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Pascal/MT+ Programmer`s Guide

1. ES MUST BE COMPATIBLI ll the elements of a set must be of a compatible type ERROR 138 TYPE OF VARIABLE IS NOT ARRAY A subscript was specified for a variable that was not declared as ARRAY OF YPE IS NOT COMPATIBLE WITH THE DECLARATION The type of the expression that specifies an array subscript is incompatible with the array type 140 VARIABLE IS NOT RECORD This error occurs when there is an attempt to access a non RECORD data structure with the dot operator or the WITH statement 141 VARIABLE MUST BE FILE OR POINTER This error occurs when the pointer reference character follows a variable that is not of type pointer or FILE 143 TYPE OF LOOP CONTROL VARIABLI The control variable in an iterative loop can be only be a locally declared non REAL scalar value 144 TYPE OF EXPRESSION The expression used as a selector in a CASE statement must be of non REAL scalar type Pascal MT Programmers Guide Compilation Errors ERROR 145 TYPE CONFLICT The selector in a CASE statement is not the same type as the selecting expression 147 YPE INCOMPATIBLE WITH SELECTING EXPRESSION The selector in a CASE statement is not the same type as the selecting expression ERROR 148 SUBRANGE BOUND
2. System Access _BDOS Call operating system directly _CHN Program chaining routine CHAIN Pascal interface for _HLT Halt routine returns to operating system _INI Run time initialization XJP Table case jump routine String Handling Routines Routine Purpose EQD String comparison routine for _NED String comparison routine for lt gt GTD String comparison routine for gt LTD String comparison routine for GED String comparison routine for gt LE D String comparison routine for lt Load concat string buffer address LBA Cae Initialize string buffer ee Concatenate a string to the buffer String store ante Read a string from a file ROT Write a string to a file WCH Run time support for strings POS Set Manipulation Routines Routine Purpose _EQS Set equality _NES Set inequality GES Set superset LES Set subset SAD Set union SSB Set difference Set intersection _SML DP Set membership Pascal MT Programmers Guide Internal Logic Errors Build singleton set Build subrange set Array comparison routine for Array comparison routine for lt gt Array comparison routine for gt Array comparison routine for lt Array comparison routine for gt Array comparison routine for lt Character Manipulation Routines Purpose Concatenate a character to the buffer Read next character from a file Write next character to a file Read a character from a file Write a character to a file Write a newline
3. MUST BE The tagfiel subrange type ELD PART E WITH lt TAGFI E variant record is not The type of the selector in a CASI compatible with the type of the tagfield 113 YPE MUST BE A SCALAR OR A SUBRANGI of an array index must be declared as a scalar or The type subrange 15 MUST BE A SCALAR OR A SUBRANGI type of a set must be a declared as a scalar or The base subrange EDURE PARAMETER 16 YPE There is an error in the type of a variant when using N OF STANDARD PROC DISPOSE 17 ED FORWARD REF ERENCE A forwardly declared pointer was never defined Pascal MT Programmers Guide Compilation Errors ERROR 119 FORWARD DECLARED PROCEDURE CANNOT RESPECIFY PARAME Self explanatory ERROR 120 TION RESULT TYPE E A SCALAR SUBRANG ER The function is declared with a return value of some nonscalar type such as STRING This is not allowed in Pascal MT ERROR 121 FILE VALUE PARAMETER NOT ALLOWED FILE types must be passed as VAR parameters ERROR 122 FORWARD DECLARED FUNCTION CANNOT RESPECIFY RESULT TYPE Self explanatory OF STANDARD PROCEDURE PARAMETER The compiler enc
4. An area reserved for stack space is immediately below the operating system First there is a lexical stack used by the run time system to keep track of the lexical level of procedure blocks Below the lexical stack is the user stack see Figure 6 1 The default size for the lexical stack is 512 bytes and the default size of the user stack is 1024 bytes You can change both values by altering the file named CPMINI which is included on the distribution disks Free memory is the area from the end of the bss segment to the top of available memory The heap grows upward from the low end of free memory and the user stack grows downward from the high end of available memory Pascal MT Programmer s Guide Stack CP M 68K bios bdos ccp system Lexical Stack 512 bytes Top of Memory Free Memory Transient Heap Program Area Exception Vectors system Figure 6 1 Memory Layout in Transient Program Area Stack The compiler always generates recursive code Return addresses and local variables for all procedures are stored on the user stack If recursion is deeply nested and the default stack size is too small the program can overwrite the top of memory Generally this is not a problem unless the heap is also very large In this case if recursion continues or the heap continues to grow it is possible for the user stack to overwrite the heap or vice versa Note The run time system does not perform any checks on memory allocatio
5. Filename TDT Filename TSY Filename TRL Filename DIS Filename o Filename LST Figure 5 1 DIS68 Operation Invoking DIS68 DIS68 is automatically invoked when you compile a program with the command line options Pd and X The compiler chains to the disassembler at the end of the compilation The object code file the listing file and the temporary files must all be on one logical disk drive You can use the Dd command line option to specify the location of the disassembled listing The Pascal MT Programmer s Guide Errors location can be a disk file or a Pascal MT logical device CON or LST The default destination is CON If you specify a disk file DIS68 supplies the default filetype DIS For example the command A gt mt68 mathlib xp compiles then disassembles the file MATHLIB and sends the disassembled listing to the console The command A gt mt68 mathlib xpbd compiles then disassembles the file MATHLIB and sends the disassembled listing to the file MATHLIB DIS on drive B Errors DIS68 generates an error message whenever it detects an error in the relocatable object code file Since the relocatable object code file should not have any errors continuing at this point produces more errors because the sequence is off To correct error s recompile the program and be sure you are disassembling Pascal MT code only Sample Disassembly The listings shown below show the source code and the disassembl
6. Kn Symbol Table Space Reduction The Kn option tells the compiler to make more room in the symbol table for user symbols by removing any predefined symbols that are unreferenced in the source program Examples of predefined symbols are the Pascal MT reserved words and names of predefined functions and procedures These predefined symbols normally take about 6K bytes of symbol table space The form of the option is Kn where n is an integer parameter ranging from 0 to 15 Each integer corresponds to a different group of routines as defined in Table 3 2 You must enter all K options before the reserved words PROGRAM or MODULE in the source code You can use as many K options as required but place only one integer parameter after each letter K Note that if the program makes any reference to a symbol removed with the K option the compiler issues the following error message UNDECLARED IDENTIFI ER Table 3 2 K Option Values Pascal MT Programmer s Guide Source Code Options Group Routines Removed 0 ROUND TRUNC EXP LN ARCTAN SQRT COS SIN 1 COPY IN SERT PO S DELETE LENGTH CONCAT 2 GNB WNB CLOSEDEL OPENX BLOCKREAD BLOCKWRITE 3 CLOSE OPEN PURGE CHAIN 4 WRD HI LO SWAP ADDR SIZEOF INLINE EXIT PACK UNPACK 5 IORESULT PAGE NEW DISPOSE 6 SUCC PRED EOF EOLN 7 TSTBIT CLRBIT SETBIT SHR SHL 8 RESET REWRITE GET PUT ASSIGN MOVEL EFT MOVER IG HT FILLCHAR 9 READ RE ADLN 10 WRI TE WRI TEL N
7. This manual describes Pascal MT Release 3 3 a system that runs under the CP M 68K operating system using a Motorola MC68000 microprocessor with at least 128K bytes of memory This manual is divided in five parts Part 1 Sections 1 2 gives a general description of the Pascal MT programming system the notational conventions used in the manual and some guidelines for configuring your own system Part 2 Sections 3 5 describes how to use software This includes the operation of the compiler linker and disassembler The command line and source code options for the compiler and the command line options for the linker are fully described Part 3 Sections 6 10 describes a variety of advanced topics including how to write large programs in segments how to inter face Pascal MT code with assembly language code how to directly access the operating system and how to write your own error handling procedures Also included is a set of guidelines for writing ROM based code Part 4 Section 11 contains some sample Pascal MT programs that illustrate various features of the language You can study these examples and then modify them to gain experience with the language Part 5 is a reference section containing appendixes and an index This manual assumes you are already familiar with general aspects of computer programming and may have programmed in a language such as BASIC If you are not familiar with Pascal refer to the Pas
8. 11 unused 12 MEMAVAIL MAXAVAIL 13 SEEKREAD SEEKWRITE 14 unused on the 68000 15 unused on the 68000 L P Listing Controls The L option controls the listing that the compiler generates during Phase 0 Enable the L option with the parameter and disable it with the parameter L is the default The P option starts a new page by placing a form feed character in the listing file R Run time Range Checking The R option tells the compiler to generate run time code that performs range checking for array subscripts and assignment to subrange variables Enable the R option with the parameter and disable it with the parameter R is the default Refer to Section 9 6 for information on range checking T W Type and ISO Standard Checking The T option controls the compiler s strict type checking non ISO standard warning facility The W option controls the display of warning messages pertaining to the T option Enable both options with the parameter and disable them with the parameter The default value for both options is The T option tells the compiler to per form strict type checking If the T and W options are both Pascal MT Programmer s Guide Source Code Options enabled and the compiler detects a non ISO standard feature the compiler displays the message NON ISO STANDARD FEATURE For example when both options are enabled string operations generate this message because the STRING data type is non ISO sta
9. 39 5 Thus the eight byte value 00 00 00 00 00 CO 43 CO is the double precision float binary representation of the decimal number 39 5 Array Representation Pascal MT represents variables of type ARRAY in row major order Figure D 9 shows the storage for the declaration A ARRAY 1 3 1 31 OF CHAR byte number 00 01 02 03 04 05 06 07 08 A 1 1 A 1 2 A 1 3 A 2 1 A 2 2 A 2 3 A 3 1 A 3 2 A 3 3 High memory gt Figure D 9 Storage for Arrays Logically this is a one dimensional array of vectors In Pascal MT all arrays are logically one dimensional arrays of some type Set Representation Pascal MT represents variables of type SET using 32 consecutive bytes with each element of the set using one bit The low order bit bit 0 of each byte is the least significant bit in the byte Figure D 10 shows the storage for the set A Z The first element in the set is capital A which occupies position 65 in the ASCII collating sequence see Appendix F Thus the first bit in the set is bit 65 the first bit in byte 8 The last bit in the set is bit 90 which is bit 2 in byte 11 and corresponds to capital Z Byte Number 00 01 02 03 04 05 06 07 08 09 0a 0b Oc 0d 0e Of 10 LE 00 00 00 00 00 00 00 00 ff ff ff 07 00 00 00 00 00 00 Higher memory gt Figure D 10 Storage for the Set A Z Static Data Alloc
10. CHAR then the stack as appears as shown below Stack 0 return address msb Pointer T1 return address 2 return address 3 return address lsb 4 byte of 00 5 d 6 byte of 00 7 c 8 address of actual string msb 9 P n P 10 d RW FLL address of actual string lsb 12 j msb 13 j lsb 14 i msb 15 i 1sb lsb least significant byte msb most significant byte Figure 8 1 Stack Containing a Parameter List The assembly language program must remove all parameters from the stack before returning to the calling routine Nonreal function values return in the D7 register Real values return on the stack They are placed below the return address before the function returns Therefore they remain on the top of the stack when the calling program reenters after the return Assembly language functions can return the simple types BOOLEAN CHAR INTEGER LONGINT or REAL Assembly language functions can also return pointers and enumerated types but cannot return the structured types STRING RECORD or arrays Pascal MT Programmer s Guide Interface Example Interface Example Listings 8 1 and 8 2 illustrate the interface between a Pascal MT program and two assembly language routines The Pascal program performs the PEEK and POKE functions found in BASIC The assembly language module simulates the PEEK and POKE PEEK returns the byte found at the ad
11. Command line Options B BCD Representation The B option tells the compiler to internally represent REAL numbers using Binary Coded Decimal BCD instead of a floating point format The default is to represent REAL numbers using floating point format Refer to Appendix D for more information about internal representation of data C Continue on Error The C option tells the compiler to continue processing the source code file whenever it encounters an error The default is to stop at each error and ask whether to continue or not Dd Disassembled File Location The Dd option tells the compiler to put the disassembled listing file on the I O device d d can be any logical disk drive A through 0 or the currently logged in drive You can also specify X the console or P the printer By default the compiler outputs the disassembled listing file at the console Ed Error File Locat ion The Ed option tells the compiler that the error message text file NTERRS TXT is located on disk d d can be any logical disk drive A through O By default the compiler searches for MTERRS TXT on the default currently logged in disk Od MT68 000 Overlay Location The Od option tells the compiler that the overlay file MT68 000 is located on disk d By default the compiler searches for MT68 000 on the same drive as the MT68 68K file Pd Print Listing File Location The Pd option tells the compiler to put the print file LIS on the I O device d d can be any l
