumerated type 2 8 example for fields of variant records 2 30 example for PACKED ARRAY OF CHAR 2 43 example for pointers 2 17 example for records 2 28 example for sets 2 32 example for STRING 2 46 example for variant records 2 29 Initial state specifier cont d example for VARYING OF CHAR 2 44 for STRING types example 4 9 on a data type 3 7 on a variable 3 10 IN operator 4 10 INPUT file variable definition of PAS INPUT C 4 definition of SYS INPUT C 4 description of
168. Summary of HP Pascal Extensions B 1 B 2 HP Pascal Extensions to Unextended Pascal HP Pascal Extensions to Extended Pascal C Description of Implementation Features Xii C 1 C 2 Implementation Defined Features 0 0000005 Implementation Dependent Features 00005 A 10 A 11 A 15 A 16 A 19 A 19 A 20 A 21 A 21 A 22 A 23 A 24 A 24 A 26 A 27 A 27 A 28 A 30 D Compiler and Run Time System Error Detection D 1 Error Message Information 0 00 e eee nee D 1 Glossary Index Examples 10 1 Using the TRUNCATE Attribute 00 0 10 40 A 1 Using Program Sections to Allocate Storage A 9 Figures 3 1 Order of Execution for TO BEGIN DO and TO END DO SecLiOHS suos ka eu gore uq emer ERE TEES C EE ERE ES 3 5 7 1 Scope of Identifiers 0 0 ce ee eee 7 4 9 1 Sequential File Organization 0 200 000 ee uee 9 3 9 2 Relative File Organization 00 eee eee 9 4 9 3 Indexed File Organization llle 9 5 9 4 A First Alternate Key 0 0 0 0 ccc eens 9 6 9 5 File Buffer Contents llle 9 8 9 6 Sequential Access to a Sequential File 9 13 9 7 Using Sequential Access to Read from a Relative File 9 14 9 8 Using Sequential Access to Write to a Relative File 9 15 9 9 Using Random Access on Sequential and Relative Files
169. T predefined data type Section 2 4 5 2 4 1 2 ARRAY Constructors Array constructors are lists of values that you can use to specify an array value they have the following form component data type f component subrange OTHERWISE component value j component valuej data type Specifies the constructor s data type If you use the constructor in the executable section or in the CONST section a data type identifier is required Do not use a type identifier in initial state specifiers elsewhere in the declaration section or in nested constructors component component subrange Specifies an element number to which the component value applies You can specify a subrange of components Array elements do not have to be specified in order The component must be a compile time value or constant component value Specifies the value to be assigned to the array elements in the component list the value must be of the same data type as the array component type This value is a compile time value if you use the constructor in the executable section you can also use a run time value OTHERWISE Specifies a value to be assigned to all array elements that have not already been assigned values Data Types and Values 2 21 When using array constructors you must initialize all elements of the array you cannot partially initialize the array For example you can use either of these constructors to assign valu
170. TIONARY IF ELIF ENDIF DEFINED ERROR WARN INFO MESSAGE ARCH_NAME SYSTEM_NAME SYSTEM_VERSION DATE TIME COMPILER_VERSION LINE FILE ROUTINE MODULE IDENT Exponentiation operator REM operator AND_THEN and OR_ELSE operators NOT IN operator continued on next page Summary of HP Pascal Extensions B 1 Table B 1 Cont HP Pascal Extensions to Unextended Pascal Category Extension Predefined types Predeclared procedures Predeclared functions Type cast operator for variables and expressions Double quotation marks as string and character delimiters Escape sequences within double quotation marks radix specifier for binary hexadecimal and octal notation for integers radix specifier for integers in bases 2 to 36 inclusive Double and quadruple precision real numbers Dollar sign and underscore _ characters in identifiers Identifiers that can begin with the dollar sign or underscore characters Alphanumeric strings for labels Extended syntax for inclusion of nonprinting characters in single quoted character strings Compile time constant expressions allowed anywhere a constant is allowed Constructors of structured types used anywhere in place of a constant of the structured type Attributes used with data items routines and compilation units Relaxed rules for assignment compatibility Structural compatibility enforced between actual and formal para
171. TK operation has filled the file buffer GET FIND FINDK RESET and RESETK procedure calls that do not fill the file buffer due to the data not being present in the file set UFB to TRUE GET FIND FINDK RESET and RESETK procedure calls that could not examine the file leave UFB in an unknown state You must use the STATUS builtin to determine if the GET FIND FINDK RESET and RESETK procedure calls were able to examine the contents of the file UFB also returns TRUE after DELETE EXTEND LOCATE PUT REWRITE TRUNCATE and UPDATE procedures have left the contents of the file buffer unknown Assigning a new value to the file buffer with an assignment statement does not change the value of UFB Consider the following example FIND Supplies December IF NOT UFB Supplies THEN Inventory Inventory Supplies If the variable December has a value of 12 the FIND procedure attempts to find the twelfth component of the file Supplies If the FIND procedure is successful Supplies assumes the value of this component and UFB Supplies is FALSE If however the FIND procedure is unable to find the twelfth component of the file UFB Supplies returns TRUE In this example the value of Supplies is subtracted from the value of Inventory only if the FIND procedure is successful UNLOCK Procedure The UNLOCK procedure releases the current file component for access by other processes UNLOCK file variable ERROR error recovery
172. Table 2 7 Description of Implementation Features C 1 Default field widths Treatment See Section 9 6 The number of digits used to represent the exponent of a floating point number Treatment REAL SINGLE F floating and IEEE S floating 2 point format DOUBLE D floating 2 DOUBLE G floating and IEEE T floating point 3 format QUADRUPLE H floating and X floating 4 The value of the exponent character Explanation E The case upper or lower in which the Boolean values TRUE and FALSE are printed as output Explanation Uppercase that is TRUE and FALSE The effect of the PAGE procedure Treatment PAGE writes a line containing only the form feed character ASCII value 12 C 2 Implementation Dependent Features The unextended Pascal standard and the Extended Pascal standard list features that can vary from implementation to implementation It is illegal for a program to depend on these features HP Pascal does not detect when a program depends on any of these features Relying on them may yield incorrect results or unexpected program terminations Any or all of these implementation dependent features may change without notice For those items in this section that pertain to order of evaluation HP Pascal does not specify the order of evaluation Depending on several heuristics in the compiler the order of evaluation can be left to right right to left or random with complete or short circuit evaluation T
173. The bits are numbered from the right 0 through 127 as shown in Figure A 8 Figure A 8 X floating Point Data Representation 15 0 FRACTION FRACTION S EXPONENT 127 126 112 ZK 8078A GE An X floating point value is specified by its address A the address of the byte containing bit 0 The form of this value is sign magnitude as follows e Bit 127 is the sign bit e Bits 112 through 126 are an excess 16 383 binary exponent e Bits 0 through 111 are a normalized 112 bit fraction with the redundant most significant fraction bit not represented For More Information e On X_floating point range and precision Section 2 2 A 26 Data Storage and Representation A 3 3 Representation of Nonstatic Types and Variables This section describes the representation of nonstatic types and variables A 3 3 1 Representation of Nonstatic Types Each nonstatic data type has some storage associated with it called the control part Figure A 9 shows the layout of a control part of a nonstatic data type Figure A 9 Storage of Nonstatic Data Types 0 Actual Discriminant 1 Actual Discriminant n Additional Information ZK 1406A GE In the top portion of the control part HP Pascal stores each actual discriminant of the schema type in a longword of storage The additional information piece of the control part varies in content and size depending on the type specification and can contain any of the following e No information
174. UDEC function requires that the parameter x be less than or equal to the size of INTEGER32 Two optional integer parameters specify the length of the resulting string and the minimum number of significant digits to be returned If you specify a length that is too short to hold the converted value the resulting string is truncated on the left If you do not specify values for the optional parameters a default length and a default minimum number of significant digits is used If the size of the parameter x is greater than 32 the defaults are 21 characters for the length and 20 characters for the minimum number of digits Otherwise the defaults are 11 characters for the length and 10 characters for the minimum number of digits Consider the following example VAR Account INTEGER In the executable section Account 3 WRITELN UDEC Account Predeclared Functions and Procedures 8 45 For More Information e On conformant parameters Section 6 3 7 e On VARYING OF CHAR Section 2 6 2 8 96 UINT Function The UINT function converts the value of the parameter and returns its unsigned equivalent UINT x The parameter x must be of an ordinal type No error results if x is an integer and has a negative value The value returned is x MOD 2 32 For More Information e On range and support for the UNSIGNED data type Chapter 2 8 97 UINT64 Function The UINT64 function converts the value of the parameter and ret
175. UNC Function eee UTRUNCG64 Function 64664 tte Geb EEk v EESeU SO bs UXOR Function ears vx y OR RR RD RP Ee WALLCLOCK Function 0 000 cece hn WRITEV Procedure 0 0 0 eene XOR Function ZERO Function 8 35 8 36 8 36 8 37 8 38 8 38 8 38 8 39 8 39 8 39 8 40 8 40 8 40 8 41 8 42 8 42 8 42 8 43 8 43 8 44 8 44 8 44 8 44 8 44 8 45 8 46 8 46 8 46 8 47 8 47 8 48 8 49 8 49 8 50 8 50 8 50 8 51 8 51 8 51 8 52 8 53 9 Input and Output Processing 9 1 9 1 1 9 1 2 9 1 3 9 2 9 2 1 9 2 2 9 2 3 9 3 9 3 1 9 3 1 1 9 3 1 2 9 3 1 3 9 3 2 9 3 2 1 9 3 2 2 9 4 9 5 9 5 1 9 5 2 9 5 3 9 5 4 9 6 9 6 1 9 6 2 9 6 3 9 6 4 Files and File Organizations lese Sequential File Organization llle leen Relative File Organization 0 00 eee eee Indexed File Organization 000 eee ee eee Component Formats 0 0 cee eee eee eee Fixed Length Component Format s s Variable Length Component Format Stream Component Format llle Component Access Modes 000 cece lees Sequential Access cee eee es Sequential Access to Sequential Files Sequential Access to Relative Files Sequential Access to Indexed Files Random Access sees Random Access by Relative Component Numbers Direct
176. User_ Error_Message and the executable block of User_Error Storage for Local_ Variable is in SSDATA on OpenVMS I64 systems DATA on OpenVMS Alpha systems and LOCAL on OpenVMS VAX systems because it was referred to in a nested block Storage for Magic_Number is in the user created program section Magic Since Magic_ Number was declared with the READONLY attribute the program section has the NOEXE NOWRT RD and SHR properties A 2 4 Allocation Sizes of Variables For every HP Pascal data type the compiler calculates the allocation size required when a variable of the type occurs in either an unpacked or a packed context The unpacked size is always represented in bytes while the packed size is represented in bits The packed size of a variable is the minimum number of bits required to represent all values of the variable s type In general the compiler uses the following 32 bit rules to determine the allocation size for a component of a packed structured variable e Acomponent whose length is 32 bits or fewer is packed into as few bits as possible and can be unaligned A 10 Data Storage and Representation e A component whose length is greater than 32 bits is allocated the smallest number of bytes possible and must be at least byte aligned If one of the size attributes BIT BYTE WORD LONG QUAD or OCTA is applied to the variable the size specified by the attribute represents the variable s packed size Objects of floa
177. VAR Short String STRING 5 VALUE You can access the CAPACITY predeclared identifier as you would a schema discriminant and you can access the LENGTH and BODY predeclared identifiers as you would access fields of a record The CAPACITY identifier allows you to access the actual discriminant of the STRING schema the LENGTH identifier allows you to access the current length of the string object and the BODY identifier contains the current string object including whatever is in memory up to the capacity of the discriminated schema as shown in the following example VAR Stringl STRING 10 VALUE Wolf In the executable section WRITELN Stringl CAPACITY prints 10 WRITELN Stringl LENGTH prints 4 The value String1 BODY contains the four character string Wolf followed by whatever is currently stored in memory for the remaining six characters To determine the current length of a STRING variable you can use the LENGTH predeclared function The result of LENGTH String1 is the same as String1 LENGTH You can refer to individual STRING components as you would individual components of any array as follows Stringl 5 t 2 46 Data Types and Values The compiler does not pad remaining characters in the current string with blanks If you specify an index that is greater than the current length of the string an error occurs Consider the following example VAR Stringl STRING 10 VALUE
178. VARYING or on conformant array and conformant VARYING parameters e A DESCR formal parameter requires actual parameters to be passed with the by descriptor mechanism and interprets the semantics as 7 REF or REFERENCE does e A STDESCR formal parameter requires actual parameters to be passed with the by string descriptor mechanism An actual parameter variable of type PACKED ARRAY OF CHAR implies variable semantics An actual parameter expression of either type PACKED ARRAY OF CHAR or type VARYING OF CHAR implies foreign value semantics You cannot use STDESCR on formal procedure and function parameters Because the semantics are implicit in the mechanism a formal parameter cannot be declared with both the reserved word VAR and a mechanism specifier Also when passing an actual parameter to a formal foreign parameter the HP Pascal compiler checks for type compatibility when an external routine is called However at the time of the declaration a formal parameter passed by immediate value that does not represent a routine is checked to ensure that it can be stored in 64 or fewer bits or 32 or fewer bits depending on the platform A formal parameter passed by immediate value that does represent a routine must be declared with the UNBOUND attribute Special considerations arise when a function that has no formal parameters of its own or that has defaults that are being used for all its formal parameters is passed as a formal parame
179. VAX systems An automatic variable cannot have alignment greater than an octaword on OpenVMS 164 systems or a quadword on OpenVMS Alpha systems or a longword on OpenVMS VAX systems The minimum alignment for an object of a structured type is the greatest alignment specified for any of its components Alignment attributes are illegal on nonstatic types components of files and on VARYING OF CHAR strings The alignment of a formal VAR parameter cannot be greater than the alignment of a corresponding actual parameter either by default or by means of an alignment attribute In an array variable passed to a conformant formal parameter alignment and size attributes are illegal on all dimensions of the actual parameter except the first that correspond to the dimensions of the formal parameter On OpenVMS 164 systems the base type of a pointer variable passed to the NEW procedure cannot have alignment greater than an octaword On OpenVMS Alpha and OpenVMS VAX systems the base type of a pointer variable passed to the NEW procedure cannot have alignment greater than a quadword If the base type of a pointer variable has a specified alignment then the base type of a pointer expression assigned to it must have an alignment equal to that of the variable 10 6 Attributes e Pointer types are structurally compatible only if their base types have identical alignment The following is an example of the ALIGNED attribute VAR Free Buffe
180. You assign a key number from 0 to 254 to each key field of a file component with the KEY attribute The file is searched for the component with the lowest value in the specified key number This component becomes the current component in the file and is locked The value of the current component is copied into the file buffer EOF and UFB are set to FALSE If the component Input and Output Processing 9 59 9 8 19 does not exist EOF and UFB become TRUE Note that a RESETK procedure on key number 0 is equivalent to a RESET procedure Consider the following example RESETK Book Index 0 This procedure searches the file Book Index for the component with the lowest value in the primary key If this component exists it becomes the current file component and is locked The function calls UFB Book Index and EOF Book Index returns FALSE If the procedure was unable to find the component UFB Book Index and EOF Book Index return TRUE For More Information e On indexed files Section 9 1 3 e On random access by key Section 9 3 2 e On the UFB function Section 9 8 22 e On the error processing parameter Section 9 7 REWRITE Procedure The REWRITE procedure puts a file into generation mode in which it can be written REWRITE file variable file name ERROR error recovery file variable The name of the file variable associated with the output file file name String expression for the file name to b
181. a family of any size 6 20 Procedures and Functions In addition two conformant parameters are equivalent if they have indexes of the same ordinal type and components that either are compatible or are equivalent conformant parameters They must also have the same number of dimensions and both must be packed or unpacked 6 3 7 1 Conformant Array Parameters The syntax for a conformant array has the following form ARRAY lower bound identifier upper bound identifier attribute list index type identifier OF attribute list type identifier conformant parameter syntax PACKED ARRAY lower bound identifier upper bound identifier attribute list index type identifier OF attribute list type identifier lower bound identifier An identifier that represents the lower bound of the conformant array s index upper bound identifier An identifier that represents the upper bound of the conformant array s index attribute list One or more identifiers that provide additional information about the conformant array index type identifier The type identifier of the index which must denote an ordinal type type identifier The type identifier of the array components which can denote any type To specify the range and type of the index you must use type identifiers that represent predefined or user defined ordinal types The identifiers that represent the index bounds can be thought of as READONLY value parameters im
182. a given call to the function HP Pascal does not define the function result The following example shows the usage of RETURN Here a function searches through the array called Data for an element that matches Suitable When it finds one it assigns values to two global variables and executes a RETURN Omitting the RETURN statement would make the function continue processing it would assign values for the last suitable element instead of the first FUNCTION FindFirst StartingPoint INTEGER INTEGER VAR i INTEGER BEGIN FOR i StartingPoint TO MaximumNumber DO BEGIN IF Data i Suitable THEN BEGIN AttributesOfDesiredData Attributes il Subscript i RETURN i END END END For More Information e On the GOTO statement Section 5 8 Statements 5 11 5 13 WHILE Statement The WHILE statement is a loop that executes a statement while a specified condition is true A WHILE statement has the following form WHILE expression DO statement expression Any Boolean expression statement Any Pascal statement Pascal checks the value of the Boolean expression before executing the loop body for the first time if the expression is FALSE the loop body is not executed If the initial value is TRUE loop iterations continue until the condition is FALSE When specifying more than one statement as the loop body to a WHILE statement enclose the statements with the BEGIN and END reserved words since the syntax calls for a s
183. a torn ee 10 34 10 2 34 READONLY 212 2 m 342 240W9pBIS35395 2499590 3223 53 10 34 10 2 35 REFERENOE c sesoseirs erri errs Erns ERKI ERII EERI 10 36 10 2 36 sro MEC ee a Es aha ok ae 10 36 10 2 37 TRUNCATE eere ote oe nee ee ee os 10 37 10 2 38 UNALIGNED 6 5 3 RR od ee ORS RA E ON Edo ea mas 10 41 10 2 39 UNBOUND 0 0 0 ccc es 10 41 10 2 40 MINS AGH i 238 ds 6s ce aeoln alocst nner mS mars medina Sd Ai SU 10 42 10 2 41 VALUE ento eoe ven Gs Mavors a ep a ere eee 10 45 10 2 42 VOLATILE oeiee enta k haa eE exea ion pee Okra ane 10 46 10 2 43 WEAK EXTERNAL 0 0 0 0 ccc een 10 50 10 2 44 WEAK GLOBAL eee e 10 51 10 2 45 WORDS icy ieu a ee ets ee ee tears oe es 10 51 10 2 46 WRITEONEY 66 dvs wie 8 5 odes Wee OSS ere BE OR ERE 10 51 10 3 Attribute Classes 0 0 0 eee ens 10 52 Directives 11 1 PINCLUDE 2 aw 08S 2 eee Ee ek DTE RESUME S RES 11 1 11 2 DICTIONARY eee RR H9 eens 11 5 11 3 TITLE and SUBTITLE 0 0 0 0 000 cae 11 6 11 4 IF ELSE ELIF and ENDIF 11 6 11 5 DEFINED 54 ike REUTERS SR Eee LE E 11 8 11 6 ERROR 6eWARN INFO and MESSAGE 11 8 11 7 ARCH_NAME SYSTEM_NAME and SYSTEM_VERSION 0 cece ec ee hn 11 9 DATE TIME and COMPILER_VERSION 11 10 LINE FILE ZROUTINE MODULE and IDENT 11 10 xi A Data Storage and Representation A 1 A 1 1 A 1 2 A 2 A 2 1 A 2 2
184. about the variables Amount Total and Tax and about the procedures Glf and Calc If there are identifiers in a compilation unit that you do not want to be included in an environment file use the HIDDEN attribute When you compile program a which contains the INHERIT attribute HP Pascal uses the specified environment file to allow the program access to the data and routines declared in the module Variables that are inherited from an environment file are not newly created variables but are the same variables that were allocated storage by the declaring compilation unit A compilation unit may create only one environment file but may inherit multiple files that must have been created by earlier compilations Declarations from inherited files are not included in any environment files created by the compilation unit An environment file must have been created by a version of the compiler that is compatible with the version that is compiling the compilation unit The identifiers in the outermost level of the declaration section of a compilation unit and all inherited identifiers must be unique However HP Pascal allows the following exceptions to the redeclaration rules e A variable identifier can be multiply declared if all declarations of the variable have the same type and all but one declaration at most are external e A procedure identifier can be multiply declared if all declarations of the procedure have congruent parameter lists an
185. ach other by a period A relative path name begins with any generation other than CDD TOP and specifies the names of the descendants after that point You can create a relative path by establishing a default directory with a logical name NO LIST LIST default Indicates that the included declarations should be printed in the listing of the program if a listing is being generated If not specified the default is determined by compilation switches Use of this parameter overrides compilation switches For More Information e On using the Oracle CDD Repository with HP Pascal HP Pascal for OpenVMS User Manual Directives 11 5 11 3 TITLE and SUBTITLE TITLE and SUBTITLE allow you to specify a compile time string expression for the listing title and subtitle lines they have the following form TITLE character string SUBTITLE character string The compiler listing header includes the TITLE and SUBTITLE strings in the title and subtitle sections If you do not specify these directives HP Pascal fills the TITLE field with blanks and the first SUBTITLE field with source listing If a specified character string is too long to fit in the predefined title and subtitle sections the string will be truncated on the right without warning If a TITLE directive appears on the first line of a page it sets the title area for the current page and any following pages until the compiler encounters another 9 T
186. action bits Within the fraction bits of increasing significance are numbered 48 through 63 32 through 47 16 through 31 and 0 through 6 For More Information e On D_floating point range and precision Section 2 2 A 3 2 4 G floating Point Numbers A G_floating point value is represented by eight contiguous bytes The bits are numbered from the right 0 through 63 as shown in Figure A 5 Figure A 5 G_floating Point Data Representation 15 14 4 3 0 63 48 ZK 1041 GE A G floating point value is specified by its address A the address of the byte containing bit 0 The form of this value is sign magnitude as follows e Bit 15 is the sign bit e Bits 14 through 4 are an excess 1024 binary exponent e Bits 3 through 0 and 63 through 16 represent a normalized 53 bit fraction without the redundant most significant fraction bit Within the fraction bits of increasing significance go from 48 through 63 32 through 47 16 through 31 and 0 through 3 For More Information e On G floating point range and precision Section 2 2 Data Storage and Representation A 23 A 3 2 5 T floating Point Numbers A 3 2 6 A TT floating point value is represented by 8 contiguous bytes The bits are numbered from the right 0 through 63 as shown in Figure A 6 Figure A 6 T floating Point Data Representation 5 0 1 EXPONENT FRACTION 63 62 52 51 48 ZK 4976A GE A TT floating point value is specified by its address A the a
187. adecimal radix respectively You can use a radix specifier only when reading from a TEXT file error recovery The action to be taken if an error occurs during execution of the routine The file must be in inspection mode before READ is called The file remains in inspection mode after execution of a READ procedure The READ procedure for a nontext file performs an assignment statement a GET procedure and an UNLOCKprocedure for each variable Consider the following example This call to READ READ file variable variable identifier is equivalent to the following code variable identifier file variable GET file variable UNLOCK file variable The READ procedure reads from the file until it has found a value for each variable in the list The first value read is assigned to the first variable in the list the second value read is assigned to the second variable and so on The values and the variables must be of assignment compatible types Reading stops if an error occurs Input and Output Processing For a TEXT file more than one component character can be read into a single variable For example many characters can be read into a string or converted into a numeric variable The READ procedure repeats the assignment GET and UNLOCK process until it has read a sequence of characters that represent a legal value for the next variable in the parameter list The procedure continues to read components from t
188. after EOF has been executed EOF returns TRUE when the file pointer is positioned after the last component in the file and returns FALSE up to and including the time when the last component of the input file is read into the file buffer You must try to retrieve another file component after the last to determine whether the file is positioned at end of file When EOF is tested for a file with relative organization opened for direct access the result is TRUE if the file is in inspection mode and the last GET or RESET operation positioned the file beyond the last existing component If the file is in generation or undefined mode the result of EOF is undefined When EOF is tested for a file with indexed organization opened for keyed access the result is TRUE if the file is in inspection mode and the last FINDK GET RESET or RESETK operation positioned the file beyond the last component with the current key number Successful attempts at FINDK GET RESET and RESETK cause EOF to be FALSE If the file is not in inspection mode EOF is undefined If you try to read a file after EOF becomes TRUE an error results Input and Output Processing 9 33 Consider the following example Coupons 0 WHILE NOT EOF DO BEGIN READLN Coupon Amount Coupons Coupons Coupon Amount END This example calculates the total value of the coupons contained in the file INPUT The loop is performed while the EOF function returns FALSE For More I
189. al extensions to B 1 to B 4 Unextended Pascal standard 1 1 definition Glossary 13 NLOCK procedure 9 64 NOT function 8 47 npacked array copying from packed array 8 47 npacked variable allocation size of A 10 NPACK procedure 8 47 NSAFE attribute 10 42 effect on formal parameter 6 9 on actual parameter 6 9 NSIGNED16 type 2 3 NSIGNEDS32 type 2 3 NSIGNED64 type 2 3 NSIGNEDS type 2 3 NSIGNED type 2 2 2 3 allocation size of A 11 and overflows 4 3 default field width of 9 23 range of values 2 3 Index 20 UOR function 8 48 UPDATE procedure 9 65 UPPER function 8 49 UROUND64 function 8 50 UROUND function 8 49 User action function definition Glossary 13 User mode code compiler support of 8 28 UTRUNC64 function 8 50 UTRUNC function 8 50 UXOR function 8 51 V VALUE attribute 10 45 Value parameter actual 6 8 formal 6 8 VALUE section 3 9 initialization in 3 9 Value semantics 6 8 by foreign mechanism 6 16 for actual parameter 6 8 Variable alignment of A 16 allocation in common block A 7 allocation in program section A 7 allocation size A 10 control in FOR statement 5 6 declaring 3 9 dynamic 2 16 dynamic allocation of 8 29 dynamic disposal of 8 15 initializing 3 7 3 9 3 10 initial state specifier for 3 10 reference to 3 10 representation of nonstatic A 28 sharing 10 15 side effects on 4 14 10 47 size in byt
190. al allows the use of spaces and tabs to make the extended digit notation easier to read To use spaces and tabs enclose the extended digit in single quotation marks The following are integer values in the extended digit notation 2410000011 2 1000 0011 3241J 164 7FFF FFFF HP Pascal provides another extended integer convention only for the sake of compatibility with previous versions of the language The following are extended integer values in the HP Pascal specific notation b 1000 0011 0 7712 x DEC When HP Pascal processes an integer constant its type is based on its apparent value Table 2 5 and Table 2 6 describe the type that is chosen for the integer constant Data Types and Values 2 5 Table 2 5 Data Types for Integer Constants for OpenVMS 164 and OpenVMS Alpha Systems Range of Integer Values Data Type MAXINT64 MAXINT 1 INTEGER64 MAXINT MAXINT INTEGER MAXINT 1 MAXINT64 INTEGER64 MAXINT64 1 MAXUNSIGNED64 UNSIGNED64 Table 2 6 Data Types for Integer Constants for OpenVMS VAX Systems Range of Integer Values Data Type MAXINT MAXINT INTEGER MAXINT 1 MAXUNSIGNED UNSIGNED To force an INTEGER constant to become UNSIGNED INTEGER64 or UNSIGNED64 you can use the UINT INT64 or the UINT64 predeclared routines respectively To force an UNSIGNED constant to become INTEGER64 or UNSIGNED64 you can use the INT64 or UINT64 predeclared routines respectively
191. al part of the value and returns its unsigned equivalent UTRUNC x The parameter x must be of type REAL SINGLE DOUBLE or QUADRUPLE No error results if the value of x is negative or greater than 4 294 967 295 In that case the unsigned result is the truncated parameter value MOD 4 294 967 296 For More Information e On range and support of the UNSIGNED data type Chapter 2 UTRUNC64 Function The UTRUNC64 function converts the value of the parameter by truncating the fractional part of the value and returns its UNSIGNED64 equivalent UTRUNC64 x The parameter x must be of type REAL SINGLE DOUBLE or QUADRUPLE No error results if the value of x is negative or greater than MAXUNSIGNED64 In that case the unsigned result is the truncated parameter value MOD MAXUNSIGNED64 8 50 Predeclared Functions and Procedures 8 107 8 108 8 109 For More Information e On range and support of the UNSIGNED64 data type Chapter 2 UXOR Function The UXOR function returns an unsigned value of a binary logical exclusive OR operation on the corresponding pair of bits of two specified parameters UXOR u1 u2 The ul and u2 parameters must be unsigned Result UXOR 16 FF9 16 703 Returns 16 8FA For More Information e On specifying extended digit notation Section 2 1 1 1 WALLCLOCK Function The WALLCLOCK function returns an integer value representing the number of seconds since the boot time for the syste
192. algorithms the compiler applies to your program to make it execute faster or use less memory component A single data item in a file component access mode A method by which HP Pascal retrieves components from a file component format A file characteristic that determines the size or maximum size of each component and any processing information needed in addition to the data portion of the component condition handler A routine that is used to resolve an event usually an error that occurs during program execution and is detected by system hardware or software or by the logic in a user application program constant expression An expression that results in a value at the time you compile your program See also run time expression constructor A list of values surrounded by brackets used to assign values to structured objects such as arrays records and sets control part A data structure internal to HP Pascal that contains information used by the compiler to create and to access the data part of nonstatic types at run time See also data part and nonstatic type current component The file component that is currently located in the file buffer variable this is the only file component accessible to the program at a given time Glossary 3 data part A data structure that contains an object of a variable whose type is nonstatic HP Pascal usually accesses the data in the data part by accessing a pointer part
193. ameter returns an error recovery code if specified For More Information e On error recovery codes HP Pascal for OpenVMS User Manual 8 28 DISPOSE Procedure The DISPOSE procedure deallocates memory for a dynamic variable DISPOSE p t1 tn The parameter p is a pointer expression The t parameters are constant expressions that match the corresponding t parameter used in the call to the NEW procedure that allocated the memory If you use t parameters in a call to NEW you must specify the same t parameters in the call to DISPOSE If you allocated memory using d parameters just specify the pointer variable to the corresponding DISPOSE call The DISPOSE procedure deallocates the object to which the pointer variable points You cannot call DISPOSE more than once for the same dynamic variable Consider the following example DISPOSE Ptr Ptr is distroyed Ptr becomes undefined For More Information e On the pointer data types Section 2 3 e On the NEW procedure Section 8 60 Predeclared Functions and Procedures 8 15 8 29 EQ Function The EQ function returns a Boolean value that specifies if the parameters are equal according to the ASCII values of the strings characters EQ str1 str2 The parameters str1 and str2 must be character string expressions If the EQ function detects unequal string lengths it stops comparison and returns FALSE Consider the following example VAR Match BOOLEAN In the exe
194. an error occurs during execution of the routine The file can be in any mode before you call RESET a call to RESET sets the file to inspection mode If the file is an external file and is not already open RESET opens it using the same defaults as the OPEN procedure You cannot use RESET to create a file A call to RESET on a sequential file positions the file at the first component and the file buffer variable contains the value of this component If the file is not empty EOF and UFB return FALSE and the first component is locked to prevent access by other processes If the file is empty EOF and UFB return TRUE If the file does not exist RESET does not create it but returns an error at run time You must call RESET before reading any file with sequential organization except the predeclared file INPUT The RESET procedure removes the end of file marker from any file connected to a terminal device including INPUT which allows reading from the file to continue If you call RESET for the predeclared files OUTPUT or ERR an error occurs A call to RESET on a relative file opened for direct access positions the file at its first existing component A call to RESET on an indexed file opened for keyed access positions the file at the first component relative to the primary key Consider the following example VAR f FILE OF INTEGER In the executable section OPEN f file dat ACCESS METHOD DIRECT RESET f 9 58
195. an expression that is normally true If ASSERT evaluates the expression as false it signals a run time error indicating that the assertion failed The optional string parameter is output as part of the error message 8 10 BARRIER Function OpenVMS 164 and OpenVMS Alpha systems only The BARRIER procedure causes a memory barrier instruction to be emitted to synchronize pending memory updates in a multi processor environment BARRIER The BARRIER procedure has no parameters This routine is used to serialize memory writes on OpenVMS I64 and OpenVMS Alpha systems Predeclared Functions and Procedures 8 7 For More Information e On memory granularity HP Pascal for OpenVMS User Manual 8 11 BIN Function The BIN function returns a character string value that is the binary equivalent of the specified parameter The return value is compatible with all other string types BIN x length digits The parameter x is the expression to be converted This parameter must have a size that is known at compile time it cannot be VARYING OF CHAR a conformant parameter or a schema type Two optional integer parameters specify the length of the resulting string and the minimum number of significant digits to be returned If you specify a length that is too short to hold the converted value the resulting string is truncated on the left If you omit the optional parameters the bit width of the converted parameter value dete
196. appear at the beginning of the compilation unit and before a TYPE or VAR section When used before a TYPE or VAR section the default alignment packing and allocation rules are modified only for the duration of the TYPE or VAR section For example ALIGN VAX TYPE vax type Array 1 10 of char TYPE alpha type Array 1 10 of char 10 4 Attributes 10 2 2 Usage and Default Information Table 10 1 lists the keywords for the ALIGN attribute See Section A 2 7 for a complete description of the alignment rules for each platform and Section A 2 4 for a complete description of the allocated sizes for objects for each platform Table 10 1 ALIGN Attribute Keywords Keyword Action Default on System NATURAL Uses natural alignment when positioning OpenVMS I64 and record fields or array components OpenVMS Alpha Natural alignment is when a field or component is positioned on a boundary based on its size For example 32 bit integers would be aligned on the nearest 32 bit boundary VAX Uses byte alignment when positioning OpenVMS VAX record fields or array components Field or components larger than 32 bits are positioned on the nearest byte boundary IPrevious versions of HP Pascal used ALPHA_AXP for this keyword The NATURAL keyword is now the recommended spelling for the same behavior The ALPHA_AXP keyword will continue to be recognized for compatibility with old source files On OpenVMS VAX systems when y
197. aracters that are neither digits nor letters If a nonnumeric or nonalphabetic character is encountered in the file the counter Err is incremented by 1 The loop is executed until the last component in the file is read For More Information On TEXT files Section 9 5 9 8 5 EXTEND Procedure The EXTEND procedure opens an existing file positions the file buffer after the last component and prepares it for writing It is commonly used to append to a file EXTEND file variable fle name ERROR error recovery file variable The name of the file variable associated with the output file file name String expression for the file name to be associated with the file variable If the file is already open an error is signaled error recovery The action to be taken if an error occurs during execution of the routine The file can be in any mode before EXTEND is called to set the mode to generation If the file is an external file and is not already open EXTEND opens it using the defaults for the OPEN procedure After execution of EXTEND the file is positioned after the last component and EOF and UFB return TRUE If the file does not exist EXTEND does not create it but returns an error at run time Input and Output Processing 9 35 A call to EXTEND on a relative file opened for direct access positions the file after its last existing component A call to EXTEND on an indexed file opened for random access by key positio
198. aration if the variables are of the same type and are being initialized either with the same value or not at all Consider the following example TYPE Hours Worked ARRAY 1 10 OF INTEGER VAR Answer Rumor BOOLEAN Temp INTEGER VALUE 60 Grade i PES Weekly Hours Hours Worked VALUE 1 3 7 OTHERWISE 5 The following rules apply to the use of initial state specifiers on variables e You must initialize a variable with a constant expression of an assignment compatible type Scalar variables require scalar constants structured variables require constant constructors e You cannot initialize file variables or variables containing file components e You can use the predeclared function ZERO to initialize all or part of a variable except file variables and components to binary zero e The constant identifier NIL or a call to the ZERO function are the only values with which you can initialize a pointer variable 3 10 Declaration Section A reference to a variable consists of the variable s use in one of the following situations The variable or one of its components is passed as a VAR REF or DESCR parameter The reference lasts throughout the call to the corresponding routine The variable or one of its components is used on the left side of an assignment statement The reference lasts throughout the execution of the statement The variable or one of its components is accessed by a WITH statement The ref
199. arithmetic 8 1 ARRAY 2 19 to 2 22 BOOLEAN 2 8 CARDINAL 2 3 CHAR 2 7 definition Glossary 4 DOUBLE 2 11 enumerated 2 8 FILE 2 32 floating point formats 2 11 initial state specifier for 3 7 INTEGER 2 2 INTEGERI6 2 2 INTEGER32 2 2 INTEGER64 2 2 INTEGER8 2 2 INTEGER_ADDRESS 2 6 internal representation of A 19 nonstatic 2 48 ordinal 2 2 to 2 11 pointer 2 16 POINTER type 2 18 QUADRUPLE 2 11 REAL 2 11 to 2 15 Index 5 Data type cont d RECORD 2 22 SET 2 30 SINGLE 2 11 size in bytes 8 40 static 2 48 STRING 2 41 structured 2 18 subrange 2 9 UNSIGNED 2 3 UNSIGNED16 2 3 UNSIGNEDS32 2 3 UNSIGNED64 2 3 UNSIGNEDS 2 3 values assigned by ZERO function 8 53 VARYING OF CHAR 2 44 Date checking 11 10 DATE directive 11 10 DATE function 8 12 DATE procedure 8 13 DBLE function 8 13 DEC function 8 14 Decimal notation in output procedure 9 25 integer 2 2 real number 2 13 Declaration See also Definition function 6 1 label 3 2 procedure 6 1 variable 3 9 Declaration section 3 1 to 3 11 CONST 3 2 contents of 3 1 definition Glossary 4 FUNCTION 6 1 LABEL 3 2 PROCEDURE 6 1 TYPE 3 7 VALUE 3 9 VAR 3 9 Default parameter values 6 26 Index 6 DEFINED directive 11 8 Definition See also Declaration constant 3 2 label 3 2 type 3 7 Delayed device access definition Glossary 4 to TEXT files 9 20 DELETE procedure 9 32 DE
200. ased on the value of the d parameters If the object is a schema record type then you must use d parameters you cannot use t parameters or a combination of the syntaxes If the schema record type contains a variant which depends on one of the formal discriminants then the d parameter discriminates the schema determines the variant and allows HP Pascal to compute the necessary size of the allocation Note If you specify t parameters to the NEW procedure you must specify the same t parameters to the DISPOSE procedure that deallocates memory for the corresponding variable Consider the following examples TYPE Meat Type Fish Fowl Beef Beef Portion Oz 10 Oz 16 Oz 32 Var Record RECORD CASE Entree Meat Type OF Fish Fish Type Salmon Cod Perch Trout Lemon BOOLEAN Fowl Fowl Type Chicken Duck Goose Sauce Orange Cherry Raisin Beef Beef Type Steak Roast Prime Rib CASE size Beef Portion OF Oz 10 Oz 16 Beef Veg Pea Mixed Oz 32 Stomach Cure Bicarb Antacid None END The Schema Upper Bound INTEGER ARRAY 1 Upper Bound OF INTEGER 8 30 Predeclared Functions and Procedures VAR To Int INTEGER To Var Record Var Record To Schema The Schema Bound INTEGER VALUE 32 In the executable section NEW To Int Memory for To Int allocated but not initialized NEW To Var Record Fish
201. at references to field identifiers or to formal discriminants alone are unambiguous When you access a variable or one of its components using a WITH statement the reference syntax lasts throughout the execution of the statement Specifying more than one variable has the same effect as nesting WITH statements Consider the following example The record Dog is nested in the record Cat WITH Cat Dog DO Specify Cat before Dog Bills Bills Cat_Vet Dog Vet WITH Cat DO This is equivalent to the previous WITH WITH Dog DO Bills Bills Cat Vet Dog Vet Statements 5 13 If you are specifying nested records their variable names must appear in the order in which they were nested in the record type definition If you are working with record and schema variables that are not nested you can specify variable names in any order If you specify record or schema variables whose field names or formal discriminants conflict with one another Pascal uses the last record or schema in the comma list Consider the following example VAR x STRING 10 y STRING 15 In the executable section WITH x y DO WRITELN CAPACITY y CAPACITY is used The following is equivalent WITH x DO WITH y DO WRITELN CAPACITY For More Information e On records Section 2 4 2 e On schema types Section 2 5 5 14 Statements 6 Procedures and Functions This chapter discusses the following information about user defined
202. ata File TYPE Natural 0 MAXINT VAR Data_File FILE OF ARRAY 0 511 OF CHAR Int Array ARRAY 0 1023 OF INTEGER A String VARYING 2048 OF CHAR Chr Array ARRAY 0 4095 OF CHAR Status BOOLEAN 10 44 Attributes FUNCTION Put_Buf VAR Buffer UNSAFE ARRAY a b Natural OF CHAR BOOLEAN VAR Cur STATIC INTEGER VALUE 0 i INTEGER BEGIN FOR i a TO b DO BEGIN Data File Cur Bufferlil Cur is Cur 1 IF Cur gt 511 THEN BEGIN PUT Data File Cur s 0 In the executable section Status Put Buf Int Array Status Put Buf A String Status Put Buf Chr Array The function Put Buf assigns successive components of the conformant array parameter to the file buffer variable of Data File If Data File is filled the function returns TRUE otherwise it returns FALSE The program issues three calls to Put Buf In the first and second calls the actual parameters are not of the same type as the formal parameter Buffer However because Buffer has the UNSAFE attribute it accepts an actual parameter of any type and treats it as though it were an array of characters The third call to Put Buf passes an actual parameter of the same type as the formal parameter For More Information e On type compatibility Section 2 10 On machine representation of data Section A 3 10 2 41 VALUE The VALUE attribute causes the variable to be a reference to an external constant or to
203. ation If the file has indexed organization the components to be written must be ordered by the primary key Before executing the first PUT statement on a file opened for direct access you must execute an EXTEND REWRITE or LOCATE procedure to position the file The PUT procedure writes the value of the file buffer variable at the end of the specified sequential file or direct access file You can use LOCATE to position a direct access file and then use PUT to write the value of the file buffer variable at that position After execution of the PUT procedure the value of the file buffer variable becomes undefined UFB returns TRUE EOF remains TRUE and the file remains in generation mode 9 50 Input and Output Processing You can call the PUT procedure for a keyed access file regardless of the file s mode inspection generation or undefined PUT causes the file buffer variable to be written to the file at the position indicated by the key If the component has more than one key the file buffer variable is inserted in each index at the appropriate location After execution of PUT a keyed access file is in generation mode Consider the following example PROGRAM Book File INPUT OUTPUT Books TYPE My String PACKED ARRAY 1 40 OF CHAR Book Rec RECORD Author My String Title My String END VAR New Book Book Rec Books FILE OF Book Rec n INTEGER In the executable section REWRITE Books FOR n
204. ations are available across environments This chapter discusses the following topics e Section 9 1 Files and File Organizations e Section 9 2 Component Formats e Section 9 3 Component Access Modes e Section 9 4 File Locking e Section 9 5 TEXT Files e Section 9 6 Formatting Output e Section 9 7 Error Processing Parameter e Section 9 8 I O Routines For More Information e On environment specific I O details HP Pascal for OpenVMS User Manual and Appendix C 9 1 Files and File Organizations A file is an organized collection of logically related data items Data items within files are called file components The file organization defines the physical arrangement of the components within the physical file what types of access information are present in each component and how components may be accessed by a program The HP Pascal I O model includes three file organizations sequential relative and indexed Input and Output Processing 9 1 To open a file you can call the OPEN procedure Also you usually call one of the EXTEND RESET and REWRITE procedures to establish a starting position for reading from or writing to a file For relative and indexed file organizations you can use procedures to locate a specific component to access HP Pascal makes distinctions between permanent external files and temporary internal files An external file has a name in a directory and exists outside the context of an HP Pascal p
205. ay be supported on your system The foreign mechanism specifier IMMED REF DESCR or STDESCR precedes a formal parameter in the declaration of an external routine If the formal parameter does not represent a routine the mechanism specifier must precede the parameter name If the formal parameter represents a routine the specifier must precede the reserved word PROCEDURE or FUNCTION in the parameter declaration In addition it is possible to use the passing mechanism attributes IMMEDIATE or REFERENCE in a formal parameter s attribute list to obtain the same behavior as IMMED or REF respectively When calling an external routine you must make sure that you pass actual parameters by the mechanism stated or implied in the routine declaration HP Pascal allows you to use the foreign mechanism specifiers 7IMMED 7o REF DESCR and STDESCR before an actual parameter in a routine call Passing mechanism attributes are valid only on formal parameters When a mechanism specifier appears in a call it overrides the type semantics mechanism specified and even the number of parameters in the formal parameter declaration Type checking is suspended for the parameter association to which the specifier applies The passing of an expression to a foreign mechanism parameter implies foreign value semantics the calling block makes a copy of the actual parameter s value and passes this copy to the called routine The copy is not retained
206. ay parameter are outside the range specified by the conformant array s index type Explanation Detected at run time if bounds checking was enabled during compilation Compiler and Run Time System Error Detection D 7 Glossary actual discriminant The boundary or selector value that you specify in a schema type to form a valid data type actual parameter A value passed to a routine in the routine call alternate key A key value in components of a file of indexed organization from which HP Pascal provides an index into the file Your program can use an alternate key to provide another collating sequence order of access for the file components argument A name in the routine header that specifies information about the type size and passing mechanism of data that is expected to be passed to the routine as an actual parameter This term is synonymous with the term formal parameter array A group of components called elements that all have the same data type and share a common identifier atomic instruction An instruction that consists of one or more discrete operations that are handled by the hardware as a single operation without interruption Glossary 1 atomic operation An operation that cannot be interrupted by other system events such as an AST asynchronous system trap service routine an atomic operation appears to other processes to be a single operation Once an atomic operation starts it will eit
207. bal and external variables and routines must be identical e Global and external variables are implicitly static Thus they conflict with the AUTOMATIC attribute e Compilation units cannot have the EXTERNAL or WEAK_EXTERNAL attribute e By default global and external routines have the characteristics of unbound routines e External routines must be followed by the directive EXTERN EXTERNAL or FORTRAN when they are declared Consider the following example PROGRAM Freshman Class GLOBAL Sort Students PROCEDURE Class List VAR Register List Sorted List Student Rec Procedure body In another compilation unit MODULE Senior Class EXTERNAL Sort Students PROCEDURE Roll Call VAR Start List End List Senior Rec EXTERNAL 10 18 Attributes This example shows the global declaration of a procedure with the name Sort_Students and an external reference to the same procedure in a different compilation unit For More Information e On default visibility attribute information Section 10 2 25 e On the GLOBAL attribute Section 10 2 17 e On the AUTOMATIC attribute Section 10 2 5 e On the UNBOUND attribute Section 10 2 39 e On compiling and linking HP Pascal for OpenVMS User Manual 10 2 16 FLOAT The FLOAT attribute selects the default format for REAL and DOUBLE data types The FLOAT attribute has the following format FLOAT keyword You can specify the following keywords f
208. be the defining point of a global constant Attributes 10 45 Usage and Default Information e You can only use the VALUE attribute on a variable that has the EXTERNAL or GLOBAL attribute e A value variable with global visibility must be initialized in the VAR TYPE or VALUE declaration sections e You cannot apply the VALUE attribute to variables larger than 64 bits on OpenVMS 164 and OpenVMS Alpha systems or 32 bits on OpenVMS VAX systems e The VALUE attribute is legal only on ordinal or real types e The VALUE attribute causes the READONLY attribute to be placed on the variable In this example the linker resolves the reference to CLI _PRESENT the example writes the decimal value to OUTPUT The example also defines a global symbol with the name My_Global and with a value of 1985 PROGRAM Value Test OUTPUT VAR CLI PRESENT VALUE EXTERNAL INTEGER My Global VALUE GLOBAL INTEGER VALUE 1985 In the executable section WRITELN The value is CLI PRESENT For More Information e On the EXTERNAL attribute Section 10 2 15 e On the GLOBAL attribute Section 10 2 17 e On the READONLY attribute Section 10 2 34 10 2 42 VOLATILE The VOLATILE attribute indicates to the compiler that the value of an object is subject to change at unusual points in program execution Normally during execution an object s value changes only under the following circumstances e When another value is assigned to
209. ble is not assignment compatible with the type of the variable that is a parameter to a READ or READLN procedure Explanation Detected at run time The type of the expression being written by a WRITE or WRITELN procedure is not assignment compatible with the type of the file buffer variable Explanation Detected at run time The current variant does not exist in the list of variants specified with the NEW procedure Explanation Not detected The DISPOSE p procedure is called to deallocate a pointer variable that was created using the variant form of the NEW procedure Explanation Not detected The variant form of the DISPOSE procedure does not specify the disposal of the same number of variants that were created by the variant form of the NEW procedure Explanation Not detected The variant form of the DISPOSE procedure does not specify the disposal of the same variants that were created by the variant form of the NEW procedure Explanation Not detected The value of the parameter to the DISPOSE procedure is NIL Explanation Detected at run time Compiler and Run Time System Error Detection D 3 The value of the parameter to the DISPOSE procedure is undefined Explanation Not detected A variant record created by the NEW procedure is accessed as a whole rather than one component at a time Explanation Not detected In the PACK a i z procedure the type of the index value i is not assignment compatib
210. ble of any type except a component of a packed structured type A compile time warning results if x is a formal VAR parameter a component of a formal VAR parameter or a variable that does not have the READONLY or VOLATILE attribute 8 4 Predeclared Functions and Procedures A pointer can only refer to a VOLATILE variable or a variable allocated by the NEW procedure For More Information e Pointer data types Section 2 3 e On the VOLATILE attribute Section 10 2 42 e On the NEW procedure Section 8 60 8 5 AND ATOMIC Function OpenVMS 164 and OpenVMS Alpha systems only The AND_ATOMIC function logically ANDs the value of an expression to the value of a variable stores the newly computed value in the variable and returns the previous value of the variable AND ATOMIC e v The type of the expression e must be assignment compatible with that of the variable v The variable v must be an INTEGER UNSIGNED INTEGER64 or UNSIGNED64 variable and must be allocated on a natural boundary such as longword for INTEGER and UNSIGNED and quadword for INTERGER64 and UNSIGNED64 The result of AND ATOMIC is the same type as the variable V The AND ATOMIC function does not provide memory synchronization between multiple processors The BARRIER predeclared routine must be used for that purpose This function is used to access data that is shared between two or more threads of execution For More Information e On atomic operations H
211. cal bars on the command line In command format descriptions braces indicate required choices you must choose at least one of the items listed Do not type the braces on the command line Bold type represents the introduction of a new term It also represents the name of an argument an attribute or a reason Italic type indicates important information complete titles of manuals or variables Variables include information that varies in system output Internal error number in command lines PRODUCER name and in command parameters in text where dd represents the predefined code for the device type Uppercase type indicates a command the name of a routine the name of a file or the abbreviation for a system privilege A hyphen at the end of a command format description command line or code line indicates that the command or statement continues on the following line All numbers in text are assumed to be decimal unless otherwise noted Nondecimal radixes binary octal or hexadecimal are explicitly indicated 1 Language Elements HP Pascal is a general purpose programming language This chapter describes the following information and components of the HP Pascal language e Section 1 1 Pascal Language Standards e Section 1 2 Lexical Elements e Section 1 3 Comments e Section 1 4 Page Breaks and Form Feeds in Programs 1 1 Pascal Language Standards The HP Pascal compiler accepts programs that comply with
212. cal error messages HP Pascal for OpenVMS User Manual D 1 Error Message Information The type of an index value is not assignment compatible with the index type of an array Explanation Detected at run time if bounds checking was enabled during compilation The current variant changes while a reference to it exists Explanation Not detected An example of a reference to a variant is the passing of the variant to a formal VAR parameter The value of a variable to which a pointer refers p is NIL Explanation Usually detected at run time Always detected if pointers checking was enabled during compilation The value of a variable to which a pointer refers p is undefined Explanation Not detected Compiler and Run Time System Error Detection D 1 The DISPOSE procedure is called to dispose of a heap allocated variable while a reference to the variable exists Explanation Not detected Examples of such references are passing the variable or a component of it to a formal VAR parameter or using the variable in a WITH statement if the variable is a record The value of file f changes while a reference to f exists Explanation Not detected An example of a reference to f is the passing of f by reference to a routine until the routine has ceased execution you cannot perform any operation on file f The ordinal type of an actual parameter is not assignment compatible with the type of the corresponding formal paramete
213. cal name as a string of decimal digits If the environment variable or logical name has not been defined there is no default line limit You can override the default by calling the LINELIMIT procedure For More Information e On TEXT files Section 9 5 e On the error processing parameter Section 9 7 Input and Output Processing 9 8 10 LOCATE Procedure The LOCATE procedure positions a random access file at a particular component so that the next PUT procedure can modify that component LOCATE file variable component number ERROR error recovery file_variable The name of the file variable associated with the file to be positioned component number A positive integer expression that indicates the relative component number of the component to be found error recovery The action to be taken if an error occurs during execution of the routine The file can be in any mode before LOCATE is called The mode is set to generation after the procedure s execution The LOCATE procedure positions the file so that the next PUT procedure writes the contents of the file buffer into the selected component After LOCATE has been performed UFB returns TRUE and EOF is undefined Because the LOCATE procedure does not perform an I O operation the value returned by the STATUS procedure is unaffected by LOCATE Consider the following example LOCATE Accounts Receivable 63 Accounts Receivable Next Account PUT Accounts R
214. ce the component is unlocked and UFB returns TRUE Consider the following example UPDATE October Sales This procedure writes the file buffer contents October Sales back into the current file component October Sales The component is then unlocked and UFB October Sales returns TRUE Input and Output Processing 9 65 9 8 25 For More Information e On component access Section 9 3 e On the error processing parameter Section 9 7 WRITE Procedure The WRITE procedure assigns data to an output file WRITE file variable expression ERROR error recovery file variable The name of the file variable associated with the output file If you omit the name of the file the default is OUTPUT expression An expression whose value is to be written multiple output values must be separated with commas An output value must have the same type as the file components however values written to a TEXT file can also be expressions of any ordinal real or string type You can specify the output format of the expression as described in Section 9 6 error recovery The action to be taken if an error occurs during execution of the routine The file unless it is a random access by key file must be in generation mode before WRITE is called it remains in that mode after WRITE has executed By definition a WRITE statement to a nontext file performs an assignment to the file buffer variable and a PUT statement for each ou
215. cedure or function In HP Pascal you can use procedure call syntax to call a function even though function calls are usually considered to be expressions If you do this the compiler invokes the function but ignores the return value For More Information On procedures and functions Chapter 6 Statements 5 9 5 11 REPEAT Statement The REPEAT statement is a looping statement and executes one or more statements until a specified condition is true A REPEAT statement has the following form REPEAT statement UNTIL expression statement Any Pascal statement expression Any Boolean expression Pascal always executes a REPEAT statement for one iteration iterations continue as long as the Boolean expression is FALSE When specifying more than one statement as the loop body to a REPEAT statement do not enclose the statements with the BEGIN and END reserved words Multiple statements are legal in the REPEAT loop body Consider the following example REPEAT READ x Attempts to read at least one character IF x IN 0 9 THEN BEGIN Keep count of numbers and increase total Digit Count Digit Count 1 Digit Sum Digit Sum ORD x ORD 0 END ELSE Char Count Char Count 1 Count characters UNTIL EOLN INPUT Reads from default device until end of line For More Information e On Boolean expressions Section 2 1 3 5 12 RETURN Statement The RETURN statement passes control back
216. cedures and Functions 6 25 6 3 9 Default Formal Parameters HP Pascal allows you to supply default values for formal parameters Using default parameter values you do not need to pass actual parameters Also you can specify an actual parameter in the position of a formal parameter whose default value you want to override To specify a default value use the following format parameter spec mechanism specifier constant expression parameter spec The parameter specification The syntax for a parameter specification depends on its semantics mechanism specifier The mechanism by which HP Pascal associates a default value with a formal parameter You can only specify a mechanism specifier on a foreign routine constant expression A constant expression representing the default value for the formal parameter This default value plus the optional mechanism specifier must be a legal actual parameter for the kind of formal parameter with which the default is associated Table 6 4 shows when HP Pascal allows a default value Table 6 4 Default Values on Formal Parameters Formal Parameter Type External Routine HP Pascal Routine Variable Requires foreign Error mechanism specifier Value Allowed Allowed Routine Requires foreign Error mechanism specifier When you declare a formal parameter with a default value you can either omit it from the routine call or if you use positional syntax you can indicate its position with
217. cell You cannot overwrite a component but you can modify the contents of the current component If the cell with the next highest relative component number contains a component and if you are trying to store data in that cell you generate an error Input and Output Processing 9 13 Figure 9 7 shows the use of sequential access to read from a relative file Figure 9 7 Using Sequential Access to Read from a Relative File User Program System software Read next component ZK 1339A GE Figure 9 8 shows the use of sequential access to write to a relative file In this figure HP Pascal writes the component to the current cell If the program requests that another component be stored sequentially then HP Pascal places that component in cell 3 If the program places another request to store a component sequentially an error occurs because cell 4 contains component B 9 14 Input and Output Processing Figure 9 8 Using Sequential Access to Write to a Relative File System software Cell 1 start of file User Program Write component F to cell 2 Cell 2 now contains record F ZK 1340A GE 9 3 1 3 Sequential Access to Indexed Files When sequentially accessing an indexed file HP Pascal uses a specified index to determine the order in which to sequentially process the file components The specified keys are called the keys of reference If you specify ACCESS METHOD SEQUENTIAL when y
218. cise type When you use a negative integer as an exponent the exponentiation operation can yield unexpected results Table 4 2 shows the defined results of integers raised to the power of negative integers Table 4 2 Results of Negative Exponents Base Exponent Result 0 Negative or 0 Error 1 Negative 1 1 Negative and odd 1 1 Negative and even 1 Any other integer Negative 0 For example the expression 1 7 equals 1 C179 equals 1 1Y7 9 equals 1 and 3 7 equals 0 Expressions and Operators 4 3 The Operator You can use the division operator on integer unsigned real DOUBLE and QUADRUPLE operands The division operator always produces a real result This result can reflect in some loss of precision as the compiler converts integer and unsigned operands to their real equivalents With one or more operands of higher precision the result is of the higher precision type The DIV REM MOD Operators You can use the DIV REM and MOD operators only on integer and unsigned operands DIV divides one integer or unsigned operand by the other producing an integer or unsigned result DIV truncates toward zero any remaining fraction and does not round the result For example the expression 23 DIV 12 equals 1 and 5 DIV 3 equals 1 REM returns the remainder after dividing the first operand by the second Thus 5 REM 3 evaluates to 2 Similarly 3 REM 3 evaluates to 0 and 4 REM 3 evaluates to 1
219. cked arrays Section 2 4 8 15 BYTE OFFSET Function The BYTE OFFSET function returns an integer value that represents the byte position of a field in a record BYTE OFFSET t f The parameter t can be of any record type or variable and the parameter f can be any field contained in that record For More Information e On records Section 2 4 2 8 16 C STR Function The C STR function takes a compile time string expression and returns a C STR T pointer to a static string literal with a terminating null character C STR e The C STR function can also accept a Pascal variable of either PACKED ARRAY OF CHAR VARYING OF CHAR or STRING C STR v In this form it will return a C STR T value that represents the first character in the string variable It does not ensure a terminating null byte The programmer must handle the null termination to treat a Pascal string variable as a null terminated string 8 10 Predeclared Functions and Procedures 8 17 CARD Function The CARD function returns an integer value indicating the number of components that are currently elements of the set expression CARD s The parameter s must be a set expression For More Information e On sets Section 2 4 3 8 18 CHR Function The CHR function returns a char value whose ordinal value in the ASCII character set is the parameter provided such a character exists CHR x The parameter x must be integer or unsigned and have a value from 0
220. comes unavailable within the block in which you redeclared the word Table 1 5 Predeclared Identifiers ABS AND ATOMIC ARGUMENT LIST LENGTH BARRIER BITSIZE CARD CHAR C STR CREATE DIRECTORY D FLOAT ADD ATOMIC ARCTAN ARGV BIN BOOLEAN CARDINAL CHR C STR T DATE ADD INTERLOCKED ARGC ASSERT BIT OFFSET BYTE OFFSET CARDINAL16 CLEAR_INTERLOCKED CLOSE DBLE ADDRESS ARGUMENT BITNEXT CARDINAL32 CLOCK COS DEC continued on next page Language Elements 1 7 Table 1 5 Cont Predeclared Identifiers DELETE EOF EPSREAL EXPO F_FLOAT FIND_FIRST_BIT_SET G_FLOAT GT H_FLOAT IADDRESS INT INTEGER32 LE LOCATE MALLOC_C_STR MAXINT MIN NE OCT ORD PACK PAS_STRCPY PUT QUAD RANDOM REAL REVERT RSHIFT S_FLOAT 1 8 Language Elements DELETE_FILE EOLN EQ EXTEND FALSE FIND_MEMBER GE HALT IADDRESS64 INTEGER INTEGER64 LENGTH LOWER MAX MAXQUADRUPLE MINDOUBLE NEW ODD OUTPUT PAD POINTER QUADRUPLE READ RENAME_FILE REWRITE SEED DISPOSE EPSDOUBLE ESTABLISH FIND FIND_NONMEMBER GET HEX INDEX INTEGER8 INTEGER_ADDRESS LINELIMIT LSHIFT MAXCHAR MAXREAL MINQUADRUPLE NEXT OPEN PAGE PRED READLN RESET ROUND SET_INTERLOCKED DOUBLE EPSQUADRUPLE EXP FIND_FIRST_ BIT_CLEAR FINDK GETTIMESTAMP INPUT INTEGER16 LN LT MAXDOUBLE MAXUNSIGNED MINREAL NIL OR ATOMIC PAS STR PRESENT READV RESETK
221. compatibility is not enforced if the statement in the loop body can never be executed D 6 Compiler and Run Time System Error Detection In a FOR statement the type of the final value is not assignment compatible with the type of the control variable and the statement in the loop body is executed Explanation Detected at run time if subrange checking was enabled during compilation Assignment compatibility is not enforced if the statement in the loop body can never be executed When an integer is being read from a text file the digits read do not constitute a valid integer value Initial spaces and end of line markers are skipped Explanation Detected at run time When an integer is being read from a text file the type of the value read is not assignment compatible with the type of the variable Explanation Detected at run time if subrange checking was enabled during compilation When reading a real number from a text file the digits read do not constitute a valid real number Initial spaces and end of line markers are skipped Explanation Detected at run time The value of the file buffer variable is undefined when a READ or READLN procedure is performed Explanation Not detected A WRITE or WRITELN procedure specifies a field width in which the integers representing the total width and the number of fractional digits are less than 1 Explanation Not detected The bounds of an array passed to a conformant arr
222. covery Input and Output Processing 9 37 file_variable The name of the file variable associated with the file to be searched key number A positive integer expression that indicates the key position key value An expression that indicates the key to be found it must be assignment compatible with the key field in the specified key position match type An identifier that indicates the relationship between the key value in the FINDK procedure call and the key value of a component error recovery The action to be taken if an error occurs during execution of the routine When you establish key fields with the KEY attribute you assign each one a key number from 0 to 254 Key number 0 represents the mandatory primary key of the file Separate indexes are built for each key number in the file The key value and the match type provide information about the key to be found The key value must be assignment compatible with the key fields of the key number being searched The match type must be one of the following identifiers e EQL equal to the key value e NXT the next key in the collating sequence after the key value e NXTEQL the next or equal key in the collating sequence after the key value If the FINDK procedure was used on an ascending collating sequence NXT and NXTEQL would be equivalent to GTR and GEQ If a descending collating sequence was used it would be the same as LSS and LEQ The match type is optional if omitt
223. cter 1 4 Backspace character 1 4 BARRIER function 8 7 Base specifying in output 9 26 Base type definition Glossary 2 ofset 2 30 of subrange 2 9 BEGIN compound statement 5 4 Bell character 1 4 Binary nondecimal output of WRITE WRITELN and WRITEV 9 26 Binary notation 2 2 in output procedure 9 26 BIN function 8 8 in output procedure 9 26 BIT attribute 10 10 BITNEXT function 8 9 A 14 32 bit rules for storage allocation A 11 BITSIZE function 8 9 A 14 BIT OFFSET function 8 9 Block allocation of A 9 contents of 7 1 BOOLEAN type 2 8 allocation size of A 11 default field width of 9 23 reading from text file 9 53 Bound procedure value 10 41 BREAK statement 5 2 BSS program section A 2 Buffer increasing internal size 9 23 Buffers file buffers 9 9 Buffer variable 9 7 Built ins See Predeclared routines BYTE attribute 10 11 BYTE OFFSET function 8 10 C CARD function 8 11 Cardinality of set 8 11 CARDINAL type See UNSIGNED type Carriage control characters 9 19 OPEN parameter options 9 19 Carriage return character 1 4 Cascade definition Glossary 2 Case label 5 3 Case selector 5 3 checking 5 4 definition Glossary 2 CASE statement 5 3 case label 5 3 case selector 5 3 checking 10 11 examples 5 4 in records with variants 2 25 with OTHERWISE clause 5 4 CDD 11 5 Cells definition Glossary 2 definition of 9 3 Character
224. ctions or for a nested constructor Data Types and Values 2 35 component value Specifies a compile time value of the same data type as the component The compiler assigns the first value to the first record component the second value to the second record component and so forth tag value Specifies a value for the tag identifier of a variant record component The value that you specify as this component of the constructor determines the types and positions of the remaining component values according to the variant portion of the type definition An example of a record constructor is as follows TYPE Player Rec RECORD Wins INTEGER Losses INTEGER Percentage REAL VAR Playerl Player Rec 18 6 24 18 In the executable section constructor type is required Playerl Player Rec 18 6 24 18 The following is an example of a nested record constructor TYPE Team Rec RECORD Total Wins INTEGER Total Losses INTEGER Total Percentage REAL Playerl Player Rec Player2 Player Rec Player3 Player Rec END VAR Team Team Rec In the executable section Team Team Rec 18 3 18 21 6 0 1 0 5 2 5 1 T X 8 3 J The following is an example of a variant record constructor 2 36 Data Types and Values TYPE Orders RECORD Part 1 9999 CASE On Order BOOLEAN OF TRUE Order Quantity INTEGER Price REAL FALSE Rec Quantity INTEGER Cost REAL
225. cutable section Match EQ exit exit Returns FALSE unequal lengths Match EQ exit exit Returns TRUE For More Information e On string data types Section 2 6 8 30 ESTABLISH Procedure The ESTABLISH procedure specifies a condition handler that executes if your program generates operating system events ESTABLISH function identifier The function identifier parameter must be the name of a function that has the ASYNCHRONOUS attribute and must return an integer value For More Information e On the ASYNCHRONOUS attribute Section 10 2 3 e On error and report processing HP Pascal for OpenVMS User Manual 8 31 EXP Function The EXP function returns a real value that represents the exponent of the specified parameter it represents e EXP x The parameter x can be an integer or REAL type 8 16 Predeclared Functions and Procedures 8 32 EXPO Function The EXPO function returns the integer exponent of the floating point representation of the parameter EXPO x The parameter x can be of any real type For More Information e On precision and support for real numbers Chapter 2 8 33 FIND_FIRST_BIT_CLEAR Function The FIND_FIRST_BIT_CLEAR function locates the first bit in a Boolean array whose value is 0 and returns an integer value that specifies the index into the array FIND_FIRST_BIT_CLEAR vector start index The vector parameter is a variable of type P
226. d all but one declaration at most are external e A function identifier can be multiply declared if all declarations of the function have congruent parameter lists and identical result types and all but one declaration at most are external Consider the following example In one compilation unit ENVIRONMENT extern pen MODULE Mod1 EXTERNAL PROCEDURE Inst EXTERN END In another compilation unit INHERIT extern pen MODULE Mod2 GLOBAL PROCEDURE Inst Body END 7 8 Program Structure and Scope For More Information e On the ENVIRONMENT attribute Section 10 2 14 e On the INHERIT attribute Section 10 2 21 e On the HIDDEN attribute Section 10 2 18 e On declaration sections Chapter 3 7 5 2 Global and External Identifiers Global and external identifiers are accessible to other compilation units even to compilation units written in other languages that make up one executable unit The GLOBAL attribute allows a declared identifier to be globally accessible by other compilation units the EXTERNAL attribute specifies that another compilation unit allocates storage for the data or routine The compiler does not check to make sure that global and external identifiers are declared as being of the same data type you must ensure that the data types are compatible You cannot use global and external names to share the declarations of user defined types However you can use the VALUE attribute to share g
227. d use a VARYING OF CHAR conformant parameter VAR Short String VARYING 40 OF CHAR PAD 40 Long String VARYING 80 OF CHAR PAD 80 PROCEDURE Dashed Line VAR String VARYING Len OF CHAR Body MW In the executable section Dashed Line Short String Dashed Line Long String In this example note that Len is not a previously declared identifier but is instead an additional implicit parameter defined by the procedure declaration The upper bound of the conformant parameter String is established by the declared maximum length of the actual parameter passed to it when the procedure Dashed Line is called The first call to Dashed Line passes a 40 character string so Len has the value 40 The second call passes an 80 character string so Len has the value 80 For More Information On VARYING OF CHAR data types Section 2 6 2 e On attributes Chapter 10 Procedures and Functions 6 23 6 3 7 3 Conformant Parameter Sections When you specify more than one conformant parameter of the same type in a single parameter section there are additional programming considerations When using value semantics if you specify more that one formal parameter separated by commas of a single user defined conformant parameter the corresponding actual parameters must have either of the following characteristics e Equivalent current lengths in the case of passing a string expression to a conformant PA
228. ddress of the byte containing bit 0 The form of this value is sign magnitude as follows e Bit 63 is the sign bit 0 for positive numbers 1 for negative numbers e Bits 62 through 52 are an excess 127 exponent e Bits 51 through 0 are a normalized 53 bit fraction with the redundant most significant fraction bit not represented For More Information e On T floating point range and precision Section 2 2 H floating Point Numbers An H floating point value is represented by 16 contiguous bytes The bits are numbered from the right 0 through 127 as shown in Figure A 7 A 24 Data Storage and Representation Figure A 7 H floating Point Data Representation 15 14 0 27 1 112 ZK 1042 GE An H floating point value is specified by its address A the address of the byte containing bit 0 The form of this value is sign magnitude as follows e Bit 15 is the sign bit e Bits 14 through 0 are an excess 16 384 binary exponent e Bits 127 through 16 are a normalized 113 bit fraction with the redundant most significant fraction bit not represented Within the fraction bits of increasing significance go from 112 through 127 96 through 111 80 through 95 64 through 79 48 through 63 32 through 47 and 16 through 31 For More Information e On H_floating point range and precision Section 2 2 Data Storage and Representation A 25 A 3 2 7 X floating Point Numbers An X floating point value is represented by 16 contiguous bytes
229. declared Functions and Procedures For More Information e On data types Chapter 2 e On ordinal types Section 2 1 e On pointers Section 2 3 e On arrays and records Section 2 4 e On parameter lists Section 6 3 e On input and output routines Section 9 8 e On data storage Appendix A 8 1 ABS Function The ABS function returns a value of the same data type as the specified parameter that is the absolute value of the parameter ABS x The parameter x can be of any arithmetic type 8 2 ADD ATOMIC Function OpenVMS 164 and OpenVMS Alpha systems only The ADD ATOMIC function adds the value of an expression to the value of a variable stores the newly computed value in the variable and returns the previous value of the variable ADD ATOMIC e v The type of the expression e must be assignment compatible with that of the variable v The variable v must be an INTEGER UNSIGNED INTEGER64 or UNSIGNED variable and must be allocated on a natural boundary such as longword for INTEGER and UNSIGNED and quadword for INTEGER64 and UNSIGNED64 The result of ADD ATOMIC is the same type as the variable V Overflow and subrange checking are never performed on the ADD ATOMIC operation even if these options are in effect for the rest of the function or compilation unit The ADD ATOMIC function does not provide memory synchronization between multiple processors The BARRIER predeclared routine must be used for that purp
230. der the following example TYPE Sub Range a b INTEGER a b VAR x requires information in two control parts X ARRAY Sub Range i j Sub Range k 1 OF INTEGER Figure A 10 shows the layout for an object of a nonstatic type A 28 Data Storage and Representation Figure A 10 Storage of Variables of Nonstatic Types Pointer Part Data Part ZK 1407A GE In Figure A 10 the pointer part is directly accessible by your program The data part is allocated in heap when you use the NEW procedure For example TYPE dstr STRING I VAR ptr dstr In the executable section NEW ptr You cannot create variables of undiscriminated types but you can also show the representation for pointers to nonstatic types except undiscriminated schema Figure A 11 shows the layout for a pointer to an undiscriminated schema type Figure A 11 Storage of Pointer Variables to Undiscriminated Schema Types Control Part Pointer Part Data Part ZK 1408A GE Data Storage and Representation A 29 In Figure A 11 the control part and data part are allocated together by a call to the NEW procedure Each object allocated this way has its own control part since the base type of the pointer is undiscriminated and does not have a control part Consider the following example VAR X y Z STRING In the executable section NEW x 10 x has a control and data part y f X y points to same control and data
231. device button Return In examples a key name enclosed in a box indicates that you press a key on the keyboard In text a key name is not enclosed in a box In the HTML version of this document this convention appears as brackets rather than a box A horizontal ellipsis in examples indicates one of the following possibilities e Additional optional arguments in a statement have been omitted e The preceding item or items can be repeated one or more times e Additional parameters values or other information can be entered A vertical ellipsis indicates the omission of items from a code example or command format the items are omitted because they are not important to the topic being discussed xix U bold type italic type UPPERCASE TYPE numbers XX In command format descriptions parentheses indicate that you must enclose choices in parentheses if you specify more than one In command format descriptions brackets indicate optional choices You can choose one or more items or no items Do not type the brackets on the command line However you must include the brackets in the syntax for OpenVMS directory specifications and for a substring specification in an assignment statement In command format descriptions vertical bars separate choices within brackets or braces Within brackets the choices are optional within braces at least one choice is required Do not type the verti
232. dexed file organization A file organization in which each file component must contain a primary key and optionally alternate keys HP Pascal uses the primary key to store components and uses program specified keys to build indexes and to retrieve data See also key initial state specifier A constant expression used with the reserved word VALUE that initializes a variable a constant or a data type in the declaration section See also constant expression inspection mode A file state that indicates when input is being read from a file interface module A module that produces an environment file that contains data that is not likely to change and that provides access to more restricted data in an implementation module See also environment file and implementation module internal file A file temporarily contained in memory that has no name and is not retained after the program finishes execution item list A data structure that contains a sequence of control structures that provide input to a OpenVMS system service and that describes where the service should place its output An item list can have an arbitrary number of cells and is terminated with a longword of value 0 key or key field A value in a component of a file of indexed organization that HP Pascal uses to build indexes into the file Each key is identified by its location within the component its length and its data type See also alternate key index
233. dinal value of the character in the ASCII character set You can specify a nonprinting character such as a control character by writing an empty string followed immediately by the ordinal value of the character in the ASCII character set or by using the CHR function followed by the ordinal value of the character in the ASCII character set The following examples show the two ways to specify the bell control character ECT CHR 7 Data Types and Values 2 7 You can also specify certain nonprinting characters with syntax like that of the C programming language Enter the predefined constant for the character within double quotation marks For example to specify the line feed character enter Wan For More Information e On the ORD function Section 8 65 e On the CHR function Section 8 18 e On the ASCII character set Section 1 2 1 e On character strings Section 2 6 e On using escape sequences within double quotation marks for nonprinting characters Section 1 2 4 2 1 3 BOOLEAN Type Boolean values are the result of testing relationships for truth or validity The BOOLEAN data type consists of the two predeclared identifiers FALSE and TRUE The expression ORD FALSE results in the value 0 ORD TRUE returns the integer 1 The relational operators operate on the ordinal real string or set expressions and produce a Boolean result For More Information e On the ORD function Section 8 65 e On relational o
234. e Three String olleH Test Strings One String Two String Illegal Test Strings One String Three String Legal When using variable semantics if you specify more than one formal parameter separated by commas of an undiscriminated STRING type the corresponding discriminated STRING actual parameters must have an equivalent maximum length For More Information e On user defined schema types Section 2 5 e On the STRING predefined schema type Section 2 6 3 6 3 7 Conformant Parameters HP Pascal provides a method of processing arrays and character strings with potentially different maximum lengths To do this you can use conformant array parameters or conformant varying parameters A conformant parameter is a syntax that represents a set of types that are identical except for their bounds The bounds of a conformant parameter are determined each time a corresponding actual parameter is passed The bounds of an actual parameter are available within the routine through identifiers declared in the conformant parameter A conformant parameter can appear only within a formal parameter list You can use conformant parameters when declaring value variable and foreign mechanism parameters When you use a conformant parameter instead of a type identifier in a formal parameter declaration a call to the routine can provide static and nonstatic arrays VARYING OF CHAR strings and discriminated strings of the STRING schem
235. e end of the file using EXTEND The following are the HP Pascal I O routines that are used for sequential access EOF EXTEND GET PUT READ RESET REWRITE STATUS TRUNCATE UFB UNLOCK WRITE For More Information e On file organization Section 9 1 e On component format Section 9 2 9 12 Input and Output Processing 9 3 1 1 Sequential Access to Sequential Files To retrieve a component in a sequential file you must retrieve all components from the time you establish a current position using either EXTEND RESET or REWRITE to the desired component After an operation to the file HP Pascal positions the file pointer to the next file component in anticipation of the next operation on the file To access a previous component you must reopen implicitly or explicitly and reread the previous components or you can reopen the file switching to random access mode You cannot add components in between any two components You can add components only to the current end of the file Figure 9 6 shows sequential access to sequential files Figure 9 6 Sequential Access to a Sequential File User Program System software Read next component ZK 1338A GE 9 3 1 2 Sequential Access to Relative Files HP Pascal can use sequential access for relative files as long as the components are fixed length HP Pascal tries to store or retrieve from the cell whose relative component number is one higher than the most recently accessed
236. e result of the operation is either a string or a Boolean value Table 4 6 lists the string operators Table 4 6 String Operators Operator Example Result A B String that is the concatenation of strings A and B A B TRUE if strings A and B have equal ASCII values lt gt A lt gt B TRUE if strings A and B have unequal ASCII values lt A lt B TRUE if ASCII value of string A is less than that of string B lt A lt B TRUE if ASCII value of string A is less than or equal to that of string B gt A gt B TRUE if ASCII value of string A is greater than that of string B gt A gt B TRUE if ASCII value of string A is greater than or equal to that of string B With the plus sign you can concatenate any combination of STRING and VARYING character strings packed arrays of characters and single characters The result of a string comparison depends on the ordinal value in the ASCII character set of the corresponding characters in the strings For example motherhood gt cherry pie 4 8 Expressions and Operators This relational expression is TRUE because lowercase m comes after lowercase c in the ASCII character set If the first characters in the strings are the same Pascal searches for differing characters as in the following example stringl lt string2 This expression is TRUE because the digit 1 precedes the digit 2 in the ASCII character set The relational operators are
237. e 2 10 Cont Predefined Identifiers for Real Data Types Identifier Value Double Precision D_floating MINDOUBLE 2 938735877055719E 39 MAXDOUBLE 1 701411834604692E438 EPSDOUBLE 2 77557561562891K 17 OpenVMS VAX 2 22044604925031E 16 OpenVMS I64 and OpenVMS Alpha Double Precision G_floating MINDOUBLE 5 56268464626800E 309 MAXDOUBLE 8 98846567431158E 307 EPSDOUBLE 2 22044604925031E 016 IEEE Double Precision T floating MINDOUBLE 2 225077385850772014E 308 MAXDOUBLE 1 7976931348623157E 308 EPSDOUBLE 2 2204460492503131E 016 Quadruple Precision H floating MINQUADRUPLE 8 40525785778023376565669454330438H 4933 MAXQUADRUPLE 5 94865747678615882542879663314004E 4931 EPSQUADRUPLE 1 92592994438723585305597794258493E 0034 IEEE Quadruple Precision X_floating MINQUADRUPLE 3 36210314811209350626267781732175E 4932 MAXQUADRUPLE 1 1897314953572317765085 75932662801E 4932 EPSQUADRUPLE 9 629649 7219361792652 79889 11292464E 0035 For More Information e On operators Section 4 2 e On the internal representation of real numbers Section A 3 2 e On compilation switches HP Pascal for OpenVMS User Manual Data Types and Values 2 15 2 3 Pointer Types A pointer type allows you to refer to a dynamic variable Dynamic variables do not have lifetimes that are strictly related to the scope of a routine module or program you can create and eliminate them at various times during program execution
238. e ASCII values of the strings characters LT str1 str2 8 26 Predeclared Functions and Procedures The parameters str1 and str2 must be character string expressions HP Pascal does not pad shorter strings with blanks Consider the following example VAR Match BOOLEAN Test STRING 8 VALUE ENTRANCE In the executable section Match LT exit exit Returns FALSE Match LT Test EXIT N less than X Returns TRUE For More Information e On string data types Section 2 6 8 54 MALLOC C STR Function The MALLOC_C_STR function takes a Pascal string expression calls the C routine malloc to allocate memory initializes the memory with the string expression and then terminates the string with a null character MALLOC C STR e The type of the expression e must be a Pascal string expression The function result is a C STR T pointer to the null terminted string The amount of memory allocated with malloc is equal to the length of the string expression plus one The memory allocated with MALLOC C STR must be deallocated with the C free routine The compiler will not allow C STR T parameters with the NEW and DISPOSE routines 8 55 MAX Function The MAX function returns a value the same type as that of the parameters that is the maximum value of a specified list of parameters MAX x1 xn The parameters can be any arithmetic type but they must all be of the same type
239. e File FILE OF BOOLEAN File of TRUE and FALSE values Experiment Records FILE OF RECORD File of records Trial INTEGER To access Experiment Records Trial Temp Pressure INTEGER Yield Purity REAL END For More Information e On file organization Section 9 1 On component formats Section 9 2 On conditions that establish a variable reference Section 3 7 e On attributes Chapter 10 2 4 5 TEXT Type The TEXT predefined type is a file containing sequences of characters with special markers end of line and end of file added to the file Although each character of a TEXT file is one file component the end of line marker allows you to process the file line by line if you choose The TEXT type has the following form attribute list TEXT attribute list One or more identifiers that provide additional information about the file components For More Information e On the FILE type Section 2 4 4 e On TEXT files Section 9 5 e On INPUT OUTPUT and ERR identifiers Section 9 5 Data Types and Values 2 33 2 4 6 Nonstandard Constructors 2 4 6 1 As an option you can use another format for constructors that is provided as an HP Pascal extension HP Pascal retains this format only for compatibility with programs written for use with previous versions of this product Also you cannot use nonstandard constructors for variables of nonstatic types For all nonstandard constructors you place constan
240. e Information e On the VOLATILE attribute Section 10 2 42 e On the ADDRESS function Section 8 4 On the NEW procedure Section 8 60 8 22 Predeclared Functions and Procedures 8 43 IADDRESS64 Function The IADDRESS64 function returns an INTEGER64 value that refers to the address of either a constant or VOLATILE variable or parameter or a routine The IADDRESS64 function is otherwise identical to the IADDRESS function IADDRESS64 x The parameter x can be of any type except a component of a packed structured type For More Information e On the IADDRESS function Section 8 42 8 44 IN RANGE Function The IN RANGE function determines if a value is in the defined subrange IN RANGE expression lower expression upper expression The parameters must be expressions of the same ordinal type The function returns TRUE if x has a value that is in the range specified by lower expression and upper expression otherwise the function returns FALSE 8 45 INDEX Function The INDEX function searches a string for a specified substring and returns an integer value that either indicates the location of the substring or the status of the search INDEX string substring INDEX requires two character string expressions as parameters a string to be searched and a substring to be found The search ends as soon as the first occurrence of the substring is located e If the substring is found INDEX returns the string component that c
241. e OUTPUT by default to your terminal Enabling bounds checking causes the length of all character strings to be checked at run time for illegal operations Expressions and Operators 4 9 For More Information e On the BOOLEAN data types Section 2 1 3 e On string data types Section 2 6 e On the CHECK attribute and the BOUNDS option for run time character string checking Section 10 2 8 e On the EQ NE GE GT LE and LT routines Chapter 8 4 2 5 Set Operators A set operator forms the union intersection difference or exclusive OR of two sets compares two sets or tests an ordinal value for inclusion in a set Its result is either a set or a Boolean value Table 4 7 lists the set operators Table 4 7 Set Operators Operator Example Result A B Set that is the union of sets A and B A B Set that is the intersection of sets A and B A B Set of those elements of set A that are not also in set B A B TRUE if set A is equal to set B lt gt A lt gt B TRUE if set A is not equal to set B lt A lt B TRUE if set A is a subset of set B gt A gt B TRUE if set B is a subset of set A IN CINB TRUE if C is an element of set B NOT IN C NOT IN B TRUE if C is not an element of B Most set operators require both operands to be set expressions The IN and NOT IN operators however require an ordinal expression as the first operand and a set expression as the second operand The ordinal expression must be o