12. and continues at the line immediately following amp END You must define the test variable using the syntax 6 SET variable The most common way to use conditional compilation is to put several amp SET directives in an Include file and select the proper version by placing comments around any directives not wanted To compile a different version simply remove the comments For example if the Include file contains the code amp SET verl amp SET ver2 Pascal MT Programmer s Guide Conditional Compilation the compiler processes the source code delimited by amp IF ver2 amp END However if the Include file contains the code amp SET verl amp SET ver2 the compiler processes the source code delimited by amp IF verl amp END The amp MSG directive outputs a diagnostic message to the console that tells you which section of code is being conditionally compiled For example amp IF ver2 amp MSG Now compiling version 2 amp END The message must be an ASCII string not exceeding 80 characters End of Section 3 4 Section Using the Linker LINK68 is the linkage editor that combines object code files into a command file You can also use LINK68 to link a program as a set of overlays see Overlays in Section 7 LINK68 accepts the object code files produced by Pascal MT compiler and produces an executable file in the 68K command file format LINK68 also accepts object code files prod
13. character CR to a file Bit Manipulation Routines Routine Purpose TSTBIT Test for a bit on SETBIT Turn a bit on CLRBIT Turn a bit off I O and File Handling Routines Set global FIB address Set default width and decimal places Reset input vector Reset output vector Set I O vectors to default addresses Read until EOLN is True on a file Read n bytes from a file Write n bytes to a file File handling routine File handling routine File handling routine File handling routine File handling routine File handling routine File handling routine File handling routine File handling routine File handling routine File handling routine File handling routine File handling routine File handling routine File handling routine File handling routine File handling routine File handling routine File handling routine P EZE OOF nw PZZ Q W W O gt Ei FO wm nj UDUUQNUXUDH UzgpooQoquuuuo Pascal MT Programmers Guide Internal Logic Errors IORESULT File handling routine COPY File handling routine INSERT File handling routine DELETE File handling routine Arithmetic Routines Routine Purpose Multiply a long integer Read integer from a file Read a long integer from a file Write an integer to a file Write a long integer to a file 32 bit DIV software routine 32 bit MOD software routine Memory Manipulatio
14. containing the old and new filenames IF BDOS 23 ADDR fl 255 THEN WRITELN Rename failed oldname not found ELSE WRITELN File oldname renamed to newname END Main Program INLINE INLINE is a built in feature that lets you insert code or data in the middle of a Pascal MT procedure or function You can insert small machine code sequences and constant tables into a Pascal MT program without using externally assembled routines The syntax for INLINE has the form INLINE argument lt argument gt lt argument gt where argument must be either a constant or a variable reference that evaluates to a constant argument can be of type BOOLEAN CHAR INTEGER LONGINT REAL or STRING Note that a string in single apostrophes does not generate a length byte but simply the data for the string Pascal MT Programmer s Guide Absolute Variables Variables evaluate to a long address All jumps are relative to the current position in the code segment Literal constants of type integer are allocated one byte if the value falls in the range O to 255 Named and declared integer constants always get two bytes Listing 9 3 demonstrates how you can use INLINE to construct compile time tables Note that the ADDR of TABLE must be added to its offset This is because ADDR does not give the address of TABLE due to additional code that recursion management produces An extra eight bytes of code is gen
15. implementation can differ in the way it internally represents data or organizes and transfers files Digital Research has implementations of Pascal MT for a variety of 8 bit and 16 bit microprocessors and operating system environments Because of differences in the capabilities of various microprocessors and operating systems not all the extensions of Pascal MT are supported in each implementation Pascal MT for CP M 68K Pascal MT for CP M 68K is a complete programming system that includes a compiler a linker a disassembler and a large library of run time subroutines to help you build better programs faster Figure 1 1 illustrates the software development process using the Pascal MT system Pascal MT Programmer s Guide Pascal MT Documentation Set Source Code File Filename pas Compiler optional Listing file Relocatable Object cod file Paslib Filename o Run time Library Other E Ce Linker Libraries Other Pascal Assembler Modules 3 Command File program filename 68k Figure 1 1 Software Development under Pascal MT Pascal MT Documentation Set The Pascal MT Language Programmer s Guide for the CP M 68K Operating System cited as Programmer s Guide contains information about using the compiler linker and disassembler It provides general guidelines for creating modular programs using overlays chaining and shared variables The Programmer s Guide also contains information o
16. os D 5 statie Data ALOCADA D 5 Global Variables ni nr D 5 Local iur PT bio D 6 E AA A A E Writing Portable e TEE E 1 Hard ware dependent Peat res rs RERO REANO UST ees que etur Add E 1 System dependent Features vecindario E 1 Tables Table 2 1 Pascal MT System Filetypes esee netten trennen tret rennen tenen een enne 2 1 Table 3 1 Compiler Command line Options eese enne tenete nre nennen 3 4 Table 3 2 K Option Values cccccesccscescessesecsseesceseeseesecseesecsecseceseeseaecsessecsesseceaeeseaecsessecsesaeseseeeesaeenenaes 3 5 Table 3 3 Compiler Source Code Optons essere enne enne trennen nen 3 7 Table 4 1 Required Libraries uri ee rH EH pe dee deet 4 2 Table 4 2 LINK68 Command line Options eese nenne nene nennen ne en ne enne enne 4 5 Table 9 1 ERR Routine Error Code 9 7 Table 11 1 Comparison of I O Methods A 11 1 Figures Figure 1 1 Software Development under Pascal MT sese enne 1 2 Fig r 4 1 LINK6S Operation ooo ete tte a 4 1 Figure IDISOS Operation iion o DRE eU e Rr b uei ete RD S Rt e e RR C 5 1 Figure 6 1 Memory Layout in Transient Program Area 6 2 Figure 7 1 Typical LINK68 Overlay Sheme oooooocccoccnocnnoccnonconoconoconocnnonononononnncnn e conc cone cono cn eene enne 7 4 Figure 7 2 Overlay Scheme Example 12 eee dia 7 5 Figure 7 3 Overlay Scheme Example nete Ro e 7 5 Figure 8 1 Stack Containing a Parameter List ooooononcnccnnccnoonconoconoco
17. source file does not fill the sector as in BLOCK I O In this case the 2K bytes of window variable for lt file a gt do not fill the sector and the last portion of data that does not fill the 2K buffer is never written to the destination file Listing 11 5 shows the transfer program using the GET and PUT procedures This method is slower than the buffered methods Comparison Table Table 11 1 shows a comparison of the code size data size and execution speed for each file transfer program The sizes are in decimal bytes the speed is in seconds and the size of the file is 8K bytes Each program was run on a 10MHz Motorola MC68000 processor with no wait states using both a dual floppy disk and a hard disk system Note Your system might not produce the same values reflected in Table 11 1 However the relative size and speed differences should be the same Table 11 1 Comparison of I O Methods Statistics Transfer BLOCK 1 0 GNB WNB E ET PUT Compiled Code Compiled Data Total Code Total Data Total Size Speed Floppy Disks Hard Disk Pascal MT Programmer s Guide Program Listings Program Listings Listing 11 1 Main Program Body for File Transfer Programs BEGIN Main Program WRITE Name of Source File READLN name ASSIGN file a name RESET file a IF IORESULT 255 THEN BEGIN WRITELN Sorry cannot open name EXIT END WRITE Name of Destination File READLN n
18. 0 file is on disk d d A O MT68 000 on same disk as MT68 68K Pd Put the print listing file on device d No print file d A O XP Q Quiet suppress any unnecessary Compiler outputs all messages console messages Rd Put the relocatable object code file Relocatable file on default disk on disk d d A O Td Put the temporary files on disk d Put temporary d A O files on default disk V Print the name of each procedure and Procedure names not printed function found in source code during Phase 0 X Generate an ex tended relocatable Relocatable file cannot be object code file including disassembled and temporary files are disassembler information do not erased erase temporary files used by the disassembler Q Make the character equivalent to not equivalent to the character Note The A option has no effect as in other implementations the compiler ignores it Pascal MT Programmer s Guide Source Code Options Source Code Options Source code options are special instructions to the compiler that you put in the program source code A source code option is a single lower or uppercase letter preceded by a dollar sign embedded in a comment The option must be the first item in the comment Certain source code options require additional parameter s You can put any number of options in a source program but only one option per comment is allowed You cannot place blanks between the dollar sign and the option l
19. 2 3 4 9162 8 Figure D 7 BCD REAL Representation In bytes 1 through 9 the decimal digits are packed two to a byte That is each digit occupies four bits Byte 10 is reserved for the sign with 0 for positive and FF11 for negative There is an implicit decimal point immediately preceding byte number 8 so the BCD format can represent a number with 18 total digits and 4 digits to the right of the decimal point IEEE Format Pascal MT represents floating point binary data using the IEEE double precision format This format uses eight consecutive bytes with the 64 bits containing the following fields a 52 bit mantissa an 1 1 bit exponent and a sign bit The least significant byte of the mantissa is stored at the highest memory address S Exponent Mantissa Pascal MT Programmers Guide REAL Representation 63 62 52 51 0 Higher Memory gt Figure D 8 Double precision Floating point Format The double precision format normalizes floating point numbers so the most significant bit of the mantissa is always 1 for nonzero numbers Because the most significant bit of the mantissa must be 1 for nonzero numbers this bit is not stored This is called using an implicit normalized bit The binary point is considered to be immediately to the right of the normalized bit In the double precision format the exponent has a bias o
20. AR T flags ARRAY O size OF BOOLEAN 8 1 i k INTEGER 9 1 prime INTEGER 101 count INTEGER 11 1 iteration INTEGER 12 1 13 1 BEGIN Main Program Si 14 1 count 0 0000000A 33FC move w 0000 count 15 1 writeln Do 10 iterations 6 Section Program Structure at Runtime Command File Structure LINK68 creates a command file in the standard CP M 68K format Each command file has a 28 byte header The header contains the size and starting address for each of the following components in the command file e A Text code segment containing the program s instructions e A Data segment containing the program s initialized data such as arithmetic and string constants e A Block storage segment bss for any uninitialized data generated by the program when it runs This space is not allocated until the operating system load the command file e An optional symbol table that defines any symbols referenced by the program e Optional relocation information that specifies the relative relocation of each word within each program segment if required At the beginning of each module is a jump table that contains jumps to each procedure or function in the module The main module also has a jump to the beginning of the code first instruction Run time Memory Map Figure 6 1 shows the memory layout at run time after CP M 68K loads a Pascal MT program into the Transient Program Area TPA
21. CLARED TWICI The compiler encountered an identifier that is declared ERROR 102 OW BOUND EXCEEDS HIGH BOUND For subrange types the low bound must be less than or equal to the high bound ERROR 103 IDENTIFIER IS NOT OF THE APPROPRIATE CLASS The compiler encountered a variable name used as a type or a type used as a variable name ERROR 104 UNDECLARED IDENTIFIER The compiler encountered an identifier that has not been declared ERROR 105 SIGN NOT ALLOWED Signs are not allowed on non INTEGER or non REAL constants Compilation Errors Pascal MT Programmers Guide ERROR 106 NUMBER EXPECT The compiler expects a number in this context occur as the compiler checks for numbers in an expression been exhausted after all other possibilities hav ED This error can ERROR 107 INCOMPATIBLE SUBRANGE TYPES Types must be compatible for subrange comparison and is not compatible with 0 For example A Z assignment BECH ERROR 108 FILE NOT ALLOWED HERE m P types is not allowed Comparison and assignment of FILI ERROR 109 E MUST NOT BE REAL hn The compiler does not allow the type REAL in this context 10 ELD gt TYPI SCALAR OR SUBRANGI ld in a CASE variant record must be a scalar or
22. DIGITAL RESEARCH Pascal MT Language Programmer s Guide For the CP M 68K Operating System COPYRIGHT Copyright 1984 by Digital Research Inc All rights reserved No part of this publication may be reproduced transmitted transcribed stored in a retrieval system or translated into any language or computer language in any form or by any means electronic mechanical magnetic optical chemical manual or otherwise without the prior written permission of Digital Research Inc Post Of f ice Box 579 Pacific Grove California 93950 DISCLAIMER Digital Research Inc makes no representations or warranties with respect to the contents hereof and specifically disclaims any implied warranties of merchantability or fitness for any particular purpose Further Digital Research Inc reserves the right to revise this publication and to make changes from time to time in the content hereof without obligation of Digital Research Inc to notify any person of such revision or changes NOTICE TO USER From time to time changes are made in the file names and in the files actually included with the distribution disk This manual should not be construed as a representation or warranty that such files or facilities exist on the distribution disk or as part of the materials and programs distributed Most distribution disks include a READ ME file which explains variations from the manual and which do constitute modification of the manual
23. E module name where module name is the module you want to load LOCALS Tells LINK68 to put local symbols in the symbol table The default is no local symbols LOCALS only Pascal MT Programmer s Guide Linker Command line Options applies from the point in the command line that it appears The NOLOCALS option turns this option of f Use LOCALS and NOLOCALS in combination to put local symbols from specific files in the symbol table LINK68 always ignores local symbols starting with L NOLOCALS See LOCALS SYMBOLS Tells LINK68 to put the symbol table in the command file The default is no symbol table in the command file TEMPFILES d Tells LINK68 to use drive d for the temporary files it creates during processing The default is the currently logged in drive If you use TEMPFILES it must precede any input files on the command line TEXTBASE n Specifies the base address for the Text segment t n is a hexadecimal value The default is OH You can use this option when linking overlaid programs UNDEFINED Tells LINK68 to ignore the presence of undefined symbols in the input files LINK68 lists the undefined symbols and then continues processing The default action is to list any undefined symbols and then stop processing The following are examples of LINK68 command lines Addresses are in hexadecimal A link68 sym tem b math mathmain mathlib This command links the files MATHMAIN and MATHLIB into a command fil