242. e On mechanism specifiers Section 6 3 5 e On conformant parameters Section 6 3 7 e On attributes Chapter 10 6 14 Procedures and Functions 6 3 4 Passing Predeclared Functions to Formal Function Parameters The following predeclared functions can be passed directly to formal function parameters ABS ARCTAN CHR CLOCK COS DBLE EOF EOLN EXP EXPO INT LN ODD ORD QUAD ROUND SIN SNGL SQR SQRT STATUS STATUSV TRUNC UAND UFB UINT UNDEFINED UNOT UOR UROUND UTRUNC UXOR For example program math output procedure a function f r real real begin writeln f 1 0 end begin a sin a cos end 6 3 5 Foreign Parameters When declaring an external routine one written in a language other than Pascal that is called by an HP Pascal routine you must specify not only the correct semantics but the correct mechanism as well To allow you to obtain these passing mechanisms HP Pascal provides foreign mechanism specifiers and the passing mechanism attributes Table 6 3 gives the method specifier or attribute used for each passing mechanism Table 6 3 Specifiers and Attributes for Passing Mechanisms Passing Mechanism Specifiers and Attributes By immediate value By reference By descriptor IMMED or IMMEDIATE 7c REF or REFERENCE DESCR or STDESCR Procedures and Functions 6 15 Note Depending on the environment in which you are programming not all passing mechanism specifiers m
243. e On the AND THEN and OR ELSE logical operators Section 4 2 3 4 2 Operators Pascal provides several classes of operators You can form complex expressions by using operators to combine constants constant identifiers variables and function designators Pascal also provides the assignment operator for use in assignment statements For More Information e On precedence of operators Section 4 2 7 e On assignment statements Section 5 1 4 2 1 Arithmetic Operators An arithmetic operator provides a formula for calculating a value 4 2 Expressions and Operators Table 4 1 lists the arithmetic operators that you can use in combination with numeric operands to perform an arithmetic operation Table 4 1 Arithmetic Operators Operator Example Result A B Sum of A and B A B B subtracted from A A B Product of A and B SUR A B A raised to the power of B A B A divided by B DIV A DIV B Result of A divided by B truncated toward zero REM A REM B Remainder of A divided by B MOD A MOD B MOD function of A with respect to B The Operators You can use addition subtraction multiplication and exponentiation operators on integer unsigned real DOUBLE and QUADRUPLE operands These operators produce a result of the same type as the values In exponentiation operations if the data types of the operands are not the same the operand of the less precise type is converted and the result is of the more pre
244. e associated with the file variable If the file is already open an error is signaled error recovery The action to be taken if an error occurs during execution of the routine The file can be in any mode before REWRITE is called to set the mode to generation If the file variable has not been opened REWRITE creates and opens it using the same defaults as the OPEN procedure The REWRITE procedure truncates sequential files to length zero and sets EOF and UFB to TRUE You can then write new components into the file with the PUT WRITE and WRITELN procedures WRITELN is defined only for text files After the file is open successive calls to REWRITE truncate the existing file to a length of zero 9 60 Input and Output Processing 9 8 20 To update an existing file with sequential organization you must either use the EXTEND procedure use the TRUNCATE procedure or copy the contents to another file specifying new values for the components you need to update When applied to a file with relative or indexed organization REWRITE deletes the contents of the file and sets the file position to the beginning of an empty file Consider the following example REWRITE Storms If the file variable Storms is already open this REWRITE procedure prepares the file for writing clears it of old data and sets the file position to the beginning of the file If Storms is not open a new version is created with the same defaults as for the OPEN p
245. e has the COMMON attribute 0n OpenVMS 164 and OpenVMS Alpha systems executable code and read only data are compiled into two separate program sections on OpenVMS VAX systems executable code and read only data can exist in the same program section The ABS and ABS program section properties are ABS NOEXE NORD NOWRT and NOSHR All other program sections except LIB INITIALIZE are position independent and relocatable all except those established by the COMMON attribute are concatenated and local Program sections established A 6 Data Storage and Representation by COMMON are overlaid and global The remaining properties are assigned as follows e The first time the compiler encounters the name of a particular program section including a common block it initializes the program section to be readable nonwritable shareable and nonexecutable Thus the program section s initial properties are LCL NOEXE NOWRT CON PIC RD REL and SHR e If storage for any writable object except common blocks on OpenVMS VAX is allocated in the same program section the program section instantly becomes writable and nonshareable Thus the program section s write property changes from NOWRT to WRT and its share property changes from SHR to NOSHR e On OpenVMS VAX if storage for a writable object in a common block is allocated in the same program section the program section becomes writable and retains the shareable property Thu
246. e input to the routine After calling the routine the value of the actual parameter remains unchanged Variable Used to allow access to the actual parameter If the rou tine makes changes to the value of the formal parameter the value of the actual parameter changes accordingly Routine Used to call another routine Foreign Used to call a routine written in another language At run time the formal parameter receives a value from the corresponding actual parameter which is located in the routine call The passing mechanism is the way in which the compiler passes the actual parameter value to the corresponding formal parameter Table 6 2 presents the parameter passing mechanisms supported by HP Pascal Table 6 2 Parameter Passing Mechanisms Mechanism Description By immediate value The information passed to the formal parameter is the data By reference The information passed to the formal parameter is the address of the data By descriptor The information passed to the formal parameter is the address of a descriptor of the data Note Depending on the environment in which you are programming not all passing mechanisms may be supported on your system Procedures and Functions 6 7 The actual parameter must be of the same data type and passing mechanism as the corresponding formal parameter HP Pascal uses the default passing mechanism for each actual parameter depending on its data type and formal defin
247. e newly computed value in the variable and returns the previous value of the variable OR ATOMIC e v 8 32 Predeclared Functions and Procedures The type of the expression e must be assignment compatible with that of the variable v The variable v must be an INTEGER UNSIGNED INTEGER64 or UNSIGNED64 variable and must be allocated on a natural boundary such as longword for INTEGER and UNSIGNED and quadword for INTEGER64 and UNSIGNED64 The result of OR ATOMIC is the same type as the variable v The OR ATOMIC function does not provide memory synchronization between multiple processors The BARRIER predeclared routine must be used for that purpose This function is used to access data that is shared between two or more threads of execution For More Information e On atomic operations HP Pascal for OpenVMS User Manual 8 65 ORD Function The ORD function returns an integer value that is the position of the parameter in the ordered sequence of values of the parameter s type ORD x The parameter x must be of an ordinal type Note that the ordinal value of an INTEGER object is the integer itself If x is of type UNSIGNED its value must not be greater than MAXINT 8 66 PACK Procedure The PACK procedure copies components of an unpacked array variable to a packed array variable PACK a i z The parameter a is an unpacked array The parameter i is a value to indicate the starting value of the index of a The param
248. e to fit in the field that you specify Pascal extends the field instead of removing digits and writing an incorrect number If you specify a field width that is larger than necessary Pascal prints blanks to the left of the number right justifying it If you try to write a value of an enumerated type a Boolean value a character or a string value in a field that is too narrow the value is truncated on the right The truncated identifier is not checked for uniqueness 9 6 2 Writing Real Numbers By default real numbers are written in exponential format Regardless of the real number s type output procedures always prefix the exponent with the letter E Each real number in exponential format is preceded by a blank or a minus sign and the value of the rightmost digit is rounded Consider the following example WRITELN Shoe Size If the value of Shoe_Size is 12 5 this procedure produces the following output 1 25000E 01 To write the value in decimal format you must specify a field width as in this example WRITELN Shoe Size 5 1 The first integer indicates that a minimum of five characters will be written The minimum includes the minus sign if needed and the decimal point The second integer specifies one digit to the right of the decimal point The resulting output is as follows 12 5 If the field specified is wider than necessary the value is written with leading blanks If you try to write a real value in a fi
249. e unpacked and packed sizes for variables of any type by using the predeclared functions BITNEXT BITSIZE NEXT and SIZE which require a parameter that is the name of either a type or a variable These functions return the following integer values e BITNEXT returns an integer value that indicates what the packed size would be for an array component of the type e BITSIZE returns an integer value that indicates what the packed size would be for a record field of the type e NEXT returns an integer value that indicates what the unpacked size would be for an array component of the type e SIZE returns an integer value that indicates what the unpacked size would be for a variable or record field of the type The maximum size for any variable is 22 bits A 14 Data Storage and Representation For More Information e On size attributes Chapter 10 e On predeclared functions Chapter 8 A 2 6 Allocation Size Examples The following examples show the effects of packing records and multidimen sional arrays at various levels Note Although packing records and arrays does save storage space and can be necessary for compatibility with other code note that accessing unaligned variables on an OpenVMS 164 or OpenVMS Alpha system takes many more instructions than accessing variables with natural alignment such as those in unpacked records and arrays Example 1 TYPE Internal Arr ARRAY 1 5 of 0 6 VAR Sampl Arr PA
250. ead of a conformant parameter or a type identifier a call to the routine provides actual parameters that are discriminated from the same schema type family However when using value semantics there are two exceptions e You cannot pass schema sets and schema subranges as value parameters since there is no assignment compatibility for undiscriminated sets and for undiscriminated subranges e You can pass a varying length string expression to a formal STRING parameter the actual parameter does not have to be of the STRING type Consider the following example TYPE Array Template lbnd hbnd INTEGER ARRAY lbnd hbnd OF INTEGER VAR Even Numbers Array Template 1 30 Odd Numbers Array Template 1 60 6 18 Procedures and Functions PROCEDURE Print Array Array To Print Array Template VAR i INTEGER BEGIN WRITELN The maximum number of elements is Array To Print hbnd WRITELN FOR I LOWER Array To Print TO UPPER Array To Print DO WRITELN Array To Print i END In the executable section Print Array Even Numbers Print Array Odd Numbers All passing mechanism specifiers and attributes REF IMMED DESCR STDSCR REFERENCE IMMEDIATE CLASS SJ CLASS A CLASS NCAJ are illegal on parameters of nonstatic types When you specify more than one formal schema parameter of the same schema type in a single parameter section there are additional programming cons
251. eceivable The LOCATE procedure positions the file Accounts Receivable before relative component number 63 The call UFB Accounts Receivable now returns TRUE and EOF Accounts Receivable is undefined The assignment statement loads the file buffer with the contents of file position 63 The PUT operation writes the file buffer into file component number 63 UFB Accounts Receivable remains TRUE For More Information e On relative files Section 9 1 2 On random access by relative component number Section 9 3 2 e On the UFB function Section 9 8 22 Input and Output Processing 9 43 e On the error processing parameter Section 9 7 9 8 11 MESSAGE Procedure The MESSAGE routine takes a list of expressions and writes them to the standard error file ERR By default the standard error file is bound to standard error The MESSAGE routine has the same result as WRITELN without a file_variable argument MESSAGE expression For More Information e On text files and standard input and output Section 9 5 9 8 12 OPEN Procedure The OPEN procedure opens a file and allows you to specify file characteristics using either positional or nonpositional syntax 1 OPEN file variable file name history record length access method record type carriage control organization disposition file sharing user_action default file name ERROR error recovery 2 OPEN FILE VARIABLE file var
252. ecifies error checking options that are to be enabled during program execution CHECK identifier An identifier specifies an option to be enabled If you omit the list of options all available positive options are enabled Table 10 2 presents the options that allow you to choose which aspects of a program should be checked The negations of an option disable checking for that option Attributes 10 11 Table 10 2 Summary of Checking Options Option Action Negation ALL Enables all forms of checking NONE BOUNDS Verifies that an index expression is NOBOUNDS CASE_SELECTORS DECLARATIONS OVERFLOW POINTERS SUBRANGE within the bounds of an array s index type and that character string sizes are compatible with the operations being performed and that schema types are compatible Verifies that the value of a case selector is contained in the corresponding case label list Verifies that schema definitions yield valid types and that uses of GOTO from one block to an enclosing block are correct Verifies that the result of an integer computation does not exceed the machine representation Verifies that the value of a pointer variable is not NIL Verifies that values assigned to variables of subrange types are within the subrange verifies that a set expression is assignment compatible with a set variable NOCASE_SELECTORS NODECLARATIONS NOOVERFLOW NOPOINTERS NOSUBRANGE Usage and
253. ed defaulting to generic Code for generic config SENDIF The following is an example of INFO IF Debug Mode STHEN INFO Building application with debug code inserted SENDIF The following is an example of 7 MESSAGE SIF DEBUG MODE THEN MESSAGE Debug mode is enabled ENDIF 11 7 SSARCH NAME 9eSYSTEM NAME and 9e SYSTEM VERSION ARCH_NAME returns a string containing IA64 Alpha or VAX depending on the architecture of the system on which the compilation is taking place SYSTEM_NAME returns a string containing OpenVMS SYSTEM_VERSION returns a string containing the value of SYI _VERSION from the GETSYI system service Directives 11 9 For example program example output begin writeln Program running on system name arch name Ssystem version end This example uses the IF directive to selectively provide declarations or code based on the architecture Sif sarch name Alpha then var handle integer 0 selif arch name IA64 then var handle integer64 0 tendif 11 8 DATE TIME and COMPILER VERSION DATE returns a string containing the date at the beginning point of the compilation TIME returns a string containing the time at the beginning point of the compilation COMPILER_VERSION returns a string containing the version string of the HP Pascal compiler performing the compilation 11 9 LINE FILE ROUTIN
254. ed it defaults to EQL The FINDK procedure can be called for any indexed file opened for keyed access regardless of the file s mode If the component described exists the file buffer is filled with that component UFB and EOF both become FALSE The mode is set to inspection and the component is automatically locked If no component is found to match the description UFB becomes TRUE and EOF is undefined The mode is set to undefined 9 38 Input and Output Processing Consider the following example FINDK Book Index 1 35 NXTEQL Assuming key number 1 is ascending this procedure searches the index for key number 1 in the file Book_Index until it finds the first component whose key value is greater than or equal to 35 If the component matching the description in the FINDK statement is found UFB Book Index and EOF Book Index return FALSE and the component is locked If the component cannot be found UFB Book Index returns TRUE and EOF Book Index is undefined Book Index must be an indexed file opened for keyed access For More Information e On indexed files Section 9 1 3 e On random access by key Section 9 3 2 e On the UFB function Section 9 8 22 e On the error processing parameter Section 9 7 9 8 8 GET Procedure The GET procedure advances the file position and reads the next component of the file into the file buffer variable If the file has relative or indexed organization the component is also l
255. effect on portable code 1 1 summary of B 1 to B 7 Extension to HP Pascal language definition Glossary 4 EXTERNAL attribute 10 18 External definitions LIST attribute 10 26 External file definition 9 2 Glossary 5 listed in heading 7 6 EXTERNAL identifier 6 3 External identifiers sharing of 7 9 External routine passing mechanisms for 6 15 to 6 18 EXTERN identifier 6 3 F Field definition Glossary 5 of record 2 22 position of in record 10 32 width of 9 23 Field width overflow 9 25 specifying in output 9 25 File access 9 11 carriage control in 9 19 closing 9 31 component format 9 7 9 9 components in 9 1 Index 8 File cont d default organization in OPEN procedure 9 2 definition 9 1 Glossary 5 external 9 2 internal 9 2 listed in heading 7 6 locking 9 17 mode 9 29 opening 9 44 preparing for input 9 39 procedure for deleting 8 15 procedure for renaming 8 38 TEXT 9 18 File buffer dereferencing the variable 9 7 undefined 9 63 variable 9 7 File component adding to sequential file 9 3 definition of 9 1 FILE directive 11 10 File levels nesting in INCLUDE 11 3 File locking 9 17 File organization definition 9 1 indexed 9 4 relative 9 3 sequential 9 2 Files file buffers 9 9 File type allocation size of A 11 FILE type 2 32 examples 2 33 FINDK procedure 9 37 FIND procedure 9 36 FIND FIRST BIT CLEAR
256. efinition in a TYPE section the item is later declared to be of that type e By appearing in the declaration of an item preceding its type 10 2 Attributes By appearing before the current declaration section Note In HP Pascal the presence of constant expressions and attribute lists leads to a minor ambiguity in the language syntax If the compiler finds a left bracket symbol when it expects to find a type or type identifier it always assumes that the bracket indicates the beginning of an attribute list The ambiguity arises because the left bracket could also represent the beginning of a set constructor that denotes the low bound of a subrange type If the latter case is in fact what you intend enclose the set constructor in parentheses the compiler will interpret the expression correctly For example TYPE X 1 lt 2 True When a type definition includes a list of attributes the type has only those attributes specified The compiler does not supply the defaults for the unspecified classes until a data item is declared to be of that type Two rules govern the use of attributes in a TYPE section The attributes of the type can neither conflict with nor duplicate any attributes explicitly stated in the data item s declaration The type cannot be used anyplace where its accompanying attributes are illegal The following example shows both legal and illegal use of attributes in type definitions TYPE
257. egardless of the results of heuristics that are normally used to automatically determine if a routine is to be inlined There are cases where a routine that is marked as INLINE preferred will not be inline expanded such as routines that have formal parameters of nonstatic types or that declare or access nonstatic types e Ifno OPTIMIZE attribute is specified for a routine in a nested scope the OPTIMIZE attribute settings from the enclosing routine are used 10 30 Attributes Usage and Default Information on OpenVMS 164 and OpenVMS Alpha systems only e f the OPTIMIZE attribute is used on a routine on OpenVMS 164 or OpenVMS Alpha systems only the INLINE and NOINLINE keywords are processed The other forms of the OPTIMIZE attribute are parsed but perform no function You cannot modifiy the optimization settings of individual routines on these systems Usage and Default Information on OpenVMS VAX systems only e On OpenVMS VAX systems if an explicit OPTIMIZE INLINE attribute exists on a routine declaration the compiler checks for anything that prohibits inline expansion of the routine such as it being an external routine However the compiler does not check the call environment such as the size of the calling and called routine Instead if it is legal to expand the routine it always expands the code regardless of the call environment This gives you more control over the decision to inline a routine e On OpenVMS VAX systems HP
258. eld that is too narrow the field width is expanded to the minimum necessary to write the value Input and Output Processing 9 25 9 6 3 Explicitly Specifying the Base To write integers in a base other than decimal supply the second run time expression which specifies the base or radix integer expression fieldwidth radix radix Any run time integer expression with a value from 2 through 36 inclusive If you specify a base greater than 10 letters A through Z denote the extra digits For example when you output in hexadecimal base 16 the characters A through F are the extra six digits If the integer expression denotes a negative number a leading minus sign is printed and the absolute value of the expression is converted into the selected radix 9 6 4 Specifying the Base with Predeclared Conversion Functions You can use the predeclared conversion functions BIN DEC UDEC HEX and OCT in combination with the WRITE WRITELN and WRITEV procedures to write binary decimal unsigned decimal hexadecimal and octal values The DEC and UDEC functions return values with leading zeros by default the T O routines use leading blank with decimal numbers not leading zeros The syntax is BIN DEC WRITE file variable 4 UDEC expression length digits HEX OCT The predeclared conversion functions convert the value of the first expression in the list to its equivalent as a binary decimal unsigned decima
259. ent that has the next higher key value in descending order the component with next lower key value e Generic match of key values Generic matching is applicable to string data type keys only PACKED ARRAY OF CHAR record fields For a generic match the program need specify only a match of some specified number of leading characters in the key e Combination of approximate and generic match 9 4 File Locking Under some circumstances if a file component is in the process of being read or written to by one program HP Pascal locks the component preventing other programs from accessing the component This prevents programs from accessing outdated or inaccurate data If you OPEN a file and specify that the file is not to be shared or that reading or writing sharing is allowed HP Pascal may not lock the record Input and Output Processing 9 17 Record locking occurs most often when accessing relative and indexed files but it can happen when accessing sequential files as well Successful calls to FIND FINDK GET RESET and RESETK lock the current component If you want to make a locked file component available to other programs on the system you can call the UNLOCK procedure For More Information e On enabling other programs to access new files created with OPEN Section 9 8 12 e On unlocking components Section 9 8 23 9 5 TEXT Files Files of type TEXT are sequences of characters with special markers end of line and
260. ents e In the set expression form Pascal checks to see if the set expression is not the empty set If this condition is met the control variable takes on the value of one of the members of the set Iterations occur for each member of the set the selection order of members of the set is undefined Looping stops after the loop body executes for each member of the set In both the TO and the DOWNTO forms how the control variable increments or decrements depends on its type For example values expressed in type INTEGER increment or decrement in units of 1 Values expressed in type CHAR increment or decrement in accordance with the ASCII collating sequence After normal termination of the FOR statement the control variable does not retain a value You must assign a new value to this variable before you use it elsewhere in the program If the FOR loop terminates with a GOTO statement the control variable retains the last assigned value In this case you can use the variable again without assigning a new value Consider the following examples FOR Year 1899 DOWNTO 1801 DO Print leap years in 1800 s IF Year MOD 4 0 THEN WRITELN Year 4 is a leap year FOR I IN Setl DO Set2 members are successors of Set1 members Set2 Set2 I 1 For More Information e On ordinal values Section 2 1 e On sets Section 2 4 3 5 8 GOTO Statement The GOTO statement causes an unconditional branch to a statement prefixed by
261. er or variable of an ordinal SET or ARRAY type The parameter n is an integer constant that denotes a dimension of x if x is an array If x is an array and if you omit the parameter n HP Pascal uses the default value 1 If x is an array LOWER returns the lower bound of the nth dimension of x If x is an ordinal type LOWER returns the lower bound or smallest value If x is a SET LOWER returns the lower bound of the SET base type For More Information e On the LOWER function Section 8 102 8 52 LSHIFT Function The LSHIFT predeclared function returns a value of the same type as its first parameter The return value represents the value of the first parameter after the bits have been shifted to the left LSHIFT expression expression The parameters are two integer or unsigned values The first parameter represents a value to shift the second represents the number of bits to shift the first value to the left LSHIFT inserts zero bits on the right as the bits shift left Note that shifting integers is not equivalent to multiplying or dividing by a power of two when the value of the integer is negative If the number of bits shifted is larger than the natural integer size of the target platform the result is undefined For More Information e On the RSHIFT function Section 8 79 8 53 LT Function The LT function returns a Boolean value that specifies if the first parameter is less than the second parameter according to th
262. er variable On OpenVMS I64 and OpenVMS Alpha systems if the pointer type was declared with the QUAD attribute the NEW procedure allocates memory from the 64 bit process address space p2 space The parameters t1 tn are constant expressions of an ordinal type that represent nested tag field values where t1 is the outermost variant If the object of the pointer is a non schema record type with variants then you have two ways of allocating memory If you do not specify t parameters HP Pascal allocates enough memory to hold any of the variants of the record If you do specify t parameters then HP Pascal allocates enough memory to hold only the variant or variants that you specify Predeclared Functions and Procedures 8 29 Since the t parameters cause HP Pascal to allocate memory for the variant alone and not for the whole record you cannot assign or evaluate the record as a whole you can assign and evaluate only the individual fields Also a call to NEW sets the tag fields of a variant record The parameters d1 dn are compile time or run time ordinal values that must be the same type as the formal discriminants of the object If the object of the pointer is of an undiscriminated schema type you must specify a d parameter for each of the formal discriminants of the schema type The d parameters discriminate the schema type in much the same way as actual discriminants in a discriminated schema The size of the allocation is b
263. erence lasts throughout the execution of the statement The existence of a variable reference sometimes prohibits certain operations from being performed on the variable Such restrictions are noted throughout this manual For More Information On constructors Section 2 4 On data types Chapter 2 On attributes Chapter 10 On the ZERO function Section 8 111 On pointers and NIL Section 2 3 On the assignment and WITH statements Chapter 5 Declaration Section 3 11 4 Expressions and Operators This chapter discusses the following topics e Section 4 1 Expressions e Section 4 2 Operators e Section 4 3 Structured Function Return Values e Section 4 4 Type Conversions 4 1 Expressions Pascal expressions consist of one or more operands that result in a single value If the expression contains more than one operand the operands are separated by operators Operands include numbers strings constants variables and function designators Operators include arithmetic relational logical string set and typecast operators Pascal recognizes two forms of expressions constant expressions and run time expressions Constant expressions result in a value at the time you compile your program These expressions can contain constants constant identifiers operators and some predeclared functions Constant expressions cannot contain the following e Variable references e Schema discriminants e Bound identifiers from
264. es 8 40 HALT Procedure The HALT procedure uses operating system resources to stop execution of your program unless you have written a condition handler using the ESTABLISH procedure that enables continued execution For More Information e On the ESTABLISH procedure Section 8 30 8 41 HEX Function The HEX function returns a character string value that is the hexadecimal equivalent of the specified parameter The return value is compatible with all other string types HEX x length digits The parameter x is the expression to be converted This parameter must have a size that is known at compile time it cannot be VARYING OF CHAR a conformant parameter or a schema type Two optional integer parameters specify the length of the resulting string and the minimum number of significant digits to be returned If you specify a length that is too short to hold the converted value the resulting string is truncated on the left If you do not specify values for the optional parameters a default length and a default number of significant digits is used By default the number of significant digits is the minimum number of characters necessary to express all the bits of the converted parameter This default length is one character more than the default number of digits which causes a leading blank to be included in the resulting string when both parameters are omitted Consider the following example VAR p Rec In the
265. es 8 40 storage allocation A 7 A 11 Variable length component format 9 10 definition Glossary 13 Variable parameter actual 6 11 formal 6 10 Variables use of files 9 9 Variable semantics 6 10 by foreign mechanism 6 16 for actual parameter 6 11 Variant record 2 24 constructor 2 29 VAR section 3 9 initialization in 3 7 3 10 VARYING OF CHAR type 2 44 allocation size of A 11 bounds checking for 10 11 reading from text file 9 54 representation of A 19 VARYING string conformant 6 22 Version checking 11 10 Vertical tab character 1 4 VEST definition Glossary 13 Visibility attributes effect on allocation of variables A 7 VOLATILE attribute 10 46 effect on allocation A 8 W WALLCLOCK function 8 51 WARN directive 11 8 WEAK EXTERNAL attribute 10 50 WEAK GLOBAL attribute 10 51 WHILE statement 5 12 CONTINUE in 5 5 WITH statement 5 13 specifying nested records 5 13 WORD attribute 10 51 WRITELN procedure 9 67 default field width for types 9 23 nondecimal notation 9 26 using predeclared conversion functions 9 26 WRITEONLY attribute 10 51 WRITE procedure 9 66 default buffer size 9 23 default field width for types 9 23 nondecimal notation 9 26 using predeclared conversion functions 9 26 WRITEV procedure 8 51 default field width for types 9 23 nondecimal notation 9 26 status of 8 42 using predeclared conversion functions 9 26 Wr
266. es to the array variable VAR Numbers Count VALUE 1 3 5 1 4 6 2 7 9 3 10 6 In the executable section constructor type is required Numbers Count 1 3 5 1 4 6 2 7 9 3 10 x 3 These constructors give the first second third and fifth component the value 1 the fourth and sixth component the value 2 and the seventh eighth and ninth components the value 3 The first constructor gives the tenth component the value 6 the second constructor since it is in the executable section can assign the run time value x 3 to the tenth component To specify values for all remaining elements you can use the OTHERWISE clause as follows Numbers Count 4 6 2 7 9 3 10 x43 OTHERWISE 1 When you specify constructors for multidimensional arrays in the executable section only specify the type of the outermost array Consider the following example TYPE One Dimension ARRAY 1 3 OF CHAR Matrix ARRAY a b OF One Dimension VAR Tic Tac Toe Matrix In the executable section Tic Tac Toe Matrix 1 3 OTHERWISE 2 ck Mende a Eos OE For More Information e On nonstandard array constructors Section 2 4 6 1 2 4 2 RECORD Types A record is a group of components called fields that can be of various data types Each record component can contain one or more data items including embedded records The record type has the following from PACKED RECORD field list
267. eter z is a packed array of the same component type as a The number of components in parameter a must be greater than or equal to the number of components in z This procedure assigns the components of a starting with ali to the array z starting with z low bound until all the components in z are filled Predeclared Functions and Procedures 8 33 In general when specifying i keep in mind that the upper bound of a that is n must be greater than or equal to i v u where v is the upper bound of z and u is the lower bound of z That is ORD n must be greater than or equal to ORD i ORD v ORD u Consider the following example VAR a ARRAY 1 25 OF 0 15 p PACKED ARRAY 1 20 OF 0 15 i INTEGER In the executable section FOR i 1 TO 20 DO READ ali PACK a 5 p fa 1 through a 4 are not used PACK a 1 p a 21 through a 25 are not used For More Information e On arrays and packed arrays Section 2 4 8 67 PAD Function The PAD function returns a character string value of the specified size that contains padded fill characters The return value is compatible with all other string types PAD str fill size The parameter str is a character string value to be padded the parameter fill is a value of type CHAR to be used as the fill character and the parameter size is an integer value indicating the size of the final string This string is composed of the original string f
268. every component of the array as specified in the declaration Consider the following example VAR States PACKED ARRAY 1 20 OF CHAR VALUE Hello Is legal States PACKED ARRAY 1 20 OF CHAR VALUE 1 H 2 e 3 1 4 1 5 0 Generates an error States PACKED ARRAY 1 20 OF CHAR VALUE 1 H 2 6 3 1 4 1 5 0 OTHERWISE Is legal but awkward Data Types and Values 2 43 For More Information e On arrays Section 2 4 1 2 6 2 VARYING OF CHAR Types The VARYING OF CHAR user defined types are an HP Pascal extension that provides a way of declaring variable length character strings with a constant maximum length If you require portable code use the STRING predefined schema types to specify variable length character strings VARYING OF CHAR types have the following form VARYING upper bound OF attribute list CHAR upper bound An integer in the range from 1 through 65 535 that indicates the length of the longest possible string attribute list One or more identifiers that provide additional information about the VARYING OF CHAR string component You can assign string constants to VARYING OF CHAR variables from length 0 to the specified upper bound The compiler allocates enough storage space to hold a string of the maximum length A VARYING OF CHAR variable with length 0 is the empty string You can only use character string constants or expressions that evaluate to character s
269. expression can be determined without complete evaluation HP Pascal can partially evaluate some logical operations Usually the order of evaluation does not prevent the correct result from being produced However order of evaluation is very important when you write logical operations involving function designators that have side effects A side effect is an assignment to a nonlocal variable or to a variable parameter within a function block For example the following IF statement contains two function designators for function f IF f a AND b THEN Statement The compiler can evaluate these two function designators in any order Regardless of which function designator the compiler evaluates first if the result is FALSE the other function designator does not have to be evaluated Suppose that function f assigns the value of its parameter to a nonlocal variable Because you cannot know which function designator was evaluated first you cannot be sure of the value of the nonlocal variable after the IF statement is performed For More Information e On expressions Section 4 1 e On the AND THEN or OR ELSE logical operators Section 4 2 3 e On user defined functions Chapter 6 e On optimization compiler switches and order of evaluation HP Pascal for OpenVMS User Manual 4 14 Expressions and Operators 4 3 Structured Function Return Values Syntactically a function call is an expression since it returns a value If a
270. f the same type as the set s base type For example 2 3 IN 1 10 5 3 NOT IN 1 10 The result of this IN operation is TRUE because 2 3 evaluates to 6 which is a member of the set 1 10 and the NOT IN operation also returns TRUE because 5 3 evaluates to 15 which is not a member of the set 1 10 4 10 Expressions and Operators The XOR predeclared routine can return the set of elements that do not appear in both sets For More Information e On the SET data type Section 2 4 3 e On the BOOLEAN data type Section 2 1 3 e On the XOR function Section 8 110 4 2 6 Type Cast Operator Normally HP Pascal associates each variable with one type the type with which the variable was declared In some systems programming applications you can perform operations more efficiently by relaxing HP Pascal s strict type checking rules HP Pascal provides the type cast operator for this purpose The type cast operator changes the context in which you can use a variable or an expression of a certain data type The actual representation of the object being cast is not altered by the type cast operator HP Pascal overrides the type only for the duration of one operation It has one of the following forms variable identifier j ipod expression d The type cast operator separates the name of a variable or an expression in parentheses from its target type the type to which it is being cast The operator alters the type o
271. f a routine directly or indirectly calling itself Glossary 10 redefinable reserved word An identifier that HP Pascal reserves for its own use but that you can redefine if you choose If you redefine these words the original function of the reserved word becomes unavailable within the block in which you redeclare the word relative component number A cell number in a file of relative organization relative file organization A file organization that consists of a series of component positions called cells numbered consecutively from 1 to n The numbered fixed length cells enable HP Pascal to calculate the component s physical position in the file reserved word An identifier that HP Pascal reserves for its use to designate data types statements and operators You cannot redefine these identifiers routine A subprogram a function or procedure See also function and procedure routine heading See heading run time expression An expression that results in a value at the time you run your program See also constant expression schema family All types that are derived only from discriminating the same schema type though the actual discriminant values may vary See also actual discriminant schema type A user defined construct that provides a template for a family of distinct data types By discriminating a schema type you create a valid data type See also data type discriminated schema type and undiscriminated schema
272. f the cast object at that point only Once you cast a variable or an expression the object has all the properties of its target type during the execution of the operation in which the type cast operator appears A variable and its target type must have the same allocation size Therefore you cannot cast a conformant array parameter but you can cast a fixed size component of a conformant array parameter A schema variable or parameter cannot be type cast since it does not have a size that is known at compile time When you cast an expression in parentheses the value of that expression can be either truncated on the left or padded on the left with zeros so that the allocation size of the expression s value and its target type become the same The type of a cast expression cannot be VARYING OF CHAR a conformant array parameter or a discriminated schema In addition the target type of a cast expression cannot be VARYING OF CHAR or a discriminated schema Expressions and Operators 4 11 Consider the following example TYPE F float PACKED RECORD Fraci 0 127 Expo 0 255 Sign BOOLEAN Frac2 0 65535 END VAR A REAL In the executable section A F float Expo A F float Expo 1 In this example the record type F_float shows the layout of an F floating real number The real variable A is cast as a record of this type allowing you to access the fields containing the mantissa exponent sign and fraction of A
273. f the routine If you use the routine identifier within the routine body with the exception of assigning a value to the routine identifier of a function the result is a recursive call to the routine The routine identifier of a procedure can be redeclared in the procedure s declaration section The routine identifier of a function cannot be redeclared in the function s declaration section however it can be redeclared in any nested routines within the function s declaration section formal parameter list A comma list of the routine s formal parameters A procedure can have as many as 255 formal parameters A function can also have as many as 255 formal parameters unless returning a structured type in which case a function is limited to 254 formal parameters Optionally you can specify a mechanism specifier and an attribute list for each parameter declaration section A routine declaration section can include all sections except TO BEGIN DO TO END DO and VALUE sections Data specified in this declaration section is local to the routine and to any nested routines you can redeclare identifiers that are declared in an outer block You cannot redeclare a formal parameter identifier to be a local variable in the routine 6 2 Procedures and Functions By default the system does not retain the values of local variables after it exits from a routine Each call to a routine creates copies of the local variables This means you can call a rout
274. f you omit the time it sets the time to be midnight Predeclared Functions and Procedures 8 19 Consider the following example VAR Time Var TIMESTAMP The Time The Date STRING 23 In the executable section GETTIMESTAMP Time Var Get current date and time GETTIMESTAMP Time Var 22 Nov 1988 12 30 15 15 GETTIMESTAMP Time Var 22 Nov 1988 Midnight at that date GETTIMESTAMP Time Var A1 Nov 1988 999 999 999 99 Invalid date sets TIME VAR to midnight on January 1 1 You can also use predefined values like TOMORROW as shown in this example GETTIMESTAMP Time Var TOMORROW Midnight tomorrow For More Information e On the DATE and TIME functions Section 8 23 e On the layout of the TIMESTAMP type Section 2 8 8 39 GT Function The GT function returns a Boolean value that specifies if the first parameter is greater than the second parameter according to the ASCII values of the strings characters GT stri str2 The parameters str1 and str2 must be character string expressions HP Pascal does not pad shorter strings with blanks Consider the following example VAR Match BOOLEAN Test STRING 8 VALUE ENTRANCE In the executable section Match GT exit exit Returns FALSE Match GT Test EXIT N less than X Returns FALSE For More Information e On string data types Section 2 6 8 20 Predeclared Functions and Procedur
275. fect of attributes 6 12 effect of POS 10 33 effect of UNBOUND 10 42 effect of UNSAFE attribute 10 43 effect of VOLATILE 10 47 effect of WRITEONLY 10 52 Structured type allocation size of 10 10 description of 2 18 effect of READONLY 10 35 effect of VOLATILE 10 47 effect of WRITEONLY 10 52 packing of A 17 Subranges determining value within 8 23 Subrange type 2 9 allocation size of A 11 bounds checking for 2 9 10 11 Subscript See Index definition Glossary 12 SUBSTR function 8 43 SUBTITLE directive 11 6 Subtraction operator 4 3 Successor of parameter 8 43 SUCC function 8 43 Symbolic constant allocation of A 9 definition 3 2 SYS INPUT C 4 SYS OUTPUT C 4 SYSCLOCK function 8 44 System name 11 9 9 SYSTEM NAME directive 11 9 SYSTEM_VERSION directive 11 9 S_FLOAT 2 13 S_floating point data representation of A 21 T Terminal prompting 9 20 before EOF and EOLN tests 9 21 writing partial lines to 9 23 Terminal output formatting 9 23 using conversion functions 9 26 Terminator definition Glossary 12 in stream component format 9 10 TEXT file compared to FILE OF CHAR 9 18 default component length 9 9 default information 9 18 delayed device access to 9 20 description of 9 18 effect of delayed device access on STATUS 9 20 T O routines 9 18 reading 9 53 TEXT type 2 33 TIE definition Glossary 12 Time checking
276. ffer variable including its implicit use in the GET READ and 9 20 Input and Output Processing READLN procedures or any test for the status of the file namely the EOF EOLN STATUS and UFB functions The RESET procedure which is required when any TEXT file is opened for input initiates the process of delayed device access Note that RESET is done automatically on the predeclared file INPUT RESET expects to fill the file buffer with the first component of the file However because of delayed device access an item of data is not supplied from the input device to fill the file buffer until the next reference to the file When writing a program for which the input will be supplied by a TEXT file you should be aware that delayed device access occurs Because RESET initiates delayed device access and because EOF and EOLN cause the file buffer to be filled you should place the first prompt for input before any tests for EOF or EOLN The information you enter in response to the prompt supplies data that is retained by the file device until you make another reference to the input file Consider the following example VAR i INTEGER In the executable section WRITE Enter an integer or an empty line WHILE NOT EOLN DO BEGIN READLN i WRITELN The integer was i l WRITE Enter an integer or an empty line END WRITELN Done The first reference to the file INPUT is the EOLN test in
277. fied address AT n The exact address is specified by the constant expression n Variables representing machine dependent entities are frequently given the AT attribute 10 8 Attributes Usage and Default Information A variable having the AT COMMON or PSECT attribute is implicitly static AT cannot be applied to routines or to compilation units AT cannot be applied to variables of nonstatic types For More Information On default allocation for variables declared in the outermost block of a program or in nested blocks Section 10 2 5 On default allocation for variables declared in the outermost block of a module Section 10 2 36 On static and nonstatic types Section 2 9 10 2 5 AUTOMATIC The AUTOMATIC attribute specifies that storage for the variable be allocated each time the program enters the routine in which the variable is declared The storage is deallocated each time the program exits from that routine An automatic variable exists as long as the declaring routine remains active Usage and Default Information By default variables declared in nested blocks are automatic By default variables declared at the outermost level of a program are automatic though for efficiency they can be made static By default the control part of the nonstatic types and the pointer part of variables of nonstatic types follow the same rules as regular variables they are static or automatic depending on the location of