24. File Locati0W occccccccncccnonononininononininonininicininoninonininininininininess 3 3 Td Temporary Pile Locator 3 3 V View Procedures and Funcnons 3 3 X Extended Relocatable Object Fille tocata irc 3 3 Pointer Character Equivalence id e A a 3 4 QUES Gode Options a ta ocean me EE 3 5 E Entry point Record CGeneraton nennen 3 5 L Include Fil s ete eite eec terret eerte ite eer be eerte 3 5 Kn Symbol Table Space Reduir 3 5 E P Listine Controls aspe O CM usn 3 6 R Run time Range Ch eking egrdeeg ieusgied die necia Virada nacionales 3 6 T W Type and ISO Standard Checking eene 3 6 X Exception Error Checking at Run time eere 3 7 Conditional Complain cei adero er cet eiat edet dia dra ede he s 3 8 d SECOS es Rr tte ER Su eR EE 4 1 sine he Linker ses cte be E ui ia mota tutam tte eat 4 1 Run time Libraries viii a Eea 4 1 E EE 4 1 Sa A nen me mn cee aA TO Cn Re MM rU 4 1 AS eene ee eege EE 4 2 A KP T IE 4 2 Redirecting W ntger ee gie 4 2 Linker Command line Options A A AA 4 2 AE DEE sa 4 3 AEEMO DSi Aid tree 4 3 BSSBASE e dd E Ud 4 3 COMMAND edel 4 3 DATABASE a a ea fte 4 3 IGNORE E 4 3 INCLUDE css ii ida a ici 4 3 89 9p PE 4 3 NOLOCALS T tb ata 4 4 SYMBOLS c P 4 4 TEMPPIBBS G it tia 4 4 TEX TEASE iia 4 4 UNDEFINED issue bai Van Ea tius t 4 4 EN 5 1 Using the Disassembler iii ic iris 5 1 A 5 1 O A dE 5 2 sample Disassembly s
25. INCLUDE IN loads a module LOCALS LO puts local symbols in symbol no local symbols table NOLOCALS NO turns off LOCALS SYMBOLS puts symbol table in no symbol table command file TEMPFILES TEM d puts temporary currently logged in disk d files on drive d TEXTBASE TEX n sets base of Text segment OH n UNDEFINED U ignores undefined symbols lists undefined symbols and and continue stop End of Section 4 5 Section Using the Disassembler DIS68 is a utility program that enables you to disassernble the machine code produced by the compiler into a series of assembly language instructions This can be very useful when debugging a program at the machine code level In order to disassemble a program you must compile the source code using the Pd and X command line options The Pd option tells the compiler to generate a print listing file with filetype LIS The X option tells the compiler to generate an extended relocatable object code file This extended file contains the assembly language code emitted by the compiler and source code line number information in encoded form The X option also tells the compiler not to erase the temporary files needed by DI S68 DIS68 combines the extended relocatable object code file the LIS file and the temporary files TRL and TSY to produce a file showing the assembly language code generated for each line of source code Figure 5 1 illustrates the operation of DIS68
26. L tells the compiler not to allocate space in the module You can declare externals only at the global outermost level of a module or program For variables put the reserved word EXTERNAL between the colon and the type in a global declaration For example VAR i j k EXTERNAL INTEGER in another module r EXTERNAL RECORD in another module x Y INTEGER st STRING END For procedures and functions declared in other modules put the reserved word EXTERNAL before the word FUNCTION or PROCEDURE These external declarations must come before the first normal procedure or function declaration in the module or program External routines cannot have procedures and functions as parameters Note The compiler does not type check declarations between modules Therefore ensure that the number and type of parameters match the declarations in the module where the space is allocated For functions the type of the returned value must match In Pascal MT external names are significant to seven characters only Internal names are significant to eight characters Listing 7 1 shows the outline of a main program and Listing 7 2 shows the outline of a module The main program references variables and subprograms in the module the module references variables and subprograms in the main program Listing 7 1 Main Program Example PROGRAM external_demo label constant and type declarations go here VAR i j INTEGER available i
27. LLOWED LINK68 does not allow you to nest command files Correct the error and relink TOO MANY OVERLAYS LINK68 allows a maximum of 255 overlays Examine your program and simplify the overlay scheme Reassemble or recompile the source code before relinking COMMAND LINE TOO LONG The command line does not fit on one line Correct the error by using a command file and relink OVERLAYS NESTED TOO DEEPLY LINK68 allows only 5 levels of overlays Examine your program and simplify the overlay scheme Reassemble or recompile the source code before relinking CANNOT SET DATA OR BSS BASE WHEN USING OVERLAYS The BSSBASE and DATABASE options are not allowed when linking overlays Correct the error end relink EGAL REFERE ERLAY SYMBOL lt symbol name gt FROM E module name The module indicated by lt module name gt contains a illegal reference to the symbol indicated by lt symbol name gt symbol name DOUBLY DEFINED IN filename The symbol symbol name is defined twice The variable filename indicates the file where the second definition occurs Rewrite the source code and provide a unique definition for each symbol Reassemble or recompile the file before relinking LINK68 FILE FORMAT ERROR IN filename The file indicated by the variable filename is not an object file or the file has been
28. NGINT in two s complement form using four consecutive bytes The high order byte is stored first and the most significant bit MSB is the sign bit Pascal MT Programmers Guide WORD Representation SB TE GT 1 0 9 8 7 6 5 9 88 8 PG 35s vAS O3 OX EE Figure D 5 LONGINT Representation WORD Representation Pascal MT represents variables of type WORD using two consecutive bytes The high order byte is stored first All the bits are considered significant X5 X4 I3 127 Td L0 D 8 7 6 5 4 3 2 A 0 Figure D 5 WORD Representation REAL Representation Pascal MT represents variables of type REAL using two different formats e Fixed point variables use the Binary Coded Decimal BCD format Fixed point numbers are decimal numbers that have a fixed total number of digits and a fixed number of digits to the right of the decimal point e Floating point variables use the Institute of Electrical and Electronic Engineers IEEE double precision format Floating point numbers are very large or very small numbers expressed in scientific notation with a mantissa and an optionally signed integer exponent BCD Format The BCD format uses 10 consecutive bytes with the high order byte stored first 2 3 4 S 6 7 8 9 10 D D D D D D D D D D D D D D D D D D 1 2 3 4 5 6 7 8 9 1 1 1 1 1 1 1 1 1 S5SIGN 0 1
29. OUTPORT W ciscccsecasoaoiet estie cda id dir 9 6 Range and Error Mec kt nS de iio 9 6 A gue nah tac Ide Hur Lanse ERR DRM e 9 7 Ioytodei zs quM 9 7 User supplicd Eror Handler iecit er rer eo Ur ASA Md 9 8 UO Error Eat 9 8 A te PERRO ONERE NNI MI HE RS eens 10 1 Writing ROM based COU 5o ert petet easiest IA OM e eda pectet n ED I oan 10 1 Programs That Use Oia bti er as Eee e kae ree NE PERS E AER TRIN V Ue VR 10 1 Rewriting the INI Routine oer aree dot eee bas 10 1 Linkme Altered ROUBnDES A A e diet ae o da ede eet 10 2 RE I oua iii 11 1 Sample Pascal MT E CEET 11 1 Eile PANS Fe Pinch ti o a es ee Rta dete T E 11 1 Late ER EE 11 1 Program LAST SS iii 11 2 A A 1 Compilation and Run time Error Messages A 1 Compilation Eeer edd A 1 hing desto rtm A 9 B Appendix ia ee B 1 LINKOSBITOD ISS AOS beet de Laso B 1 et ee tn BA C UADDOBGOEX reni er Pre ae ee o PCS OPE o weld eee C 1 Run time Library Route erugeet festege Ro Eyre nae danilo ones Po Pea C 1 D APDO E D 1 Internal Data RepresentatiODis a besos I editae dead A D 1 Size and Range of Data types isis iaa atraca Ed de D 1 NA SIOEABO e tub stulte eti dte D 1 BOOLEAN Representa D 2 BYTE REE e od D 2 et Te D 2 INTEGER Representa isis D 2 LONGINT Representation mision dictar inalterada dadas D 2 WORD RepreS nO aaa D 3 REAL E od Mom D 3 J51 DE SLON u a e1 eege vienen ema e idR D 3 IEEE Or EE D 3 Array Representation ia dales D 5 SEL Representations
30. R globals ABSOLUTE 8000 comm_area BEGIN Main program 2 WITH globals DO WRITELN Result of i times j is k END End chain 2 return to operating system 8 Section Interfacing Pascal MT with Assembly Language Routines This section describes the conventions for interfacing Pascal MT programs with code written in assembly language Interface Conventions Both the AS68 assembler and the Pascal MT compiler generate entry point and external reference records in the same relocatable object code format These records contain external symbol names The relocatable object code format allows up to seven characters in an external name To access assembly language variables or routines from a Pascal MT program you must follow these conventions e Declare them globl in the Data segment of the assembly language module e Declare them EXTERNAL in the Pascal MT program To access Pascal MT global variables and routines from an assembly language routine you must perform the following steps e Declare the name globl in the Data segment of the assembly language program e Declare the variable or routine at the global level in the Pascal MT program e Compile the program using the E source code option to generate entry point records The following example shows how an assembly language module references a variable that is declared in a Pascal MT module program test s globl pqr ext
31. RR Heap Error is a predefined BOOLEAN variable used by NEW to return the result of an allocation request Always use HERR in conjunction with NEW because the heap management system does not signal an error if there is no space available when you make an allocation request Direct Operating System Access You can make direct function calls to the CP M 68K operating system by using the BDOS routine which you declare in a Pascal MT program as follows EXTERNAL FUNCTION BDOS lt func gt INTEGER lt parm gt PTR INTEGER lt func gt is the BDOS function number Refer to your operating system documentation for the list of functions lt parm gt is a generic pointer You can use the ADDR function to generate the value The following example demonstrates direct access to the operating system in a function definition The function KEYPRESSED returns TRUE if a key is pressed and FALSE if not FUNCTION keypressed BOOLEAN BEGIN keypressed _BDOS 11 ADDR keypressed lt gt 0 END Listings 9 1 and 9 2 illustrate calls to BDOS Functions 6 and 23 respectively Pascal MT Programmer s Guide Direct Operating System Access Listing 9 1 Calling BDOS Function 6 PROGRAM BDOS_6 Use BDOS Function 6 for console I o TYP Since the BDOS call requires a pointer parameter we must define a record that allows us to pass an INTEGER as a pointer type In the record the FALSE tagfield occupies the sa
32. Represents a blank space Source code in examples and program listings has a bracket on the left side to illustrate and emphasize the block structure of the language Items in color represent literal examples including source code listings sections of code or single statements Also any system output such as error messages and system prompts are in color User input is in boldface color In the text CTRL represents a control character Thus CTRL C means Control C In any listing that shows example console interaction the symbol is the echo of a control character A numeric value indicates a decimal number unless otherwise stated A numeric value followed by the capital letter H indicates the number is a hexadecimal base 16 value Variable information in example statements is in lowercase Words in uppercase are Pascal MT reserved words or predefined identifiers For example ARRAY ELSE RECORD INTEGER TEXT WRITELN Names of procedures and sample programs when referenced in the text are also in uppercase This manual also uses the following symbolic convent ions to formally describe the syntax of Pascal MT statements The vertical bar indicates a choice between the items it separates You pronounce the symbol or Items inside curly braces are optional Optional items can be repeated any number of times lt gt Items inside angle brackets in lowercase letters or in a combination of lowerca
33. S MUST BE SCALAR The lower and upper bounds of a subrange must be scalar types ERROR 149 INDEX TYPE MUST NOT BE INTEGER An array bound cannot be declared type INTEGER or LONGINT it must be a subrange type ERROR 151 ASSIGNMENT TO FUNCTION IS NOT ALLOWED A value cannot be assigned to a function ERROR 152 NO SUCH FIELD IN THIS RECORD The compiler cannot find the specified field in the record ERROR 155 CONTROL VARIABLE CANNOT BE FORMAL OR NONLOCAL he control variable in a FOR loop must be locally declared 6 ED CASE LABEL A label in a CASE statement has been defined more than once INO SUCH VARIANT IN THIS RECORD The compiler cannot find the specified variant in the record 199 RING TAGFIELDS NOT ALLOWED The tagfield in a CASE variant record must be a scalar or subrange type E MUST BE CONSTANT Co This error occurs when using NEW or DISPOSE with a variant that is not a constant Pascal MT Programmers Guide Compilation Errors ERROR 165 ULTIDEFINED LABEL This error occurs when more than one statement is assigned the same label ERROR 168 UNDEFINED LABEL This error occurs when a declared label was not used to label a statement ERROR 169 ERROR IN BASE SET The ba
34. ame ASSIGN file b name REWRITE file Db IF IORESULT 255 THEN BEGIN WRITELN Sorry cannot open name EXIT END Call specific TRANSFER procedure transfer file a file bi END Main Program Pascal MT Programmer s Guide Program Listings Listing 11 2 File Transfer with BLOCKREAD and BLOCKWRITE PROGRAM file transfer 1 Transfer file a to file b using BLOCKREAD and BLOCKWRITE CONST Buffer size 2047 TYPE paoc ARRAY O buffer size OF CHAR fyle FILE VAR file a file b fyle name STRING buffer paoc PROCEDURE transfer VAR source fyle VAR destination fyle VAR result i INTEGER quit BOOLEAN BEGIN Body of TRANSFER procedure i 1 REPEAT BLOCKREAD source buffer result SIZEOF buffer i IF result 0 THEN BLOCKWRITE destination buffer result SIZEOF buffer i ELSE quit TRUE UNTIL quit CLOSE destination result IF result 255 THEN WRITELN Error closing destination file END TRANSFER procedure Body of Main Program in Listing 11 1 Pascal MT Programmer s Guide Program Listings Listing 11 3 File Transfer with GNB and WNB PROGRAM file transfer 2 Transfer file a to file b using GNB and WNB CONST buffer size 2047 TYPE paoc ARRAY 1 buffer size OF CHAR text file FILE OF paoc char file FILE OF CHAR VAR file a text file file b char file name STRING PROCEDURE transfer VAR source t
35. ammer s Guide Conditional Compilation Conditional Compilation Pascal MT supports conditional compilation directives so that you can compile alternative versions of a single source code file This facility can be very useful when compiling large application programs that are designed to run in different hardware or operating system environments You can isolate the environment dependent code and then compile different versions based on some conditional test The conditional compilation directives are amp SET amp IF amp ELSE amp END amp MSG Put conditional compilation directives in the source code as you do for other options Each directive begins with an ampersand character amp and must be in the first column You use the amp IF and amp END directives to delimit the section of source code you want to conditionally compile The syntax is shown below amp IF lt variable gt lt source line 1 gt lt source line n gt amp ELSE lt alternate source line 1 gt lt alternate source line n gt amp END If the value of the lt variable gt is TRUE the source code in lines 1 through n is compiled If the value is FALSE the compiler ignores the lines and continues compiling at the line immediately following amp END If the value is FALSE and you use the optional amp ELSE directive to specify an alternative section of code the compiler ignores lines 1 through n compiles the alternate source code instead
36. ancements that make it suitable for writing professional applications and system level programs The enhancements fall into four categories additional data types enhanced file handling and input output capability accesses both the run time and operating systems writes modular programs using overlays and chaining Collectively these enhancements make Pascal MT more suitable for commercial programming in both data processing and real time control applications The Pascal MT language is also the basis of a complete software development system that includes compilers linkers subroutine libraries and other programming tools Pascal MT Implementation An implementation of the Pascal MT language is a particular combination of software and hardware components that can translate the language s statements into machine readable instructions for a target system Software components include the compiler linker run time libraries and other tools such as assemblers disassemblers and symbolic debuggers Hardware components include microprocessors random access memory disk storage and peripheral devices such as consoles and printers Thus there can be many implementations of the Pascal MT language each tailored for a particular hardware software combination Every implementation of Pascal MT must support all the syntactical constructs of the language and translate language statements in conformance with the ISO standard However each
37. and the items included therewith Be sure to read that file before using the software TRADEMARKS Digital Research and its logo are registered trademarks of Digital Research Inc CB68K CP M 68K Digital Research C Pascal MT and TEX are trademarks of Digital Research Inc Motorola is a registered trademark of Motorola Inc The Pascal MT Language Programmer s Guide for the CP M 68K Operating System was prepared using the Digital Research TEX Text Formatter and printed in the United States of America LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLI First Edition May 1984 LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLI Foreword The Pascal MT M language is formally based on the definition of standard Pascal as described in the International Standards Organization ISO standard DPS 7185 Pascal MT also has several additions to standard Pascal that make it more suitable for commercial programming You can use Pascal MT to develop high quality efficient maintainable software for both data processing and real time control applications The Pascal MT system which includes compilers linkers and programming tools is implemented on a variety of operating systems and microprocessors Pascal MT programs are easily transportable between various target processors and operating systems because the language is consistent The Pascal MT system can also generate software for use in a ROM based environment to operate with or without an Operating system
38. ation Pascal MT allocates space for variables in the order you declare them The exception is variables appearing in an identifier list before a type These are allocated in reverse order For example given the declaration VAR a b c INTEGER cis allocated first then b then a Global Variables Pascal MT stores global variables contiguously with no space left between one declaration and the next For example given the declaration VAR a INTEGER b CHAR d suede BYTE Pascal MT Programmers Guide 1 INTEGER p INTEGER Pascal MT stores the variables as shown below Static Data Allocation 00 01 02 03 04 06 08 10 11 12 14 A A 0 b k i L L p p msb 1sb msb 1sb msb 1sb Higher memory gt Figure D 11 Contiguous Variable Storage Local Variables All local variables are allocated on the stack If a single byte variable BYTE or CHAR falls on an odd byte boundary the compiler pads the variable with one byte and aligns it on a word boundary to improve code efficiency End of Appendix D E Appendix Writing Portable Programs This appendix describes certain features of Pascal MT that are not portable to other implementations This does not mean that these features are not available in other implementations but only indicates that if they are available they are implemented differently If you want to write portable programs you should avo
39. avia adios NX d sois 5 2 A E E EAA 6 1 Propram Structure at Runtime tens etiani el peal aie tuin 6 1 Command Pd E a e a dead 6 1 R n time Memory Mapri rrien cid 6 1 MICI EE 6 2 I a Lar EE 6 2 A A UE 7 1 Writing Segmented Programs viii sehn eee quae rine Saee e Peau ne ee ee ene REL UN 7 1 Modules id di 7 1 Overlay Singa aa e e a a a a a a ae a aE 7 3 TEAM O eeh ee Ee EE 7 3 General Overlay SOM ia 7 3 Overlay File Format E 7 4 Lankine A E RA ea re ee taies 7 4 Channis teans LER D 7 5 MrisnpABrim D 7 5 Miamtamime the Heap zs i ri o tere IRR e P REED ERE ut Rd A M DR d 7 6 t E EE 8 1 Interfacing Pascal MT with Assembly Language Routnes esses 8 1 Interface Conventions A Umi traia 8 1 Ii EE 8 2 Interface Example ineen A seas tnczatesh A E TA IET INR PU OU ONE Te 8 3 A oor RITIENI ROI US INQUE 9 1 Controlling the Run time Environment 9 1 Heap IEA a ee Eege Ee 9 1 Using the OS e ee 9 1 Using the PASLIB Routines iicccisceccdianscceacissesteteaneztesseavecseavenucdedndenevsdensanesevaneds 9 1 LMAXAVAIL and LMEMAV AIL e eeeeeeeeeeet eene enne enne 9 2 Mio c S 9 2 Direct Operating System ACC688 4 uds cerit eost tee ieee staecesvhessedtasusdactednnccdenndesaane 9 2 IC EC xa nme onc mM cue 9 4 Absolute Varia Des cos doses O E 9 5 Manipulating VO POS 4 code dee Ee 9 6 INP and ODE cssc etie Debet ou eb o bob abeo f died 9 6 INPORT W and
40. ay specifications are always last in the command line For example the following command creates the overlay scheme shown in Figure 7 2 A gt link68 myfile parta ovlmgr partbl partb2 Pascal MT Programmer s Guide Chaining Overlay Part B1 Overlay Part B2 Part A Root Module Figure 7 2 Overlay Scheme Example 1 You can nest overlays by nesting the enclosing parentheses in the command line For example the following command creates the overlay scheme shown in Figure 7 3 A gt link68 myfile parta ovlmgr partbl partb2 Overlay Part B2 Overlay Part B1 Root Module Part A Figure 7 3 Overlay Scheme Example 2 Chaining Chaining allows one program to call another program into memory and transfer control to that program Chaining is an implementation dependent feature that is not be available on all implementations of Pascal MT see Appendix E Writing Portable Programs To chain to another program you execute a call to the CHAIN procedure and pass the name of the file variable as a single string parameter Sharing Data There are two ways that chained programs can share data shared global variables and absolute variables Using the shared global variable method you must guarantee that at least the first section of global variables is the communication area The remainder of the global variables do not need to be the same in each program You must also declare the shared variables identicall
41. cal MT Language Reference Manual for a bibliography of textbooks This manual also assumes that you are familiar with the CP M 68K operating system and your own hardware components Contents A iri rers sites tes rok etit vias i eui SX a uas 1 1 Inttoduction To Pascal MEE essei enu i Ga hec aue e afia dereud E RN 1 1 ThedPascab WE E TE 1 1 Pascal MEE Ip Menta ia 1 1 Pascal M T F for EE 1 1 Pascal MT Documentation Set s ss csssiassecceses soaateavacancesttecuennnccaatesedenedoasncaaeasedeeans 1 2 Notanonal Conventions A E eae 1 3 e O A ts 2 1 Getting Started isnie 2 1 A A E UM one a Tit 2 1 PascaUNTTAZS e EE 2 1 Installing ee E 2 2 System with Hard disk Drive oet ete rhe deae tapa eee aida dde 2 2 System with Floppy disk Drives teet tete teet e Edge eo eec eo sis edo 2 2 Compiling and Linking a Progr 2 3 E 3 1 Using the Compiler rev 3 1 Compiler Orsaniza doin 3 1 Compiler A O ES 3 1 AA AA sedan soe a a aa 3 1 Compilation Dat A ee UP ath de da OR UNS TRIBUERE 3 1 Compilation secu M 3 2 Compiler Command line Options eese 3 2 B BCD Representation et tna ode de Ee 3 3 C Contimnue on BEEOE vs iecore te tecto ke e Select sb seus be Ee ers eee c to dies 3 3 Dd Disassembled File Locapon esee eene enne 3 3 Ed Error Eile Eocat linia aia 3 3 Od MT68 000 Overlay Kee eene 3 3 Pd Print Listing File Location ai in iaa REUS 3 3 O Cher Operation e nie E E E a 3 3 Rd Relocatable
42. char is not a legal character in the command line Correct the error and relink LINK68 SYNTAX ERROR EXPECTED item There is a syntax error in the command line LINK68 expected to encounter item Correct the error and relink LINK68 UNEXPECTED END OF COMMAND STREAM LINK6S unexpectedly encountered the physical end of the command stream before the logical end Check the command line for proper syntax and options LINK68 UNRECOGNIZED OR MISPLACED OPTION NAME option The option given by option is not a valid LINK68 option or it is misplaced in the command line Correct the error and relink LINK68 HEAP OVERFLOW NOT ENOUGH MEMORY There is not enough memory for LINK68 to continue processing Pascal MT Programmers Guide Run time Errors LINK68 IMPROPERLY FORMED HEX NUMBER lt num gt The hexadecimal number h contains an invalid digit Correct the error and relink LINK68 PARSE END BEFORE COMMAND STREAM END LINK68 has unexpectedly encountered the logical end of the command line before the physical end Check the command line for proper syntax and options LINK68 CANNOT OPEN lt filename gt FOR INPUT The file indicated by the variable lt filename gt is invalid or the file does not exist Check the filename before you reenter the LINK68 command line LINK68 NESTED COMMAND FILES NOT A
43. cond indication is the amount of memory left for user symbols Both amounts are shown in decimal During Phase 1 the compiler also outputs a pound sign to the console each time it reads a procedure or function At completion of Phase 1 the compiler indicates the total number of bytes remaining in memory Phase 2 generates the relocatable object code During this phase each time the compiler encounters a procedure or function it displays the procedure s name its offset from the beginning of the module and its size in decimal When the processing is completed at the end of Phase 2 the compiler displays the following diagnostic information Lines lines of source code compiled Errors number of error s detected Code bytes of code generated in decimal Bss bytes of block storage used in decimal Compilation Errors During Phase 0 when the compiler detects a syntax error it displays the line containing the error If you are using the MTERRS TXT file the compiler also displays an error description In all other phases the compiler displays an error identification number When the compiler is building the symbol table in Phase 1 over flow occurs if not enough space remains for the current symbol Symbol table over flow is a non recoverable error You can overcome the problem by using the Kn option to eliminate unused symbols from the table see Source Code Options in this section You can also try to segment the pro
44. corrupted Ensure that the file is an object file output by the assembler or compiler Reassemble or recompile the file before relinking Pascal MT Programmers Guide Run time Errors LINK68 LINK68 LINK68 LINK68 LINK68 LINK68 LINK68 LINK68 INVALID SYMBOL FLAG IN lt filename gt LINK68 does not recognize the symbol flags indicated by the variable lt filename gt The file is not an object file or it has been corrupted Ensure that the file is an object file output by the assembler or compiler Reassemble or recompile the file before relinking INVALID RELOCATION FLAG IN lt filename gt The contents of the file indicated by the variable lt filename gt are incorrectly formatted The file is not an object file or it has been corrupted Ensure that the file is an object file output by the assembler or compiler If the file is an object file and this error occurs the file has been corrupted Reassemble or recompile the file before relinking NO RELOCATION BITS IN lt filename gt The file indicated by the variable lt filename gt is not an object file or has been corrupted Ensure that the file is an object file output by the assembler or compiler If the file is an object file and this error occurs the file has been corrupted Reassemble or recompile the file before relinking WRITE ERROR ON FILE filename The disk to which LINK68 is writing is full Erase unnecessary file
45. ction but is included in the symbol table e You can simulate UCSD Pascale MARK and RELEASE routines by using the built in routines MRK and RLS as shown in this example MODULE ucsd heap EXTERNAL FUNCTION MRK LONGINT EXTERNAL FUNCTION _RLS 1 LONGINT PROCEDURE mark VAR p LONGINT BEGIN p e MRK END Pascal MT Programmer s Guide Direct Operating System Access PROCEDURE release p LONGINT BEGIN _RLS p END MODEND LMAXAVAIL and LMEMAVAIL You can use the predefined functions LMAXAV AIL and LMEMAV AIL to determine the amount of heap space remaining at any given time LMAXAV AIL and LMEMAV AIL are not included in PASLIB You must explicitly declare them in your program as EXTERNAL FUNCTION LMEMAVAIL LONGINT EXTERNAL FUNCTION LMAXAVAIL LONGINT When used in conjunction with the NEW and DISPOSE routines in FULLHEAP LMAXAV AIL returns the size of the largest contiguous block of unallocated free memory LMEMAV AIL returns the total of all currently unallocated blocks of memory When used in conjunction with the NEW and DISPOSE routines in PASLIB LMAXAVAIL and LMEMAVAIL return identical values You should always use LMAXAV AIL and LMEMAV AIL instead of the standard PASLIB routines MEMAV AIL and MAXAV AIL which return true values only if the total amount of heap space is less than 32 767 bytes If the heap space is greater than 32 767 bytes both MEMAVAIL and MAXAV AIL return 7FFFH HERR HE
46. dress passed to it and POKE puts the bytes in the specified address Listing 8 1 Pascal MT PEEK_POKE Program PROGRAM peek_poke TYPE byte ptr BYTE pointerkludge RECORD CASE BOOLEAN OF TRUE p byte ptr FALSE q LONGINT END VAR choice INTEGER bbb BYTE ppp pointerkludge EXTERNAL PROCEDURE poke b BYTE p byte ptr EXTERNAL FUNCTION peek p byte ptr BYTE BEGIN Main Program REPEAT WRITE Which address READIN ppp q WRITE 1 Peek 2 Poke 3 Exit READLN choice IF choice 1 THEN WRITELN ppp q contains peek ppp p ELSE IF choice 2 THEN BEGIN WRITE Enter byte of data READLN bbb POKE bbb ppp p END UNTIL choice 3 END Main Program Pascal MT Programmer s Guide Interface Example Listing 8 2 Assembly Language PEEK and POKE Routines PEEK and POKE Routines globl peek Entry point for peek routine globl poke Entry point for poke routine text Tell assembler we are writing code PEEK Address to peek is on stack Return result in D7 peek move 1 a7 a0 pop return address move 1 a7 al pop address to peek moveq 0 d7 clear function return move P al d7 get byte from memory jmp aQ return POKE Byte to poke is on top of stack as the lower byte of a word Address to poke follows on stack poke move 1 a7 a0 pop return address move w a7 d7 byte to stor