278. function 8 17 FIND FIRST BIT SET function 8 17 FIND MEMBER function 8 18 FIND NONMEMBER function 8 18 Fixed length component format 9 10 definition Glossary 6 FLOAT attribute 10 19 Floating data types 2 13 Floating point data representation of A 20 Floating point notation See Exponential notation Foreign mechanism parameter actual 6 17 formal 6 15 Foreign semantics value 6 16 variable 6 16 Formal discriminant 2 37 definition Glossary 6 Formal parameter associated with actual 6 25 congruence of 6 13 10 26 default value for 6 26 definition Glossary 6 description of 6 6 effect of attributes 6 9 effect of LIST 6 13 effect of READONLY 6 11 10 35 effect of UNSAFE 6 9 foreign mechanism 6 15 function 6 12 passing mechanisms 6 9 procedure 6 12 routine 6 12 semantics of 6 7 value semantics 6 8 variable 6 10 Form feed character 1 4 1 10 FOR statement 5 6 CONTINUE in 5 5 examples 5 7 execution and termination of 5 6 FORTRAN identifier 6 3 FORWARD identifier 6 3 Function 6 1 calling of 6 4 declaration of 6 1 definition Glossary 6 heading 6 1 predeclared Function predeclared cont d See Predeclared routines or individual functions by name used as actual parameter 6 13 used as formal parameter 6 12 Function call 6 4 accessing structured return values 4 15 Function designators side effects 4 14 functions RETURN statement 5 11 F FLOAT 2 13
279. function 8 28 MINQUADRUPLE 2 14 MINREAL 2 14 Mode of file 9 29 MOD operator 4 4 use with negative integers 4 4 Module definition 7 5 Glossary 8 finalization 3 6 heading 7 6 initialization 3 3 MODULE directive 11 10 Module heading definition Glossary 8 MTPR procedure 8 28 Multidimensional array 2 20 definition Glossary 8 packing A 17 examples of A 15 Multiplication operator 4 3 N Name string definition Glossary 8 in attribute list 10 2 Natural alignment definition Glossary 9 NE function 8 29 Negation operator 2 14 Nesting file levels 11 3 NEW procedure 8 29 NEXT function 8 31 A 14 Nondecimal notation in WRITE WRITELN and WRITEV 9 26 Nonpositional syntax 6 25 definition Glossary 9 Nonprinting character 2 7 Nonstandard constructor 2 34 array 2 34 record 2 35 Nonstatic type definition Glossary 9 description of 2 48 example of data layout A 28 field in record object A 30 parts of 2 49 representation of A 27 representation of variables of A 28 NOOPTIMIZE attribute 10 28 Notation binary 2 2 decimal integer 2 2 real numbers 2 13 exponential 2 13 extended digit 2 5 hexadecimal 2 2 octal 2 2 NOT IN operator 4 10 NOT operator 4 6 Null Terminated STRING 2 47 O OCTA attribute 10 29 Octal nondecimal output of WRITE WRITELN and WRITE 9 26 Octal notation 2 2 in output procedure 9 26 Octal number representation
280. h like the SUBSTR built in HP Pascal also provides features for handling null terminated strings These are useful for communicating with routines written in the C language and on UNIX systems Data Types and Values For More Information e On the CHAR data type Section 2 1 2 e On the ASCII character set Section 1 2 1 e On null terminated strings Section 2 7 2 6 1 PACKED ARRAY OF CHAR Types User defined packed arrays of characters with specific lower and upper bounds provide a method of specifying fixed length character strings The string s lower bound must equal 1 The upper bound establishes the fixed length of the string The following example shows a declaration of a character string variable of twenty characters VAR My String PACKED ARRAY 1 20 OF CHAR Note If the upper bound of the array exceeds 65 535 if the PACKED reserved word is not used or if the array s components are not byte sized characters the compiler does not treat the array as a character string To assign values to fixed length character strings you can use a character string constant or an expression that evaluates to a character string When assigning into fixed length strings the compiler adds blanks to extend a string shorter than the maximum characters declared If you specify a string longer than the maximum characters declared an error occurs You can also use an array constructor as long as you specify characters for
281. hat specifies if the first parameter is less than or equal to the second parameter according to the ASCII values of the strings characters LE str1 str2 The parameters str1 and str2 must be character string expressions HP Pascal does not pad shorter strings with blanks 8 24 Predeclared Functions and Procedures The expression LE Str1 Str2 is equivalent to the following LENGTH Strl lt LENGTH Str2 OR Strl lt Str2 Consider the following example VAR Match BOOLEAN Test STRING 8 VALUE ENTRANCE In the executable section Match LE exit exit Returns TRUE Match LE Test EXIT N less than X Returns TRUE For More Information e On string data types Section 2 6 8 49 LENGTH Function The LENGTH function returns an integer value that is the length of a specified string expression LENGTH str The str parameter must be a character string expression For More Information e On character strings Section 2 6 8 50 LN Function The LN function returns a real value that represents the natural logarithm of the specified parameter LN x The parameter x can be an integer or REAL type The value of x must be greater than zero 8 51 LOWER Function The LOWER function returns the lower bound for ordinal types SET base types and array indexes LOWER x n Predeclared Functions and Procedures 8 25 The parameter x is a type identifi
282. he environment file in all subsequent compile time checking for users of this environment file This is the default DENT STRING Uses the IDENT string of the environment file in all subsequent compile time checking for users of this environment file e NONE Disables all compile time checking for users of this environment file 10 2 31 POS The POS attribute forces the field to a specific bit position within the record POS n n The constant expression n specifies the bit location relative to the beginning of the record at which the field begins Usage and Default Information e You can apply the POS attribute to a field of a packed or an unpacked record e The constant expression n cannot denote a negative integer The beginning position of a field must be greater than the ending position of the field preceding it e The POS attribute cannot be used on a field that follows not necessarily immediately a field whose type has run time size and is nonstatic e Inside a record variant the beginning position of a field must be greater than the ending position of the preceding field within the same variant The variants themselves can overlap e A field whose allocation size is greater than 32 bits must be positioned according to the allocation size rules for the platform 10 32 Attributes A record variable containing a field of a file type cannot include a POS attribute for any field The specified bit posit
283. he file until it has assigned a value to each variable in the list After the last character has been read from a line of a TEXT file EOLN returns TRUE and the file buffer variable contains a space Unless you are reading into a character or string variable a call to READ at this point skips over the end of line marker and positions the file at the beginning of the next line If you are reading into a variable of type CHAR when EOLN returns TRUE the space is read and assigned to the variable and the file position advances If you are reading into a string variable when EOLN becomes TRUE the file position does not change In the latter case you should use the READLN procedure to advance the file position past the end of line marker Values from a TEXT file can be read into variables of integer real Boolean character string and enumerated types TEXT file values to be read into integer real Boolean and enumerated variables can be preceded in the file by any number of spaces tabs and end of line markers Values to be read into character variables however must not be separated because they are read and assigned character by character In a TEXT file when HP Pascal encounters a character that forms an object of a data type that does not match the data type of the parameter reading stops Consider the following example VAR i INTEGER In the executable section READ i If the object in the input file is 123ABC the read
284. he order of evaluation is allowed to vary between invocations of the compiler and even between individual uses of source language features C 2 Description of Implementation Features The order of evaluation of the following items e Expressions used as discriminant values e Index expressions and access to the array or string variable in a indexed variable e Index values of an array variable e Expressions d1 dn in new p d1 dn e Expressions of a set member designator e Set member designators in a set constructor e Operands of a dyadic binary operator except for AND_THEN and OR_ELSE e Component values of a structured value constructor e Index expressions in an indexed constant e Expressions in a set constructor Treatment Random order Order of selecting members of the set value in the FOR IN statement Treatment Random order Whether the first character read when reading an integer or real from a text file is the value of the buffer variable or the value of the next character from the input record Treatment HP Pascal uses the next character in the input record and ignores the contents of the file buffer Order of evaluating and accessing of actual parameters of a function call Treatment Random order Order of evaluating and accessing of actual parameters of a procedure call Treatment Random order Order of accessing the variable and evaluating the expression in an assignment statement Treatment Random
285. her complete without interruption or will restart itself from the beginning Read modify write operations are typically not atomic at an instruction level on a RISC machine attribute An identifier that directs the HP Pascal compiler to change its behavior in some way attribute class A category that indicates a common affect that a group of attributes has on programming such as data alignment storage allocation and optimization classes automatic variable allocation An attribute of a variable that indicates that the variable be allocated each time the program enters the routine in which the variable is declared and is deallocated each time the program exits from that routine base type The data type of the data items in a set or of the object of a pointer See also set cascade An environment file inheritance path that involves a compilation unit inheriting another compilation unit that inherits another compilation unit and so forth See also compilation unit and environment file case selector An ordinal expression whose value at run time determines which statement in a CASE statement executes cells A fixed length file component in a file of relative file organization Each cell is numbered consecutively from 1 to n Glossary 2 compilation unit A unit of code that can be compiled independently the term compilation unit refers to either a program or a module compiler optimization A set of processes or
286. hows legal statements involving write only variables The write only variable Writ Int is assigned the result of the square root operation and is then passed as an actual parameter to a write only formal parameter For More Information e For information on the READONLY attribute Section 10 2 34 10 3 Attribute Classes An attribute class can consist of a single attribute or of several attributes with a common characteristic Table 10 7 lists the classes and their attributes 10 52 Attributes Table 10 7 Attribute Classes Class Attributes Description of Attributes Alignment ALIGN ALIGNED Indicate whether the object should be UNALIGNED aligned on a specific address boundary in memory Allocation AT AUTOMATIC Indicate the form of storage that the COMMON STATIC object should occupy PSECT Asynchronous ASYNCHRONOUS Indicates that the routine can be called by an asynchronous event such as a condition handler Check CHECK Indicates error checking options to be enabled or disabled Double FLOAT Indicates the type of precision to use for precision objects of type DOUBLE Enumeration ENUMERATION_ SIZE Indicates the sizes used for enumerated types and Boolean types Environment ENVIRONMENT Indicate that HP Pascal creates PEN CHECKING STYLE an environment file which allows compilation units to share data definitions and declarations Hidden HIDDEN Indicates exclusion of a declaration or definition from a created envi
287. iable FILE NAME file name HISTORY history RECORD_LENGTH record_length ACCESS METHOD access_method RECORD_TYPE record_type CARRIAGE CONTROL carriage control ORGANIZATION organization DISPOSITION disposition SHARING file_sharing USER_ACTION user_action DEFAULT default_file_name 9 44 Input and Output Processing ERROR error_recovery file_variable no default The name of the file variable associated with the file that HP Pascal is to open file_name environment specific default A character string expression containing the external file name HP Pascal determines the default file name according to the environment in which you are programming history NEW default for OPEN REWRITE openings OLD default for EXTEND RESET openings A value that indicates whether the file exists or if HP Pascal must create the file If you specify OLD and if HP Pascal cannot find the file an error occurs Other values are READONLY and UNKNOWN If you specify READONLY you can only read from the file if you attempt to write to the file an error occurs If you specify UNKNOWN HP Pascal looks for an existing file but creates a new file if an existing file does not exist If you specify OLD or UNKNOWN and if the attempt to open the file generates a file protection error HP Pascal tries again using READONLY record_length 255 bytes defaul
288. ibute are zero extended if necessary and all bits are written When you fetch from variables with a size attribute the compiler need only reference sufficient bits to access the legal value of the type The contents of a variable are undefined if it does not contain a zero extended legal value of the variable s type A size attribute is illegal on a conformant parameter on a component of a VARYING string on an object of a structured type having a file component or on a nonstatic type In an array variable passed to a conformant formal parameter size and alignment attributes are illegal on all dimensions of 10 10 Attributes 10 2 7 10 2 8 the actual parameter except the first that correspond to the dimensions of the formal parameter e Two variables of the same type that have different allocation sizes are assignment compatible but are not structurally compatible For More Information e On alignment attributes Section 10 3 e On type compatibility Section 2 10 e On size attributes and return values of size functions Section 8 83 e On allocation sizes of objects Section A 2 4 BYTE The BYTE attribute specifies the amount of storage in bytes to be received by the object BYTE n The optional constant n indicates the number of byte storage units For More Information e On allocation sizes of objects Section A 2 4 e On size allocation restriction Section 10 2 6 CHECK The CHECK attribute sp
289. iderations If you specify more than one formal parameter separated by commas of a single user defined undiscriminated schema type the corresponding actual parameters must be discriminated from the same type as the formal parameter they must be of the same schema type family and the actual schema parameters must have equivalent actual discriminant values Consider the following example TYPE Array Template Upper Bound INTEGER ARRAY 1 Upper Bound OF INTEGER VAR Actual 1 Actual 2 Array Template 10 Actual 3 Array Template 20 PROCEDURE Schema Procl Only One Array Template Body PROCEDURE Schema Proc2 One Two Array Template Body In the executable section Schema Procl Actual 1 Legal Schema Procl Actual 3 Legal Schema Proc2 Actual 1 Actual 2 Legal Schema Proc2 Actual 1 Actual 3 Illegal Procedures and Functions 6 19 When using value semantics if you specify more than one formal parameter separated by commas of an undiscriminated STRING type the corresponding actual parameters must have equivalent current lengths not necessarily equivalent maximum lengths Consider the following example VAR One String Two String STRING 15 Three String STRING 20 PROCEDURE Test Strings One Two STRING Body In the executable section Test Strings a b Legal Test Strings a bb Illegal One String Hello Two String Hello ther
290. if the schema type is simple as follows TYPE A Char x y CHAR x y e Control parts of nested discriminated schema types as follows TYPE My Record a b INTEGER RECORD fl STRING a f2 STRING b END Data Storage and Representation A 27 e Values for all expressions appearing in the type definition as follows TYPE My Subrange a b INTEGER a atb HP Pascal evaluates the expression a b when the schema type is discriminated and saves the result in the control part e The total size of the data part if it can vary based on actual discriminants as follows TYPE Arr a b INTEGER ARRAY a b OF REAL Note The order of information and the content of the additional information section of the control part cannot be guaranteed If you declare more than one variable of a discriminated schema type each variable shares the information in the control part for that type A 3 3 2 Representation of Variables of Nonstatic Types When allocating storage for a variable of a nonstatic type HP Pascal allocates a pointer part and a data part HP Pascal allocates and initializes the pointer part to point to the data part you cannot access the pointer part in your program HP Pascal associates each object with a control part according to its data type If the type of the object involves more than one nonstatic type HP Pascal associates that object with all applicable control parts Consi
291. ifier being defined HP Pascal initializes all variables declared to be of this type with the constant value or values provided unless there is an overriding initial state specifier in the variable declaration Declaration Section 3 7 The following rules apply to the use of initial state specifiers on data types e You must initialize a type with a compile time expression of an assignment compatible type Scalar types require scalar constants structured types require constant constructors e You cannot initialize file types or types containing file components e The predeclared function ZERO can be used to initialize an entire type except file types and TIMESTAMP types to binary zero e The constant identifier NIL or a call to the ZERO function are the only values with which you can initialize a pointer type This example declares variables of user defined types Note that in the declaration of variable week5 the VALUE Sun overrides the initial state specified in the TYPE declaration by VALUE Mon TYPE Days of Week Sun Mon Tues Wed Thurs Fri Sat VALUE Mon Array Template Upper Bound INTEGER ARRAY 1 Upper Bound OF INTEGER VAR Declaring variables of user defined ou weekl week2 week3 week4 Days of Week Initial value Mon week5 Days of Week VALUE Sun Initial value gt array_type2 array_template x x is a run time expression HP Pascal requires that all user defined type identifiers exce
292. igned 0 integer Pointer to a byte aligned integer By default all pointer types on OpenVMS 164 and OpenVMS Alpha systems are 32 bits You can declare a 64 bit pointer by using the QUAD attribute in a pointer declaration For example var long ptr integer quad ptr quad integer begin new long ptr quad ptr long ptr quad ptr 5 if quad ptr long ptr then quad ptr long ptr end Data Types and Values 2 17 When comparing a 32 bit and a 64 bit pointer the 32 bit pointer will be sign extended before the comparison Also when assigning a 32 bit pointer value into a 64 bit pointer variable the value will be sign extended You cannot assign a 64 bit pointer value into a 32 bit pointer variable For More Information e On the NEW procedure Section 8 60 e On the DISPOSE procedure Section 8 28 e On records Section 2 4 2 e On pointers to schema types Section 2 5 On linked lists HP Pascal for OpenVMS User Manual e On compiler switches for selecting alignment packing and allocation rules for each platform HP Pascal for OpenVMS User Manual 2 3 4 POINTER Type The POINTER predefined type is compatible with all pointer types Variables or functions of type POINTER cannot be dereferenced or used with the NEW and DISPOSE procedures In order to access the data you must assign the pointer value into a variable of a particular pointer type or typecast the pointer to a particular pointer type
293. ile must be in inspection mode before DELETE is called the mode does not change after the procedure s execution When the DELETE procedure is called the current component as indicated by the file buffer must already have been locked by a successful FIND FINDK GET RESET or RESETK procedure before it can be deleted After deletion the component is unlocked and the UFB function returns TRUE Consider the following example DELETE Accounts Payable This procedure call deletes the current component When the component has been deleted it is unlocked and UFB Accounts Payable returns TRUE A run time error occurs if the current component of Accounts Payable is not locked Input and Output Processing For More Information e On file organizations Section 9 1 e On component access Section 9 3 e On the UFB function Section 9 8 22 e On the error processing parameter Section 9 7 9 8 3 EOF Function The EOF function indicates whether the file pointer is positioned after the last component in a file by returning a Boolean value EOF file variable file_variable The name of the file variable associated with the input file If you omit the name of the file the default is INPUT The file can be in either inspection or generation mode before EOF is called however end of file must be defined The input operations GET RESET and FINDK are guaranteed to leave end of file defined The file mode does not change
294. ine recursively without affecting the values held by the local variables at each activation of the routine To preserve the value of a local variable not the copy from one call to the next you must declare the local variable with the STATIC attribute statement Any Pascal statement In a function executable section there must be either a RETURN statement containing a value or at least one statement of the following form routine identifier result The routine identifier is the name of the function The result is a value of either an ordinal real structured or pointer type that HP Pascal returns when the function is called This value cannot be a file type or a structured type with a file component This value must be of the same type as the result type id EXTERN EXTERNAL FORTRAN FORWARD Predeclared identifiers that direct HP Pascal to find the body of the routine elsewhere The EXTERN EXTERNAL and FORTRAN identifiers declare routines that are independently compiled by HP Pascal or that are written in other languages In HP Pascal these identifiers are equivalent Although not part of the Pascal standard many Pascal compilers only accept the FORTRAN identifier for external routines actually written in FORTRAN if portability is a concern you may wish to use FORTRAN only for external FORTRAN routines The FORWARD identifier declares a routine whose block is specified in a subsequent part of the same procedure and funct
295. ingle statement to follow the DO reserved word If you do not use a compound statement for the loop body Pascal executes the first statement following the DO reserved word as the loop body Consider the following examples WHILE NOT EOF Filel DO If EOF from the start the loop READLN Filel body is not executed WHILE NOT EOLN INPUT DO BEGIN Use compound statement READ x IF NOT x IN A Z a z 0 9 THEN Err Err 1 Count odd characters as errors END For More Information e On Boolean expressions Section 2 1 3 e On compound statements Section 5 4 5 12 Statements 5 14 WITH Statement The WITH statement provides an abbreviated notation for references to the fields of a record variable or to the formal discriminants of a discriminated schema type A WITH statement has the following form record variable STRIS schema variable Vie DO statement record variable The name of the record variable being referenced schema variable The name of the variable being referenced whose type is a discriminated schema type This underlying type of the schema can be a record statement Any Pascal statement The WITH statement allows you to refer to the fields of a record or to a formal discriminant of a schema by their names alone rather than by the record field identifier or schema variable formal discriminant syntax In effect the WITH statement opens the scope so th
296. integer Error encountered 1 The actual number is environment specific and indicates the exact error that occurred A test by the STATUS function on a TEXT file causes delayed device access to occur which fills the file buffer with the next file component Therefore EOF EOLN UFB and STATUS never return an error code following a successful STATUS function call Consider the following example ESET Filel ERROR CONTINUE F STATUS Filel gt 0 THEN WRITELN Cannot access first record LSE F STATUS Filel 0 THEN WRITELN File is empty LSE READ Filel E HF IH 20 If the RESET procedure encounters either an error condition or an end of file an appropriate error message is displayed If the STATUS function indicates that the RESET procedure was successful the first record is read from the file For More Information e On TEXT files Section 9 5 e On the error processing parameter Section 9 7 e On delayed device access Section 9 5 3 e On status code translations HP Pascal for OpenVMS User Manual Input and Output Processing 9 8 21 9 8 22 TRUNCATE Procedure The TRUNCATE procedure indicates that the current file component and all components following it are to be deleted You can only use TRUNCATE on a file that has sequential organization TRUNCATE file variable ERROR error recovery file variable The name of the file variable associated with the file to be t
297. ion allows variable length components those variable length components are contained in a fixed length cell that must be large enough to contain the largest stored component For More Information e On TEXT files Section 9 5 9 2 1 Fixed Length Component Format Fixed length components are all the same length The fixed length component format is supported in all file organizations HP Pascal determines the length of a component at the time of file creation You cannot change the length of the components after you create the file 9 2 2 Variable Length Component Format The variable length component format enables components to be only as long as the data requires The variable length format is supported in all file organizations When you use OPEN to create a file of variable length components you can specify the value in bytes of the largest component permitted in the file Any attempt to store a component containing more bytes than the specified value results in an error 9 2 3 Stream Component Format 9 10 The stream component format is a continuous stream of bytes that contains special delimiting characters called terminators that separate components In addition to being recognized as delimiters HP Pascal considers the terminators to be a valid part of the component data The stream format is supported only in sequential files on disk Input and Output Processing Table 9 3 contains the acceptable types of stream co
298. ion must not conflict with the alignment explicitly required by an alignment attribute Two record types in which corresponding fields are not identically positioned are neither assignment compatible nor structurally compatible Consider the following example TYPE Control RECORD Flag 1 BIT POS 0 BOOLEAN Flag 2 BIT POS 1 BOOLEAN Count BYTE ALIGNED 0 100 Error BIT POS 31 BOOLEAN END This example uses the POS attribute to position the fields of an unpacked record such that Flag 1 occupies bit 0 Flag 2 occupies bit 1 and Error occupies bit 31 Because the Count field has size and alignment attributes it is allocated one byte of storage and is aligned on the byte boundary following Flag 2 that is storage for Count occupies bits 8 through 15 Bits 2 through 7 and 16 through 30 are left empty you cannot refer to them For More Information On allocation sizes of objects Section A 2 4 On alignment boundaries in packed and unpacked records Section A 2 7 On static and nonstatic types Section 2 9 On type compatibility Section 2 10 10 2 32 PSECT The PSECT attribute is useful for placing static variables and executable blocks in program sections that are shared among executable images PSECT I identifier T1 Attributes 10 33 identifier Identifier passed designating the program section in which storage for a variable routine or compilation is to be allocated If
299. ion section allowing you to call a routine before you specify its routine body As an extension HP Pascal will allow the body to be in a different declaration part If the body and heading are specified in different procedure and function sections a FORWARD declared function should not be used as an actual discriminant to a schema type When you specify the body of the routine in subsequent code include only the FUNCTION or PROCEDURE predeclared identifier the routine identifier and the body of the routine Do not repeat the formal parameter the attribute list or the result type id Procedures and Functions 6 3 result type id The type specification of the function return value The function s result must be of this data type This type cannot be a file type or a structured type with a file component Consider the following example Function body contained in subsequent code FUNCTION Adder Opl Op2 Op3 REAL REAL FORWARD PROCEDURE Introduction VAR a b c z REAL Variables local to the procedure BEGIN WRITELN This is the Inventory Program Version 5 6 WRITELN WRITELN Press Ctrl H for help Press Return to continue a 4 6 b 12 1 C 201 45 z Adder a b c Call the function Adder END System Routine Tanh available with the operating system FUNCTION System Routine Tanh Angle REAL REAL EXTERNAL FUNCTION Adder Do not repeat attributes or
300. ist is applicable according to the variant portion of the record OTHERWISE ZERO Sets all remaining components to their binary zero value If you use OTHERWISE ZERO it must be the the last component in the constructor You can use either of the following constructors to assign values to the record variable VAR Playerl Player Rec VALUE Wins 18 Losses 3 Percentage 21 18 In executable section constructor type is required and run time expressions are legal Playerl Player Rec Wins 18 Losses y Percentage y 18 18 When you specify constructors for records that nest records specify the type of the outermost record but do not specify the type of the constructors for any nested records Consider the following example 2 28 Data Types and Values TYPE Team Rec RECORD Total Wins INTEGER Total Losses INTEGER Total Percentage REAL Playerl Player Rec Player2 Player Rec Player3 Player Rec END VAR Team Team Rec In the executable section Team Team Rec Total Wins 18 Total Losses 3 Total Percentage 21 18 Playerl Wins 6 Losses 0 Percentage 1 0 Player2 Wins 5 Losses 2 Percentage 7 5 Player3 Wins 7 Losses 1 Percentage 8 7 You can call the ZERO function within record constructors to initialize all nonspecified components to their binary zero values which are determined by the data type of each component Consider the following examples VAR Tea
301. itialize a record using the VALUE predeclared identifier on individual fields as follows Data Types and Values 2 23 VAR Player RECORD Wins INTEGER VALUE 18 Initial value for one field Losses INTEGER Percentage REAL END A record type can include fields that are themselves records In this case the name of the field includes the name of every record within which it is nested Consider the following TYPE Team Rec RECORD Total Wins INTEGER Total Losses INTEGER Total Percentage REAL Playerl Player Rec Defined in previous example Player2 Player Rec Player3 Player Rec END VAR Team Team Rec You can calculate the team s wins with the following code Team Total Wins Team Playerl Wins Team Player2 Wins Team Player3 Wins For More Information e On variant clauses Section 2 4 2 1 e On record constructors Section 2 4 2 2 e On specifying record fields using the WITH statement Section 5 14 e On attributes Chapter 10 2 4 2 1 Records with Variants A record can include one or more fields or groups of fields called variants which can contain different types or amounts of data at different times during program execution When you use a record with variants two variables of the same record type can represent different data You can define a variant clause only for the last field in the record The syntax for record variants is as follows CASE tag identifier at
302. iting to standard error 9 44 X XOR function 8 52 X FLOAT 2 13 X floating point data representation of A 26 Z ZERO function 8 53 use within record constructor 2 29 Index 21
303. ition Ifthe called routine is external to HP Pascal you can specify an explicit passing mechanism on the actual parameter that overrides the type and number of formal parameters For More Information e On undiscriminated schema types Section 2 5 e On external routines Section 6 3 5 6 3 1 Value Parameters By the rules of value semantics defined by the Pascal standard a formal value parameter represents a local variable within the called routine When you specify value semantics the address of the actual parameter is passed to the called routine which then copies the value from the specified address to its own local storage The routine then uses this copy The copy is not retained when control returns to the calling block Therefore if the called routine assigns a new value to the formal parameter the change is not reflected in the value of the actual parameter When you do not include a reserved word before the name of a formal parameter you automatically cause HP Pascal to use value semantics to pass data to that parameter A formal value parameter has the following form type identifier identifier tues undiscriminated schema name conformant parameter syntax mechanism specifier default value identifier The name of the formal parameter Multiple identifiers must be separated with commas attribute list One or more identifiers that provide additional information about the formal parameter type identifie
304. l hexadecimal or octal number The resulting digits are returned in a VARYING OF CHAR string For every expression whose binary decimal unsigned decimal hexadecimal or octal value you wish to write you must call the appropriate conversion function separately with an actual parameter list You can call more than one conversion function in the same output procedure call You can write variables of any type including pointers to text files in binary decimal unsigned decimal hexadecimal or octal notation 9 26 Input and Output Processing You can specify field widths with the conversion functions however the results are not likely to be what you expect For example if you want to convert the value of i to its hexadecimal equivalent and you want the converted value to be written in a field three characters wide you might write the following procedure call WRITELN HEX i 3 However because the converted value is longer than the field width specification the value is truncated on the right rather than on the left Therefore the output generated by this procedure would be as follows 00 Be careful about specifying field widths with BIN DEC UDEC HEX and OCT when the converted value could exceed the field width given Consider the following example WRITE HEX Payroll 10 HEX Salary 12 The values of the variables Payroll and Salary are converted to their hexadecimal equivalents Payroll is printed with 10
305. l alignment An attribute of certain data items that refers to the placement of the data such that the lowest addressed byte has an address that is a multiple of the size of the data in bytes Natural alignment for a byte is any byte address natural alignment for a word is any byte address that is a multiple of 2 natural alignment for a longword is any byte address that is a multiple of 4 and so on nonpositional syntax A syntax for passing actual parameters that allows you to specify parameters in any order you want The syntax requires that you specify the name of the formal parameter followed by the assignment operator followed by the actual parameter nonstatic type A type whose objects contain a run time component a type is nonstatic if it is a schema type or if its type is derived from a schema type optimization See compiler optimization parameter passing mechanism The method by which Pascal passes the actual parameter to the formal parameter HP Pascal passing mechanisms include passing by immediate value by reference and by descriptor parameter passing semantics The characteristics of a parameter expected by a routine declaration as specified by the formal parameter HP Pascal parameter passing semantics include value variable routine and foreign parameters passing mechanism See parameter passing mechanism position independent code Machine code that operates successfully wherever it is positio
306. l still uses the discriminant identifier to determine type compatibility Discriminant identifiers can appear anywhere a value is required in this definition Consider the following example TYPE Array_Template Upper Bound INTEGER ARRAY 1 Upper Bound OF INTEGER The identifier Upper_Bound is the formal discriminant of the Array_Template schema The Array_Template schema is not a complete description of data It is not a valid data type until you provide an actual discriminant that designates the upper boundary of the array template Schema types that have not been provided actual discriminants are called undiscriminated schema in the previous example Array_Template is an undiscriminated schema You can use an undiscriminated schema in the following instances e As the domain type of a pointer e As the type of a formal parameter In an undiscriminated schema declaration you can use a combination of formal discriminants compile time values and nested discriminants to form subrange bounds These types of expressions are called nonvarying expressions Consider the following TYPE Vector d INTEGER ARRAY 0 d 1 OF BOOLEAN Number Line Starting Distance INTEGER Starting Starting Distance My Subrange l u INTEGER l u Shift Array Index 12 u2 Length INTEGER ARRAY My Subrange 12410 u2 10 OF STRING Length The following example provides the Array Template schema with actual discriminants to f
307. le Component of a packed Follows the 32 bit rules Follows the 32 bit rules array or record variable Dynamic variables Octaword alignment on Quadword alignment allocated by the NEW OpenVMS 164 quadword procedure alignment on OpenVMS Alpha 1Previous versions of HP Pascal used ALPHA_AXP for this keyword The NATURAL keyword is now the recommended spelling for the same behavior The ALPHA_AXP keyword will continue to be recognized for compatibility with old source files The compiler can align such variables on a larger storage boundary if it can access them more efficiently by doing so 3If a variable of type VARYING OF CHAR on an OpenVMS 164 or OpenVMS Alpha system requires alignment it is aligned on a word boundary 4Tf a variable of type VARYING OF CHAR on an OpenVMS VAX system requires alignment it is aligned on a byte boundary You can save storage space by packing variables of structured types but you must be careful to pack at the proper level Except for its alignment a record field whose type is an unpacked array set or record occupies the same amount of space in a packed or an unpacked record variable To pack such a field you must explicitly declare its type to be packed When packing multidimensional arrays you must specify packing at the innermost level to gain any significant space advantage For example there is no advantage in packing an array of an unpacked structured type the unpacked components will s
308. le with the index type of a Explanation Detected at run time if subrange checking was enabled during compilation The PACK procedure is attempted when the value of at least one component of a is undefined Explanation Not detected The index value i in the PACK procedure is greater than the upper bound of the index type of a Explanation Detected at run time if subrange checking was enabled during compilation In the UNPACK z i a procedure the type of the index value i is not assignment compatible with the index type of a Explanation Detected at run time if subrange checking was enabled during compilation The UNPACK procedure is attempted when the value of at least one component of z is undefined Explanation Not detected The index value i in the UNPACK procedure is greater than the upper bound of the index type of a Explanation Detected at run time if subrange checking was enabled during compilation The resulting value of SQR x does not exist Explanation Detected at run time for integers if overflow checking was enabled during compilation always detected at run time for real numbers In the expression LN x the value of x is negative Explanation Detected at run time D 4 Compiler and Run Time System Error Detection In the expression SQRT x the value of x is negative Explanation Detected at run time The resulting value of TRUNC x does not exist after the following calculations
309. lement you can use the following syntax for a component value n OF value 2 34 Data Types and Values For example the following component value assigns the value of 15 to the first three components of an array VAR Arrayl ARRAY 1 4 OF INTEGER VALUE Arrayl 3 OF 15 78 You cannot use the OF reserved word in a REPEAT clause REPEAT Specifies a value to be assigned to all array elements that have not already been assigned values An example of an array constructor is as follows TYPE Count ARRAY 1 10 OF INTEGER VAR Numbers Count VALUE Count 30F 1 2 1 2 30F 3 3 In the executable section constructor type is required Numbers Count 3 OF 1 2 1 2 REPEAT 3 An example of a constructor for a multidimensional array is as follows TYPE One Dimension ARRAY 1 3 OF CHAR Matrix ARRAY a b OF One Dimension VAR Tic Tac Toe Matrix In the executable section Tic Tac Toe Matrix 3 OF X 30F For More Information On standard array constructors Section 2 4 1 2 2 4 6 2 Nonstandard Record Constructors The format for a nonstandard record constructor is as follows data type component valuej tag value component valuej data type Specifies the constructor s data type If you use the constructor in the executable section a data type identifier is required Do not use a type identifier in the VAR or VALUE se
310. ll to the procedure reads Richard M Nixon into Pres and Spiro T Agnew into Veep The procedure then skips past the end of line marker to the beginning of the next line If you call READLN again EOF becomes TRUE and EOLN becomes undefined The READLN procedure is implemented as one or more READ calls followed by a READLN call A STATUS call after a READLN procedure tests if the file was properly positioned not whether the last READ was successful To test if READLN successfully read data replace the call to READLN with an explicit call to READ to read the line then call STATUS to test the results of the READ and finally call READLN to advance the file buffer variable for the next READLN For More Information e On the effect of delayed device access on tests of STATUS after a READLN procedure call Section 9 5 3 e On the READ procedure Section 9 8 15 e On the error processing parameter Section 9 7 e On the radix specifiers Section 9 6 3 and Section 9 6 4 Input and Output Processing 9 57 9 8 17 RESET Procedure The RESET procedure puts a file into inspection mode in which it can be read RESET file variable fle name ERROR error recovery file variable The name of the file variable associated with the input file file name String expression for the file name to be associated with the file variable If the file is already open an error is signaled error recovery The action to be taken if
311. llowing scope rules e An identifier can be declared only once within a particular scope e A previously declared identifier can be redeclared in a nested block e An identifier declared in the main program or module block is accessible in all nested blocks except where it is redeclared Some Pascal identifiers observe additional scope rules e A procedure identifier can be redeclared within its own declaration section e A function identifier can also be redeclared but not in a declaration section of the function s outermost block The identifier can be redeclared only in a nested block because you need to be able to assign a value to it in the outermost block unless a RETURN statement is used e A formal parameter name follows the same rules of scope as a function identifier and can be redeclared only in a nested block e A label declaration must respect GOTO statement restrictions These restrictions prevent control passing from an outer to an inner block 7 3 Redeclaring Routine Names Routine names can be redeclared like any other identifier A block in its declaration section can specify routines with the same names as those outside the block This changes the meaning of function and procedure calls when they occur within the block A procedure can redeclare its own identifier For example the declaration section of the procedure Sum can declare a different procedure called Sum The scope of this second declaration is only wi
312. lobal and external literals The following example shows how to use global and external identifiers Contained in one file PROGRAM a INPUT OUTPUT VAR Amount Total Tax EXTERNAL REAL HORA o EXTERNAL PROCEDURE Calc EXTERNAL Defined elsewhere GLOBAL PROCEDURE Glf Body Available outside BEGIN READ Amount Calc WRITELN Purchase Amount Amount 10 2 WRITELN t Tax 10 2 WRITELN Pay This Total Total 10 2 END Program Structure and Scope 7 9 Contained in a separate file MODULE B CONST Rate 0 06 VAR Amount Total Tax GLOBAL REAL Available outside EXTERNAL PROCEDURE Glf EXTERNAL Defined elsewhere GLOBAL PROCEDURE Calc Available outside BEGIN Tax Amount Rate Total Tax Amount Glf END END The file containing the module can be compiled separately from the file containing the program For More Information e On the GLOBAL attribute Section 10 2 17 e On the EXTERNAL attribute Section 10 2 15 7 10 Program Structure and Scope 8 Predeclared Functions and Procedures HP Pascal supplies predeclared procedures and functions that perform various commonly used operations You do not have to declare these routines in order to call them from your code In this chapter the routines are presented in alphabetical order Also in this chapter the term arithmetic types refers to those data types you can use in arithmetic operations
313. lt Formal Parameters 4 10 4 11 4 12 4 15 4 15 5 2 5 2 5 3 5 4 5 5 5 6 5 7 5 9 5 10 5 10 5 12 5 13 6 4 6 6 6 10 6 12 6 15 6 15 6 18 6 20 6 21 6 22 6 24 6 25 6 26 7 Program Structure and Scope 7 1 doce 7 1 7 2 Scope of Identifiers 0 nnan nanana 7 2 7 3 Redeclaring Routine Names llle eee 7 2 7 4 Modules and Programs eee 7 5 7 5 Compilation Units and Data Sharing 7 7 7 5 1 Environment Files llle 7 7 7 5 2 Global and External Identifiers llli 7 9 8 Predeclared Functions and Procedures 8 1 ABS Function ifs 63 ous Pane baad SERA eed bow Heese eee s 8 3 8 2 ADD_ATOMIC Function OpenVMS I64 and OpenVMS Alpha systems only 0 644 508 edes b duree ew gees eae dee 8 3 8 3 ADD INTERLOCKED Function eee 8 4 8 4 ADDRESS Function lle eee 8 4 8 5 AND ATOMIC Function OpenVMS 164 and OpenVMS Alpha systems Only s bee oeque ker qoe ue dee Oe ale Pes 8 5 8 6 ARCTAN Function i445 cc a edad eee eae Ree ad eda Ree Pe A 8 5 8 7 ARGUMENT Function 0 00 000 ees 8 6 8 8 ARGUMENT LIST LENGTH Function 8 6 8 9 ASSERT Procedure 0 0 cece ee ees 8 7 8 10 BARRIER Function OpenVMS I64 and OpenVMS Alpha systems only 525a hoa Gata es dasha RO ADR es CR TR RO Rs a 8 7 8 11 BIN Function ereere cosh os Oe e X Oe ew Oa ER a Oe eS 8 8 8 12 BIT OFFSET Function eee 8
314. lude minus zero On OpenVMS VAX systems the UNDEFINED routine returns TRUE if the floating point value has an exponent of 0 together with a sign bit of 1 otherwise it returns FALSE 8 99 UNOT Function 8 100 The UNOT function returns an unsigned value that represents a binary logical NOT operation on each bit of the specified parameter UNOT u The u parameter must be an unsigned expression Consider the following example Result UNOT 16 FF9 Returns 16 FFFFF006 For More Information e On specifying extended digit notation Section 2 1 1 1 UNPACK Procedure The UNPACK procedure copies components of a packed array to an unpacked array variable UNPACK z a i The parameter z is a packed array The parameter a is an unpacked array variable The parameter i is the starting value of the index of a Predeclared Functions and Procedures 8 47 8 101 The number of components in parameter a must be greater than or equal to the number of components in z The UNPACK procedure assigns the components of z starting with z low bound to the array a starting with ali until all the components in z are used In general when specifying i keep in mind that the upper bound of a that is n must be greater than or equal to i v u where v is the upper bound of z and u is the lower bound of z That is ORD n must be greater than or equal to ORD i ORD v ORD u Normally you cannot pass the individual c
315. lves For example TYPE Orders RECORD Part 1 9999 VALUE 25 CASE On_ Order BOOLEAN OF TRUE Order Quantity INTEGER VALUE 18 Price REAL VALUE 4 65 FALSE Rec Quantity INTEGER VALUE 10 Cost REAL VALUE 46 50 END For More Information e On the ZERO function Section 8 111 e On nonstandard record constructors Section 2 4 6 2 2 4 3 SET Type A set is a collection of data items of the same ordinal type called the base type The SET type definition specifies the values that can be elements of a variable of that type The SET type has the following form PACKED SET OF attribute list base type 2 30 Data Types and Values attribute list One or more identifiers that provide additional information about the base type base type The ordinal type identifier or type definition or discriminated schema type from which the set elements are selected Real numbers cannot be elements of a set type You define a set by listing all the values that can be its elements A set whose base type is integer or unsigned has two restrictions First the set can not contain more than 256 elements Second the ordinal value of the elements in a set must be within the range of 0 and 255 For sets of other ordinal base types elements can include the full range of the type The INTSET predefined type is equivalent to TYPE INTSET SET OF 0 255 For More Information On the INTEGER type Section 2 1 1 1