47. e Figure 7 1 Typical LINK68 Overlay Sheme Overlay File Format An overlay file has the same format as a regular 68K command file The first word in the header is always 601AH An overlay file can be either absolute or relocatable An overlay file can have any filetype The default filetype is 068 If you use the SYMBOLS option LINK68 places the overlay s symbols in the root module If you use the common directive in AS68 to specify a common area shared by separate overlay modules LINK68 resolves all common areas with the same name to the same address in the root module s bss segment If more than one overlay file specifies static storage with the same name LINK68 uses the largest size for allocation The bss size for the root module is set to contain the area into which the overlays are loaded The symbol _end is resolved to the top of the overlay area Linking Overlays You determine a specific overlay scheme by the manner in which you link the programs That is overlays do not require any special construct or syntax in the source code However you must ensure that the root module contains the overlay manager and loader The general form of the command line for linking overlays is LINK68 root lt ovimgr gt lt overlay I gt lt overlay 2 gt lt overlay n gt where lt ovlmgr gt is the overlay manager in the run time system and lt overlay i gt through lt overlay n gt are the overlay modules The overl
48. e move l a7 al address to poke move b d7 al poke byte jmp aO return end End of Section 8 9 Section Controlling the Run time Environment This section describes several Pascal MT features that let you control your program s run time environment The features provide the ability to e manage the heap as a standard heap or as a stack e access the operating system through direct function calls e insert machine code into the Pascal MT source code using INLINE e declare variables with absolute addresses e address the processor s I O ports e perform range and error checking Heap Management Pascal MT supports two alternative methods for managing the heap as a standard heap or as a stack Using the FULLHEAP Routines You can manage the heap using the ISO standard routines NEW and DISIOSE as they are implemented in the library named FULLHEAP When you use the FULLHEAP routines e NEW assumes a standard heap and dynamically allocates data to the smallest space that can hold the requested item e DISPOSE frees the memory allocated to the requested item Using the PASLIB Routines You can also manage the heap using the NEW and DISPOSE routines as they are implemented in the PASLIB run time library When you use the PASLIB routines e NEW treats the heap area as an ordinary stack NEW puts the dynamic data on top of the stack which grows upward from the end of the bss segment e DISPOSE performs no fun
49. e flag is TRUE and _ERR takes appropriate action Table 9 1 summarizes the error codes associated with the _ERR routine Table 9 1 ERR Routine Error Codes Value Meaning 1 Divide by zero check 2 Heap overflow check unused 3 String overflow check unused 4 array and subrange check 5 Floating point underflow 6 Floating point overflow The various error conditions produce the following results e For floating point underflow ERR does not print an error message and the result of the operation is 0 0 e Forfloating point overflow ERR prints the error message FLOATING POINT OVERFLOW The result of the operation is a large number e For division by zero ERR prints the error message DIVIDE BY ZERO DETECTED The result is the representation of the largest possible number e For heap overflow ERR takes no action and does not print an error message You should always test the value of HERR to detect heap overflow e For string overflow ERR prints the error message Pascal MT Programmer s Guide Range and Error Checking STRING OVERFLOW TRUNCATED and the string is truncated User supplied Error Handlers You can write your own _ERR routine instead of using the one supplied with the system To use your own version of ERR instead of the one in PASLIB link your routine ahead of PASLIB to resolve the reference to ERR Declare your version of ERR as follows PROCEDURE_ERR lt error gt BOOLEAN lt
50. e named MATH It also tells LINK68 to include the symbol table in MATH and place the temporary files on drive B A link68 com linkit inp This command tells LINK68K to read the command line from the file LINKIT INP Note that closing brackets are not needed The file LINKIT INP might contain the following commands link68 Lab tex 500 d 2a00 b 3000 screen too long scrns1 1 iolib al This command creates the file SCREEN from the files SCRNS1 and IOLIB The command tells LINK68 to create SCREEN as an absolute command file with the Text segment starting at 500H the Data segment starting at 2AOOH and the uninitialized Data segment starting at 3000H It also tells LINK68 to include local symbols from SCRNSI and all the modules in IOLIB Table 4 2 lists the LINK68 options their abbreviations and default s Pascal MT Programmer Guide Linker Command line Options Table 4 2 LINK68 Command line Options Option Abbrev Purpose Default ABSOLUTE AB generates an absolute file generates relocatable file ALLMODS AL loads all modules loads only the modules referenced BSSBASE n B n sets base address of bss first even word after Data segment segment COMMAND C gets command line from a file DATABASE D n sets base of the Data first even word after Text n segment segment IGNORE IG ignores 16 bit address stop issue error message overflow
51. e to its shortest unambiguous form The command line options are listed below ABSOLUTE Tells LINK68 to generate an absolute command file with no relocation bits The default is a relocatable command file ALLMODS Tells LINK68 to load all modules from a library even if they are not referenced The default action is to include only those modules that are actually referenced BSSBASE n Specifies the base address for the Block Storage Segment bss containing the uninitialized data in discontiguous programs n is a hexadecimal value The default value is the first even word after the Data segment You cannot use this option when linking overlaid programs COMMAND Tells LINK68 that the following named file contains the rest of the command line LINK68 ignores the rest of the main command line Nested command files are not allowed The format of this option is COMMAND filename where filename is the file containing the rest of the command line DATABASE n Specifies the base address of the Data segment in discontiguous programs n is a hexadecimal value The default is the first even word after the Text segment You cannot use this option when linking overlaid programs IGNORE Tells LINK68 to ignore 16 bit address overflow and continue processing The default action is to issue an error message and stop processing INCLUDE Tells LINK68 to load an unreferenced module from a library The format for this option is filename INCLUD
52. er s Guide Program Listings Listing 11 5 File Transfer with GET and PUT PROGRAM file transfer 4 Transfer file a to file b using GET and PUT TYPE char file FILE OF CHAR VAR file a file b char file name STRING PROCEDURE transfer VAR source char file VAR destination char file VAR result INTEGER BEGIN Body of TRANSFER procedure WHILE NOT EOF source DO BEGIN destination source PUT destination GET source END CLOSE destination result IF result 255 THEN WRITELN Error closing destination file END TRANSFER procedure Body of Main Program in Listing 11 1 End of Section 11 A Appendix Compilation and Run time Error Messages This appendix contains a list of the error messages output by the compiler and run time system The compilation errors have the same numbering sequence as described in the Pascal User Manual and Report second edition by Kathleen Jensen and Niklaus Wirth New York Springer Verlag 1978 In most cases the error description is self explanatory and the user response is obvious In certain cases where the error can occur in more than one context suggested user responses are given In each case you must correct the error and recompile the program Compilation Errors Table A 1 Compiler Error Messages essage Meaning ERROR 3 PROGRAM EXPECTED The compiler expects the reserved word PROGRAM
53. erated Note also that the procedure TABLE must be in the same module as the statement that takes the ADDR of TABLE Listing 9 3 Using INLINE to Construct Compile time Tables PROGRAM demo_inline CONST element 3 Third array element TYPE Id_field ARRAY 1 8 OF CHAR Id ptr id field pointerkludge RECORD CASE BOOLEAN OF TRUE p id ptr FALSE 1 longint END VAR table ptr id ptr P pointerkludge offset integer PROCEDURE table BEGIN INLINE Digital Research Software END BEGIN Main Program p p ADDR table p l p l 14 offset sizeof table ptr element 1 p l p l long offset table ptr p p WRITELN table ptr Should write Software END Main Program Absolute Variables You can declare a variable with an absolute address if you know the address at compile time The syntax for declaring ABSOLUTE variables is lt variable name gt ABSOLUTE lt address gt The following examples are valid declarations of ABSOLUTE variables int ABSOLUTE 8000 INTEGER Pascal MT Programmer s Guide Manipulating I O Ports screen ABSOLUTE SCO ARRAY 0 15 0 63 OF CHAR The compiler does not allocate space in your Data segment for absolute variables Ensure that no compiler allocated variables conflict with the ABSOLUTE variables Manipulating I O Ports Pascal MT supports direct manipulation of the p
54. ernal variable from pascal program text test move w pqr d7 get contents of pascal integer end Pascal program fragment VAR in globals POR INTEGER accessible by as68 routine Pascal MT Programmer s Guide Parameter Passing Parameter Passing When you call an assembly language routine from Pascal MT or a Pascal MT routine from assembly language parameters pass on the stack On entry to the routine the top of the stack is a double word containing the return address The parameters are below the return address in reverse order from declaration Each parameter requires at least one 16 bit word of stack space A character or Boolean passes as a 16 bit word with a high order byte of 00 VAR parameters pass by address Address operands and pointers use two words of stack space The address represents the byte of the actual variable with the lowest memory address Nonscalar parameters except sets always pass by address If the parameter is a value parameter the compiler generates code that calls MVL to move the data The _SS2 routine handles set parameters If passed by value the actual value of the set goes on the stack Sets are stored on the stack with the least significant byte on top and the most significant byte on bottom Figure 8 1 shows how a typical parameter list appears on the stack on entry to a procedure If the procedure is declared as PROCEDURE demo i j INTEGER VAR q STRING c d
55. error number gt INTEGER Your version should check the lt error gt variable and exit if it is FALSE If the value is TRUE decide what action to take Your version should also use the same values of lt error number gt listed in Table 9 1 VO Error Handling The run time routine BDOS does not handle I O errors However it returns the CP M 68K error code in IORESULT You can rewrite BDOS using the supplied assembly language source to make more extensive checks for disk I O errors End of Section 9 10 Section Writing ROM based Code The Pascal MT system can generate code for use with or without an operating system This section presents some guidelines for writing programs in a ROM based system Note The guidelines presented here are just a suggestion Digital Research does not provide detailed application support for ROM based applications Programs That Use I O There are three ways you can write a ROM based program that performs I O e Use redirected I O for all READ and WRITE statements This replaces the run time character I O routines with user written I O routines Refer to the Language Reference Manual e Rewrite the GET routine because the read integer and read real routines call it Also rewrite the run time subroutines _RNC read next character and _WNC write next character e Ifyou want the program to run in a totally stand alone environment you must write an assembly language module that simulate
56. etter The compiler accepts blanks between the option letter and the parameter The source code options are listed below E Entry point Record Generation The E option controls the generation of entry point records in the relocatable object code file Enable the E option using a parameter and disable it using a parameter E is the default E tells the compiler to generate entry point records for variables procedures and functions declared at the outermost global level o f the program You can reference a global variable procedure or function in a separate module if the module uses the same declaration and the reserved word EXTERNAL E tells the compiler not to generate entry point records thus making all variables procedures and functions local to the block where they are defined I Include Files The I option tells the compiler to include a specified file for compilation in the input stream of the original program The compiler supports only one level of file inclusion so you cannot nest Include files The form of the option is I lt filespec gt where lt filespec gt must be in standard format If you omit the drive specification the compiler looks on the default drive If you omit the filetype the compiler supplies the same filetype as the original source file If the compiler cannot find the file it displays an error message and stops processing The file must end with a carriage return line feed and CTRL Z
57. ext file VAR destination char file VAR ch CHAR result INTEGER stop it BOOLEAN BEGIN Body of TRANSFER procedure stop it FALSE WHILE NOT EOF source AND NOT stop it DO BEGIN ch GNB source IF WNB destination ch THEN BEGIN WRITELN Error writing character stop it TRUE END CLOSE destination result IF result 255 THEN WRITELN Error closing END TRANSFER procedure Body of Main Program in Listing 11 1 Pascal MT Programmer s Guide Program Listings Listing 11 4 File Transfer with SEEKREAD and SEEKWRITE PROGRAM file transfer_3 Transfer file a to file b using SEEKREAD and SEEKWRITE CONST buffer size 2047 TYPE paoc ARRAY O buffer size OF CHAR text_file FILE OF paoc char_file FILE OF paoc VAR file_a text_file file_b text_file name STRING PROCEDURE transfer VAR source text_file VAR destination text_file VAR result i INTEGER stop_it BOOLEAN ch CHAR BEGIN Body of TRANSFER procedure ch A result 0 i e 0 WHILE result lt gt 1 DO BEGIN SEEKREAD source i result IORESULT IF result 0 THEN BEGIN destination source SEEKWRITE destination i END i i 1 END CLOSE destination result IF result 255 THEN WRITELN Error closing destination file END TRANSFER procedure Body of Main Program in Listing 11 1 Pascal MT Programm
58. f 1023 decimal or 3FF hexadecimal so 400 represents an exponent of 1 while 3FE represents an exponent of 1 Suppose a double precision floating point binary number appears in memory as the eight byte value CO 43 CO 00 00 00 00 00 higher memory gt You can visualize this value as a string of 64 bits in the form c 04 3 C 00 0 0 0 0 0 0 0 1100 0000 0100 0011 1100 0000 0000 0000 0000 0000 0000 0000 0000 0000 The high order bit equal to 1 indicates the sign is negative C 0 4 3C0 ges 1100 0000 0100 0011 1100 0000 Ignoring the sign bit yields a biased exponent value of 4 0 4 0100 0000 0100 s ignored Subtracting the bias 3FF from the exponent 404 gives a true binary exponent of 5 Restoring the implicit normalized bit to the mantissa produces the bit pattern shown below 3 c 0 0011 1100 0000 1001 1110 0000 implicit normalized bit restored Because the binary point is one position to the right of the implicit normalized bit the value of the mantissa is 1 001 1110 0000 Since the true binary exponent is 5 the binary point must be shifted to right 5 places giving a new value to the mantissa as shown below 1001 11 10 0000 To calculate the value represented by the mantissa multiply by the true binary exponent which is now 2 because the binary point has been shifted to the right Pascal MT Programmers Guide Array Representation 2 2 24 24 2 2 32 4 4 2 1 1 2 1
59. fy and recompile ERROR 398 IMPLEMENTATION RESTRICTION Normally used for arrays and sets that are too big to be manipulated or allocated ERROR 407 SYMBOL TABLE ERF LOW There is not enough space left in the symbol table Use the Kn compiler option to eliminate unused entry points or segment the program into smaller modules ERROR 496 INVALID OPERAND TO INLINI Usually due to reference that requires address calculation at run time ERROR 500 NON ISO STANDARD FEATURE BEING USED This is a warning only and does not prevent the program from compiling ERROR 998 ERROR IN CONDITIONAL COMPILATION PARAMETER There is an error in one or more conditional compilation parameters ER UNABLE TO CONTINUE DUE TO PREVIOUS ERRORS It is possible for a program to be syntactically correct and still have semantic errors that can confuse the compiler The compiler stops early with this error number Look carefully at the line on which the compilation halts Make some corrections and recompile Pascal MT Programmers Guide Run time Errors Run time Errors Table A 2 lists the error messages reported by the run time system Table A 2 Run tine Error Messages ERFLOW TRUNCATED This error occurs when a string constant is assigned to a variable whose declared length is insufficient to ho
60. gram into smaller modules and compile them separately see Section 7 Writing Segmented Programs In all phases when the compiler detects an error it asks if you want to continue or stop unless you use the C command line option See Command Line Options in this section Note You must ensure that all the compiler overlays are on the same disk If the overlay manager in the run time system cannot find an overlay it displays an error message and stops processing Usually you can find a missing overlay by ensuring that the filename is correct and that it is on the disk If you cannot find it recopy the overlay file from your distribution disk If you are sure the overlay is on the disk and you still get an error message then the file is corrupted When all processing is completed the ERR file generated by the compiler summarizes all non syntactic errors Appendix A contains a complete list of the error messages their causes and suggested responses Compiler Command line Options Command line options control specific actions of the compiler such as where it writes the output files All command line options are single letters that start with a dollar sign or a pound sign If you specify more than one option do not put any blanks between the options Certain options require an additional parameter to specify a disk drive or other I O device The command line options are listed below Pascal MT Programmer Guide Compiler
61. grams that are easier to maintain and take up less memory than monolithic programs If you are not an experienced Pascal MT programmer you should start by writing programs without overlays Modules The Pascal MT system lets you do modular programming with little preliminary planning You can develop programs until they become too large to compile and then split them into modules The E compiler source code option lets you make variables functions and procedures local to the module There are two main differences between modules and programs e A module must contain at least one procedure or function However a module does not have a main body of statements other than those contained in procedures and functions e Ina module the reserved words MODULE and MODEND replace the reserved words PROGRAM and END The following example shows a typical module MODULE sample mod VAR mainfile EXTERNAL TEXT PROCEDURE echo st STRING times INTEGER VAR i INTEGER BEGIN FOR i 1 TO times DO WRITELN mainfile st END MODEND Pascal MT Programmer s Guide Modules Modules can have free access to global variables functions and procedures in any other module If you want to keep variables functions and procedures local to a module use the E compiler source code option Use the reserved word EXTERNAL to declare variables functions and procedures that are allocated in other modules or in the main program EXTERNA
62. ib L68 End of Section 10 11 Section Sample Pascal MT Programs This section contains sample programs that illustrate various features of Pascal MT The best way to learn any programming language is to study working examples You should study the programs in this and other sections and cross check with the material in the Language Reference Manual when necessary Once you understand the operation of a program you can modify or enhance it and thereby gain further experience with Pascal MT File Transfer Listing 11 1 shows the main body of a file transfer program The main program calls one of four different transfer procedures that illustrate different ways to implement such a file transfer Listing 11 2 shows the transfer program using the BLOCKREAD and BLOCKWRITE procedures This program uses untyped files and a large 2K byte buffer to transfer the data Note that the program only works for files whose size is an even multiple of 2K bytes Thus if the size of the source file is 9K the last 1K is not written because the variable result is nonzero after the call to BLOCKREAD Using a 128 byte buffer guarantees that all the data is transferred Listing 11 3 shows the transfer program using the GNB and WNB routines for byte level access to the file Listing 11 4 shows the transfer program using the SEEKREAD and SEEKWRITE procedures for performing random access I O Note that IORESULT returns a 1 indicating end of file if the
63. id using the implementation dependent features listed below but if you do isolate them so that they are easy to locate and modify when you port the program Hardware dependent Features All the following Pascal MT features depend on detailed knowledge of a particular processor s architecture and native instruction set e ABSOLUTE variable addressing e INLINE e INTERRUPT procedures e O port addressing e Redirected I O System dependent Features All the following Pascal MT features either depend on a particular implementation s run time system or operating system s file structure Thus they can vary from one implementation to another e logical device names such as CON and RDR e the values returned by IORESULT e chaining from one program to another e having overlays call other overlays e dependence upon EOF for non TEXT files Some operating systems keep track of how much data is in the file to the exact byte while others only keep track to the sector block level and the last sector block can contain uninitialized data e BLQCKREAD BLOCKWRITE depends on knowledge of the correct allocation block size in the BIOS Use SEEKREAD SEEKWRITE instead e temporary files In general if compliance with the ISO standard is desired you should avoid using variant records that circumvent type checking End of Appendix E
64. ilt in exponential function Built in natural log function Table C 4 FULLHEAP Routines Routine Purpose _NEW Allocate memory from heap _DSP Return memory space to heap End of Appendix C D Appendix Internal Data Representation This appendix describes how Pascal MT internally represents the constants and variables declared in your programs This information is useful when you want to interface Pascal MT code with assembly language programs see Section 8 Each Pascal MT implementation differs in the way it internally represents data The information presented here is specific to the Motorola MC68000 microprocessor running under the CP M 68K operating system Size and Range of Data types The table below summarizes the size and range of Pascal MT data types for the 68K implementation Table D 1 Size and Range of Pascal MT Data Types Data Type Size Range BOOLEAN 2 bytes FALSE TRUE BYTE 1 byte O 2255 CHAR 1 byte 024 255 INTEGER 2 bytes 32768 32767 LONGINT 4 bytes 2 32 232 WORD 2 bytes Q sy 65535 BCD REAL 10 bytes 18 total digits 4 decimal places FLOATING REAL 8 bytes One 107 SET 32 bytes 0 22 255 STRING 1 256 bytes Multibyte Storage All data represented by multiple bytes is stored in memory with the high order most significant byte first That is the high order byte appears at the lowest address then the other bytes appear at increas
65. in this context ED The compiler expects the token 1 1 in this context This error can be caused by using an equal sign in a VAR declaration ERROR 6 EGAL SYMBOL POSSIBLY MISSING ON LINE ABOVE The compiler does not allow the symbol in this context ED The compiler expects the token in this context ECTED The compiler expects an integer value in this context ED The compiler the token in this context This error can be caused by colon in a TYPE or CONST declaration Pascal MT Programmers Guide Compilation Errors ECTED The compiler expects the reserved word BEGIN in this context 18 IN DECLARATION PART The compiler encountered an error in the declaration This error can be caused by an illegal backward reference to a type in a pointer declaration 50 IN CONSTANT The compiler encountered a syntax error in a literal constant This error can occur when using recursion or improperly using INP and ERROR 55 OR DOWNTO EXPECTED IN FOR STATEMENT The compiler expects the reserved word TO or DOWNTO in this context ERROR 58 ERROR IN lt FACTOR gt BAD EXPRESSION The compiler encountered a syntax error in the expression ERROR 101 IDENTIFIER DE
66. ing addresses with the low order least significant byte at the highest address Pascal MT Programmers Guide BOOLEAN Representation BOOLEAN Representation Pascal MT represents variables of type BOOLEAN using two consecutive bytes The high order byte is stored first The least significant bit LSB in the low order byte determines the value If the bit is O the value is TRUE if the bit is 1 the value is FALSE Cup ot 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 Figure D 1 BOOLEAN Representation BYTE Representation Pascal MT represents variables of type BYTE using one byte All the bits are considered significant Figure D 2 BYTE Representation CHAR Representation Pascal MT represents variables of type CHAR using one byte to contain the ASCII representation The most significant bit MSB is ignored o pun z 6 5 4 3 2 1 0 Figure D 3 CHAR Representation INTEGER Representation Pascal MT represents variables of type INTEGER in two s complement form using two consecutive bytes The high order byte is stored first and the most significant bit MSB is the sign bit SB L II S GT B N Lo Wa T9 J2 JL EO 9 8 7 6 5 4 3 2 1 0 Figure D 4 INTEGER Representation LONGINT Representation Pascal MT represents variables of type LO
67. ing form LINK68 Error Message Most linkage errors are nonrecoverable and prevent your program from linking Appendix B contains a complete list of the LINK68 errors with explanations and suggested user responses Redirecting Output Normally LINK68 sends all diagnostic output to the console However you can redirect this output by using the gt character in the command line For example the command A gt link68 tem b myfile 68k moda modb d lnkmsgs txt creates MYFILE 68K on drive A using drive B for the temporary files and sends the diagnostic output to the file LNKMSGS TXT on drive D Linker Command line Options When you invoke LINK68 you can specify command line options that control the link operation Pascal MT Programmer s Guide Linker Command line Options There are two kinds of options global and local Global options apply to the entire link operation Local options apply only to the individual files being linked You enclose both kinds of options in square brackets You enclose global options in square brackets immediately preceding the command filename if specified in the command line You enclose local options in square brackets immediately following the filename to which they apply You can use spaces between filenames to improve readability in the command line and you can put more than one option in square brackets by separating the options with commas LINK68 also allows you to abbreviate an option nam
68. ion and size of the overlay areas and specify them at link time e Overlay static variables global variables or variables local to a run time or assembly language routine in the overlay All Pascal MT modules are recursive Recursion reduces the amount of static data It does not necessarily eliminate it because run time code linked with the overlay might contain static data When you link the overlay the linker determines the amount of space required for static variables General Overlay Scheme LINK68 supports a simple tree structured overlay scheme with a maximum of 255 overlays You can create overlays to a depth of five levels below the root module Only one overlay on a given level can be memory resident at a time LINK68 places all global static data in the root module no matter where it is originally defined An overlay can reference any symbol in another overlay that is one level above it in the tree or in an overlay on any level below An overlay cannot reference any symbol in an overlay on the same level or Pascal MT Programmer s Guide Overlays in an overlay that is more than one level above itself Figure 7 1 shows a typical overlay scheme In this scheme overlays A and B can both reference symbols in the root but overlay A cannot reference symbols in B because they cannot be coresident Overlays B and C can reference symbols in each other and the root but not in overlay A Overlay C Overlay A Overlay B Root Modul