316. m WALLCLOCK For More Information e On the SYSCLOCK function Section 8 90 e On the CLOCK function Section 8 20 WRITEV Procedure The WRITEV procedure writes characters to a character string variable of type VARYING OF CHAR or discriminated STRING by converting the values of the parameters in the procedure call to textual representations The behavior of WRITEV is similar to that of the WRITELN function the character string parameter is similar to a one line file WRITEV str parameter list ERROR error recovery The str parameter is the string to be written to The parameter list parameter is the variables to be assigned to str Predeclared Functions and Procedures 8 51 8 110 The error recovery parameter is the action to be taken if an error occurs during execution of the routine The str parameter cannot appear within the parameter list if you attempt to do this unexpected results may occur An error occurs if WRITEV reaches the maximum length of the character string before the values of all the parameters in the procedure call have been written into the string The error recovery parameter indicates the action to be taken if an error occurs while the WRITEV procedure is executing Consider the following example TYPE Flower Daisy Lily Orchid Tulip VAR Real Var REAL VALUE 232 705 Write String VARYING 21 OF CHAR Bouquet Flower VALUE Orchid In the executable section WRITEV Write
317. m Team Rec VALUE ZERO Team Team Rec VALUE Total Wins 5 Total Losses 2 Total Percentage 7 5 Player2 Wins 5 Losses 2 Percentage 7 5 OTHERWISE ZERO Initializes Playerl and Player3 To create a constructor for a record that contains a variant use the reserved word CASE followed by one of the following Atag identifier and a colon followed by a constant expression if you use both a tag identifier and a tag type identifier in the declaration e A constant expression if you use only a discriminant identifier or a tag type identifier in the declaration To complete the constructor use the reserved word OF followed by component list values contained in a nested constructor Consider the following valid constructors Data Types and Values 2 29 TYPE Orders RECORD Part 1 9999 CASE On_Order BOOLEAN OF TRUE Order Quantity INTEGER Price REAL FALSE Rec Quantity INTEGER Cost REAL END VAR An Order Orders VALUE Part 2358 CASE On Order FALSE OF Rec Quantity 10 Cost 293 99 In the executable section constructor type is required An Order Orders Part 2358 CASE On Order FALSE OF Rec Quantity 10 Cost 293 99 Note that if you use a constructor in the type definition you can specify an initial state for only one variant in the type To specify an initial state for more than one variant you must put initial state specifiers on the fields themse
318. mal parameter value in a routine to be passed by reference using foreign semantics Usage and Default Information e The REFERENCE attribute is not allowed on formal parameters of schema types Consider the following example PROCEDURE Test1 P1 REFERENCE INTEGER P2 IMMEDIATE INTEGER EXTERNAL This example defines a procedure Test1 which has two parameters The first parameter P1 is passed by reference The second parameter P2 is passed by immediate value For More Information e On default parameter passing Section 6 3 e On the IMMEDIATE attribute Section 10 2 20 10 2 36 STATIC The STATIC attribute causes HP Pascal to create a static object which is allocated only once and exists as long as the executable image in which it is allocated remains active Usage and Default Information e You can override the default automatic for variables declared in nested blocks or in the outermost level of compilation units by specifying the STATIC attribute on the variable e By default variables declared at the outermost level of a module are static 10 36 Attributes e Global and external variables are implicitly static so they conflict with the AUTOMATIC attribute e A variable having the AT COMMON or PSECT attribute is implicitly static e Allocation attributes can not be applied to nonstatic types Consider the following example PROGRAM Print Random OUTPUT VAR i AUTOMATIC INTEGER FUN
319. mant schema is the length of the string being passed Consider the following example PROCEDURE Print String String Parm CLASS S PACKED ARRAY LOW HIGH INTEGER OF CHAR BEGIN WRITELN The CLASS S string is String Parm WRITELN The lowerbound is Low WRITELN The upperbound is High END The previous example defines the procedure Print_String which has one parameter The CLASS_S attribute on the HP Pascal routine specifies that the calling routine passes the String Parm parameter by a CLASS S descriptor For More Information e On HP Pascal parameter defaults Section 6 3 On mixed language programming HP Pascal for OpenVMS User Manual On CLASS A and CLASS S descriptors HP OpenVMS Calling Standard 10 14 Attributes 10 2 12 COMMON The COMMON attribute specifies that storage for a variable be allocated in an overlaid program section called a common block COMMON identifier identifier An identifier that indicates the name of the common block If you omit the identifier the name of the variable is used as the name of the common block This attribute allows you to share variables with other HP languages such as HP Fortran Usage and Default Information A variable having the AT COMMON or PSECT attribute is implicitly static The COMMON attribute can be applied only to variables Only one variable can be allocated in a particular common block Therefore the na
320. mation e On programs and modules Section 7 4 e On compilation switches and separate compilation HP Pascal for OpenVMS User Manual 10 2 22 INITIALIZE You can apply the INITIALIZE attribute to procedures to indicate that the procedure is to be called before the main program is entered A compilation unit might include any number of INITIALIZE procedures all of which are called in an unspecified order before the main program is entered Usage and Default Information e In the absence of the INITIALIZE attribute the compiler assumes that a routine can be activated only by actual calls within the program e Within modules you should use the TO BEGIN DO section instead of the INITIALIZE attribute All TO BEGIN DO clauses are executed before INITIALIZE routines e By default INITIALIZE procedures have the characteristics of unbound routines e An INITIALIZE procedure cannot have a formal parameter list 10 22 Attributes e An INITIALIZE procedure cannot be external Consider the following example PROGRAM Routine Activate INITIALIZE PROCEDURE Check Open Procedure body In the executable section BEGIN HP Pascal activates Check Open Body of program In this example the body of the INITIALIZE procedure Check_Open is executed before the main program is activated For More Information e On procedures Section 6 1 e On the UNBOUND attribute Section 10 2 39 10 2 23 KEY You can apply the KEY at
321. me of the common block cannot be used as the name of another common block or program section If an HP Pascal program shares a record variable with a FORTRAN program the fields must be laid out identically in both common blocks Variables declared with the COMMON attribute are longword aligned by default for compatibility with other HP languages For More Information On default allocation for variables declared in the outermost block of a program or in nested blocks Section 10 2 5 On default allocation for variables declared in the outermost block of a module Section 10 2 36 On environment specific information on common blocks Appendix A Attributes 10 15 10 2 13 ENUMERATION SIZE The ENUMERATION SIZE attribute controls the allocation size of unpacked enumerated types and Booleans which are considered enumerated types containing two elements The ENUMERATION SIZE attribute can be used on compilation units TYPE sections and VAR sections When used before a TYPE or VAR section the allocation size for enumerated types is modified only for the duration of the TYPE or VAR section Note that specifying the ENUMERATION SIZE attribute overrides any value that you previously specified with the ENUMERATION SIZE qualifier The ENUMERATION SIZE attribute has the following format ENUMERATION_SIZE keyword For example ENUMERATION SIZE Byte TYPE enum red blue green enum2 circle square triangle
322. ment for that expression To initialize a set to the empty set do the following VAR Day SET OF 1 31 VALUE 2 4 4 FILE Type 2 32 A file is a sequence of components of the same type The number of components is not fixed a file can be of any length The FILE type definition identifies the component type and has the following form PACKED FILE OF attribute list component type attribute list One or more identifiers that provide additional information about the file components component type The type of the file components This type can be any ordinal real pointer or structured type except for the following e A nonstatic type e A structured type with a nonstatic component e A file type e A structured type with a file component The arithmetic relational Boolean and assignment operators cannot be used with file variables or structures containing file components You cannot form constructors of file types Data Types and Values When you declare a file variable in your program HP Pascal automatically creates a file buffer variable of the component type This variable takes on the value of one file component at a time To reference the file buffer variable write the name of the associated file variable followed by a circumflex No operations can be performed on the file while a reference to the file buffer variable exists The following example shows two ways to declare files VAR True Fals
323. ments in the programs indicate the names of the program sections used Example A 1 Using Program Sections to Allocate Storage PROGRAM Allocate Variables INPUT OUTPUT CONST Message String Random String Literal SLITERAL on OpenVMS 164 SLITERAL on OpenVMS Alpha SCODE on OpenVMS VAX VAR Magic Number READONLY PSECT Magic INTEGER VALUE 42 Magic Local Variable INTEGER SSDATAS on OpenVMS 164 SDATAS on OpenVMS Alpha SLOCAL on OpenVMS VAX PSECT Error Routines PROCEDURE User Error CONST User Error Message Internal Error Error Routines continued on next page Data Storage and Representation A 9 Example A 1 Cont Using Program Sections to Allocate Storage VAR Error Count STATIC INTEGER VALUE 0 SDATAS on OpenVMS 164 i SDATAS on OpenVMS Alpha LOCAL on OpenVMS VAX Message Buffer VARYING 132 OF CHAR Automatic Storage BEGIN Error Routines Error Count Error Count 1 Local Variable Error Count END BEGIN SCODE or CODE END Storage for all variables with static allocation is allocated in SDATA DATA or LOCAL Storage for the executable block of the main program is allocated in CODE or CODE Storage for the symbolic constant Message_ String is allocated in LITERAL on OpenVMS I64 and OpenVMS Alpha systems and in CODE on OpenVMS VAX systems Storage is allocated in the user created program section Error_Routines for the symbolic constant
324. meters for end of line comments ALFA CARDINAL CARDINAL16 C_STR_T INTEGER_ADDRESS CARDINAL32 INTEGERS INTEGER16 INTEGER32 INTEGER64 INTSET POINTER UNIV PTR UNSIGNED8 UNSIGNED16 UNSIGNED32 UNSIGNED64 SINGLE F floating and S floating DOUBLE D floating G_ floating and T floating QUADRUPLE H floating and X floating STRING TIMESTAMP VARYING OF CHAR structured type and concatenation operator for all strings ARGV ASSERT BARRIER CLOSE CREATE DIRECTORY DATE DELETE DELETE FILE ESTABLISH EXTEND FIND FINDK HALT LINELIMIT LOCATE MESSAGE OPEN READV REMOVE RENAME FILE RESETK REVERT STLIMIT TIME TRUNCATE UNLOCK UPDATE WRITEV GETTIMESTAMP Transfer functions DBLE INT INT64 QUAD ROUND64 SNGL TRUNC TRUNC64 UINT UINT64 UROUND UROUND64 UTRUNC UTRUNC64 continued on next page B 2 Summary of HP Pascal Extensions Table B 1 Cont HP Pascal Extensions to Unextended Pascal Category Extension READ READLN WRITE WRITELN extensions Implicitly declared type conversion and type casting routines for predefined data types Dynamic allocation function ADDR ADDRESS IADDRESS IADDRESS64 Character string functions BIN DEC HEX INDEX LENGTH OCT PAD STATUSV SUBSTR UDEC GT GE LT LG EQ NE Parameter functions ARGUMENT ARGUMENT LIST LENGTH PRESENT Privileged routines MFPR MTPR Arithmetic functions BITAND BITNOT BITOR BITXOR LSHFT LSHIFT MIN M
325. module that inherited it If a module or program inherits more than one module that contains an initialization section the order of execution of the inherited modules is undefined Consider the following example ENVIRONMENT Modl MODULE Modi VAR i INTEGER TO BEGIN DO l 25 In a separate compilation unit INHERIT Modi MODULE Mod2 VAR j INTEGER TO BEGIN DO j i 1 First execute code in Modl for correct results Figure 3 1 shows the order of execution of initialization and finalization sections Each circle is a module that contains both a TO BEGIN DO and a TO END DO section and each arrow indicates the order of inheritance for the environment files 3 4 Declaration Section Figure 3 1 Order of Execution for TO BEGIN DO and TO END DO Sections Order of Execution TO BEGIN DO TO END DO om First Third qu qu Second Second Module 4 Third First ZK 1321A Al The execution order for initialization and finalization sections in Modules 2 and 3 cannot be determined The headers for the modules in Figure 3 1 are as follows ENVIRONMENT MODULE Modi ENVIRONMENT INHERIT Modl MODULE Mod2 ENVIRONMENT INHERIT Mod1 MODULE Mod3 INHERIT Mod2 Mod3 MODULE Mod4 The name of the compiler generated initialization routine is formed by taking the module name and appending INIT If you wish to provide a different name you can use the GLOBAL attribute o
326. mponent component ZK 1332A GE You cannot insert components between any two existing components because no physical space separates them You can only add records to the end of the file the most recently added component truncate the file from a specified component to the end of the file or rewrite the file For More Information e On component formats in sequential files Section 9 2 e On access methods for sequential files Section 9 3 9 1 2 Relative File Organization Relative file organization consists of a series of fixed length component positions called cells numbered consecutively from 1 to n The numbered fixed length cells enable HP Pascal to calculate the component s physical position in the file The cell numbers are called relative component numbers HP Pascal supports this organization on disk files only Figure 9 2 shows this file organization Input and Output Processing 9 3 Figure 9 2 Relative File Organization Relative Cells First Second Third Fourth Fifth component component component component component written written written written written ZK 1333A GE Each component in the file may be randomly assigned to a specific cell You can place components in unused cells and in cells from which components have been deleted You cannot replace a component in a cell but you can modify an existing component The length of the actual component may vary even though the cell containing the co
327. mponent formats Table 9 3 Acceptable Types of Stream Component Formats Type Description STREAM_CR This type recognizes a carriage return character as the component terminator STREAM LF This type recognizes a line feed as the component terminator STREAM This type uses a terminator from a limited set of special characters the carriage return CR the carriage return line feed combination CR LF or the form feed FF 9 3 Component Access Modes A component access mode is a method by which HP Pascal retrieves components from a file You cannot change the file organization or component format after file creation but you can change the component access mode each time you access a file The HP Pascal I O model defines two component access modes sequential and random access Random access can be further broken down into the categories of random access by number also called direct access and random access by key value also called keyed access The following sections describe these access methods in further detail You specify the access method using the OPEN procedure when you open a file You cannot change the access method unless you first use the CLOSE routine and then reopen the file specifying a new access method Before trying to use any of the access methods on a file HP Pascal determines the organization of the file The organization determines how the specified access method works For instance sequential access
328. mponent is of a fixed length If the component is smaller than the cell the remaining space in the cell is unused For More Information e On component formats in relative files Section 9 2 e On access methods for relative files Section 9 3 9 1 3 Indexed File Organization 9 4 Indexed file organization specifies that in addition to the stored components there exists at least a primary key and possibly alternate keys first alternate key second alternate key and so forth HP Pascal uses the primary key to store components and uses a program specified key or keys to retrieve data HP Pascal supports this organization on disk files only To define a key and certain characteristics of keys use the KEY attribute You can define up to 254 alternate keys Input and Output Processing An index is a structure that provides a component collating sequence for the file that is a mechanism for accessing components in different orders depending on the specified index name address telephone number and so forth Figure 9 3 shows an indexed file organization that uses only a primary key Figure 9 3 Indexed File Organization KEY DEFINITION Primary Index Em iployee Name ADAMS eee BAKER CLARK JONES SMITH TAYLOR WYMAN i Y ADAMS PINEST 35112 coe CLARK ELM AVE 24379 JONES
329. multiplying or dividing by a power of two when the value of the integer is negative If the number of bits shifted is larger than the natural integer size of the target platform the result is undefined For More Information e On the LSHIFT function Section 8 52 8 80 SEED Function The SEED function has a single integer parameter that sets the random number generator seed for the RANDOM function The function returns an integer that represents the previous seed value SEED expression The expression parameter is an integer For More Information e On the RANDOM function Section 8 73 Predeclared Functions and Procedures 8 39 8 81 SET INTERLOCKED Function The SET_INTERLOCKED function assigns the value TRUE to the parameter and returns its original Boolean value SET_INTERLOCKED b The parameter b must be a variable of type BOOLEAN The variable does not have to be aligned therefore it can be a field of a packed record 8 82 SIN Function The SIN function returns a real value that represents the sine of the specified parameter SIN x The parameter x can be an integer or REAL type and is expressed in radians 8 83 SIZE Function The SIZE function returns an integer value that indicates the possible or actual number of bytes that are allocated for a specified data type or variable SIZE x tt tn The parameter x can be a type identifier or variable If x is a type identifier then the functions
330. must be local to the asynchronous routine or must themselves be asynchronous either by default or by an explicit attribute Attributes 10 7 10 2 4 e All nonlocal variables accessed from within the block of an asynchronous routine must be declared VOLATILE or READONLY e Ifa formal routine parameter is asynchronous all actual parameters passed to it must also be asynchronous e An asynchronous routine can be passed as an actual parameter to a formal routine parameter that does not have this attribute Consider the following example PROCEDURE Do Something VAR i VOLATILE INTEGER j INTEGER ASYNCHRONOUS FUNCTION Handler Two array parameters BOOLEAN BEGIN i i 41 Remaining function body In the executable section of the procedure ESTABLISH Handler This example shows the declaration of the asynchronous function Handler The executable section of Handler cannot access variables declared in the enclosing block of the procedure Do_Something unless those variables are declared VOLATILE Handler can access the variable i which has the VOLATILE attribute but cannot access the variable j For More Information e On the VOLATILE attribute Section 10 2 42 e On the READONLY attribute Section 10 2 34 e On the ESTABLISH procedure Section 8 30 AT The AT attribute specifies that HP Pascal allocates no storage for the object storage has already been allocated and that it resides at the exact speci
331. n 2 5 Schema Types e Section 2 6 String Types e Section 2 7 Null Terminated Strings e Section 2 8 TIMESTAMP Type e Section 2 9 Static and Nonstatic Types e Section 2 10 Type Compatibility For More Information e On user defined types and the TYPE section Section 3 5 e On variable declarations and the VAR section Section 3 7 e On automatic type conversions Section 4 4 e On type conversion functions Chapter 8 e Internal representation of data types Section A 3 Data Types and Values 2 1 2 1 Ordinal Types This section describes the ordinal types that are predefined by HP Pascal and user defined ordinal types types that require you to provide identifiers or boundary values to completely define the data type The ranges of values for these types are ordinal in nature the values are ordered so that each has a unique ordinal value indicating its position in a list of all the values of that type There is a one to one correspondence between the values in an ordinal type and the set of positive integers 2 1 1 Integer Types HP Pascal makes available the INTEGER INTEGER64 UNSIGNED UNSIGNED64 and INTEGER ADDRESS predeclared types These data types are described in Section 2 1 1 1 Section 2 1 1 2 and Section 2 1 1 4 respectively 2 1 1 1 INTEGER and INTEGER64 Types HP Pascal provides the INTEGER and INTEGERGO4 not available on all systems integer types Also provided are the INTEGER8 INTEGER16 and INTEGER3
332. n 9 7 e On specifying radixes for output Section 9 6 3 and Section 9 6 4 Input and Output Processing 9 55 9 8 16 READLN Procedure The READLN procedure reads lines of data from a TEXT file READLN file variable variable identifier radix specifier ERROR error recovery file variable The name of the file variable associated with the TEXT file to be read If you omit the name of the file the default is INPUT variable identifier The name of the variable into which a value will be read multiple identifiers must be separated with commas If you do not specify any variable names READLN skips a line in the specified file radix specifier One of the format values BIN OCT or HEX These values when used on a variable identifier read the variable in binary octal or hexadecimal respectively You can use a radix specifier only when reading from a TEXT file error recovery The action to be taken if an error occurs during execution of the routine The file must be in inspection mode before READLN is called it remains in that mode after the procedure s execution The READLN procedure reads values from a TEXT file After reading values for all the listed variables the READLN procedure skips over any characters remaining on the current line and positions the file at the beginning of the next line The values need not all be on a single line READLN continues until values have been assigned to all the
333. n apply this attribute to routines and formal routine parameters In the absence of an UNBOUND attribute the compiler assumes that the bound procedure value of a routine includes the static scope pointer By default all predeclared routines and all routines declared at program or module level have the characteristics of unbound routines All routines declared in nested blocks are considered bound unless they have an UNBOUND GLOBAL WEAK_GLOBAL or INITIALIZE attribute All routines called from within the block of an unbound routine must be local to the unbound routine or be unbound whether by default or by an explicit attribute Attributes 10 41 e Nonlocal variables accessed from within the block of an unbound routine cannot have automatic allocation e Ifa formal routine parameter is unbound all actual routine parameters passed to it must also be unbound e You can pass an unbound routine as an actual parameter to a formal routine parameter that is not unbound Consider the following example EXTERNAL FUNCTION f IMMEDIATE UNBOUND PROCEDURE Count BOOLEAN EXTERNAL PROCEDURE a VAR i STATIC INTEGER b BOOLEAN UNBOUND PROCEDURE p BEGIN i i 41 Additional statements END b ss fp END This example shows the declaration of the unbound procedure p and the unbound formal procedure parameter Count The executable section of p cannot access variables declared in the enclosing block of procedure a
334. n the top of the module to specify a different name For example ENVIRONMENT GLOBAL MYINIT MODULE Modl This alternate name is encoded in the resulting environment file so all modules that inherit this environment will automatically call the initializaton routine by its new alternate name For More Information e On modules Section 7 4 e On environment files Section 7 5 1 Declaration Section 3 5 3 4 TO END DO Section The TO END DO section allows you to specify a statement in a module that is to be executed after the executable section of the main program it has the following form TO END DO statement statement A Pascal statement The TO END DO section can only appear in modules can only appear once in a module and must appear as the last section in the declaration section If appearing together the TO END DO section must come after the TO BEGIN DO section at the end of the declaration section As a general rule if a compilation unit inherits an environment file the finalization section in the inheriting compilation unit must be executed before the finalization section in the inherited compilation unit Also if more than one module with a finalization section inherits a single module the order of finalization of the inheriting modules cannot be determined Figure 3 1 shows an example of the order of execution of TO END DO sections The compiler implements a TO END DO section by creating an invisible T
335. ndent of the setting of the FLOAT qualifier or attribute Table 2 8 identifies the built in types available by system 2 12 Data Types and Values Table 2 8 Floating Data Types Data Type System F_FLOAT OpenVMS 164 OpenVMS Alpha OpenVMS VAX D_FLOAT OpenVMS 164 OpenVMS Alpha OpenVMS VAX G_FLOAT OpenVMS 164 OpenVMS Alpha OpenVMS VAX H_FLOAT OpenVMS VAX S_FLOAT OpenVMS 164 OpenVMS Alpha OpenVMS VAX T_FLOAT OpenVMS I64 and OpenVMS Alpha X_FLOAT OpenVMS I64 and OpenVMS Alpha To express REAL numbers you can use either decimal or exponential notation To express DOUBLE or QUADRUPLE numbers you must use exponential notation To express REAL numbers in decimal notation use the set of decimal digits and a decimal point At least one digit must appear on either side of the decimal point The following are valid real numbers in decimal notation 2 4 893 2497 8 0 0 0 To express real numbers in exponential notation you include a real number or an integer an uppercase or lowercase letter indicating the type of precision and an integer exponent with its minus sign or optional plus sign For example 2 3E2 10 0E 1 9 14159e0 Table 2 9 presents the letters that indicate precision in exponential notation Data Types and Values 2 13 Table 2 9 Precision in Exponential Notation Letters Meaning E ore Single precision real number The integer exponent following this letter specifies the power of 10 Dord
336. ned in memory positional syntax A syntax for passing actual parameters that specifies that the parameters in the actual and formal lists must correspond exactly from left to right item by item through both lists Glossary 9 predeclared identifier A character string that is predeclared by the compiler to have a given meaning but that can be redefined in a program HP Pascal predeclared identifiers include names of data types symbolic constants file variables procedures and functions primary key A key value in components of a file of indexed organization that indicates the order in which HP Pascal stores the file components procedure A subprogram that contains one or more statements to be executed once the procedure is called program A set of instructions that can be compiled and executed by itself Program blocks contain a declaration and an executable section program heading See heading property A characteristic of a program section PSECT that determines memory allocation and sharing The term property is synonymous with the OpenVMS term attribute random access An access method that allows you to access a specified component in a relative or indexed file and also in sequential files with fixed length components The order of access is not dependent on the order in which the components are stored record A group of components called fields which can be of various data types recursion The act o
337. nents 1 Not allowed on variables larger than INTEGER or structured variables 10 56 Attributes 11 Directives Your source code can contain embedded directives which will be evaluated at compile time These directives can appear in any column and do not have to be on a line by themselves You can use directives to control your compilation and to extract immediate information at compile time The directives implemented in HP Pascal are shown in the following table Directives Section 7c INCLUDE 11 1 76 DICTIONARY 11 2 9C TITLE and SUBTITLE 11 3 9o F YELSE ELIF and ENDIF 11 4 9o DEFINED 11 5 ERROR WARN INFO and MESSAGE 11 6 ARCH_NAME SYSTEM_NAME and SYSTEM_VERSION 11 7 DATE TIME and 7COMPILER_VERSION 11 8 LINE FILE ROUTINE MODULE and IDENT 11 9 11 1 INCLUDE INCLUDE inserts the contents of a file at the location of the directive in the code and has the following form YINCLUDE file spec NOT LIST Directives 11 1 file spec environment specific default The name of the file to be included NO LIST LIST default The LIST qualifier indicates that the included file should be printed in the listing of the program if a listing is being generated If you do not specify the LIST qualifier the default is determined by the use of compilation switches Use of this parameter overrides compilation switches This directive can appear anywhere that a comment i
338. nformation e On component access Section 9 3 e On the error processing parameter Section 9 7 e On retrieval of file components Section 9 5 3 9 8 4 EOLN Function The EOLN function tests for the end of line marker within a text file and returns a Boolean value EOLN file variable file variable The name of a file variable associated with a text file If you omit the name of the file the default is INPUT The file must be in inspection mode and EOF must return FALSE before EOLN is called EOLN leaves the file in inspection mode The Boolean EOLN function returns TRUE when the file pointer is positioned after the last character in a line When the EOLN function returns TRUE the file buffer contains a blank character The EOLN function returns FALSE when the last component in the line is read into the file buffer Another character must be read to cause EOLN to return TRUE and to cause the file buffer to be positioned at the end of line marker following the last character of the line If you use the EOLN function on a nontext file an error occurs 9 34 Input and Output Processing Consider the following example WHILE NOT EOF Master File DO BEGIN WHILE NOT EOLN Master File DO BEGIN READ Master File x IF NOT x IN A 2 a z 0 9 THEN Err Err 1 END READLN Master File END This example scans the characters on each line of a TEXT file called Master File and checks for ch
339. nism specifiers Section 6 3 5 e On the UNSAFE attribute Section 10 2 40 e On type conversions Section 4 4 6 3 2 Variable Parameters By the rules of variable semantics defined by the Pascal standard a formal variable parameter represents another name for a variable in the calling block It is preceded by the reserved word VAR When you specify variable semantics the address of the actual parameter is passed to the called routine In contrast to value semantics the called routine directly accesses the actual parameter Thus the routine can assign a new value to the formal parameter during execution and the changed value is reflected immediately in the calling block the value of the actual parameter changes HP Pascal uses variable semantics to pass data to a formal parameter often called a formal VAR parameter and has the following form type identifier VAR identifier tues undiscriminated schema name conformant parameter syntax mechanism specifier default value 6 10 Procedures and Functions identifier The name of the formal parameter Multiple identifiers must be separated with commas attribute list One or more identifiers that provide additional information about the formal parameter type identifier The type identifier of the parameters in this parameter section undiscriminated schema name The name of an undiscriminated schema type conformant parameter syntax The type syntax of a conf
340. nment Software Translator to run on OpenVMS Alpha systems See also Translated Image Environment and VAX Environment Software Translator Translated Image Environment An OpenVMS Alpha systems shareable image that is applied to a translated image at run time TIE provides an environment similar to OpenVMS VAX for the translated image and processes all interactions with the native OpenVMS Alpha system TIE is selected with a switch at compile time undefined mode A file state that indicates when the file is in an undefined state of processing undiscriminated schema type A schema type that has not been provided actual discriminants These types are used as the domain type of a pointer or as a formal parameter unextended Pascal standard The International Standard ISO 7185 1989 See also Extended Pascal standard user action function A function that you write and provide to HP Pascal to use Record Management Services RMS features to open or close a file variable length component format A component format that specifies that file components have lengths that vary See also component and component format VAX Environment Software Translator VEST A software application that analyzes a VAX system binary image and creates a functionally equivalent translated image that runs on OpenVMS Alpha systems Glossary 13 A ABS program section A 2 ABS function 8 3 Absolute value of a parameter 8 3 Access methods 9 11 to 9
341. ns the file after the last component relative to the primary key Consider the following example VAR f FILE OF INTEGER In the executable section OPEN File Variable f File Name sample dat History OLD Organization Relative Access Method Direct EXTEND f F 20 PUT f These statements open an existing relative file named sample dat The file will be positioned after the last record in the file Subsequent PUT statements will append new components to the end of the file For More Information e On component access Section 9 3 e On default values for the OPEN procedure Section 9 8 12 e On the error processing parameter Section 9 7 9 8 6 FIND Procedure 9 36 The FIND procedure positions a file at a specified component The file must be open for direct access and must contain fixed length components FIND file variable component number ERROR error recovery file_variable The name of a file variable associated with a file that is open for direct access component number A positive integer expression that indicates the component at which the file is to be positioned If the component number is zero or negative a run time error occurs Input and Output Processing error recovery The action to be taken if an error occurs during execution of the routine The FIND procedure allows direct access to the components of a file You can use the FIND procedure t
342. ns the file SUBMIT_DELETE HP Pascal submits to a queue or places the print job in a background process and deletes the file file_sharing READONLY default for HISTORY READONLY NONE default for other histories A value that specifies whether another program can access the file while it is open A value of READONLY indicates that other programs can read but not write to the file A value of READWRITE indicates that a program can both read and write to the file while it is open A value of NONE indicates that a program cannot read or write from the open file default_file_name no default A string expression containing default file specification information For instance you can use this value to set a default directory specification user_action no default A name of a user written routine that HP Pascal calls to open the file instead of allowing HP Pascal to open the file with the OPEN procedure You can use a user action routine to open the file using environment specific capabilities of the I O system underlying HP Pascal error_recovery stops execution after first error default The action to be taken if an error occurs during execution of the routine Input and Output Processing 9 47 Using the OPEN procedure Before the OPEN procedure is called the file is in undefined mode its mode does not change after OPEN has been executed You cannot use OPEN on a file variable that is already open If you use IN
343. nteger and a real value RESET DataFile MyInt DataFile Fieldl MyReal DataFile Field2 Read component into the file buffer Copy the integer field into MyInt Copy the real field into MyReal The assignments use the FILE variable to refer to components of the file buffer In each file all components are of the same file component format Component format defines the size or maximum size of each component and any processing information needed in addition to the data portion of the component The HP Pascal I O model supports the following formats for file components e Fixed length format Section 9 2 1 e Variable length format Section 9 2 2 e Stream format Section 9 2 3 Default Information For new TEXT and VARYING OF CHAR files HP Pascal creates variable length components by default For other types of new files HP Pascal creates fixed length components If you access an existing file your specified component type must match the component type specified at the creation of the file if it does not you generate an error Table 9 2 shows which of the file organizations support which of the component formats Input and Output Processing 9 9 Table 9 2 File Organization Support for Component Formats Organization Supported Component Format Sequential All component formats Relative Fixed length Variable length Indexed Fixed length Variable length Although the relative file organizat
344. o a formal parameter of a routine and indicates that the routine can be called with multiple actual parameters that correspond to the last formal parameter named in the routine heading You can also use the ARGUMENT and ARGUMENT LIST LENGTH predeclared routines when writing procedures and functions that use the LIST attribute Usage and Default Information e In the absence of a LIST attribute an error results if the number of actual parameters exceeds the number of formal parameters e You can apply the LIST attribute only to the last formal parameter in a parameter list e You can supply zero one or more than one actual parameter to correspond to a LIST formal parameter but you must use positional syntax when supplying them The number of actual parameters you can supply is limited to 255 Attributes 10 25 e You can use the LIST attribute on the parameter list of a routine parameter but you must use positional syntax when specifying them Using the LIST attribute on routine parameters is allowed only on external routines e You can use the LIST attribute on conformant parameters to indicate that an external routine can take an arbitrary number of arrays or VARYING OF CHAR parameters respectively Using the LIST attribute on conformant parameters is allowed only on external routines e All actual parameters that correspond to a LIST formal parameter must be compatible or congruent with the type of the formal parameter e Fo
345. o move forward or backward in a file After execution of the FIND procedure the file is positioned at the specified component The file buffer variable assumes the value of the component and the file mode is set to inspection If the file has relative organization the current file component is locked If there is no file component at the selected position the file buffer is undefined UFB becomes TRUE and the mode becomes undefined After any call to FIND the value of EOF is undefined You can use the FIND procedure only when reading a file that was opened by the OPEN procedure If the file is open because of a default open that is with EXTEND RESET or REWRITE a call to FIND results in a run time error because the default access method is sequential Consider the following example FIND Albums Current 2 If the value of Current is 6 this procedure causes the file position to move to the eighth component the file buffer variable Albums assumes the value of the component If no eighth component exists Albums is undefined and UFB Albums returns TRUE For More Information e On component access Section 9 3 e On the UFB function Section 9 8 22 e On the error processing parameter Section 9 7 9 8 7 FINDK Procedure The FINDK procedure searches the index of an indexed file opened for keyed access and locates a specific component FINDK file variable key number key value match type ERROR error re
346. object can accept values of any type without type checking Value VALUE Indicates that the variable is a reference to an external constant or is the defining point of a global constant Visibility LOCAL EXTERNAL Indicate the ability of an object to be GLOBAL shared by compilation units WEAK EXTERNAL WEAK GLOBAL Volatile VOLATILE Indicates that the value of an object can change at unusual points in program execution Write only WRITEONLY Indicates that the object can be written to but cannot be read 10 54 Attributes Some attributes are allowed to appear on routine declarations routine parameters and compilation units Table 10 8 lists these attribute classes Table 10 8 Attributes on Routines and Compilation Units Program Element Class Routine Compilation Parameter Routine Unit Allocation No Yes Yes Asynchronous Yes Yes No Check No Yes Yes Double precision No No Yes Enumeration No No Yes Environment No No Yes Ident No No Yes Inherit No No Yes Initialize No Yes No List Yes No No Optimization No Yes Yes Truncate Yes No No Unbound Yes Yes No Visibility No Yes Yes 1 PSECT is the only allocation attribute allowed Allowed only on EXTERNAL routine definitions 3 EXTERNAL and WEAK EXTERNAL are not allowed Attribute classes are allowed on various data items Table 10 9 lists the classes that can be applied to various data items Attributes 10 55 Table 10 9 Attributes on Data I
347. ocked to prevent access by other processes GET file variable ERROR error recovery file variable The name of the file variable associated with the input file error recovery The action to be taken if an error occurs during execution of the routine Before the GET procedure is used for the first time to read one or more file components the file must be in inspection mode and prepared for reading input Depending on the access method specified when the file was opened you can prepare the file for input in the following ways e If the file is open for sequential access call the RESET procedure RESET sets the mode to inspection advances the file position to the first component and assigns the component s value to the file buffer variable e If the file is open for direct access call either the RESET or the FIND procedure to position the file Input and Output Processing 9 39 e If the file is open for keyed access call the FINDK RESET or RESETK procedure to position the file As a result of the GET procedure the file remains in inspection mode and the file position advances to the next component If a component is found other than the end of file marker the component is locked EOF is set to FALSE the file buffer variable takes on the value of the component and UFB is set to FALSE If a component is not found or the end of the file is reached EOF and UFB are set to TRUE If the GET procedure fails UFB is se
348. of an option disables that optimization The valid options are ALL NONE INLINE NOINLINE Table 10 5 lists the options Attributes 10 29 Table 10 5 OPTIMIZE Attribute Options Option Action OPTIMIZE Enables all optimization components Inline OPTIMIZE ALL expansion of user defined routines is enabled in automatic selection mode OPTIMIZE NOINLINE Disables inline expansion for user defined routines All other optimization components are enabled or disabled according to the command line or the setting of the OPTIMIZE attribute on an enclosing scope routine OPTIMIZE INLINE Enables preferential inline expansion of user defined routines All other optimization components are enabled disabled according to the command line on an enclosing scope routine OPTIMIZE ALL NOINLINE Enables all optimization components disables inline expansion for user defined routines OPTIMIZE NONE INLINE Disables all optimization components enables inline expansion of user defined routines NOOPTIMIZE OPTIMIZE NONE Disables all optimization components disables inline expansion of user defined routines Usage and Default Information e This attribute can be applied to routines and compilation units e Optimization features specified with the OPTIMIZE attribute override command line settings and settings inherited from outer scopes e The INLINE option specifies that a routine should be inlined preferentially r
349. ollowed by the fill character which is repeated as many times as is necessary to extend the string to its specified size The final size must be greater than or equal to the length of the string to be padded For More Information e On character strings Section 2 6 8 34 Predeclared Functions and Procedures 8 68 PAS_STR Function The PAS_STR function returns a Pascal string value from a C_STR_T value PAS_STR e The type of the expression e must be C_STR_T It is an error if the expression is NIL 8 69 PAS STRCPY Function The PAS STRCPY function copies a Pascal string expression into memory pointed to by C STR T PAS STRCPY v e The type of the variable v must be C STR T The type of the expression e must be a Pascal string expression The Pascal string is copied into the memory pointed to by the variable v The memory is then terminated with a null character The function returns a C STR T value representing the destination such as the same value as contained by the variable v The behavior of PAS STRCPY is undefined if the length of the Pascal string expression is greater than or equal to the amount of memory pointed to by the variable v It is an error if the variable v is NIL 8 70 PRED Function The PRED function returns the value preceding the parameter according to the parameter s data type PRED x The parameter x can be of any ordinal type however there must be a predecessor value for x in the type
350. omponents of a packed array to formal VAR parameters you must unpack the array first Consider the following example VAR p PACKED ARRAY 1 10 OF CHAR ARRAY 1 10 OF CHAR i INTEGER PROCEDURE Process Components VAR Ch CHAR Body In the executable section READ p UNPACK p a 1 FOR i 1 TO 10 DO Process Components a i Pass each component to procedure For More Information e On arrays and packed arrays Section 2 4 1 UOR Function The UOR function returns an unsigned value of a binary logical OR operation on the corresponding pair of bits of two specified parameters UOR ut u2 The u1 and u2 parameters must be unsigned Consider the following example Result UOR 16 FF9 168703 Returns 16 FFB For More Information e On specifying extended digit notation Section 2 1 1 1 8 48 Predeclared Functions and Procedures 8 102 8 103 UPPER Function The UPPER function returns the upper bound for ordinal types SET base types and array indexes UPPER x n The parameter x is a type identifier or variable of an ordinal SET or ARRAY type The parameter n is an integer constant that denotes a dimension of x if x is an array If x is an array and if you omit the parameter n HP Pascal uses the default value 1 If x is an array UPPER returns the upper bound of the nth dimension of x If x is an ordinal type UPPER returns the upper bound or largest value If x is a S
351. on 10 2 17 On linking HP Pascal for OpenVMS User Manual 10 2 45 WORD The WORD attribute specifies the amount of storage in words to be received by the object WORD n I The optional constant n indicates the number of word storage units For More Information e On allocation sizes of objects Section A 2 4 e On size attribute restriction Section 10 2 6 10 2 46 WRITEONLY The WRITEONLY attribute specifies that an object can have values assigned to it but cannot be read by a program Attributes 10 51 Usage and Default Information e You can apply this attribute to variables formal parameters the base types of pointer variables and components of structured variables e By default objects can be both read and written e A write only object cannot be used in expressions e A write only component in an object of a structured type prohibits the object from being read e A write only actual variable parameter can be passed only to a formal variable parameter that is write only e A pointer expression whose base type is write only is assignment compatible only with a pointer variable whose base type is write only Consider the following example PROGRAM SAMPLE TYPE W Only WRITEONLY INTEGER VAR Writ Int W Only Norm Int INTEGER PROCEDURE Try Access VAR Write Param W Only EXTERNAL In the executable section Writ Int SQR Norm Int Try Access Writ Int This example s
352. on when combined with subrange checking Consider the following type word word 0 65535 procedure take_a_word p word begin writeln p end begin take_a_word 90000 end When HP Pascal passes value parameters of a subrange type the actual parameter is evaluated as an expression of the base type INTEGER in the above case This allows the actual parameter to be larger than the size attribute in the subrange This is done to allow the subrange check in the called routine to function properly For value parameters HP Pascal allocates a local variable of the parameter s type and then assigns the parameter into the local variable That local variable is then used throughout the body of the routine wherever the parameter is referenced Subrange checking is performed when an expression of the base type is assigned into a subrange variable Therefore the above routine is similar to the following procedure take a word p_ integer var p word Local copy begin pimp Make local copy and do range check from longword integer expression into word subrange on assignment writeln p end This means that HP Pascal will fetch an entire longword from P when making the local copy If you call Pascal functions from non Pascal routines with value parameters that are subranges you must pass the address of a value with the size of the base type If subrange checking is disabled the compiler can 2 10 Data Types and Val