69. l the compilation process The compiler can read the source file from any disk The lt filespec gt must be in Digital Research standard filespec format and end with a carriage return line feed and CTRL Z When you create Pascal MT programs make sure that your text editor does not insert nonprintable formatting characters in the source file The compiler cannot process a file containing any nonprintable control characters except tabs Some text editors use nonprintable ASCII characters to control formatting If you do not specify a filetype the compiler searches for the file with no filetype If the compiler cannot find the file it assumes a SRC filetype then a PAS filetype If the compiler still cannot find the file it displays an error message and stops processing The compiler generates a relocatable object code file with the same filename as the input source program The relocatable file has the filetype O Compilation Data The Pascal MT compiler periodically outputs information during Phases O and 1 to assure you it is running properly During Phase 0 the compiler outputs a plus sign to the console after scanning every 16 lines of Pascal MT Programmer Guide Compilation Errors source code At the beginning of Phase 1 the compiler indicates the total amount of memory space available The compiler also indicates the amount of memory space available after the predefined internal compiler symbols are loaded This se
70. ld the constant SUBSCRIPT SUBRANGE OUT OF BOUNDS This error occurs when a subscripted array reference or a subrange reference is not within the declared bounds POINT OVERFLOW This error occurs when a REAL number becomes larger than the largest possible number that can be represented in internal floating point form End of Appendix A B Appendix LINK68 Error Messages LINK68 returns two types of error messages diagnostic and logic Both types of error messages have the following form LINK68 Error Message A diagnostic error prevents your program from linking You should make the appropriate correction to your program and try again A logic error is a non recoverable error in the internal logic of LINK68 If you receive one of these messages contact the place you purchased your system for assistance You should provide the following e The version of the operating system you are using e A description of your system s hardware configuration e Sufficient information to reproduce the error Indicate which program was running at the time the error occurred If possible also provide a disk with a copy of the program Diagnostic Error Messages Table B 1 list the LINK68 diagnostic errors in alphabetic order with explanations and suggested user responses Table B 1 LINK68 Diagnostic Error Messages Message Meaning LINK68 ILLEGAL CHARACTER lt char gt The character
71. ling and Linking a Program Compiling and Linking a Program If you have never used Pascal MT before the following step by step example shows you how to compile link and run a simple program This example assumes that you are using a CP M 68K system with two disk drives and that you are familiar with CP M 68K 1 2 Put the compiler disk in drive A Using the text editor create a file called TEST1 PAS and enter the following program Use PIP to put the file on drive B PROGRAM simple example VAR i INTEGER BEGIN WRITELN This is just a test FOR x ze 1 IO IO DO WRITELN i WRITELN A11 Done END Now compile the program with the following command A gt mt68 b testl If you examine your directory you will see a file named TEST1 0 that contains the relocatable object code emitted by the compiler If the compiler detects any errors correct your source program and try again Now log on to drive B and link the program using the following command B gt 1ink68 testl paslib 168 Your directory will now contain a file named TEST1 68K that runs directly under CP M 68K To run the program enter the command B testl Although the test program shown above is very simple it demonstrates the essential steps in the development process of any program editing compiling and linking End of Section 2 3 Section Using the Compiler Compiler Organization The Pascal MT compiler i
72. me memory as the two INTEGERS in the TRUE tagfield E ptr CHAR VAR i INTEGER ch CHAR pchar ptr EXTERNAL FUNCTION _BDOS func INTEGER parm ptr INTEGER The main program echoes any input character at the console until you input a colon BEGIN Main Program ne RE UN END w pchar PEAT pchar chr 255 REPEAT Read a character ch CHR _BDOS 6 pchar UNTIL ch lt gt CHR 0 IF ch lt gt THEN BEGIN convert ch to INTEGER pass as a pointer pchar ch i BDOS 6 pchar Write a character END TIL ch Main Program Pascal MT Programmer s Guide INLINE Listing 9 2 Calling BDOS Function PROGRAM BDOS_23 Use BDOS Function 23 to rename files TYPE ptr INTEGER fcblk PACKED ARRAY 0 36 OF CHAR VAR oldname newname STRING 1 2 cblk d INTEGER EXTERNAL FUNCTION _BDOS func INTEGER parm ptr INTEGER EXTERNAL PROCEDURE PARSE VAR f fcblk S STRING PARSE converts a string into internal CP M filename format BEGIN Main Program WRITE Enter old filename Get the old filename READLN oldname PARSE fl oldname WRITE Enter new filename Get the new filename READLN newname _PARSE 2 newname Create the FCB required by BDOS call 23 MOVE 2 1 16 12 Now call the rename function passing pointer to FCB
73. n Routines Routine Purpose MOVELEFT Block move left end to left end MOVERIGH Block move right end to left right _NEW Allocate memory for NEW procedure _DSP Deallocate memory for DISPOSE procedure MEMAVAIL MEMAVAIL function MAXAVAIL MAXAVAIL function L L EMAVAI LMEMAVAIL function MAXAVAI LMAXAVAIL function Table C 2 BCDREALS Routines Routine Purpose Real comparison for Real comparison for Real comparison for Real comparison for Real comparison for Real comparison for Floating point operations Real add Real subtract Real multiply Real divide Real negate Real absolute value Store a real Convert integer to float Built in truncate function Pascal MT Programmers Guide Internal Logic Errors ROUND Built in round function Table C 3 FPREALS Routines Routine Purpose Real comparison for Real comparison for lt gt Real comparison for gt Real comparison for lt Real comparison for gt Real compasison for lt El E Co 3 EH Real add Real subtract Real multiply Real divide Real negate Real absolute value Floating point operations Read a real from a file Write a real to a file Store a real Convert integer to float Built in truncate function Built in round function Built in square function Built in square root function Built in sine function Built in cosine function Built in arctangent function Bu
74. n advanced programming topics including how to write large programs in segments interfacing Pascal MT programs with assembly language modules direct access to the operating system from Pascal MT programs and writing your own error handling routines There is also a set of guidelines for writing ROM based code The Pascal MT Language Reference Manual cited as Language Reference Manual describes the Pascal MT language its syntax and semantics It is not a programming tutorial Rather it is primarily a reference document and should be used in conjunction with the Programmer s Guide The Pascal MT documentation set assumes you have general experience with computer programming and possibly with standard Pascal If you are a beginning programmer or if you are not familiar with Pascal you should refer to the bibliography of textbooks listed in the Language Reference Manual The documentation set also assumes you are familiar with your own hardware components and operating system Pascal MT Programmer s Guide Notational Conventions Notational Conventions The following notational conventions are used throughout this manual 5 Bracket color CTRL nH lowercase UPPERCASE Horizontal ellipses indicate the immediately preceding item can occur once or any number of times in succession Vertical ellipses indicate an omitted portion of a source program or example only the relevant part is shown
75. n bounds If the user stack overwrites the heap the program halts with unpredictable results Heap The heap is the area of free memory from which storage for certain variables is dynamically allocated and deallocated at run time Refer to Section 9 for more in formation about managing the heap End of Section 6 7 Section Writing Segmented Programs One major advantage of Pascal MT is the ability to write a large complex program as a series of small independent modules You can code test debug and maintain each module separately and thereby greatly simplify the overall task of program design The process of breaking a program into separate units is called segmenting Pascal MT provides three methods for segmenting programs modules overlays and chaining e Modules are separately compiled program sections You can link modules together to build overlays libraries or entire programs e Overlays are sets of modules linked together as a unit that load into memory from disk when a procedure or function in one of the modules is referenced from somewhere else in the program Overlays need to be in memory only when a routine in the overlay is called otherwise they remain on the disk Overlays have hexadecimal filetypes for example PROG OIF e Chaining allows one program to call another and leave data in memory that can be shared by the new program You can use these three features in any combination to produce modular pro
76. n other modules k l EXTERNAL INTEGER located elsewhere EXTERNAL PROCEDURE sort VAR q list len INTEGER EXTERNAL FUNCTION iotest INTEGER PROCEDURE procl BEGIN IF iotest 1 THEN normal external function call END BEGIN sort normal external procedure call END Pascal MT Programmer s Guide Overlays Listing 7 2 Module Example MODULE module demo label constant and type declarations go here VAR i j EXTERNAL INTEGER use those from main program k l INTEGER define these here EXTERNAL PROCEDURE prod from main program PROCEDURE SORT define sort here FUNCTION iotest INTEGER define iotest here maybe other procedures and functions here MODEND Overlays Using overlays you can link programs so that parts of them automatically load from the disk as they are needed Thus a whole program does not have to fit in memory simultaneously You can use overlays to store infrequently used modules and module groups that need not be co resident Terminology The following terms are used when describing overlays e Root module the portion of the program that is always in memory Root modules have the 68K filetype A root module consists of a main program the run time routines it requires and optionally the run time routines that the overlays require e Overlay area an area of memory where the overlay manager loads overlays Plan the locat
77. ndard X Exception Error Checking at Run time The X option tells the compiler to generate code that performs error checking at run time Error checking covers division by zero both integer and real numbers and real number over flow underflow You enable the X option with the parameter and disable it with the parameter By default error checking is always enabled in this version Refer to Section 9 6 for information on run time error handling The following examples show proper source code compiler options p Set kO i d userfile lib For reference Table 3 3 summarizes the source code compiler options Table 3 3 Compiler Source Code Options Option Function Default E quA controls entry point generation E makes variables and routines either global or local I lt filespec gt includes another source file into the input stream for example SI MATH LIB Kn removes predefined routines to save space in symbol tab le n 0 15 L controls the listing of source code L P enters a form feed in the LIS file Rt controls range checking code R T controls strict type checking T W generates warning messages for non W ISO standard features X controls exception checking code X Note The Cn Qn S and Z options have no effect as they do in other implementations the compiler ignores them Pascal MT Progr
78. nerate this Pascal MT Programmer s Guide Compiler Command line Options e information and you cannot disassemble the object code file The X option also tells the compiler not to erase the temporary files at the end of compilation because these files are used by the disassembler Pointer Character Equivalence The E option tells the compiler to treat the 2 character as equivalent to the standard pointer reference character When you use this option you cannot use the character as the first character in an identifier By default the compiler does not treat as equivalent to The following is an example command line A mt68 a testprog Srbtbvpp This command line tells the compiler to read the source code file from drive A write the relocatable object code file and the temporary files to drive B print procedure and function names during Phase 0 and send the listing file to the printer Table 3 1 summarizes the compiler command line options and their de fault values Table 3 1 Compiler Command line Options Option Meaning Default B Use BCD rather than floating point Floating point binary reals binary for real numbers C Continue compiling when error is Compiler stops and ask s on each error encountered Dd Put the disassembled listing on Show disassembled listing on console device d d A O X P Ed MTERRS TXT file is on disk d d MTERRS TXT on default disk A O Od MT68 00
79. nes in each library Pascal MT Programmer s Guide Invoking the Linker Table 4 1 Required Libraries Library Contents BCDREALS BCD real number routines FPREALS Floating point real number routines FULLHEAP Memory management routines Note You must use LINK68 to create an executable command file even when a single object code file contains no undefined symbols Invoking the Linker You invoke LINK68 with a command line of the form LINK66 file object file 1 object file 2 object file n where file is the name of the command file you want to create and object f ile 1 through object file n are the object code files to link If you invoke LINK68 without a command tail the linker lists the options and returns control to the operating system If you enter a filename to the left of the equal sign LINK68 creates the output file with that name For example the command A gt 1ink68 math sin cos tan creates the command file MATH However if you omit the filename to the left of the equal sign LINK68 creates the command file using the first filename in the command line and assigns the default filetype 68K For example A gt link68 sin cos tan creates the command file SIN 68K LINK68 ignores anything past a backslash Y character so you can put comments in a command line See the example below Errors When LINK68 detects an error while processing it returns an error message in the follow
80. nocononononononnncnn cono cnn conc cn nennen rennen enne 8 2 Listings Listing 5 1 PPRIME PAS Deet UD ao ee 5 3 Listing 5 2 PPRIMBEB DIS 2 il eae 5 4 Listing 7 1 Main Program Example enne enne nnne innen tnnt nnne tenr entente entretenir en 7 2 Listing 7 2 Module Example oil ma a petente Deeg 7 3 Listing 7 3 Chain Demonstration Program 1 sess eene enne eene tenente tren 7 6 Listing 8 1 Pascal MT PEEK POKE Program 8 3 Listing 9 1 Calling BDOS Function 6 ener easi ier eks teres i EED E tenere 9 3 Listing 9 2 Calling BDOS Function ierit rer Dee Reti k rete pE ET Er iE 9 4 Listing 9 3 Using INLINE to Construct Compile time Tables eee 9 5 Listing 11 1 Main Program Body for File Transfer Program 11 2 Listing 11 2 File Transfer with BLOCKREAD and BLOCKWRITE eene 11 3 Listing 11 3 File Transfer with GNB and WNB eese nennen eene enne enne enne ene 11 4 Listing 11 4 File Transfer with SEEKREAD and SPEKWRIIR eene 11 5 Listing 11 5 File Transfer with GET and PUT AAA 11 6 1 Section Introduction To Pascal MT The Pascal MT Language Pascal MT is a high level block structured programming language It is formally based on the definition of standard Pascal as described in the International Standards Organization ISO standard 7185 The Pascal MT language is a superset of standard Pascal That is Pascal MT has all the features and constructs of standard Pascal as well as enh