353. ons among compilation units The following sections discuss ways of sharing data 7 5 1 Environment Files Environment files contain the definitions and declarations from the outermost level of declaration section of a compilation unit that can be shared with other compilation units that inherit the environment file Environment files exist in a form that the compiler can process more easily The following example shows how to use environment files Contained in one file INHERIT file name PROGRAM a INPUT OUTPUT BEGIN READ Amount Calc WRITELN Purchase Amount Amount 10 2 WRITELN Tax 10 2 WRITELN Pay This Total Total 10 2 END Contained in a separate file ENVIRONMENT file name MODULE B Keep all global data in one module CONST Compile this unit first to create file Rate 0 06 VAR Amount Total Tax REAL PROCEDURE Glf BEGIN END PROCEDURE Calc BEGIN Tax Amount Rate Total Tax Amount Glf END END Since the declarations in module b compose the environment file to be inherited by another compilation unit you must compile module b first to create the environment file When compiling module b HP Pascal creates an environment file by the name of file name HP Pascal adds a file type of PEN for Pascal Environment Program Structure and Scope 7 7 The environment file contains declaration information about the constant Rate
354. onsider the following example TYPE A String PACKED ARRAY 1 20 OF CHAR VAR Names TEXT Pres Veep A String In the executable section READ Names Pres Veep This program fragment declares and reads the file Names which contains the following character strings John F Kennedy Lyndon B Johnson Lyndon B Johnson lt EOLN gt Hubert H Humphrey lt EOLN gt Richard M Nixon Spiro T Agnew lt EOLN gt The first call to the READ procedure sets Pres equal to the 20 character string John F Kennedy and Veep equal to Lyndon B Johnson The second call to the procedure assigns the value Lyndon B Johnson to Pres and after encountering the end of line marker fills the array Veep with spaces The file position does not advance to the beginning of the next line until a READLN is performed You can abbreviate values to be read into enumerated variables as shown in the next example TYPE Color Red Fire Engine Green Blue Black VAR Light Color In the executable section READ Light In this example if the letter R is read the variable Light is assigned the value Red However if the letters Redx are read an error occurs If the letters Bl are read an error also occurs because Bl is not unique However the letters Blu are unique and would be interpreted as the constant identifier Blue For More Information e On TEXT files Section 9 5 e On the error processing parameter Sectio
355. ontains the first letter of the substring e Ifthe substring is not found INDEX returns the value 0 e Ifthe substring is an empty string INDEX returns the value 1 e If the string to be searched is an empty string INDEX returns the value 0 unless the substring is also empty in which case INDEX returns the value I Predeclared Functions and Procedures 8 23 e If the substring is found it does not return the string component but the index such as subscript of the component Consider the following example The String The Pilgrims landed at Plymouth Rock Substring Plymouth Rock Position INDEX The String Substring Returns 24 Substring Mayflower Position INDEX The String Substring Returns 0 For More Information e On character strings Section 2 6 8 46 INT Function The INT function converts the parameter and returns its INTEGER equivalent INT x The parameter x must be of an ordinal type Overflow can occur and is detected at runtime if overflow checking is enabled and the value of x is outside the range of INTEGER 8 47 INT64 Function The INT64 function converts the parameter and returns its INTEGER64 equivalent INT64 x The parameter x must be of an ordinal type Overflow can occur and is detected at run time if overflow checking is enabled and the value of x is outside the range of INTEGER64 8 48 LE Function The LE function returns a Boolean value t
356. or this attribute D FLOAT yields REAL F_FLOATING DOUBLE D_FLOATING e G FLOAT yields REAL F FLOATING DOUBLE 2G FLOATING e EEE FLOAT yields REAL S FLOATING DOUBLE T FLOATING For More Information e On floating point numbers Section 2 2 10 2 17 GLOBAL The GLOBAL attribute provides a strong definition of a variable or routine so that other independently compiled units can refer to it GLOBAL d identifier j TT string literal identifier Identifier passed to the linker It is passed in uppercase If you omit the identifier the name of the variable is used as the name of the common block string literal Literal passed unmodified to the linker Attributes 10 19 Usage and Default Information e You can apply the GLOBAL attribute to variables routines and compilation units When used on a MODULE the GLOBAL attribute changes the name of the compiler generated TO BEGIN DO section if present e Global and external variables are implicitly static Thus they conflict with the AUTOMATIC attribute e By default global and external routines have the characteristics of unbound routines e You cannot apply the GLOBAL attribute to variables of nonstatic types For More Information e On default visibility attribute information Section 10 2 25 e On an example of GLOBAL and on the EXTERNAL attribute Section 10 2 15 On compiling and linking HP Pascal for OpenVMS User Manual 10 2 18 HIDDEN The HID
357. orm complete data types the remaining examples in this section use the Array Template declaration TYPE Array Template Upper Bound INTEGER i ARRAY 1 Upper Bound OF INTEGER VAR Arrayl Array Template 10 ARRAY 1 10 OF INTEGER Array2 Array Template x Upper boundary determined at run time by variable or function call 2 38 Data Types and Values In the previous example the actual discriminants 10 and x complete the boundaries for Array_Template forming two complete data types within the same schema type family A schema type that has been provided actual discriminants is called a discriminated schema discriminated schema can appear in either the TYPE or VAR sections The type specifiers Array_ Template 10 and Array_Template x are examples of discriminated schema Actual discriminants can be compile or run time expressions This expression must be assignment compatible with the ordinal type specified for the formal discriminant Also the actual discriminant value must be inside the range specified for the formal discriminant in the case of subranges the upper value must be greater than or equal to the lower value In the previous example 10 and x must be within the range MAXINT MAXINT If you want to use a discriminated schema type as the domain type of a pointer or as the type of a formal parameter give the discriminated schema type a name by declaring it in the TYPE section Consider the following
358. ormant array or a conformant VARYING parameter mechanism specifier The mechanism by which a default value is to be associated with the formal parameter A mechanism specifier can be used only on a declaration for an external routine default value A compile time expression representing the default value for the parameter A default value can be used only on an external routine When you use variable semantics the actual parameter must be a variable or a component of an unpacked structured variable you can pass an entire packed structure no expressions are allowed unless the formal parameter has the READONLY attribute The type of a variable passed to a routine must be structurally compatible with the type of the corresponding formal parameter except for schema parameters For a formal parameter that is an undiscriminated schema type the type of the variable must be discriminated from the same type as that of the formal parameter they must be of the same schema type family For a formal parameter that is a discriminated schema type the type of the variable must be of the same type family and must have equivalent actual discriminants The names of routines are never allowed as variable parameters In addition you must use variable semantics when passing a file variable as an actual parameter Also you cannot pass the tag field of a variant record to a formal VAR parameter Procedures and Functions 6 11 Consider the following exam
359. ormats Acceptable Types of Stream Component Formats File Organization Support for Component Access Modes Carriage Control Characters Default Field Widths File Mode During I O Processing ALIGN Attribute Keywords Summary of Checking Options ENUMERATION SIZE Attribute Keywords KEY Attribute Options OPTIMIZE Attribute Options Allowed Combinations of Volatile and Nonvolatile Parameters 22 909 4 PG GU HE bo pee Attribute Classes sese Attributes on Routines and Compilation Units Attributes on Data Items Program Section Properties Program Section Data on OpenVMS I64 Systems Program Section Data on OpenVMS Alpha Systems Program Section Data on OpenVMS VAX Systems Required Program Section Properties Storage Allocation of Types Conditions Determining Boundary Alignment HP Pascal Extensions to Unextended Pascal HP Pascal Extensions to Extended Pascal XV Preface This manual describes the HP Pascal programming language It contains information on e HP Pascal language syntax and semantics e HP Pascal adherence to Pascal standards e HP Pascal extensions to standards All references to OpenVMS systems refer to the OpenVMS 164 OpenVMS Alpha and OpenVMS VAX operating systems unless o
360. ose Predeclared Functions and Procedures 8 3 This function is used to access data that is shared between two or more threads of execution For More Information e On atomic operations HP Pascal for OpenVMS User Manual 8 3 ADD_INTERLOCKED Function The ADD_INTERLOCKED function adds the value of an expression to the value of a variable stores the newly computed value in the variable and returns an integer value 1 if the new value is negative 0 if it is zero and 1 if it is positive ADD_INTERLOCKED e v The type of the expression e must be assignment compatible with that of the variable v The variable v must be an integer or an unsigned subrange v must have an allocation size of two bytes and must be aligned on a word boundary The type of e must be assignment compatible with that of v Note that unless the type of v is an integer subrange that includes negative values the result of the ADD INTERLOCKED function is never 1 Overflow and subrange checking are never performed on the ADD INTERLOCKED operation even if these options are in effect for the rest of the function or compilation unit This function is used to access data that is shared between two or more threads of execution For More Information e On atomic operations HP Pascal for OpenVMS User Manual 8 4 ADDRESS Function The ADDRESS function returns a pointer value that is the address of the parameter ADDRESS x The parameter x can be a varia
361. ou open an indexed file you can only access components sequentially according to the primary key If you specify ACCESS KEYED when you open an indexed file you can access components sequentially according to any key When sequentially writing components to an indexed file HP Pascal stores the component according to the primary key If your program uses secondary keys HP Pascal updates the secondary key pointers to include the newly stored component 9 3 2 Random Access Random access allows you to access file components in an order that is not dependent on the file organization or on the order in which the components are stored Random access is available for all relative and indexed files and for sequential files composed of fixed length components the fixed length components allow HP Pascal to count component positions in the sequential file without having to worry about variations in the lengths of the components Input and Output Processing 9 15 9 3 2 1 9 16 HP Pascal supports the following types of random access e Random access by relative component number direct access e Random access by key value keyed access The following are the HP Pascal I O routines that are used for random access Random access by relative component number DELETE EOF FIND LOCATE UFB UNLOCK UPDATE Random access by key EOF FINDK RESETK UFB UNLOCK UPDATE For More Information e On file organization Section 9 1
362. ou specify a value of NATURAL automatic variables are aligned on longword boundaries instead of quadword boundaries This occurs because the largest allowable alignment for the stack is longword alignment For More Information e On allocation sizes of objects Section A 2 4 e On storage allocation Section A 2 5 ALIGNED The ALIGNED attribute indicates the object is to be aligned on a specific memory boundary ALIGNED n Attributes 10 5 An aligned object is aligned on the memory boundary indicated by n The constant expression n indicates that the address of the object must end in at least n zeros ALIGNED 0 specifies byte alignment ALIGNED 1 specifies word alignment ALIGNED 2 specifies longword alignment ALIGNED 3 specifies quadword alignment ALIGNED 4 specifies octaword alignment and ALIGNED 9 specifies alignment on a 512 byte boundary Usage and Default Information The default alignment of an object depends on its size The constant expression n must denote an integer If you omit n the default is 0 indicating byte alignment If the expression provided to the ALIGNED attribute is greater than the largest supported alignment on the target platform the compiler will print a warning message and default to the largest supported value Note that ALIGNED 13 is the largest alignment allowed on OpenVMS I64 and OpenVMS Alpha systems and ALIGNED 9 is the largest alignment allowed on OpenVMS
363. parameters BEGIN Adder Opl Op2 Op3 Assign a function return value END For More Information e On attributes Chapter 10 e On declaration sections Chapter 3 e On the scope of identifiers Section 7 2 e On parameters and passing mechanisms Section 6 3 e On recursive function calls HP Pascal for OpenVMS User Manual e On calling external routines HP Pascal for OpenVMS User Manual 6 2 Routine Calls A routine call executes all statements in the body of the declared routine You must declare a routine before you can call it Syntactically procedure calls are statements and function calls which return a single value are expressions You can call a function anywhere that an expression of the declared result type is legal If the result of a function is irrelevant you can call the function as a statement in the same way that you call a procedure You can call routines in 6 4 Procedures and Functions the executable section of a program or in the body of another routine Routine calls have the following forms IMMED REF DESCR STDESCR IMMED REF DESCR STDESCR procedure identifier actual parameter function identifier actual parameter procedure identifier function identifier The declared routine identifier The scope of a routine identifier is the block in which it is declared excluding any nested blocks that redeclare the same identifier actual parameter The act
364. part as x NEW z 10 z has separate control and data parts Each variable created by NEW contains a unique control part attached to the data part A 3 3 3 Representation of Nonstatic Record Fields If a record object contains a field of a nonstatic type HP Pascal stores the field in one piece of storage within the record s storage HP Pascal does not create a pointer part and a data part HP Pascal determines the offset of the object by accessing the information in the control part of the field s data type and information in the control part of the record A 30 Data Storage and Representation Summary of HP Pascal Extensions If you need to write portable code you should not use the language features that are HP Pascal extensions The following sections provide information on HP Pascal extensions Extensions to the unextended Pascal standards Section B 1 Extensions to the Extended Pascal standard Section B 2 For More Information On Pascal standards Section 1 1 B 1 HP Pascal Extensions to Unextended Pascal Table B 1 summarizes the language features provided in HP Pascal that are not part of the unextended Pascal language definitions Table B 1 HP Pascal Extensions to Unextended Pascal Category Extension Lexical and syntactical extensions Reserved words BREAK CONTINUE ERR EXIT MODULE NEXT OTHERWISE REM RETURN VALUE VARYING DESCR STDESCR IMMED REF INCLUDE TITLE SUBTITLE DIC
365. perators Section 4 2 2 2 1 4 Enumerated Types An enumerated type is a user defined ordered set of constant values specified by identifiers It has the following form enumerated identifier enumerated identifier The identifier of the enumerated type being defined HP Pascal allows a maximum of 65 535 identifiers in an enumerated type The values of an enumerated type begin with the value 0 and follow a left to right order Subsequent identifiers have a value one greater than the identifier preceding it Consider the following 2 8 Data Types and Values TYPE Seasons Spring Summer Fall Winter VAR Some Seasons Seasons VALUE Winter Initialized In this enumerated type Spring value 0 and Summer value 1 are less than Fall value 2 because they precede Fall in the list of constant values Winter value 3 is greater than Fall because it follows Fall The ORD function accepts expressions of an enumerated type An identifier in an enumerated type cannot be defined for any other purpose in the same block Consider the following TYPE Seasons2 Fall Winter Spring This enumerated type cannot be defined in the same block as the previous type because the identifiers Spring Fall and Winter would not be unique For More Information On the ORD function Section 8 65 2 1 5 Subrange Types A subrange type is user defined and specifies a limited portion of another ordinal type called the base
366. ple VAR My String VARYING 20 OF CHAR VALUE Harry Hayes PROCEDURE Name VAR A String VARYING String Size OF CHAR Body In the executable section Name My String WRITELN The new name is My String This example declares a procedure Name which returns a new name through the formal parameter A String Procedure Name modifies the value of A String since My String is passed by variable semantics upon completion of the routine the modified value is reflected in the variable My String In HP Pascal certain attributes in a routine declaration or a routine call affect the rules of compatibility between actual and formal VAR parameters These rules also apply to the corresponding components of structured types and to the base types of pointer types used as formal parameters The attributes that result in rule changes are the alignment POS READONLY size UNSAFE VOLATILE and WRITEONLY attributes You can also use the attributes CLASS S CLASS A and CLASS NCA on variable parameters if a routine requires a specific type of descriptor for HP Pascal to build A CLASS AJ CLASS NCA or CLASS S formal variable parameter requires the actual variable parameters to be passed with the by descriptor mechanism For More Information e On blocks and scope Section 7 2 e On conformant parameters Section 6 3 7 e On default values for formal parameters Section 6 3 9 e On mechanism specifiers Section 6 3 5
367. plicitly declared in the procedure declaration Unless the conformant array is packed the component can be either a type identifier or another conformant parameter therefore only the last dimension of a conformant parameter can be packed The following example is illegal because the component of the packed array is another conformant parameter PACKED ARRAY 11 u1 INTEGER 12 u2 INTEGER OF CHAR Procedures and Functions 6 21 However the following is allowed because only the last component is packed ARRAY 11 u1 INTEGER OF PACKED ARRAY 12 u2 INTEGER OF CHAR Consider the following example TYPE Workdays 1 31 Feb Days 1 28 Mar Days 1 31 VAR Feb Arr ARRAY Feb Days OF INTEGER Mar Arr ARRAY Mar Days OF INTEGER Feb Total Mar Total INTEGER FUNCTION Inventory VAR Amt Sold ARRAY First Day Last Day Workdays OF INTEGER INTEGER In executable section Amt Sold ARRAY 1 28 OF INTEGER Feb Total Inventory Feb Arr Amt Sold ARRAY 1 31 OF INTEGER Mar Total Inventory Mar Arr The formal parameter Amt Sold can have index values from 1 to 31 to indicate the number of workdays in each month Thus an actual parameter passed to Amt Sold could be an array whose index type is either Feb Days or Mar Days Using a conformant parameter in this example allows you to write a general purpose routine that sums the components of Amt Sold and returns the monthly inventory total to
368. pression whose value is to be written multiple output values must be separated by commas The expressions can be of any ordinal real or string type and are written with a default field width which you can override as described in Section 9 6 error recovery The action to be taken if an error occurs during execution of the routine The file must be in generation mode before WRITELN is called it remains in that mode after WRITELN has been executed Input and Output Processing 9 67 9 68 The WRITELN procedure writes the specified values into the TEXT file inserts an end of line marker after the end of the current line and then positions the file at the beginning of the next line When applied to several expressions WRITELN performs the following sequence WRITE file variable expression WRITELN file_variable Consider the following example WRITELN User Guide This manual describes how to interact This procedure writes the string to the TEXT file User_Guide follows it with an end of line marker and skips to the next line You can specify a carriage control character as the first item in an output line When you use carriage control characters make sure that the file is open with either the CARRIAGE or FORTRAN option Consider the following example WRITELN Tree Stringl String2 The first item in the list is a space character The space indicates that the values of String1 and String2 are prin
369. ps a line before starting output 1 Paging starts output at the top of a new page Prompting starts output at the beginning of the next line and suppresses carriage return at the end of the line 0 Prompting with overprinting suppresses line feed at the beginning of the line and carriage return at the end of the line note that this character is the ASCII character NUL Input and Output Processing 9 19 9 5 2 Prompting on a Terminal Normally when you call the WRITE procedure to access a TEXT file connected to a terminal HP Pascal accumulates the characters in a line buffer until a subsequent WRITELN procedure is executed In effect WRITELN generates an end of line marker When you complete a line or close a file HP Pascal writes a full line of characters to the specified TEXT file HP Pascal can manipulate partial lines in a TEXT file however when characters are being written to a terminal output file opened with the LIST carriage control option LIST is the default partial lines are written to the terminal before input is transferred from any terminal to the line buffer of a TEXT file In this situation HP Pascal searches for all TEXT files opened for output on terminals it then writes to those files any partial lines contained in the files respective line buffers These partial lines called prompts appear on the screen You respond to a prompt by typing a line of input data terminated by pressing Return Con
370. pt base types of pointers be defined before they are used in the definitions of other types A base type must be defined before the end of the TYPE section in which it is first mentioned as shown in the this example TYPE Ptr to Movie Movie Movie is defined later Name PACKED ARRAY 1 20 OF CHAR Defined before used Movie RECORD Title Director Name Year INTEGER Stars FILE OF Name Next Ptr to Movie END For More Information e On data types Chapter 2 e On schema types Section 2 5 e On pointers Section 2 3 e On attributes Chapter 10 3 8 Declaration Section 3 6 VALUE Section If you choose you can use the VALUE section as an HP Pascal extension that initializes ordinal real array record set and string variables If you require portable code use the VALUE reserved word in either TYPE definitions or VAR declarations The exact format of an initialization depends on the type of the variable being initialized The VALUE section has the following form VALUE variable identifier constant expression variable identifier The name of the variable to be initialized You cannot specify a list of variable identifiers You can initialize a variable or variable component only once in the VALUE section Any variables appearing in the VALUE section must appear in a previous VAR section constant expression Any constant expression that is assignment compatible with the variable identifier
371. r Explanation Detected at run time if subrange checking was enabled during compilation of the called routine The set type of an actual parameter is not assignment compatible with the type of the corresponding formal parameter Explanation Detected at run time if subrange checking was enabled during compilation of the called routine A file is not in generation mode when a PUT WRITE WRITELN or PAGE procedure is attempted Explanation Detected at run time A file is in undefined mode when a PUT WRITE WRITELN or PAGE procedure is attempted Explanation Not detected The result of an EOF function is not TRUE when a PUT WRITE WRITELN or PAGE procedure is attempted Explanation Detected at run time The operation is illegal only when the file is accessed sequentially The value of the file buffer variable is undefined when a PUT procedure is attempted Explanation Not detected A file is in undefined mode when a RESET procedure is attempted Explanation Not detected D 2 Compiler and Run Time System Error Detection A file is not in inspection mode when a GET READ or READLN procedure is attempted Explanation Detected at run time A file is in undefined mode when a GET READ or READLN procedure is attempted Explanation Not detected The result of an EOF function is TRUE when a GET READ or READLN procedure is attempted Explanation Detected at run time The type of the file buffer varia
372. r The type identifier of the parameters in this section undiscriminated schema name The name of an undiscriminated schema type 6 8 Procedures and Functions conformant parameter syntax The type syntax of a conformant array or a conformant VARYING parameter mechanism specifier The mechanism by which a default value is to be associated with the formal parameter default value A compile time expression representing the default value for the formal parameter Any attributes associated with a formal parameter become attributes of the local variable They do not affect the values that can be passed to the parameter they affect the behavior of the formal parameter only within the routine block When a formal parameter has the UNSAFE attribute the types of the actual parameters passed to it are not checked for compatibility An actual value parameter must be an expression whose type is assignment compatible with the type of the corresponding formal parameter Because there is no assignment compatibility for file variables undiscriminated schema sets and undiscriminated schema subranges they can never be passed as value parameters Also the names of routines are not allowed as value parameters If necessary the type of an actual parameter is converted to the type of the formal parameter to which it is being passed In this case HP Pascal follows the same type conversion rules that it uses to perform any other assignment You may fo
373. r some members of the ASCII character set including the bell the backspace and the carriage return are nonprinting characters The extended string format for character strings with nonprinting characters is as follows printing string ordinal value Data Types and Values 2 41 2 42 printing string A character string constant Consider the following example Two bells 7 7 in a null terminated ASCII string 0 HP Pascal provides the substring access notation to denote a piece of a string variable string constant or string function The lower bound and upper bound are index expressions Consider the following string access lower bound upper bound The following is an example var S packed array 1 10 of char S 1 5 hello s 6 10 world In the executable section of a block these lower and upper bound expressions can be run time expressions and are checked for validity if compiled with checking code enabled You can also pass these string pieces to VAR parameters For example procedure do buf var p packed array 1 u integer of char begin p 12345 end var buff packed array 1 10 of char do buff buff 1 5 do buff buff 6 10 writeln buff 1 1 To avoid compile time warning messages about passing components of PACKED structures to VAR parameters use USAGE NOPACKED_ACTUALS to compile In expressions substring access behaves muc
374. r 10 2 4 2 2 Record Constructors Record constructors are lists of values that you can use to initialize a record they have the following form data type component component value J CASE tag identifier tag value OF component component value OTHERWISE ZERO J data type Specifies the constructor s data type If you use the constructor in the executable section or in the CONST section a data type identifier is required Do not use a type identifier in initial state specifiers elsewhere in the declaration section or in nested constructors Data Types and Values 2 27 component Specifies a field in the fixed part of the record Fields in the constructor do not have to appear in the same order as they do in the type definition If you choose you can specify fields from the variant part as long as the fields do not overlap component value Specifies a value of the same data type as the component The value is a compile time value if you use the constructor in the executable section you can also use run time values CASE Provides a constructor for the variant portion of a record If the record contains a variant its constructor must be the last component in the constructor list tag identifier Specifies the tag identifier of the variant portion of the record This is only required if the variant part contained a tag identifier tag value Determines which component l
375. r example pass an integer expression to a formal parameter of a real type If an actual parameter has the UNSAFE attribute no conversion occurs If you have a user defined formal parameter of an undiscriminated schema type the corresponding actual parameter must be discriminated from the same schema type as that of the formal parameter When you pass a string expression to a formal value parameter of type STRING the actual parameter s current length not its declared maximum length becomes both the maximum length and the current length of the formal parameter You can also use the attributes CLASS S CLASS A and CLASS_NCA on value parameters if a routine requires a specific type of descriptor for HP Pascal to build A CLASS A CLASS NCA or CLASS S formal value parameter requires the actual value parameters to be passed with the by descriptor mechanism Procedures and Functions 6 9 The following examples show the use of value parameters VAR Old Number x y INTEGER FUNCTION Random Seed INTEGER INTEGER Function body PROCEDURE Alpha a b INTEGER C CHAR Procedure body In the executable section New Number Random Old Number Alpha x y 11 G Actual parameters are integer and character expressions For More Information e On blocks and scope Section 7 2 e On conformant parameters Section 6 3 7 e On default values for formal parameters Section 6 3 9 e On mecha
376. r formal and actual parameter lists of routine parameters to be congruent the actual routine parameter and the corresponding formal routine parameter must either both have the LIST attribute or both lack the LIST attribute Consider the following example PROCEDURE Foo PROCEDURE q x LIST CHAR This defines the routine Foo with the formal routine parameter q that defines the formal list parameter x Consider the following example PROCEDURE Bar x LIST CHAR This defines Bar to have a formal list parameter x Consider this call to Foo Foo Bar This calls Foo passing the actual routine parameter Bar The formal parameters of q and Bar contain the LIST attribute so this is a legal call For example the function Average demonstrates the use of the LIST attribute which allows any number of like expressions to be passed to a function 10 26 Attributes PROGRAM Use List OUTPUT FUNCTION Average P list INTEGER REAL VAR SUM REAL VALUE 0 0 I INTEGER BEGIN FOR I 1 TO ARGUMENT LIST LENGTH P DO SUM SUM ARGUMENT P I AVERAGE SUM ARGUMENT LIST LENGTH P END BEGIN WRITELN AVERAGE 3 6 9 AVERAGE 10 3 4 17 END For More Information e On the ARGUMENT function Section 8 7 e On the ARGUMENT LIST LENGTH function Section 8 8 On type compatibility Section 2 10 10 2 25 LOCAL The LOCAL attribute indicates that an object is unavailable to other independently compiled unit
377. r recovery stops execution after first error default The action to be taken if an error occurs during execution of the routine Execution of the CLOSE procedure causes the system to close the file and if the file is internal to delete it Each file is automatically closed when control passes from the block in which it is declared You cannot close a file that has not been opened either explicitly by the OPEN procedure or implicitly by the EXTEND RESET or REWRITE procedure If you try to close a file that was never opened an error occurs Input and Output Processing 9 31 The file can be in any mode inspection generation or undefined before the CLOSE procedure is called Execution of CLOSE sets the mode to undefined For More Information e On positional and nonpositional syntax Section 6 3 8 e On the OPEN procedure and parameters Section 9 8 12 e On the error processing parameter Section 9 7 9 8 2 DELETE Procedure 9 32 The DELETE procedure deletes the current file component DELETE can be used only on files with relative or indexed organization that have been opened for direct or keyed access it cannot be used on files with sequential organization DELETE file_variable ERROR error recovery file_variable The name of the file variable associated with the file from which a component is to be deleted error recovery The action to be taken if an error occurs during execution of the routine The f
378. rage called the control part includes information that cannot be determined until execution time HP Pascal needs this information to allocate and to access variables and record fields of this type Consider the following nonstatic types TYPE Template is nonstatic Template Upper INTEGER ARRAY 1 Upper OF INTEGER a Template a s base type is nonstatic b Template 5 b is nonstatic My Subrange x y INTEGER X y c is nonstatic c ARRAY My Subrange j k My Subrange 1 m OF INTEGER d ARRAY 1 10 OF Template 5 d is nonstatic e RECORD e is nonstatic fl TEMPLATE 5 END f SET OF My Subrange 10 20 f is nonstatic Do not confuse static and nonstatic types with automatic and static variable allocation For More Information e On automatic variable allocation Section 10 2 5 e On static variable allocation Section 10 2 36 e On storage representation of nonstatic types Section A 3 3 2 10 Type Compatibility 2 10 1 The following sections discuss the two forms of type compatibility structural and assignment compatibility Structural Compatibility Two types are structurally compatible only if they have the same allocation size and the same type structure HP Pascal requires that the type of a variable passed to a routine as an actual parameter be structurally compatible with the type of the corresponding formal variable parameter HP Pascal also checks the
379. ram sections A 5 Common block definition of 10 15 description of A 5 properties of A 6 variable allocation A 6 Compatibility assignment 2 51 structural 2 49 Compilation identification 11 10 Compilation unit attributes 10 55 definition 7 5 Glossary 3 sharing data 7 7 Compiler optimization definition Glossary 3 COMPILER_VERSION directive 11 10 Compile time directives DEFINED 11 8 ELIF 11 6 ELSE 11 6 ENDIF 11 6 ERROR 11 8 FILE 11 10 IDENT 11 10 IF 11 6 INFO 11 8 LINE 11 10 MESSAGE 11 8 MODULE 11 10 ROUTINE 11 10 SYSTEM_NAME 11 9 SYSTEM_VERSION 11 9 WARN 11 8 Index 4 Compile time expressions 4 1 Component access mode 9 11 definition Glossary 3 format of 9 7 ina file 9 1 length of 9 4 of structured type 2 18 Component access mode definition Glossary 3 Component format 9 9 definition Glossary 3 fixed length 9 10 stream 9 10 variable length 9 10 Components of array 2 20 Compound statement 5 4 Concatenation of string operators 4 8 Conditional compilation ELIF 11 6 ELSE 11 6 ENDIFIF 11 6 IF 11 6 Conditional statements CASE 5 3 IF 5 8 Condition handler canceling 8 38 definition Glossary 3 establishing 8 16 Conformant array effect of UNSAFE attribute 10 43 Conformant parameter array 6 21 description of 6 20 VARYING string 6 22 Congruence of formal routine parameters 6 1
380. rameter list 8 6 ARGUMENT LIST LENGTH function 8 6 Arithmetic operators 4 2 to 4 5 Array 2 19 conformant 6 21 copying 8 33 8 47 definition Glossary 1 indexing when returned from a function 4 15 multidimensional 2 20 ARRAY components 2 16 2 20 ARRAY constructor 2 21 ARRAY type 2 19 allocation size of A 11 bounds checking 10 11 character strings 2 43 component of 2 19 index of 2 19 packed 2 43 packing A 17 examples of A 15 use of multidimensional array 2 20 ASCII character set 1 3 2 7 nonprinting characters in 2 7 ASSERT procedure 8 7 Assignment compatibility 2 51 effect of POS 10 33 effect of read only 10 35 effect of UNSAFE 10 43 Assignment operator 5 2 Assignment statement 5 2 Asynchronous attribute 10 7 AT attribute 10 8 Atomic instruction definition Glossary 1 Atomic operation definition Glossary 2 Attribute definition Glossary 2 Attribute class 10 1 default for 10 2 definition Glossary 2 Index 2 Attribute class cont d list of 10 52 Attributes 10 1 to 10 56 See also individual attributes by name associating with data 10 2 effect on compatibility 10 4 effect on formal parameter 6 9 effect on structural compatibility 6 12 specified in TYPE section 10 3 syntax of 10 1 Automatic allocation of variables A 8 AUTOMATIC attribute 10 9 Automatic variable allocation 10 9 definition Glossary 2 Backslash chara
381. rated type 2 8 allocation size of A 11 default field width of 9 23 reading from text file 9 53 Enumerated types output of 9 28 ENUMERATION SIZE attribute 10 16 ENVIRONMENT attribute 10 16 effect on allocation A 8 Environment file creation of 10 17 definition Glossary 5 example of 7 7 inheriting 10 21 rules for creating 7 8 EOF function 9 33 EOLN function 9 34 EPSDOUBLE 2 14 EPSQUADRUPLE 2 15 EPSREAL 2 14 EQ function 8 16 ERR file variable description of 9 18 Error detection D 1 to D 7 processing 9 29 ERROR directive 11 8 Error messages violating language standard D 1 to D 7 ERROR parameter 9 29 ESTABLISH procedure 8 16 Executable image memory allocation by linker A 1 Executable section definition Glossary 5 EXP function 8 16 EXPO function 8 17 Exponent of real number 8 17 value returned 8 16 Exponential notation 2 13 in output procedure 9 25 Exponentiation operator 4 3 Expression definition Glossary 5 function call 4 15 Expressions 4 1 to 4 14 compile time 4 1 order of evaluation 4 2 4 12 to 4 14 run time 4 1 use of parentheses in 4 13 Index 7 Extended digit notation 2 5 definition Glossary 5 Extended Pascal extensions to B 5 to B 7 Extended Pascal standard 1 2 definition Glossary 5 Extended string format 2 41 definition Glossary 5 Extending field width 9 25 EXTEND procedure 9 35 Extensions
382. rators to make sure that it is interpreted as you intend The expression 2 0 2 produces the result 4 0 Table 4 3 lists the result types of arithmetic operations with operands of various types Table 4 3 Result Types of Arithmetic Operators Operator Type of Operands Result Type INTEGER INTEGER64 Same as the operands if both are UNSIGNED UNSIGNED64 of the same type otherwise the REAL DOUBLE operand of the lower ranked type is ok QUADRUPLE converted and the result is of the higher ranked type INTEGER INTEGER64 One of the real types REAL if UNSIGNED UNSIGNED64 the operands are of type REAL or REAL DOUBLE QUADRUPLE SINGLE or a lower ranked type otherwise the operand of the lower ranked type is converted and the result is of the higher ranked type DIV INTEGER INTEGER64 Same as the operands if both are REM UNSIGNED UNSIGNED64 of the same type otherwise the MOD operand of the lower ranked type is converted and the result is of the higher ranked type For More Information e On integers Section 2 1 1 1 e On real numbers Section 2 2 e On more precise and less precise operands and on type conversions Section 4 4 e On using the CHECK attribute and SUBRANGE option for MOD run time checking Section 10 2 8 4 2 2 Relational Operators A relational operator tests the relationship between two ordinal real DOUBLE or QUADRUPLE expressions and returns a Boolean result If
383. ressed if the user presses an Exit key The BREAK statement exits the loop here without storing data in the array Use caution when using the BREAK statement because future additions to the code can result in the BREAK statement leaving a different loop than was originally intended 5 3 CASE Statement The CASE statement causes one of several statements to be executed Execution depends on the value of an ordinal expression called the case selector A CASE statement has the following form CASE case selector OF case label list statement E OTHERWISE statement M END case selector An expression of an ordinal type case label list One or more case labels of the same ordinal type as the case selector separated by commas A case label can be a single constant expression such as 1 or a range of expressions such as 5 10 statement Any statement to be executed depending on the values of both the case selector and the case label Statements 5 3 You can specify case labels in any order within the case label list Each case label can appear only once within a given CASE statement At run time the system evaluates the case selector expression and chooses which statement to execute If the value of the case selector does not appear in the case label list the system executes the statement in the OTHERWISE clause If you omit the OTHERWISE clause the value of the case selector must be equal to one of
384. retained the value A because no further assignments had been made directly to a c However the value of a c changed unexpectedly through the assignment to a i Therefore unless the record a is declared VOLATILE the result of the assignment x a c would be undefined because the compiler s legitimate assumptions had been incorrect Consider the following example PROGRAM Volatility OUTPUT VAR Pint VOLATILE INTEGER i INTEGER j VOLATILE INTEGER a ARRAY 0 10 OF INTEGER In the executable section NEW Pint y 0 j 0 Pint 0 Compiler may assume i 0 makes no assumptions about j WRITELN i j Pint ali Values are 0 0 0 a 0 Pint ADDRESS j Pint now j Pint 1 Therefore j now 1 Compiler may assume i 0 makes no assumptions about j WRITELN i j Pint alil Values are 0 1 1 a 0 Pint ADDRESS i Causes a warning message because i is not VOLATILE Pint 2 Compiler may assume i 0 and a I a 0 May make no assumptions about j WRITELN i j Pint ali Actual values are 2 1 2 a 2 This example assigns values to the variables i and j and to the newly created variable Pint The comments show the difference between the assumptions the compiler can legally make about the values of the variables and the values actually contained in the variables The compiler s assumption about the value of i was incorrect because the val
385. riable appeared as a cell in a packed array BITNEXT x The parameter x can be a variable or any type identifier Cells in a packed array are affected by any alignment attributes placed on them Therefore the size returned includes the actual size of the type or variable in addition to trailing space required to ensure proper alignment The BITNEXT and BITSIZE functions return the same bit size for a given type or variable except where the components of the packed array are padded to ensure proper alignment For More Information e On examples of return values for this function Table 8 2 e On packed arrays Section 2 4 8 14 BITSIZE Function The BITSIZE function returns an integer value that indicates the number of bits that would be allocated for one field of the specified type in a packed record or if the specified variable appeared as a field in a packed record BITSIZE x The parameter x can be a variable or any type identifier Predeclared Functions and Procedures 8 9 Fields in a packed record are not affected by any alignment attributes placed on subsequent fields Therefore the size returned indicates the actual size of the type or variable The BITNEXT and BITSIZE functions return the same bit size for a given type or variable except where the components of the packed array are padded to ensure proper alignment For More Information e On possible return values for this function Table 8 2 e On pa
386. rmation e On string types Section 2 6 e On sets Section 2 4 3 8 37 GE Function The GE function returns a Boolean value that specifies if the first parameter is greater than or equal to the second parameter according to the ASCII values of the strings characters GE str1 str2 The parameters str1 and str2 must be character string expressions HP Pascal does not pad shorter strings with blanks Consider the following example VAR Match BOOLEAN Test STRING 8 VALUE ENTRANCE In the executable section Match GE exit exit Returns TRUE Match GE Test EXIT N less than X Returns FALSE For More Information e On string data types Section 2 6 8 38 GETTIMESTAMP Procedure The GETTIMESTAMP procedure initializes its parameter for use with the DATE and TIME functions GETTIMESTAMP t str The parameter t is a variable of the TIMESTAMP type which is a predeclared record type The parameter str is a string type that represents a date or both a date and time The following rules apply to the specification of the str parameter e Ifyou do not specify the parameter str the GETTIMESTAMP procedure initializes the variable to be the date and time at execution of the procedure e If you specify an invalid date the GETTIMESTAMP procedure sets the date to be January 1 1 If you omit the date this procedure uses the current date If you specify an invalid time or i
387. rmines the string length and the number of significant digits By default the number of significant digits is the minimum number of characters necessary to express all the bits of the converted parameter This default length is one character more than the default number of digits which causes a leading blank to be included in the resulting string when both parameters are omitted Consider the following example TYPE Month Dates SET OF 0 31 VAR Days Of Rain Month Dates In the executable section Days Of Rain 1 2 6 10 12 14 18 22 25 30 Result BIN Days Of Rain 32 Returns 01000010010001000101010001000110 32 characters The binary representation is from right to left with the leftmost bit being bit 31 and the rightmost bit being bit 0 For More Information e On character strings Section 2 6 e On conformant parameters Section 6 3 7 8 8 Predeclared Functions and Procedures 8 12 BIT_OFFSET Function The BIT_OFFSET function returns an integer value that represents the bit position of a field in a record BIT_OFFSET t f The parameter t can be of any record type or variable and the parameter f can be any field contained in that record For More Information On records Section 2 4 2 8 13 BITNEXT Function The BITNEXT function returns an integer value that indicates the number of bits that would be allocated for one component of the specified type in a packed array or if the specified va
388. rocedure Consider the following example VAR Ratings FILE OF INTEGER In the executable section OPEN Ratings cars dat HISTORY OLD RECORD TYPE FIXED REWRITE Ratings The OPEN procedure opens the file variable Ratings which is associated with the file cars dat The REWRITE procedure discards the current contents of the file f and sets the file position to the beginning of the file After execution of this procedure EOF Ratings returns TRUE For More Information e On component access Section 9 3 e On the default parameters for OPEN Section 9 8 12 e On the error processing parameter Section 9 7 STATUS Function The STATUS function indicates the status of a file following the last operation performed on it The LOCATE procedure does not perform an operation but sets internal data in the run time library for use by future operations Therefore this procedure does not affect the result of the STATUS function STATUS file_variable Input and Output Processing 9 61 9 62 file_variable The name of the file variable associated with the file to be tested The file can be in any mode before STATUS is called unless an error occurs STATUS does not change the file mode upon execution The STATUS function returns one of the following integer codes that indicate the previous operation s effect on the file Code Description 0 Successful operation 1 End of file encountered Positive
389. rogram An internal file has no name and is deleted after the program finishes execution A file declared in the program heading is external by default A file declared in a nested block is internal by default To change the default for internal files call the OPEN procedure or specify a file name in the EXTEND RESET or REWRITE procedures The file is then considered external and is retained with the specified name after the program has finished execution If you open an internal file with the EXTEND RESET or REWRITE procedure without a file name the file remains an internal file Default Information If you do not specify a file organization at the time of file creation using the OPEN procedure HP Pascal creates a file with sequential organization The following sections describe file organizations 9 1 1 Sequential File Organization 9 2 Sequential file organization specifies that file components are stored one after the other in the order in which they were entered into the file HP Pascal supports this organization for files on disk This is the only organization supported for files on magnetic tape on terminals on card readers and on line printers Figure 9 1 shows this file organization Input and Output Processing Figure 9 1 Sequential File Organization Fourth component is located between third and fifth components First Second Third Fourth Fifth Sixth component component component component co
390. ronment file Ident IDENT Indicates the identification of a compilation unit to be passed to the linker Inherit INHERIT Indicates that the compilation unit can use the definitions and declarations specified in the inherited environment file Initialize INITIALIZE Indicates that the procedure is to be called before execution of the main program Key KEY Indicates key information for a record field that is used when accessing data in an indexed file continued on next page Attributes 10 53 Table 10 7 Cont Attribute Classes Class Attributes Description of Attributes List LIST Indicates that the routine can be called with actual parameter lists of various lengths Optimization OPTIMIZE NOOPTIMIZE Indicate whether HP Pascal should optimize code Parameter CLASS A CLASS NCA Indicate the passing mechanism to be passing CLASS S IMMEDIATE used for a parameter REFERENCE Position POS Indicates that a record field should be forced to a specific bit position Read only READONLY Indicates that the object can be read but cannot be written to Size BIT BYTE WORD Indicate the amount of storage to be LONG QUAD reserved for the object OCTA Truncate TRUNCATE Indicates that the actual parameter list can be truncated at the position of this attribute in the formal parameter list Unbound UNBOUND Indicates that the routine does not access automatic variables outside its scope Unsafe UNSAFE Indicates that an
391. routines e Section 6 1 Routine Declarations e Section 6 2 Routine Calls e Section 6 3 Parameters Procedures and functions are subprograms A procedure contains one or more statements to be executed once the procedure is called A function contains one or more statements to be executed once the function is called in addition functions return a single value This manual refers to functions and procedures collectively as routines In addition to user defined routines HP Pascal also allows you to access external routines routines that are globally available on your system and that may or may not be written in HP Pascal and routines that are predeclared by the compiler For More Information e On predeclared routines Chapter 8 e On calling external routines HP Pascal for OpenVMS User Manual 6 1 Routine Declarations You must declare a routine before you call it Routine declarations have the following formats Procedures and Functions 6 1 attribute list PROCEDURE routine identifier formal parameter list declaration section BEGIN statement END EXTERN EXTERNAL FORTRAN FORWARD attribute list FUNCTION routine identifier formal parameter list attribute list result type id declaration section BEGIN statement END EXTERN EXTERNAL FORTRAN FORWARD attribute list One or more identifiers that provide additional information about the type denoter routine identifier The name o
392. rrays A 17 examples of A 15 of structured types A 17 PACK procedure 8 33 PAD function 8 34 Page break character 1 10 PAGE procedure 9 49 Parameter absolute value of 8 3 actual variable 6 11 address of 8 4 arctangent of 8 5 Index 14 Parameter cont d association of formal and actual 6 25 conformant array 6 21 conformant VARYING string 6 22 congruence of 6 13 cosine of 8 12 default value for 6 26 effect of attributes 6 9 effect of UNSAFE 6 9 error processing 9 29 foreign mechanism 6 15 6 17 formal schema 6 19 formal value 6 8 formal variable 6 10 function 6 12 6 13 ordinal value of 8 33 passing mechanisms 6 7 predecessor of 8 35 procedure 6 12 6 13 rounding numbers in 8 38 8 39 routine 6 12 6 13 sine of 8 40 square of 8 42 square root of 8 42 successor of 8 43 truncating numbers in 8 44 Parameter passing mechanism definition Glossary 9 Parameter passing semantics definition Glossary 9 PAS GLOBAL program section A 2 PAS INPUT C 4 PAS OUTPUT C 4 Pascal language standards 1 1 Passing mechanisms for parameters 6 7 PAS STRCPY function 8 35 PAS STR function 8 35 PEN CHECKING STYLE attribute 10 31 Pointer dereferenced when returned from a function 4 15 part of a nonstatic type A 28 A 29 Pointers 64 bit 2 17 Pointer type 2 16 allocation size of A 11 checking 10 11 effect of READONLY 10 35 effect of UNSAFE 10 4
393. rs ALIGNED 1 WORD 2 15 2 15 1 In the executable section IF ADD INTERLOCKED 1 Free Buffers 0 THEN Statement The predeclared function ADD INTERLOCKED requires that the second parameter passed to it have word alignment and an allocation size of one word In this example the variable Free Buffers is declared with alignment and size attributes to meet these restrictions For More Information e On automatic and size attribute classes Section 10 3 e On static and nonstatic types Section 2 9 e On default alignments HP Pascal for OpenVMS User Manual 10 2 3 ASYNCHRONOUS The ASYNCHRONOUS attribute indicates that a routine can be called asynchronously to the main program execution For example AST routines or condition handlers are asynchronous routines because they are called without an explicit procedure call in your program Routines with the ASYNCHRONOUS attribute can only access local variables and up level VOLATILE variables Additionally asynchronous routines can only call other asynchronous routines Usage and Default Information e This attribute can be applied to routines and to routine parameters declared in external routines e In the absence of the ASYNCHRONOUS attribute the compiler assumes that the routine can be activated only by actual calls within the program e All predeclared routines are asynchronous by default e Any routines called from within the block of an asynchronous routine
394. rs and parameter passing attributes for passing parameters to external procedures and functions IMMED REF DESCR STDESCR IMMEDIATE REFERENCE CLASS_S CLASS_A CLASS_NCA MODULE syntax differs from the syntax provided by Extended Pascal ENVIRONMENT and INHERIT attributes to control independent compilation Summary of HP Pascal Extensions B 7 C Description of Implementation Features The standards for Pascal allow some features of the language to be defined by a particular implementation or to be dependent on an implementation This appendix describes the HP Pascal treatment of the following features e Section C 1 Implementation Defined Features e Section C 2 Implementation Dependent Features For More Information On Pascal standards Section 1 1 C 1 Implementation Defined Features The value of each character allowed in a character string Treatment See Section 1 2 1 The range of real number values represented by the type REAL Treatment See Section 2 2 The characters represented by the type CHAR and their ordinal values Treatment See Section 1 2 1 The point at which the REWRITE PUT RESET and GET procedures are performed on a file Treatment Performed immediately unless the file is a terminal file in which case delayed device access occurs see Section 9 5 3 The value of MAXINT Treatment See Table 2 2 The accuracy to which the results of real number operations are calculated Treatment See
395. runcated error recovery The action to be taken if an error occurs during execution of the routine The file must be in inspection mode before TRUNCATE is called After the procedure has been executed the mode is set to generation so that you can write to the file After the appropriate components have been deleted the file remains positioned at the new end of file but the file buffer itself is undefined Thus EOF and UFB are both set to TRUE Consider the following example TRUNCATE Master File This procedure deletes components from Master File beginning with the current component and continuing until EOF returns TRUE When the operation is complete EOF Master File and UFB Master File are TRUE and new data can be written at the end of Master File For More Information e On sequential files Section 9 1 1 e On the error processing parameter Section 9 7 UFB Function The UFB Undefined File Buffer function returns a Boolean value to indicate whether the last file operation gave the file buffer an undefined status UFB file variable Input and Output Processing 9 63 9 8 23 file_variable The name of the file variable associated with the file whose buffer is being tested The file can be in any mode before UFB is called the execution of UFB does not change the file mode UFB tests the effect of the last I O operation on the file UFB returns FALSE if a successful GET FIND FINDK RESET or RESE
396. s Usage and Default Information e By default all variables and routines are local e Variables with any visibility attribute other than LOCAL are implicitly static e Routines with any visibility attribute other than LOCAL cannot refer to automatic variables declared in enclosing blocks and can call only those routines that are local predeclared or unbound By default routines declared at program or module level have the characteristics of unbound routines For More Information e On the AUTOMATIC attribute Section 10 2 5 e On static and nonstatic types Section 10 2 36 e On the UNBOUND attribute Section 10 2 39 Attributes 10 27 10 2 26 LONG The LONG attribute specifies the amount of storage in longwords to be received by the object LONG n J The optional constant n indicates the number of longword storage units Consider the following example PROGRAM Size TYPE Status LONG BOOLEAN VAR Return Status Status FUNCTION Example Paraml Param2 INTEGER Status EXTERNAL Function body The program Size defines a BOOLEAN type Status and declares a variable Return Status of this type So the result type of the function is declared to have a size of one longword The machine code that references the result type can not copy the entire longword however if the default size for a Boolean is less than a longword For More Information e On allocation sizes of objects Section A 2 4 e
397. s xvii 2 2 2 2 2 2 2 3 2 4 2 6 2 7 2 8 2 8 2 9 2 11 2 16 2 18 2 18 2 10 2 10 1 2 10 2 ARRAY Types ARRAY Components 0 0 00 eee eee ees ARRAY Constructors llle RECORD Types Records with Variants 0 000 ce eee eee Record Constructors 0 000 cece cece ee eee SET Type Set Constructors 0 0 00 eee eee ee FILE Type TEXT Type Nonstandard Constructors lees Nonstandard Array Constructors 005 Nonstandard Record Constructors 00 Schema Types String Types PACKED ARRAY OF CHAR Types 0000005 VARYING OF CHAR Types 000 0c eee eee STRING Schema Type 0 00 eee eee ees Null Terminated Strings leere TIMESTAMP Type Static and Nonstatic Types 0 cece eee ee nes Type Compatibility Structural Compatibility 0 0 0 0 0 0 cece eee Assignment Compatibility 0 0 0 0 0 eee eee 3 Declaration Section 3 1 3 2 CONST Section LABEL Section TO BEGIN DO Section eee TO END DO Section TYPE Section VALUE Section VAR Section 4 Expressions and Operators 4 1 4 2 4 2 1 4 2 2 4 2 3 4 2 4 Expressions Operators Arithmetic Operators lees Relational Operators lise Logical Operators String Operators 2 19 2 20 2 2
398. s the program section s write property changes from NOWRT to WRT and its share property remains SHR If you want to guarantee that read only variables can never be modified you can allocate storage exclusively for them in a separate program section that will always remain nonwritable A 2 Storage Allocation The following sections discuss storage allocation of variables symbolic constants and executable blocks Static types require no allocation Nonstatic data types require allocation to store possible run time values Section A 2 3 gives an example For More Information e On allocation for nonstatic data types Section A 2 1 A 2 1 Allocation of Variables When allocating storage for a variable the compiler first determines an allocation attribute for the variable If the allocation attribute is STATIC or COMMON the compiler then chooses a program section in which to allocate storage The compiler applies the following rules sequentially to determine the allocation attribute e If the variable is declared with an allocation attribute the attribute specifies the variable s allocation Data Storage and Representation A 7 If the variable is declared with a visibility attribute other than LOCAL its allocation is static If the variable is declared in a routine its allocation is automatic If the variable is declared at the outermost level of a module its allocation is static If the variable is declared at the o
399. s descriptions of the constant type variable procedure and function identifiers contained in the outermost level of a compilation unit Compilation units that inherit this file using the INHERIT attribute have access to the data items declared in the other compilation unit See also attribute compilation unit and declaration section executable section A part of a program or routine containing statements to execute See also declaration section and heading expression A group of identifiers and operators that result in a value See also constant expression and run time expression extended digit notation A standard format for integers that includes the specification of a base value bases 2 to 32 are allowed followed by the number sign and followed by the extended digit value Extended Pascal standard The International Standard ISO 10206 1989 HP Pascal supports many features of this standard but not all of them extended string format A format for character string constants that allows you to place nonprinting ASCII characters such as the bell and the backspace into the character string extensions See HP Pascal extension external file A physical file that has a name and exists outside the context of a Pascal program See also file field A component of a record The component can be of various data types file An organized collection of logically related data items Glossary 5 file component See
400. s legal In the following example the INCLUDE directive specifies the file CONDEF PAS which contains constant definitions In the Program PROGRAM Student Courses INPUT OUTPUT Sched CONST INCLUDE CONDEF PAS LIST TYPE Schedules RECORD Year Fr So Jr Sr Name PACKED ARRAY 1 30 OF CHAR Parents PACKED ARRAY 1 40 OF CHAR College Arts Engineering Architecture Agriculture Hotel END File CONDEF PAS Max Class 300 N Profs 140 Frosh 3000 The main program Student Courses is compiled as though it were written as follows 11 2 Directives PROGRAM Student Courses INPUT OUTPUT Sched CONST Max Class 300 N Profs 140 Frosh 3000 TYPE Schedules RECORD Year Fr So Jr Sr Name PACKED ARRAY 1 30 OF CHAR Parents PACKED ARRAY 1 40 OF CHAR College Arts Engineering Architecture Agriculture Hotel END You can use the INCLUDE directive in another included file however two files cannot attempt to include each other A file included at the outermost level of a program is said to be included at the first level A file included by a first level file is said to be included at the second level and so on In general a program may not include any files beyond the fifth level it may not include any files beyond the fourth level if you have included a DICTIONARY directive in the fourth level Nesting levels may be further restricted by the number of file
401. s you are allowed to have open at one time Figure 11 1 shows the legal levels of included files Directives 11 3 Figure 11 1 INCLUDE File Levels PROGRAM P INCLUDE a pas level 1 a pas TYPE definitions 9eINCLUDE b pas level 2 b pas VAR declarations INCLUDE c pas level 2 c pas CONST definitions INCLUDE d pas level 3 d pas VAR declarations INCLUDE e pas level 4 E PAS FUNCTION declaration INCLUDE f pas level 5 f pas Included files not allowed at level 6 ZK 0285 GE 11 4 Directives For More Information e On the Oracle CDD Repository CDD Section 11 2 e On default file specifications and on including text libraries HP Pascal for OpenVMS User Manual 11 2 DICTIONARY DICTIONARY allows access to data definitions stored in the Oracle CDD Repository CDD which is a product that must be purchased separately and may not be available on your environment the directive has the following form DICTIONARY cdd path name NO LIST cdd path name A character string that represents the full or relative path name of a CDD record description to be extracted The resulting path name must conform to the rules for forming CDD path names A full path name is one that begins with CDD TOP and specifies the names of all its descendants it is a complete path to the record definition Descendant names are separated from e
402. scal for OpenVMS User Manual for more information continued on next page A 12 Data Storage and Representation Table A 6 Cont Storage Allocation of Types Unpacked Packed Data Type Size in Bytes Size in Bits Unpacked The sum of the unpacked Unpacked size in bytes 8 RECORD sizes in bytes of the fields in the fixed part and the largest variant plus the sum of the sizes in bytes of any holes created to meet alignment requirements PACKED The sum of the packed sizes The sum of the packed sizes ARRAY in bits of all components in bits of all components plus plus the sum of sizes in bits the sum of sizes in bits of any of any holes created to meet holes created to meet alignment alignment requirements requirements if the sum is this sum is rounded up to greater than 32 the sum is a multiple of 8 and then rounded up to the next multiple divided by 8 of 8 PACKED The sum of the packed sizes The sum of the packed sizes in RECORD in bits of all fields in the fixed bits of all fields in the fixed part part and the largest variant and the largest variant plus plus the sum of sizes in bits the sum of sizes in bits of any of any holes created to meet holes created to meet alignment alignment requirements requirements if the sum is this sum is rounded up to greater than 32 the sum is a multiple of 8 and then rounded up to the next multiple divided by 8 of 8 STRING Maximum length 2 Maximum length 4 2 8 VARYING OF CHAR Nonsta
403. scribes the innermost dimension of Sample Next five 15 bit components require 75 bits Because of the 32 bit rules each 75 bit component is rounded up to 80 bits This size describes the middle and inner dimensions of Sample Finally five 80 bit components require 400 bits 50 bytes The entire array Sample then requires 400 bits Example 5 VAR Sample Rec PACKED RECORD Field 1 BOOLEAN Field 2 INTEGER32 Field 3 DOUBLE END In this example Field 1 requires only 1 bit of storage Field 2 is 32 bits in size declared as INTEGER32 and starts immediately following Field 1 Because Field 3 is larger than 32 bits it will start on the next byte boundary The entire record Sample Rec therefore requires 104 bits A 2 7 Alignment Boundaries The memory addressing boundary on which a variable or a component is aligned depends on the variable s or the component s allocation size You can change the alignment by using the ALIGNED and UNALIGNED attributes Table A 7 lists the conditions that determine boundary alignment A 16 Data Storage and Representation Table A 7 Conditions Determining Boundary Alignment Object Arguments to the Alignment Switch NATURAL VAX Variable declared with Specified alignment Specified alignment an alignment attribute Variable declared Natural alignment Byte alignment without an alignment attribute Component of an Natural alignment Byte alignment unpacked array or record variab
404. se the statement in the THEN clause cannot be followed with a semicolon since that completes the IF statement and separates it from the following statement The following examples contain correct code IF x gt 10 THEN y 4 IF x gt 10 THEN BEGIN y 4 ELSE y 5 zo 53 END ELSE y 5 5 8 Statements The ELSE clause always modifies the closest IF THEN statement Use caution to avoid logic errors in nested IF statements as in the following IF A 1 THEN em IF IF B 1 THEN Second IF C 1 ELSE Appears to modify first IF C t 0 Actually modifies second IF HP Pascal can not always evaluate all the terms of a Boolean expression if it can evaluate the entire expression based on the value of one term Either do not write code that depends on actual evaluation or evaluation order of Boolean expressions or use the AND_THEN and OR_ELSE operators for a predictable order of evaluation For More Information e On Boolean expressions Section 2 1 3 e On forming and evaluating expressions Section 4 1 e On the AND THEN and OR ELSE logical operators Section 4 2 3 5 10 Procedure Call Syntactically a procedure call is a statement A procedure call has the following form routine identifier actual parameter routine identifier The name of a procedure or function actual parameter An expression that is of a type that is compatible with the type of the formal parameter or the name of a pro
405. served word definition Glossary 11 Reference to variable 3 10 REFERENCE attribute 10 36 Reference mechanism 6 7 REF foreign mechanism on actual parameter 6 17 Relational operators 4 5 evaluating 4 13 Relative component number 9 3 definition Glossary 11 use with random access 9 16 Relative file cells 9 38 organization 9 3 sequential access to 9 13 Relative file organization definition Glossary 11 REM operator 4 4 RENAME FILE procedure 8 38 REPEAT statement 5 10 CONTINUE in 5 5 Repetitive statements FOR 5 6 REPEAT 5 10 WHILE 5 12 Reserved word definition Glossary 11 Reserved words 1 5 redefinable 1 6 RESETK procedure 9 59 RESET procedure 9 58 initiating delayed device access 9 21 Result values returning 5 11 Returning result values 5 11 RETURN statement 5 10 in function 5 11 REVERT procedure 8 38 REWRITE procedure 9 60 ROUND64 function 8 39 ROUND function 8 38 Rounding numbers of a parameter 8 38 8 39 Routine 6 1 attributes 10 55 calling of 6 4 categories 8 1 declaration of 6 1 definition Glossary 11 heading 6 1 predeclared 8 1 See also individual routines by name structured function return values 4 15 used as actual parameter 6 13 used as formal parameter 6 12 Routine call 6 4 76 ROUTINE directive 11 10 Routines T O processing 9 29 to 9 69 redeclaring names of 7 2 RSHIFT function 8
406. sful unless error undefined if unsuccessful FINDK Any Inspection TRUNCATE Inspection Generation if successful undefined if unsuccessful GET Inspection Inspection UFB Any No change LINELIMIT Any No change UNLOCK Inspection Inspection LOCATE Any Generation UPDATE Inspection Inspection OPEN Undefined Undefined WRITE Generation Generation unless keyed access which may be any mode PAGE Generation No change WRITELN Generation Generation PUT Generation Generation 9 30 Input and Output Processing 9 8 1 CLOSE Procedure The CLOSE procedure closes an open file You can use either positional or nonpositional syntax in the call 1 CLOSE file_variable disposition user_action ERROR error_recovery 2 CLOSE FILE_VARIABLE file_variable DISPOSITION disposition USER_ACTION user action ERROR error recovery file variable no default The name of the file variable associated with the file that HP Pascal is to close disposition same as for OPEN procedure A value that determines what HP Pascal is to do with the file after closing it The disposition values are the same as those used for the OPEN procedure The disposition value in the CLOSE procedure supersedes a disposition value specified in the OPEN procedure user action no default A routine name that HP Pascal calls to close the file You can use a user action routine to close the file using environment specific capabilities erro
407. sider the following example WRITE Name three presidents READ Presl Pres2 Pres3 HP Pascal stores the string Name three presidents in the output buffer when executing the READ procedure HP Pascal locates the TEXT file opened for output to the appropriate terminal and the partial output buffer is written causing the string Name three presidents to appear on the terminal screen The user can then begin typing on the same line as the prompt providing the names of three presidents Note that prompting works only for files associated with interactive terminals For any other files HP Pascal does not write output until you start the new line with a WRITELN procedure 9 5 3 Delayed Device Access to Text Files The Pascal standard requires that the file buffer always contain the next file component that will be processed by the program This definition can cause problems when the input to the program depends on the output most recently generated To alleviate such problems in the processing of the TEXT files HP Pascal uses a technique called delayed device access also known as lazy lookahead As a result of delayed device access HP Pascal does not retrieve an item of data from a physical file device and does not insert it in the file buffer until the program is ready to process it HP Pascal fills the file buffer when the program makes the next reference to the file A reference to the file consists of any use of the file bu
408. specified parameter The return value is compatible with all other string types OCT x length digits The parameter x is the expression to be converted This parameter must have a size that is known at compile time it cannot be VARYING OF CHAR a conformant parameter or a schema type Two optional integer parameters specify the length of the resulting string and the minimum number of significant digits to be returned If you specify a length that is too short to hold the converted value the resulting string is truncated on the left By default the number of significant digits is the minimum number of characters necessary to express all the bits of the converted parameter This default length is one character more than the default number of digits which causes a leading blank to be included in the resulting string when both parameters are omitted Consider the following example Int Var 427 Result OCT Int Var 10 3 Returns 653 For More Information e On character strings Section 2 6 8 63 ODD Function The ODD function returns a Boolean value that indicates if the parameter is odd ODD x The parameter x must be integer or unsigned This function returns TRUE if the value of x is odd and FALSE if the value of x is even 8 64 OR ATOMIC Function OpenVMS 164 and OpenVMS Alpha systems only The OR ATOMIC function logically ORs the value of an expression to the value of a variable stores th
409. specified variables even if this process results in the reading of several lines of the input file When applied to several variables READLN performs the following sequence READY file variable variable identifier READLN file variable EOLN returns TRUE after a READLN procedure only if the new line is empty You can use the READLN procedure to read integers real numbers Booleans characters strings and constants of enumerated types The values in the file must be separated as for the READ procedure The rules governing the reading of values from text files are presented with the READ procedure 9 56 Input and Output Processing Consider the following example TYPE String PACKED ARRAY 1 20 OF CHAR VAR Names TEXT Pres Veep String In the executable section READLN Names Pres Veep This program fragment declares and reads the file Names which contains the following characters John F Kennedy Lyndon B Johnson Lyndon B Johnson lt EOLN gt Hubert H Humphrey lt EOLN gt Richard M Nixon Spiro T Agnew lt EOLN gt lt EOLN gt lt EOF gt The READLN procedure reads the values John F Kennedy for Pres and Lyndon B Johnson X for Veep It then skips to the next line ignoring the remaining characters on the first line Subsequent execution of the procedure assigns the value Hubert H Humphrey to Pres and the space detected as the end of line marker to Veep A third ca
410. stops at the character A and i contains the value 123 When reading constant identifiers of an enumerated type from a TEXT file HP Pascal reads all characters in the identifier but recognizes only the first 31 characters You need input only enough characters to make the identifier unique among the other constant identifiers of its type text input data for enumerated types can consist of both lowercase and uppercase characters Boolean input data in TEXT files follow the same rules as other enumerated types For example the following character combinations all of which could appear in a TEXT file are equivalent TRUE True T t tr Input and Output Processing 9 53 When using a radix specifier values from a TEXT file can be read into a variable of any type except a type containing a file component If the input stream does not provide sufficient data the high order bits are set to zero When reading structured types the input stream must account for any padding required for alignment You can use the READ procedure to read a sequence of characters from a TEXT file into a variable of type PACKED ARRAY OF CHAR Successive characters from the file are assigned to components of the array in order until each component has been assigned a value If any characters remain on the line after the array is full the next READ procedure begins with the next character on that line If the end of the line is encountered before the array is full
411. storage is allocated in the program section in which storage for executable code is currently being allocated by default CODE On all other systems its storage is allocated in the program section LITERAL All other static variables are allocated in the program section LOCAL For More Information On attributes Chapter 10 A 8 Data Storage and Representation A 2 2 Allocation of Symbolic Constants and Executable Blocks When allocating storage for symbolic constants and executable blocks the compiler determines the appropriate program section by applying the same rules of scope to program section names that it applies to identifiers The compiler always allocates storage in the program section whose name appeared in the most recent heading of a routine or compilation unit Table A 3 and Table A 4 describe the program sections established for each kind of data in a program unless a PSECT attribute appears in the heading of routine or compilation unit and directs that storage to be allocated in a different program section For More Information e On the scope of HP Pascal identifiers Section 7 2 e On the PSECT attribute Section 10 2 32 e On the INITIALIZE attribute Section 10 2 22 On LIB INITIALIZE HP OpenVMS Programming Concepts Manual A 2 3 Allocation Example Example A 1 shows how the compiler establishes program sections to allocate storage for symbolic constants variables and executable blocks The com
412. t declaration section A Pascal declaration section statement A Pascal statement The program or module heading includes all information preceding the program or module block If your program contains any input or output routines you must list all the external file variables that you are using in the compilation unit s heading File variables listed in a heading must also be declared locally in the block except for the predeclared file variables INPUT and OUTPUT The INPUT identifier corresponds to a predefined external file that accepts input from the default device usually your terminal The OUTPUT identifier corresponds to a predefined external file that sends output to the default device usually your terminal the ERR identifier corresponds If you redeclare INPUT and OUTPUT in a nested block you lose access to the default input and output devices Consider the following example PROGRAM Write Var OUTPUT Header VAR Declaration section Number INTEGER VALUE 3 BEGIN Executable section WRITELN Number Writes 3 to the default device END For More Information e On INPUT and OUTPUT Section 9 5 e On compilation and command line syntax HP Pascal for OpenVMS User Manual e On the TO BEGIN DO section Section 3 3 e Onthe TO END DO section Section 3 4 7 6 Program Structure and Scope 7 5 Compilation Units and Data Sharing When dividing code into programs and modules you may want to share declarati
413. t for TEXT and FILE OF VARYING ignored default for other file types A positive integer that specifies the maximum size in bytes for a line in a TEXT file or a file of type FILE OF VARYING Record length is equivalent to component length The default is 255 bytes For all other types of files HP Pascal ignores this parameter If you do not specify a length for an existing file HP Pascal uses the length specified at the file s creation If you use OPEN to create a sequentially organized file with variable length components HP Pascal records the maximum length of each component in the file only if you specify a value for the record_type field access_method SEQUENTIAL default A value that specifies the component access method to use The possible values include SEQUENTIAL DIRECT and KEYED The DIRECT access method Input and Output Processing 9 45 is equivalent to random access by relative component number The KEYED access method is equivalent to random access by key record_type VARIABLE default for new TEXT and VARYING OF CHAR FIXED default for other new files A value that indicates the component format Record format and component format are equivalent The available values are FIXED fixed length components VARIABLE variable length components STREAM stream component format with either carriage return combination carriage return and line feed or form feed delimiters STREAM_CR stream component format wi
414. t key number specified The KEY attribute is ignored except when the record is a component of a file A key field can be of any ordinal type or of type PACKED ARRAY OF CHAR If the key field is of type PACKED ARRAY OF CHAR its length cannot exceed 255 characters The KEY attribute does not affect type compatibility rules A key field cannot be unaligned A key field of an ordinal type must be allocated in exactly one byte one word one longword or one quadword Key fields can be allocated in a quadword only on OpenVMS 164 and Alpha systems An integer key field that is allocated one byte cannot have negative values 10 24 Attributes Consider the following example TYPE Register RECORD Student_No KEY 0 DESCENDING INTEGER Student_Name RECORD Last_Name PACKED ARRAY 1 20 OF CHAR First Name PACKED ARRAY 1 15 OF CHAR Initial CHAR END Course Load INTEGER Grade Average REAL Class KEY 1 PACKED ARRAY 1 9 OF CHAR END This example defines the identifier Register to denote a record type The first field Student No is the primary key of the record It has been defined as a DESCENDING NOCHANGES and NODUPLICATES key Register contains another field Class which is established as the alternate ASCENDING CHANGES and DUPLICATES key For More Information e On indexed files Section 9 1 3 e On the UNALIGNED attribute Section 10 2 38 10 2 24 LIST You can apply the LIST attribute t
415. t of attributes can appear anywhere in the VAR TYPE and CONST declaration sections and anywhere in a program that a type a type identifier or the heading of a routine or compilation unit is legal However only one attribute from a particular class can appear in a given attribute list The use of attribute lists is shown in examples throughout this chapter The names of attributes when used in a suitable context cannot conflict with other identifiers with the same name in the program Syntactically an attribute list can appear before a VAR TYPE and CONST section in the declaration section In this case the attributes would apply to all elements in that particular section However HP Pascal only allows you to use the ALIGN ENUMERATION_SIZE and HIDDEN attribute in this way Some attributes require a special form of constant expression called a name string The syntax of a name string differs from that of other strings in HP Pascal only in that a name string cannot use the extended string syntax Every program element must be associated with one property for each applicable attribute class The HP Pascal compiler automatically supplies the defaults for the unspecified classes at the time of the element s declaration In some classes as described in the following sections the default property is not available through an explicit attribute Attributes can be associated with data items in the following ways e By appearing in a type d
416. t to TRUE and EOF becomes undefined The following example shows the use of the GET procedure RESET Books New Rec Books GET Books After execution of the RESET procedure the value of the file buffer variable Books is equal to the value of the first component of the file The assignment statement assigns this value to the variable New Rec The GET procedure then assigns the value of the second component to Books advancing the file position to the second component Another GET procedure advances the file position to the Third component Figure 9 10 shows this sequence of events 9 40 Input and Output Processing Figure 9 10 File Position After GET Procedure Beginning EOF of File I I I RESET GET Books Books Beginning 4 4 l l l RESET GET GET Books Books Books ZK 0103 GE By using the GET procedure repeatedly you can read sequentially through a file When called for a file with relative organization GET skips any nonexistent components to find the next component When you reach the end of the file and EOF returns TRUE a GET procedure results in a run time error Consider the following example GET Phones This example reads the next component of the file Phones into the file buffer variable Phones Prior to executing GET the value of EOF Phones must be FALSE if it is TRUE an error occurs For More Information e On component access Section 9 3 e On the UFB func
417. t to a new page of the specified TEXT file The next component written to the file begins on the first line of a new page You can use this procedure only on TEXT files If you specify a file of any other type an error occurs Input and Output Processing 9 49 9 8 14 The value of the page eject component that is output to the file depends on the carriage control format for that file When CARRIAGE or FORTRAN is enabled the page eject record is equivalent to the carriage control character 1 When LIST NOCARRIAGE or NONE is enabled the page eject record is a single form feed character Consider the following example PAGE User Guide This PAGE procedure causes a page eject record to be written in the text file User Guide For More Information e On TEXT files Section 9 5 e On the error processing parameter Section 9 7 PUT Procedure The PUT procedure adds a new component to a file PUT file variable ERROR error recovery file variable The name of the file variable associated with the output file error recovery The action to be taken if an error occurs during execution of the routine Before executing the first PUT procedure on a file opened for sequential access you must execute an EXTEND REWRITE or TRUNCATE procedure to set the file to generation mode EXTEND REWRITE and TRUNCATE set EOF to TRUE thus preparing the file for output TRUNCATE is legal only on files with sequential organiz
418. t values of the same type as the corresponding component in a comma list within parentheses The compiler matches the values with the components using positional syntax you must provide a value for each component in the variable Nested structured components are designated by another comma list inside of another set of parentheses Nonstandard constructors are legal in the VAR and VALUE initialization sections and in the executable section Specifying a type identifier as part of a constructor is optional for constructors used in the VAR and VALUE initialization sections are required for constructors in the executable section and cannot be used for nested constructors For More Information e On Pascal standards Section 1 1 e On standard constructors Section 2 4 Nonstandard Array Consiructors The format for nonstandard array constructors is as follows data type component value REPEAT component value data type Specifies the constructor s data type If you use the constructor in the executable section a data type identifier is required Do not use a type identifier in the VAR or VALUE sections or for a nested constructor component value Specifies the compile time value to be assigned to the corresponding array element The compiler assigns the first value to the first element the second value to the second element and so forth If you want to assign more than one value to more than one consecutive e
419. tandard constructs during compilation HP Pascal for OpenVMS User Manual 1 1 2 Extended Pascal Standard The Extended Pascal standard is a superset of the unextended Pascal standards The Extended Pascal standards are as follows e American National Standard ANSI IEEE770X3 160 1989 e International Standard ISO 10206 1989 In the HP Pascal documentation set the term Pascal standard refers to these standards Because HP Pascal supports most Extended Pascal standard features it cannot compile all programs that comply with Extended Pascal For your convenience the HP Pascal extensions to the Extended Pascal standard are printed in blue in this manual For More Information e On HP Pascal support for Extended Pascal features Appendix B e On flagging nonstandard constructs during compilation HP Pascal for OpenVMS User Manual 1 2 Lexical Elements This section discusses lexical elements of the HP Pascal language 1 2 Language Elements 1 2 1 Character Set HP Pascal uses the extended American Standard Code for Information Interchange ASCII character set This extended ASCII character set contains 256 characters which include the following e Uppercase letters A through Z and lowercase letters a through z e Integers 0 through 9 e Special characters such as the ampersand amp question mark and equal sign e Nonprinting characters such as the space tab line feed carriage return and form feed use of these
420. te or the time If the day of the month is a 1 digit number the leading zero does not appear in the result that is a space appears before the date string The time is returned in 24 hour format For More Information e On standard ways to obtain the date and the time Section 8 23 8 25 DBLE Function The DBLE function converts the parameter and returns its DOUBLE equivalent DBLE x The parameter x must be of an arithmetic type The value of x must not be too large to be represented by a double precision number Predeclared Functions and Procedures 8 13 For More Information e On precision and support for the DOUBLE data type Chapter 2 8 26 DEC Function The DEC function returns a character string value that is the decimal equivalent of the specified parameter The return value is compatible with all other string types DEC x length digits The parameter x is the expression to be converted The DEC function can take a parameter of any type except VARYING OF CHAR conformant parameters or schema types The DEC function requires the size of x to be less than or equal to the size of INTEGER64 if supported or less than or equal to the size of INTEGER32 Two optional integer parameters specify the length of the resulting string and the minimum number of significant digits to be returned If you specify a length that is too short to hold the converted value the resulting string is truncated on the left
421. ted on a new line when the file is written to a terminal line printer or similar carriage control device If you specify a carriage format but use an invalid carriage control character the first character in the line is ignored and the output appears with the first character truncated Consider the following example TYPE A String PACKED ARRAY 1 25 OF CHAR VAR New Hires TEXT n INTEGER New Rec RECORD Id INTEGER Name Address A String END In the executable section OPEN New Hires new hires dat CARRIAGE CONTROL FORTRAN REWRITE New Hires WITH New Rec DO BEGIN WRITELN New Hires lNew hire ID 1 is Name WRITELN New Hires Name lives at WRITELN New Hires toros WRITELN New Hires Address END Input and Output Processing In this example four lines are written to the TEXT file New_Hires The output starts at the top of a new page as directed by the carriage control character 1 and appears in the following format New hire 73 is Irving Washington Irving Washington lives at 22 Chestnut St Seattle For More Information e On TEXT files Section 9 5 e On carriage control characters in new files Section 9 8 12 e On the error processing parameter Section 9 7 e On formatting output Section 9 6 Input and Output Processing 9 69 10 Attributes An attribute is an identifier that directs the HP Pascal compiler to change its beha
422. tems Class Data Item Pointer Formal Base Function Various Variable Parameter Type Component Result Items Alignment Yes Yes Yes Yes Yes No Allocation Yes 9 No No No No No Hidden Yes No Yes No No No Key No No No Yes No No List No Yes No No No No Parameter No Yes No No No No passing Pos No No No Yes No No Read only Yes Yes Yes Yes No No Size Yes Yes 1 Yes Yes Yes No Truncate No Yes No No No No Unsafe Yes Yes Yes Yes Yes Yes Value Yes No No No No No Visibility Yes No No No No No Volatile Yes Yes Yes Yes Yes No Write only X Yes Yes Yes Yes No No 1 Component of a record array VARYING OF CHAR string or file includes conformant parameters Index of an array tag field of a variant record when no tag identifier is present base type of a set formal discriminant Variables of nonstatic types must be at least byte aligned UNALIGNED not allowed 5 Not allowed on components of files or VARYING OF CHAR strings Not allowed on variables of nonstatic types 7 Allowed only on record fields including the tag field of a variant record 8 Procedure parameters and conformant parameters are allowed only on EXTERNAL routines 9 Not allowed on conformant VARYING parameters not allowed on schematic parameters 10 Not allowed on conformant parameters not allowed on schematic parameters H Not allowed on components of files or VARYING OF CHAR strings or on structured types with file compo
423. ter to another routine The appearance of the function identifier in an actual parameter list could indicate the passing of either the address of the function or the function result In HP Pascal the address of the function is passed by default as shown in this example p IMMED f Address of function f is passed Procedures and Functions 6 17 To cause the function result to be passed you must enclose the function identifier in parentheses as shown in this example p SIMMED f Result of function f is passed For More Information e On conformant parameters Section 6 3 7 e On type conversions Section 4 4 e On attributes Chapter 10 e On calling external routines HP Pascal for OpenVMS User Manual e On compiler messages HP Pascal for OpenVMS User Manual 6 3 6 Schema Parameters HP Pascal provides a method of processing schematic arrays records sets subranges and STRINGs with potentially different actual discriminants To do this you can use undiscriminated schema parameters An undiscriminated schema formal parameter is a type name that represents a specific schema family The actual discriminants are determined each time you pass a corresponding actual parameter The actual discriminants are available within the routine through the formal parameter You can use undiscriminated schema formal parameters when declaring value and variable parameters When you use a formal undiscriminated schema parameter inst
424. ters is to give the parameters in each list the same position That is the association of actual and formal parameters proceeds from left to right item by item through both lists This form of association is called positional syntax Another way of establishing correspondence is to specify the formal parameter name and the actual parameter being passed to it In HP Pascal you can associate an actual parameter with a formal parameter using the assignment operator The actual parameters in the call do not have to appear in the same order as the formal parameters appeared in the declaration This form of association is called nonpositional syntax You can use both positional and nonpositional actual parameters in the same call However after you specify one parameter in nonpositional syntax all remaining parameters must be in nonpositional syntax all parameters in positional syntax must be at the front of the list Consider the following example PROCEDURE Compute Sum x y INTEGER VAR z INTEGER Body In the executable section Positional syntax Compute Sum Quantity 6 15 Total Nonpositional syntax Compute Sum z Total x Quantity 6 y 15 Both syntaxes Compute Sum Quantity 6 z Total y 15 For More Information e On using the LIST and TRUNCATE attributes to specify variable length parameter lists Sections 10 2 24 and 10 2 37 e On scope Section 7 2 Pro
425. th carriage return delimiters and STREAM LF stream component format with line feed delimiters carriage control LIST default for TEXT and VARYING OF CHAR files NONE default for all other file types A value that indicates the carriage control format for the file The value LIST indicates single spacing between components The values CARRIAGE and FORTRAN are equivalent and indicate that the first character of every output line is a carriage control character The values NONE and NOCARRIAGE indicate that the file has no carriage control organization SEQUENTIAL default for new files A value that specifies the file organization If you are accessing an existing file the specified organization must match the organization of the existing file if it does not an error occurs The choices for this parameter are SEQUENTIAL RELATIVE and INDEXED disposition SAVE default for external files DELETE default for internal files A value that indicates what HP Pascal should do with the file after you close the file The dispositions are as follows 9 46 Input and Output Processing Disposition Description SAVE HP Pascal retains the file DELETE HP Pascal deletes the file PRINT HP Pascal prints the file on a line printer and retains the file PRINT_DELETE HP Pascal prints the file on a line printer and then deletes the file SUBMIT HP Pascal submits to a queue or places the print job in a background process and retai
426. th of 9 23 representation of A 21 Size default for objects A 11 Size attributes effect on allocation A 11 SIZE function 8 40 A 14 SNGL function 8 41 Special characters 1 4 Special symbols 1 4 SQR function 8 42 SQRT function 8 42 Square of parameter 8 42 Square root of parameter 8 42 Statement 5 1 to 5 14 assignment 5 2 BREAK 5 2 CASE 5 3 compound 5 4 description of 5 1 empty 5 5 FOR 5 6 GOTO 5 7 IF 5 8 procedure call 5 9 REPEAT 5 10 RETURN 5 10 WHILE 5 12 WITH 5 13 Statements CONTINUE 5 5 Static allocation 10 36 type 2 48 Static allocation of variables A 7 STATIC attribute 10 36 effect on allocation of variables A 7 Static type definition Glossary 12 Index 18 Static variable allocation definition Glossary 12 STATUS function 9 61 return value from READLN procedure 9 22 9 57 STATUSV function 8 42 STDESCR foreign mechanism on actual parameter 6 17 Storage allocation A 7 to A 19 default size for objects A 11 example of A 9 Stream component format 9 10 definition Glossary 12 String See Character string String delimiters 1 4 String descriptor mechanism 6 17 String operators 4 8 concatenation of 4 8 STRING schema type 2 45 String types 2 41 to 2 42 initial state specifier for example 4 9 LENGTH and LENGTH functions example 4 9 Structural compatibility 2 49 affected by ASYNCHRONOUS 10 8 effect of allocation size 10 11 ef
427. the SUBSTR function e The value of the starting position must be greater than 0 e The value of the length must be greater than or equal to 0 e There must be enough characters following the starting position to construct a substring of the specified length Consider the following example Original String This is the original string Start Position 13 Substring Length 15 New String SUBSTR Original String Start Position Substring Length New String contains original string For More Information e On character strings Section 2 6 8 89 SUCC Function The SUCC function returns the value that succeeds the parameter according to the parameter s data type SUCC x The parameter x can be of any ordinal type however there must be a successor value for x in the type Predeclared Functions and Procedures 8 43 8 90 SYSCLOCK Function The SYSCLOCK function returns an integer value for the number of milliseconds of system time used by the current process The result is the same as that returned by the CLOCK function SYSCLOCK For More Information e On the WALLCLOCK function Section 8 108 e On the CLOCK function Section 8 20 8 91 TIME Procedure See Section 8 24 8 92 TRUNC Function The TRUNC function converts the value of the parameter by truncating the fractional part of the value and returns its integer equivalent TRUNC x The parameter x must be of type REAL SINGLE DOUBLE or
428. the case labels If the value is not equal to a label the CASE statement result is undefined Consider the following example CASE Age OF 1 4 School preschool Subranges 5 8 School elementary 9 13 School middle 14 18 BEGIN School high WRITELN Difficult years END Compound statements 19 School reform Single ordinal value OTHERWISE School graduated If 1 gt Age gt 18 END For More Information e On ordinal values Section 2 1 e On using the CHECK attribute to check selectors at run time Section 10 2 8 5 4 Compound Statement A compound statement groups a series of statements so that they can appear anywhere that language syntax calls for a single statement A compound statement has the following form BEGIN statement END statement Any Pascal statement including other compound statements The statements that make up the compound statement must be separated with semicolons although the semicolon before the END delimiter is optional 5 4 Statements Consider the following example IF a lt 10 THEN BEGIN A compound statement x fe I0 y t 20 Z xX Vy END No semicolon in THEN clause before an ELSE ELSE z 29 A single statement For More Information e On program executable sections Section 7 4 e On function and procedure executable sections Section 6 1 5 5 CONTINUE Statement The body of a
429. the declaration and the usage of the data Global and external variables are implicitly static Thus they conflict with the AUTOMATIC attribute Program level variables with the AUTOMATIC attribute are not recorded in environment files AUTOMATIC cannot be applied to routines and compilation units AUTOMATIC cannot be applied to nonstatic types Attributes 10 9 For More Information On an example of the STATIC attribute Section 10 2 36 On the GLOBAL attribute Section 10 2 17 On the EXTERNAL attribute Section 10 2 15 On static and nonstatic types Section 2 9 10 2 6 BIT The BIT attribute specifies the amount of storage in bits to be received by the object BIT n I The optional constant n indicates the number of bit storage units Usage and Default Information The following size attribute restrictions apply to BIT BYTE LONG WORD QUAD and OCTA The default size of an object depends on its type The constant expression n must denote a positive integer If you omit n the default value is 1 Objects of floating point or pointer types must have a size equal to their allocation size Ordinal types cannot exceed their maximum size which is determined by the platform and the value of the data switch for the compile command The amount of storage described must be large enough to contain an object of the specified type otherwise a compile time error occurs Assignment to variables with a size attr
430. the same type 8 58 MTPR Procedure OpenVMS VAX systems only The MTPR procedure assigns a value into a VAX internal processor register MTPR ipr register expression source expression The ipr register expression and source expression parameters are expressions compatible with the unsigned type HP Pascal stores the value specified by source expression into the internal processor register specified by the ipr register expression 8 28 Predeclared Functions and Procedures For More Information e On running in kernel mode or on using the MFPR procedure Section 8 56 8 59 NE Function The NE function returns a Boolean value that specifies if the parameters are not equal according to the ASCII values of the strings characters NE str1 str2 The parameters str1 and str2 must be character string expressions HP Pascal does not pad shorter strings with blanks Consider the following example VAR Match BOOLEAN In the executable section Match NE exit exit Returns TRUE Match NE exit exit Returns FALSE For More Information e On string data types Section 2 6 8 60 NEW Procedure The NEW procedure allocates memory for the dynamic variable to which a pointer variable refers The value of the newly allocated variable is set to the initial value of the base type if defined otherwise the value of the variable is undefined Hath NEW PI ray tH The parameter p is a point
431. therwise specified Intended Audience This manual is for experienced applications programmers with a basic understanding of the Pascal language Some familiarity with your operating system is helpful This is not a tutorial manual Document Structure This manual consists of the following chapters and appendixes e Chapter 1 describes Pascal language standards and lexical elements e Chapter 2 describes data types and values e Chapter 3 describes declaration sections e Chapter 4 describes expressions and operators e Chapter 5 describes statements e Chapter 6 describes user written procedures and functions e Chapter 7 describes program structure and scope e Chapter 8 describes predeclared procedures and functions except those that perform input and output xvii Chapter 9 describes the predeclared procedures and functions that perform input and output Chapter 10 describes attributes Chapter 11 describes directives Appendix A describes the storage allocation and alignment for data types and the internal representation of each data type Appendix B describes the HP Pascal extensions to the Pascal standards Appendix C describes the HP Pascal implementation features that the Pascal standards allow each implementation to define Appendix D describes how the HP Pascal compiler detects errors defined by the Pascal standard The Glossary provides a glossary of HP Pascal terminology Related Documents The following doc
432. thin the first block calls to Sum within the block are not recursive but are calls to the locally declared routine 7 2 Program Structure and Scope You can also redeclare a function identifier within its own declaration However the function then cannot use the function identifier in an assignment to return a value to the caller A function that redeclares its own identifier must use the RETURN statement see Section 5 12 to specify a return value In the declaration section you cannot redeclare an identifier used in the formal parameter list of the routine However a block nested in the declaration section can do so The following example shows the scope of identifiers that appear in several blocks in a program Figure 7 1 shows the scope of identifiers that appear in several blocks in a program Pascal scope rules make the following statements about Figure 7 1 true e Variable identifiers a and b are declared at the outer level of the example Scope rules make them accessible throughout the example In the main program Levella and Levellb identifiers a and b represent integers In Level2 variable identifer a still represents an integer variable but b is redeclared as a Boolean variable e Type identifier c and variable identifiers d and e are declared at the next lower level Levella Scope rules make them accessible only in this block They cannot be accessed from the higher level main program They cannot be accessed from a lower
433. tialize variables the types of expressions assigned to variables with the assignment operator and the types of actual parameters passed to formal value parameters A variable or formal parameter is always compatible with expressions of its type Table 2 11 shows the contexts in which the type of an expression is assignment compatible with the type of a variable or a formal parameter when the types are not the same Data Types and Values 2 51 2 52 Table 2 11 Assignment Compatibility Type of Variable Type of Assignment Compatible Expression or Parameter INTEGER UNSIGNED INTEGER64 UNSIGNED64 Subrange REAL SINGLE DOUBLE QUADRUPLE PACKED ARRAY OF CHAR VARYING OF CHAR STRING Pointer INTEGER UNSIGNED INTEGER64 UNSIGNED64 INTEGER UNSIGNED INTEGER64 UNSIGNED64 INTEGER UNSIGNED INTEGER64 UNSIGNED64 INTEGER UNSIGNED INTEGER64 UNSIGNED64 Base type of the subrange REAL SINGLE UNSIGNED INTEGER INTEGER64 UNSIGNED64 DOUBLE REAL SINGLE UNSIGNED INTEGER INTEGER64 UNSIGNED64 QUADRUPLE DOUBLE REAL SINGLE UNSIGNED INTEGER CHAR unpacked array of CHAR PACKED ARRAY OF CHAR with the same or smaller length VARYING or STRING string whose current length is equal to or less than the packed array CHAR unpacked array of CHAR PACKED ARRAY OF CHAR VARYING STRING string whose current value does not exceed the maximum length of the variable or parameter CHAR unpacked array
434. tic 32 if the set base type is a Compute ORD upper bound PACKED subrange of INTEGER or 1 if the result is less than SET UNSIGNED else compute or equal to 64 the result is Unpacked ORD upper bound of ordinal rounded up to 8 16 32 or 64 SET type that is base type of sets and if the result is greater than base type 8 DIV 8 and if this result is less than or equal to 8 the result is rounded up to 1 2 4 or 8 64 the result is rounded to next higher multiple of 8 3This is known as the ceiling function where the smallest integer is greater than or equal to X continued on next page Data Storage and Representation A 13 Table A 6 Cont Storage Allocation of Types Unpacked Packed Data Type Size in Bytes Size in Bits PACKED SET The result of ORD upper Compute ORD upper bound bound 8 DIV 8 1 if the result is greater than 32 the result is rounded to next higher multiple of 8 FILE Not specified Not specified 3This is known as the ceiling function where the smallest integer is greater than or equal to X The formula to compute the size of a packed subrange is MAX X Y Z where X Y and Z are computed as follows LOW represents the low bound of the subrange HIGH represents the upper bound IF LOW 1 IF HIGH 0 THEN THEN X log2 LOW 1 1 Y log2 HIGH 1 ELSE ELSE X 0 Y 0 IF LOW gt 0 THEN Z gs 0 ELSE Z lt l You can discover both th
435. till be aligned on byte boundaries which leaves holes in the storage space To gain storage space you must specify a packed array of a packed structured type Data Storage and Representation A 17 The following examples show the use of alignment boundaries Note Although packing records and arrays does save storage space and can be necessary for compatibility with other code note that accessing unaligned variables on an OpenVMS I64 or OpenVMS Alpha system takes many more instructions than accessing variables with natural alignment such as those in unpacked records and arrays Example 1 VAR X STATIC ALIGNED 3 INTEGER QUADWORD ALIGNED SDATA on OpenVMS 164 DATA on OpenVMS Alpha LOCAL on OpenVMS VAX In this example X is declared a static variable that is aligned on a QUADWORD boundary Example 2 VAR X PACKED RECORD AUTOMATIC Fieldl BOOLEAN Field2 REAL Field3 BOOLEAN Field4 DOUBLE END In this example Field1 begins at bit position 0 and is 1 bit long Field2 begins at bit position 1 and is 32 bits long Field3 begins at bit position 33 and is 1 bit long However because Field4 is greater than 32 bits long DOUBLE requires 64 bits Field4 must be byte aligned For this reason Field4 begins on bit position 40 and is 64 bits long Example 3 VAR X RECORD AUTOMATIC Fieldi BIT 3 0 7 Field2 UNALIGNED INTEGER32 END In this example Field1 of record X is
436. tine in a IF control expression as you can in any constant expression One use of IF is to compile for various configurations or environments as shown in the preceding example Rather than defining a constant in the Pascal source as shown in the examples here you might want to define the constant from the command line with the CONSTANT qualifier See the description of the CONSTANT qualifier for more information 11 5 DEFINED DEFINED takes a name and returns TRUE if a name has a meaning in the current scope otherwise it returns FALSE This is shown in the following example IF DEFINED X STHEN writeln x SENDIF 11 6 ERROR WARN INFO and e MESSAGE These directives will accept one or more string expressions and at compile time will produce an error message warning message informational message or terminal only output respectively The syntax is as follows ERROR string expression 9e WARN string expression YoINFO string expression MESSAGE string expression 11 8 Directives The following is an example of 7 ERROR TYPE Some Type SIF SIZE Some Type gt 8 STHEN SERROR We do not handle types greater than 8 bytes SENDIF The following is an example of WARN SIF Config Configl STHEN Code for Configl SELIF Config Config2 or Config Config3 STHEN Code for Config2 Config3 SELSE SWARN Config not support
437. ting point or pointer types must have a size equal to their allocation size Ordinal types cannot exceed their maximum size which is determined by the platform and the value of the data switch for the compile command If no size attribute is applied to the variable the compiler calculates the unpacked size so that it is structurally compatible with the base type of the variable s type Storage for variables of type VARYING OF CHAR is allocated as one byte per character with an initial field of two bytes to indicate the total length Storage allocation for a variable of type VARYING OF CHAR whose maximum length is less than or equal to 32 bits follows the 32 bit rules in that the variable can be unaligned On OpenVMS I64 and OpenVMS Alpha systems variables of type VARYING OF CHAR that need alignment are aligned on a word boundary On OpenVMS VAX systems variables of type VARYING OF CHAR that need alignment are aligned on a byte boundary Structured objects ARRAY and RECORD take their maximum alignment from their components for example if the largest object is a word the structure is aligned on a word boundary The maximum size for any variable is 231 1 bits A 2 5 Storage Allocation of Types Table A 6 shows the allocation size for variables of each type when the variables occur in either a packed or an unpacked context Table A 6 Storage Allocation of Types Unpacked Packed Data Type Size in Bytes Size in Bits INTEGER 4 3
438. tion GETTIMESTAMP Procedure llle GT Function HALT Procedure HEX Function IADDRESS Function leere IADDRESS64 Function eeeeee eens IN RANGE Function lee es INDEX Function INT Function INT64 Function LE Function LENGTH Function eee hh hs LN Function LOWER Functions secere 286 608 Re ER EesthswResg LSHIFT Punch Oris 2o Se RU RR CXII RSS LT Function MAX Function MIN Function NE Function NEW Procedure NEXT Function OCT Function ODD Function MALLOC C STR Function 0 0 00 00 ee MFPR Function OpenVMS VAX systems only MTPR Procedure OpenVMS VAX systems only OR_ATOMIC Function OpenVMS I64 and OpenVMS Alpha systems only ORD Function PACK Procedure PAD Function PAS STR IUDctio soe oe a eae ate atte ot stica sete euet ro ot Ghats PAS STRCPY Function 33 0458 6 eS ee eo ew E or ees PRED Function 8 16 8 16 8 16 8 17 8 17 8 17 8 18 8 18 8 19 8 19 8 20 8 21 8 21 8 22 8 23 8 23 8 23 8 24 8 24 8 24 8 25 8 25 8 25 8 26 8 26 8 27 8 27 8 27 8 28 8 28 8 29 8 29 8 31 8 32 8 32 8 32 8 33 8 33 8 34 8 35 8 35 8 35 vii viii 8 71 8 72 8 73 8 74 8 75 8 76 8 77 8 78 8 79 8 80 8 81 8 82 8 83 8 84 8 85 8 86 8 87 8 88 8 89 8 90 8 91 8 92 8 93 8 94 8 95 8 96 8 97 8 98 8 99 8 100 8 101 8 102 8 103 8 104 8 105
439. tion e Ifa parameter with the TRUNCATE attribute is present in the actual parameter list explicitly with a null actual parameter or by being skipped over by a nonpositional actual parameter then the list is not truncated at the TRUNCATE parameter All parameters including the current TRUNCATE parameter up to the next parameter that specifies TRUNCATE must be present or have a default value The first parameter is present in this call from Example 10 1 so the list is not truncated at the first parameter The second parameter has a default value so it is included in the result The third parameter however is not present in the actual parameter list so the parameter list is truncated pO DEFAULT a AND b TRUNCATE AT c ab e Ifa parameter with the TRUNCATE attribute is present by default the list is not truncated at that point In this line of code from Example 10 1 the first second and third parameters are present by default Because the third parameter is present the parameter list is not truncated and all four parameters are present in the result pG DEFAULT a b c AND d abcd e You can specify actual parameters either positionally or nonpositionally it is the order in the formal parameter list that is used to determine where the list has been truncated and which parameters are required Because c the third parameter is present in the actual list the parameter list is not truncated p c y DEFAULT a b AND
440. tion Section 9 8 22 e On the error processing parameter Section 9 7 Input and Output Processing 9 41 9 8 9 LINELIMIT Procedure 9 42 The LINELIMIT procedure stops execution of the program after a specified number of lines has been written into a TEXT file LINELIMIT file variable n ERROR error recovery file variable The name of the file variable associated with the TEXT file to which this limit applies n A positive integer expression that indicates the number of lines that can be written to the file before execution terminates error recovery The action to be taken if an error occurs during execution of the routine The file can be in any mode before LINELIMIT is called the file mode does not change after LINELIMIT has been executed HP Pascal first uses environment specific means to determine if there is a default line limit If there is no environment specific default there is no default line limit You can use a call to LINELIMIT to override the default After the number of lines written into the file has reached the line limit program execution terminates unless the WRITELN procedure that exceeded the line limit includes the ERROR CONTINUE parameter Consider the following example LINELIMIT Debts 100 Execution of the program terminates after 100 lines have been written into the text file Debts HP Pascal determines the default line limit by translating an environment variable or logi
441. to the caller of a PROCEDURE FUNCTION PROGRAM or module initialization or finalization section A RETURN statement is equivalent to a GOTO to a label placed just before the END of the body and in a PROGRAM has the effect of stopping the program A RETURN statement has the following form RETURN return value 5 10 Statements return value Inside a FUNCTION return value specifies an ending value for the FUNCTION If no return value is provided the last value assigned to the function identifier is used as the function result The return value type and function type must be the same Inside a PROGRAM the return value specifies an ending value for the PROGRAM If you do not provide a return value HP Pascal uses the value 1 A function returns a result to its caller A function can specify its result by assigning a value to the function identifier This does not cause a return to the caller and can occur many times per call When the function finally returns the last assignment becomes the result of the function If a function uses the RETURN statement and includes a value then the function returns immediately and returns the specified value This value overrides any previous values specified by an assignment If a function uses the RETURN statement but does not specify a value the return value is the last value that the function specified by assignment If the function has not assigned a value to the function identifier during
442. tput value For nontext files the types of the output values must be assignment compatible with the component type of the file For example WRITE file variable expression This procedure call is similar to the following example file variable expression PUT file variable For TEXT files the WRITE procedure converts the value of each expression to a sequence of characters It repeats the assignment and PUT process until all the values have been written to the file 9 66 Input and Output Processing 9 8 26 Consider the following example TYPE String PACKED ARRAY 1 20 OF CHAR VAR Names FILE OF String Pres String In the executable section WRITE Names Millard Fillmore Pres This example writes two components in the file Names The first is the 20 character string constant Millard Fillmore The second is the value of the string variable Pres For More Information e On TEXT files Section 9 5 e On component format Section 9 2 e On output format Section 9 6 e On prompting from the terminal Section 9 5 2 e On the error processing parameter Section 9 7 WRITELN Procedure The WRITELN procedure writes a line of data to a text file WRITELN file_variable expression ERROR error recovery file_variable The name of the file variable associated with the text file to be written If you omit the name of the file the default is OUTPUT expression An ex
443. tribute list tag type identifier discriminant identifier case label list field list E OTHERWISE field list oF 2 24 Data Types and Values tag identifier The name of the tag field attribute list One or more identifiers that provide additional information about the variant tag type identifier The type identifier for the tag field discriminant identifier The name of the formal discriminant of a schema type The value of the corresponding actual discriminant selects the active variant Once you select the variant by discrimination you cannot change it again Consider the following TYPE Record Template a INTEGER RECORD Field 1 REAL CASE a OF 0 x INTEGER 1 y READ END case label list One or more case constant values of the tag field type separated by commas A case constant is either a single constant value for example 1 or a range of values for example 5 10 You must enumerate one label for each possible value in the tag type identifier field list The names types and attributes of one or more fields At the end of a field list you can specify another variant clause The field list can be empty The tag field consists of the elements between the reserved words CASE and OF The tag field is common to all variants in the record type The tag field data type corresponds to the case label values and determines the current variant As the syntax description shows the
444. tribute to record fields to indicate that the field is to be used as a key field when the record is part of an indexed file KEY i n options j y options n The parameter n represents the key number A key number of 0 indicates that the field is the primary key of the record All other key numbers indicate alternate keys The key number must be a constant expression that denotes an integer value in the range from 0 through 254 options The options parameter lets you specify certain characteristics of the record key by listing the desired options on the KEY attribute Table 10 4 lists the possible KEY attribute options Attributes 10 23 Table 10 4 KEY Attribute Options Option Action Negation ASCENDING Specifies an ascending collating DESCENDING sequence CHANGES Specifies that changes can be NOCHANGES performed on the key DUPLICATES Specifies that duplicates of the key NODUPLICATES are allowed Usage and Default Information If you omit the key number the default value is 0 By default the primary key is ASCENDING NOCHANGES and NODUPLICATES It is possible to override these defaults with the exception of the NOCHANGES option It is illegal to specify CHANGES on the primary key The default for an alternate key is ASCENDING CHANGES and DUPLICATES When you create a new indexed file with more than one key field you cannot omit any key numbers in the range from 0 through the highes
445. trings to assign values to variables of these types you cannot use standard array constructors Also you can initialize a character string to the empty string as follows VAR Stringl VARYING 10 OF CHAR VALUE The VARYING OF CHAR variable is stored as though it were a record with two fields as follows RECORD LENGTH WORD 0 upper bound Length of current string BODY PACKED ARRAY 1 upper bound OF CHAR Current string END You can access the LENGTH and BODY predeclared identifiers as you would access fields of a record For example to determine the maximum length of a VARYING OF CHAR variable use the SIZE predeclared function and the BODY predeclared identifier as follows 2 44 Data Types and Values VAR Stringl VARYING 10 OF CHAR VALUE Wolf In the executable section Max Length SIZE stringl BODY WRITELN Max Length writes 10 To determine the current length of a VARYING OF CHAR variable use the LENGTH predeclared function From the previous example the result of LENGTH Stringl is the same as String1 LENGTH You can refer to individual array components as you would individual components of any array as follows Stringl 8 L You cannot specify an index value that is greater than the length of the current string HP Pascal does not pad remaining characters in the current string with blanks If you specify an index that is greater than the current
446. ts Pay Fedtax Food REAL Housing INTEGER FUNCTION Income Salary Tax REAL REAL Function body FUNCTION Expenses Rent INTEGER Grocery REAL REAL Function body FUNCTION Budget FUNCTION Credit Earnings UStax REAL REAL FUNCTION Debit Housing INTEGER Eat REAL REAL REAL VAR Deduct REAL BEGIN FUNCTION Budget Deduct Debit Eat Food Housing Housing Budget Credit Pay Fedtax Deduct END In the executable section Costs Budget Income Expenses When the function Budget is called the function Income is passed to the formal function parameter Credit and the function Expenses is passed to the formal function parameter Debit When Credit is called the program level variables Pay and Fedtax are substituted for Credit s formal parameters Earnings and UStax In the call to Debit nonpositional syntax is used to associate Debit s formal parameters Housing and Eat with the program level variables Housing and Food The names of program level variables do not conflict with formal parameters of routine parameters The presence of the ASYNCHRONOUS and UNBOUND attributes in routine declarations causes additional requirements to be imposed on the routines that can legally be passed as actual parameters For More Information e On routine headings Section 6 1 e On positional syntax Section 6 3 8 e On default values for formal parameters Section 6 3 9
447. u can use schema and data types to store and to manipulate character strings These types have the following order of complexity 1 CHAR type 2 PACKED ARRAY OF CHAR user defined types 3 VARYING OF CHAR user defined types 4 STRING predefined schema Objects of the CHAR data type are character strings with a length of 1 and are lowest in the order of character string complexity You can assign CHAR data to variables of the other string types The PACKED ARRAY OF CHAR types allow you to specify fixed length character strings The VARYING OF CHAR types are a HP Pascal extension that allows you to specify varying length character strings with a constant maximum length The STRING types provide a standard way for you to specify storage for varying length character strings with a maximum length that can be specified at run time To provide values for variables of these types you should use a character string constant or an expression that evaluates to a character string instead of an array constructor Using array constructors with STRING and VARYING OF CHAR types generates an error to use array constructors with PACKED ARRAY OF CHAR types you must specify component values for every element in the array otherwise you generate an error Consider the following example VAR Stringl VARYING 10 OF CHAR VALUE abc Generally you can use any member of the ASCII character set in character string constants and expressions Howeve
448. ual parameter whose data type matches the type of the corresponding formal parameter Optionally you can specify a passing mechanism for each parameter When a mechanism specifier appears in a call it overrides the type semantics mechanism specified and even the number of parameters in the formal parameter declaration Thus type checking is suspended for the parameter association to which the specifier applies Consider the following example which includes a procedure that takes no parameters and a function used as an expression VAR a b C z REAL PROCEDURE Introduction BEGIN WRITELN This is the Inventory Program Version 5 6 WRITELN WRITELN Press Ctrl H for help Press Return to continue END FUNCTION Adder Opl Op2 Op3 REAL REAL BEGIN Adder Opl Op2 Op3 Assign a function return value END Procedures and Functions 6 5 In the executable section Introduction No parameters necessary in the call a 3 14 b 14 78 112 456 z Adder a b c Function used as an expression evaluating to a REAL value If a function returns a value of an array record or pointer type you can index select or dereference the object at the time of the function call without first assigning the function result to a variable as shown in this example TYPE Player Rec RECORD Wins INTEGER Losses INTEGER Percentage REAL END VAR Number INTEGER FUNCTION Ret
449. uctured types Section 2 4 e On schema types Section 2 5 e On string types Section 2 6 e On attributes that affect assignment compatibility POS READONLY and UNSAFE Chapter 10 Data Types and Values 2 53 3 Declaration Section The declaration section contains declarations or definitions of constants labels user defined data types variables and user defined functions and procedures In addition only modules can contain initialization and finalization sections Each appears in a subsection introduced by Pascal reserved words This chapter discusses the following topics e Section 3 1 CONST Section e Section 3 2 LABEL Section e Section 3 3 TO BEGIN DO Section e Section 3 4 TO END DO Section e Section 3 5 TYPE Section e Section 3 6 VALUE Section e Section 3 7 VAR Section These sections appear after the header and before the executable section Gf any The TO BEGIN DO and TO END DO sections can appear only in modules and only once within a module The remaining sections can appear in programs modules functions or procedures they can appear more than once and in any order in a single declaration section If you use one kind of section more than once in a declaration section be sure to declare types variables and constants before you use them in subsequent sections For More Information e On user defined procedures and functions Chapter 6 e On program structure Chapter 7 e On modules Section 7
450. ue of i changed unexpectedly The ADDRESSY i call caused Pint to point to i that is Pint and i became the same variable When Pint was assigned the value 2 the variable i also received the value 2 Since i had been initialized to 0 and was not directly referred to in the rest of the program the compiler assumed that a reference to i at this point would be equivalent to a reference to 0 Likewise the compiler also assumed that a reference to ali would be equivalent to a reference to a 0 However when execution ceases the value of i is 2 and the value of ali is the value of a 2 Attributes 10 49 Depending on the optimizations the compiler made based on the value of i any operations performed after the unanticipated assignment to i could yield unexpected results Because j was declared VOLATILE the compiler did not optimize code based on the value of j Therefore any reference to j yields the expected results The ADDRESS i call in this program causes a warning message The HP Pascal compiler assumes that pointer variables point only to variables in heap allocated storage and not to statically allocated nonvolatile variables such as i So ADDRESS i in this case differs from the expected usage For More Information e On use of VOLATILE with the ASYNCHRONOUS attribute Section 10 2 3 e On exception handlers HP Pascal for OpenVMS User Manual e On Volatility HP Pascal for OpenVMS User Manual 10 2 43 WEAK EXTERNAL
451. ues assume that the actual parameter is in range and can only fetch a word since that is sufficient to represent all valid values If the parameter was a VAR parameter then the compiler would indeed only fetch a word since the formal parameter is an alias for the actual parameter and you are not allowed to pass expressions to a VAR parameter The compiler assumes that the VAR parameter contains a valid value of the subrange In other words subranges are checked at assignment time and are considered valid when fetched For More Information e On ordinal types Section 2 1 e On compile time and run time expressions Section 4 1 e On attributes Chapter 10 e On predeclared routines Chapter 8 e On using schema types HP Pascal for OpenVMS User Manual e On the ORD function Section 8 65 e On the TYPE section Section 3 5 e On discriminant identifiers in subranges Section 2 5 e On using the CHECK attribute for subrange checking Section 10 2 8 2 2 Real Types HP Pascal predefines the REAL SINGLE DOUBLE and QUADRUPLE data types in the floating point formats listed in Table 2 7 In this manual the term REAL type refers to both the REAL and SINGLE types Data Types and Values 2 11 Table 2 7 Supported Floating Point Formats Data Type Format Precision Default on Single precision VAX F floating point 1 part in 2 OpenVMS VAX REAL types format 7 decimal digits OpenVMS Alpha IEEE S_floating point 1 part in 2
452. uments might also be useful when programming in HP Pascal HP Pascal for OpenVMS User Manual Provides information about programming tasks about using features in conjunction with one another and about increasing the efficiency of program execution HP Pascal for OpenVMS Installation Guide Provides information on how to install HP Pascal on your OpenVMS system Reader s Comments HP welcomes your comments on this manual Please send comments to either of the following addresses xviii Internet openvmsdoc hp com Postal Mail Hewlett Packard Company OSSG Documentation Group ZKO3 4 U08 110 Spit Brook Rd Nashua NH 03062 2698 HP Pascal Home Page You can access the HP Pascal home page at http h71000 www7 hp com commercial pascal pascal index html Conventions The following product names may appear in this manual e HP OpenVMS Industry Standard 64 for Integrity Servers e OpenVMS I64 e 164 All three names the longer form and the two abbreviated forms refer to the version of the OpenVMS operating system that runs on the Intel Itanium architecture The following typographic conventions might be used in this manual Ctrl x A sequence such as Ctrl x indicates that you must hold down the key labeled Ctrl while you press another key or a pointing device button PF1 x A sequence such as PF1 x indicates that you must first press and release the key labeled PF1 and then press and release another key or a pointing
453. unction returns an integer value indexing the first element containing the value 1 If no bit is 1 the result is 1 plus the vector s upper bound If the vector or the indexed part of the vector has a size of 0 the result is start index Consider the following example VAR Boo PACKED ARRAY 0 31 OF BOOLEAN In the executable section Boo INTEGER 128 WRITELN FIND FIRST BIT SET BOO For More Information e On the type cast operator Section 4 2 6 8 35 FIND MEMBER Function The FIND MEMBER function locates the first character in a string that is a member of a specified set and returns an integer value indicating the position of the character in the string the function returns 0 if the characters in the string were not members of the set FIND MEMBER string char set The string parameter is a string value and char set is a value of type SET OF For More Information e On string types Section 2 6 e On sets Section 2 4 3 8 36 FIND NONMEMBER Function The FIND NONMEMBER function locates the first character in a string that is not a member of a specified set and returns an integer value indicating the position of the character in the string the function returns 0 if the characters in the string were all members of the set FIND NONMEMBER string char set The string parameter is a string value and char set is a value of type SET OF CHAR 8 18 Predeclared Functions and Procedures For More Info
454. urn Player Info Player Num INTEGER Player Rec In the function body Return Player Info Player Rec Wins 3 Losses 18 Percentage 21 3 In the executable section WRITELN Return Player Info Number Losses losses is poor For More Information e On expressions Section 4 1 e On structured function return values Section 4 3 e On parameters and passing mechanisms Section 6 3 6 3 Parameters In HP Pascal there are two types of parameters formal and actual parameters A formal parameter also called an argument is located in the header of the routine declaration You cannot redeclare a formal parameter in a routine s declaration section but you can redeclare it in nested routines within the routine s declaration section The formal parameter establishes the semantics the data type and the required passing mechanism of the parameter The general format of the formal parameter list is as follows value parameter spec variable parameter spec IK routine parameter spec k foreign parameter spec 6 6 Procedures and Functions The specific format of a formal parameter specification depends on the semantics value variable routine foreign of the formal parameter you are declaring conformant parameters also have a unique syntax Table 6 1 presents the HP Pascal semantics for formal parameters Table 6 1 Formal Parameter Semantics Parameter Type Description Value Used only to provid
455. urns its UNSIGNED64 equivalent UINT64 x The parameter x must be of an ordinal type No error results if x is an integer and has a negative value The value returned is x MOD 2 64 For More Information e On the UNSIGNED64 data type Chapter 2 8 98 UNDEFINED Function The UNDEFINED function returns a Boolean value that specifies whether the parameter contains an undefined invalid operand UNDEFINED x The parameter x must be a variable of type REAL SINGLE DOUBLE or QUADRUPLE 8 46 Predeclared Functions and Procedures On OpenVMS I64 and OpenVMS Alpha systems the UNDEFINED routine returns FALSE if the floating point value is finite and returns TRUE if the value is not finite A finite number is a floating point value with a definite in range value Specifically all numbers in the inclusive ranges MAX through MIN zero and MIN through MAX where MAX is the largest non infinite representable floating point number for the variable s type and MIN is the smallest non zero representable normalized floating point number for the variable s type These correspond to the MINREAL MAXREAL MINDOUBLE MAXDOUBLE MINQUADRUPLE and MAXQUADRULE predeclared constants For F_Float D_Float and G_Float finites do not include reserved operands and dirty zeros this differs from the VAX interpretation of dirty zeros as finite For S_Float T_Float and X_Float finites do not include infinites NaNs or denormals but do inc
456. use no input has been supplied yet the prompt does not appear on the screen until you have supplied input to fill the INPUT file buffer A sample run of a program containing this loop might be as follows 10 Enter an integer or an empty line The integer was 10 99 Enter an integer or an empty line The integer was 99 Return The prompt always appears after you type a value for i Delayed device access can produce unexpected results if you try to use the STATUS function to test the status of a TEXT file after you have performed a READLN procedure on the file Remember that a READLN procedure call actually performs a READ procedure on each variable listed as a parameter then performs a READLN procedure to position the file at the beginning of the next line Therefore a call to STATUS after a READLN procedure actually tests whether the file was successfully positioned To test the status of the file STATUS causes delayed device access to occur which fills the file buffer with the next component If you want to test the successful reading of data from the input file read the data with the READ procedure call the STATUS function and then perform a READLN procedure to advance the file to the beginning of the next line Input and Output Processing 9 5 4 Writing Partial Lines to Terminals The WRITE procedure buffers output to the terminal until the WRITELN procedure is called If too many characters are buffered it can ca
457. use the HP Pascal buffer to overflow The default size for this buffer is 255 characters for TEXT files If you want to increase the internal buffer size you can explicitly open the predeclared file OUTPUT with a larger record length Consider the following example OPEN OUTPUT RECORD LENGTH 512 If you want each record to go directly to the terminal without buffering until the next WRITELN you can explicitly open the predeclared file variable OUTPUT without carriage control In this mode the WRITELN procedure will write the information to the file without adding any carriage control However you need to include the carriage return and the line feed characters in the output strings the WRITELN procedure no longer provides these automatically Consider the following example CONST LF 10 ASCII control characters CR 13 In the executable section OPEN OUTPUT CARRIAGE CONTROL NONE WRITELN LF Output this WRITELN string directly WRITELN to the terminal CR This is useful when you are writing escape sequences or other graphics characters to terminal devices 9 6 Formatting Output The output values of a WRITE WRITELN or WRITEV procedure can be compile time or run time expressions with values of any ordinal real or string type Each value is written with a default field width which specifies the minimum number of characters to be written for the value You can however override the
458. utermost level of a program the compiler must choose between static and automatic allocation Whenever possible the compiler uses automatic allocation for variables that are referred to only in the body of the main program because automatic allocation is more efficient The compiler uses static allocation if the variable is declared with the VOLATILE attribute initialized at its declaration referred to in a nested block or if the program has an ENVIRONMENT attribute Because program level variables can be statically allocated HP Pascal does not support recursive calls on the main program block The compiler applies the following rules sequentially to choose the program section in which to allocate storage for nonexternal common and static variables If the variable has the COMMON attribute storage is allocated in a common block that has either the same name as the variable or the name specified by the identifier that accompanies the attribute If the variable has the PSECT attribute the identifier that accompanies the attribute supplies the name of the program section in which storage is to be allocated If the variable does not have the COMMON PSECT or STATIC attribute but is declared at the outermost level of an overlaid compilation unit storage is allocated in the program section PAS GLOBAL If the variable has the READONLY attribute but does not have the PSECT COMMON or VOLATILE attributes On OpenVMS VAX systems its
459. value representing the number of arguments in a variable length parameter list that was created using the LIST attribute ARGUMENT_LIST_LENGTH parameter name The parameter name argument specifies the name of the parameter declared with the LIST attribute When creating a variable length parameter list you can place the LIST attribute on only the last formal parameter When you call the routine you can specify any number of actual parameters or arguments that correspond to the last formal parameter declared with LIST Consider the following example 8 6 Predeclared Functions and Procedures PROGRAM Show Arg OUTPUT Ax corresponds to any number of char arguments PROCEDURE Variable Write Fl VARYING len OF CHAR Ax LIST CHAR VAR i INTEGER BEGIN WRITE Fl For however many arguments there are FOR i 1 TO ARGUMENT LIST LENGTH Ax DO WRITE ARGUMENT Ax i Write an argument WRITELN END In the executable section Variable Write hello One argument Writes hello Variable Write hello 8 a 1 o pt E ys Seven arguments Writes hello sailor For More Information e On parameters Section 6 3 e On the LIST attribute Section 10 2 24 8 9 ASSERT Procedure The ASSERT procedure signals a run time error if the value of its parameter is FALSE ASSERT takes this form ASSERT expression string The parameter expression is a Boole
460. vel of an overlaid compilation unit 1On OpenVMS VAX systems executable code and read only data can exist in the same program section A 4 Data Storage and Representation You can also establish user defined program sections with the HP Pascal PSECT and COMMON attributes The PSECT attribute directs the compiler to establish a separate program section for static variables or executable blocks In this way you can ensure particular program section properties for these objects You can also choose to group them with related static variables and blocks to reduce the amount of paging overhead The COMMON attribute directs the compiler to establish a particular program section called a common block A common block is an overlaid program section that contains one variable By storing variables in common blocks a HP Pascal program can share variables with programs written in other Hewlett Packard languages The following example uses a common block to pass information between HP Pascal and HP Fortran HP Pascal Program PROGRAM Common Example OUTPUT VAR Myrec COMMON Example RECORD Intfld INTEGER Strfld PACKED ARRAY 1 10 OF CHAR END EXTERNAL PROCEDURE Call Fort EXTERNAL BEGIN Myrec ZERO Call Fort WRITELN Intfld WRITELN Strfld END Myrec Intfld Myrec Strfld Wo HPFortran Subroutine SUBROUTINE CALL FORT C STRUCTURE TEST INTEGER 4 ITEM CHARACTER 10 ITEM NAME END STRUCTURE
461. vior in some way This chapter discusses the following information about attributes e Attribute syntax Section 10 1 e Attributes Section 10 2 e Attribute classes Section 10 3 When an attribute is not explicitly stated the compiler follows the default rules to assign properties to program elements However using attributes to override the defaults allows additional control over the properties of data items routines and compilation units For convenience in description the attributes are grouped in attribute classes All attributes in a given class share common characteristics sometimes there is only one attribute to a class For More Information e For information on environment specific issues about attributes Appendix A 10 1 Attribute Syntax The following syntax applies to all HP Pascal attributes identifier tq oo oe Dee Attributes 10 1 identifier1 The name of the attribute constant expression A compile time integer expression represented in this chapter by n that qualifies several of the HP Pascal attributes identifier2 The name of an option available in one of the following instances e With the CHECK OPTIMIZE or KEY attributes e With COMMON and PSECT attributes indicating the name of a storage area e With the GLOBAL EXTERNAL WEAK_GLOBAL and WEAK_ EXTERNAL attributes indicating an external name If entered as a quoted string passed to the linker with case unmodified A lis
462. wing example PROCEDURE Test2 P3 CLASS S PACKED ARRAY L U INTEGER OF CHAR P4 CLASS A ARRAY L2 U2 INTEGER OF REAL EXTERN This example defines a procedure Test2 which has two parameters The first parameter P3 is passed by descriptor of CLASS S The second parameter P4 is passed by a CLASS A descriptor For More Information On HP Pascal parameter defaults Section 6 3 e On CLASS A descriptors HP OpenVMS Calling Standard 10 2 10 CLASS NCA The CLASS NCA attribute causes a formal parameter to be passed by a noncontiguous array descriptor This attribute is illegal on parameters of schema types Attributes 10 13 For More Information e On HP Pascal parameter defaults Section 6 3 e On CLASS_NCA descriptors HP OpenVMS Calling Standard 10 2 11 CLASS S The CLASS 8 attribute causes a formal parameter to be passed by a single descriptor form that is used for scalar data and fixed length strings On OpenVMS systems this attribute allows routines written in HP Pascal to accept actual parameters from languages such as FORTRAN that generate CLASS S descriptors Usage and Default Information e In order to pass a CLASS S string descriptor you must use a packed conformant array of characters e This attribute is illegal on parameters of schema types e When the packed conformant array is passed by CLASS S descriptor the lower bound of the conformant schema is always 1 and the upper bound of the confor
463. you omit the identifier the name of the variable is used as the name of the program section Usage and Default Information e A variable having the AT COMMON or PSECT attribute is implicitly static e PSECT is the only allocation attribute that can be applied to routines and compilation units For More Information e On default allocation for variables declared in the outermost block of a program or in nested blocks Section 10 2 5 e On default allocation for variables declared in the outermost block of a module Section 10 2 36 e On program sections Appendix A 10 2 33 QUAD The QUAD attribute specifies the amount of storage in quadwords to be received by the object QUAD n JI The optional constant n indicates the number of quadword storage units For More Information e On storage allocation for objects Section A 2 5 e On default sizes of objects Section A 2 4 e On size allocation restriction Section 10 2 6 10 2 34 READONLY The READONLY attribute specifies that an object can be read by a program but it cannot have values assigned to it 10 34 Attributes Usage and Default Information e You can apply this attribute to variables formal parameters the base types of pointer variables and components of structured variables e By default an object can be both read and written e No value of any type is assignment compatible with a read only object e The presence of a read only component in

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