81. ogical disk drive A through 0 or the currently logged in drive designated by Q You can also specify X the console or P the printer By default the compiler does not create a print file Q Quiet Operation The Q option tells the compiler not to display any unnecessary diagnostic messages on the console By default the compiler displays all diagnostic messages on the console Rd Relocatable File Location The Rd option tells the compiler to put the relocatable object code file on disk d d can be any logical disk drive A through O By default the compiler puts the relocatable object code file on the default currently logged in disk Td Temporary File Location The Td option tells the compiler to put the temporary files on disk d d can be any logical disk drive A through O By default the compiler puts the temporary files on the default currently logged in disk V View Procedures and Functions The V option tells the compiler to print at the console the name of each procedure and function it encounters in the source code file during Phase 0 Such procedure and function names can be useful for finding errors during Phase 0 By default the compiler does not print the names of procedures and functions during Phase 0 X Extended Relocatable Object File The X option tells the compiler to generate an extended relocatable object code file containing encoded source code line number information By default the compiler does not ge
82. or Checking The Pascal MT system supports two types of run time checking range and error exception Pascal MT Programmer s Guide Range and Error Checking checking By default the compiler disables range checking and enables error checking Range checking Range checking monitors array subscripts and subrange assignments It does not check when you read into a subrange variable When range checking is enabled the compiler generates calls to CHK for each array subscript and subrange assignment The _CHK routine leaves a Boolean value on the stack and error code number 4 see Error Checking in this section The compiler generates calls to ERR after the _CHK call If an error occurs ERR asks you whether it should continue or abort When range checking is disabled and an array subscript falls outside the valid range you get unpredictable results For subrange assignments the value truncates at the byte level Error checking By default the run time system checks for the following error conditions e integers and real numbers divided by 0 e real number under flow and overflow e string overflow The run time error checking routines set internal Boolean flags At run time these flags are loaded onto the stack along with an error code Then the predefined routine ERR is called to test the Boolean flag If there is no error the flag is FALSE so _ERR returns to the compiled code and continues execution If an error occurs th
83. or insert a new disk before you reenter the LINK68 command line Pascal MT Programmers Guide Internal Logic Errors LINK68 UNDEFINED SYMBOL S The symbol or symbols which are listed one per line on the lines following the error message are undefined Provide a valid definition and reassemble the source code before you reenter the LINK68 command line If the symbols are not referenced by the program you can use the UNDEFINED option in the command line Internal Logic Errors The following list identifies the LINK68 internal logic error messages LINK68 LINK68 LINK68 LINK68 LINK68 LINK68 INTERNAL ERROR IN lt procname gt TEXT SIZE ERROR IN lt filename gt RELATIVE ADDRESS OVERFLOW AT Lx IN lt filename gt SEEK ERROR ON FILE lt filename gt SHORT ADDRESS OVERFLOW IN lt filename gt UNABLE TO REOPEN FILE lt filename gt End of Appendix B C Appendix Run time Library Routines This appendix describes the run time library routines that are specific to the implementation for the Motorola MC68000 microprocessor and the CP M 68K operating system The following tables list the names of the routines and their purposes Knowledge of what these routines do can be helpful when you are disassembling a program Note You should not call these routines from your program because Digital Research does not guarantee parameter list compatibility between releases Table C 1 PASLIB Routines
84. ountered an error in the type of a parameter to a procedure This error can be caused by not having the parameters in the proper order for built in procedures It can also be caused by attempting to read or write pointers numerated types etc ERROR 126 NUMBER OF PARAMETERS DOES NOT AGREE WITH DECLARATION The number of parameters passed to the procedure does not match the number specified in the procedure s declaration ERROR 127 ILLEGAL PARAMETER SUBSTITUTION The type of a parameter passed to the procedure does not match the corresponding formal parameter in the procedure s declaration ERROR 129 TYPE CONFLICT OF OPERANDS The operands in the expression have incompatible types ERROR 130 EXPRESSION IS NOT OF SET TYPE The context of the expression requires the typ SET ERROR 131 TESTS ON EQUALITY ALLOWED ONLY SET types can only be compared for equality no other comparison is allowed Pascal MT Programmers Guide Compilation Errors ERROR 134 ILLEGAL TYPE OF OPERAND S The operands are not valid for this operator ERROR 135 E OF OPERAND MUST BE BOOLEAN The operands to AND OR and NOT must be BOOLI ENT TYPE MUST BE SCALAR OR SUBRANGI An element of a set must be a scalar of subrange type
85. rocessor s input and output ports through two features e INP and OUT e INPORT W and OUTPORT_W INP and OUT INP and OUT are two predeclared arrays of type BYTE that can be subscripted with INTEGER port number constants in the range 0 to 255 The syntax is lt variable gt INP lt INTEGER constant gt OUT lt INTEGER constant gt lt variable gt OUT can be used only on the left side of an assignment statement If it is not convenient to use a literal constant you can put the values you want to send out in a CASE statement For example CASE lt expression gt OF N1 OUT N1 lt value 1 N2 OUT N2 lt value 2 N3 OUT N3 value 3 where N1 N2 etc are literal constants If you assign values from INP to an INTEGER type use the following construct to zero the high order byte variable INP N SFF The following examples illustrate INP and OUT OUT 0 2 88 j INP portnum INPORT W and OUTPORT W You can also manipulate the processor s I O ports using the function INPORT_W and the procedure OUTPRT W Although they are present in PASLIB you must explicitly declare them as follows EXTERNAL FUNCTION INPORT_W lt portnumber gt INTEGER WORD EXTERNAL PROCEDURE OUTPRT_W lt portnumber gt INTEGER data WORD The following examples illustrate INPORT W and OUTPORT W inchar INPORT_W portnum OUTPRT_W portnum outchar OUTPRT_W 004F outchar Range and Err
86. s if any or insert a new disk before you reenter the LINK68 command line READ ERROR ON FILE filename The object file indicated by the variable filename does not have enough bytes The file either is incorrectly formatted or has been corrupted This error is commonly caused when the input to LINK68 is a partially assembled or compiled object file The assembler AS68 and some compilers create partial object files when they receive the disk full abort message while assembling or compiling a file Ensure that the file is a complete object file Reassemble or recompile the file before relinking SYMBOL TABLE OVERFLOW The object code contains too many symbols for the size of the symbol table Rewrite the source code using fewer symbols Reassemble or recompile the file before relinking UNABLE TO CREATE FILE filename Either the output file indicated by filename has an invalid drive code or the disk to which LINK6B is writing is full Check the drive code If it is correct the disk is full Erase unnecessary files if any or insert a new disk before you reenter the LINK6B command line UNABLE TO OPEN TEMPORARY FILE filename Either the file indicated by filename has an invalid drive code specified by the f option or the disk to which LINK68 is writing is full Check the drive code If it is correct the disk is full Erase unnecessary files if any
87. s composed of two files e MT68 68K e MT68 000 When you invoke the compiler CP M 68K loads the root module MT68 68K which performs the initial processing then chains to the second module MT68 000 to continue processing Compiler Operation The Pascal MT compiler processes a source code file in three separate steps called passes or phases e Phase 0 checks the syntax and generates a token file named PASTMP TOK This file contains an intermediate language tokenized version of the source code e Phase 1 generates a table of the symbols that are defined in the source code The compiler uses this symbol table when generating the relocatable object code file in Phase 2 e Phase 2 generates the relocatable object code f ile The compiler also creates temporary files on the same disk containing the source code file Under normal conditions the compiler deletes the temporary files when finished processing However if the compiler terminates abnormally the temporary files can remain in the directory When you compile the program make sure there is enough space on the disk or use the Td option to specify a different disk for the temporary files See Command line Options in this section Invoking the Compiler You invoke the compiler with a command line of the form MT68 lt filespec gt opt ions gt where lt filespec gt is the source code file to be compiled and the lt options gt are a list of optional parameters that contro
88. s the CP M 68K BDOS in your PROM This routine can jump around the standard code that simulates the BDOS and can simulate the following BDOS functions e Function 1 Console Input e Function 2 Console Output e Function 5 List Output The function number is in the DO register the data for output is in DI To simulate Function 1 return the data in the DO register All registers are free to use and the stack contains nothing but the return address Rewriting the NI Routine In a ROM based environment you might also want to rewrite the INI routine to shorten or eliminate the INPUT and OUTPUT FIB File Information Block storage which is needed for TEXT file I O compatibility Make sure any changes to INPUT and OUTPUT are also handled in RST read a string from a file and _CWT wait for EOLN to be TRUE on a file If your program does not do READLN or WRITELN calls and does not use the heap or overlays you can rewrite the _INI procedure in your program as PROCEDURE INI BEGIN END Note The distribution disks include source code outlines for the INI RNC WNC and GET routines that you can customize for your ROM based environment Pascal MT Programmer s Guide Linking Altered Routines Linking Altered Routines If you alter any of the standard run time routines to run in a ROM based environment remember to link them before PASLIB to resolve the references For example A gt link68 userproq mywnc myrnc myget myini pasl
89. se letters and digits separated by a hyphen represent variable information for you to select These items are described or defined more explicitly in the text 1f necessary literals Any item not in angle brackets or curly braces are literal Enter them just as they appear in text End of Section 1 2 Section Getting Started Hardware Requirements The Pascal MT system runs under the CP M 68K operating system using a Motorola MC68000 microprocessor The compiler and linker need at least 192K bytes of memory but it is recommended that your system have 256K bytes to handle large programs The size of a program developed with Pascal MT depends on the size of the source code and on the number of run time subroutines it uses For example compiling linking and then using the RELOC utility on the minimal program TEST1 PAS described later in this section generates a command file of 5K bytes Pascal MT System Files Digital Research supplies the Pascal MT system in a variety of disk formats When you receive your distribution disks be sure to examine the file named READ ME This file completely describes the contents of all the other files on each of the distribution disks The Pascal MI system uses a variety of filetypes described in Table 1 1 Table 2 1 Pascal MT System Filetypes Filetype Contents S assembly language source file for AS68 DIS disa
90. se type of a set must be a scalar or subrange type ETER EXPECTED This error occurs when an array is passed as a value parameter ERROR 174 PASCAL FUNCTION OR PROCEDURE EXPECTED The compiler expects a function or procedure at this lexical level ERROR 183 EXTERNAL DECLARATION NOT ALLOWED AT THIS NESTING LEVEL This error occurs when an EXTERNAL variable is declared anywhere except at the outermost global level EAL NUMBER The integer part of a REAL constant exceeds the valid range tah TOO MANY SCOPES OF NESTED IDENTIFIERS There is a limit of 15 nesting levels at compile time This includes WITH and procedure nesting Simplify the program and recompile ERROR 251 TOO MANY NESTED PROCEDURES OR FUNCTIONS There is a limit of 15 nesting levels at run time This error can also occur when more than 200 routines are in one compiled module Simplify and recompile Pascal MT Programmers Guide Compilation Errors OR PROGRAM BODY TOO LONG A procedure generated code that overflowed the internal procedure buffer The limit is 4096 bytes Reduce the size of the procedure and recompile ERROR 397 TOO MANY FOR OR WITH STATEMENTS IN A PROCEDURE There is a limit of 16 FOR or WITH statements in a single procedure Simpli
91. ssembled listing de fault DOC document file contains printable text in ASCII form ERR error message file output by compiler L68 library file contains subroutines LIS print file output by compiler 0 relocatable 68K format object file contains relocatable object code emitted by the compiler PAS Pascal source file contains source code in ASCII form the compiler also accepts SRC as a source file type TDT temporary initialized data file used by disassembler DIS68 normally erased at end of compilation TNP temporary file used by compiler normally erased at end of compilation TRL temporary object file used by disassembler DIS68 normally erased after compilation TSY temporary symbol table file used by disassembler DIS68 normally erased at end of compilation TXT text file contains text of messages output by compiler 68K command file runs directly under CP M 68K nnn hexadecimal n used for numbering overlays Pascal MT Programmer s Guide Installing Your System Installing Your System The first thing you should do when you receive your Pascal MT system is make a backup copy of all the distribution disks Note You have certain responsibilities when copying Digital Research products Read your licensing agreement When installing your own system you might find it convenient to copy only specific files from the distribution disks The way in which you configure your system depends on its actual hardware capabili
92. ties System with Hard disk Drive If your system has a hard disk the easiest way to configure it is to put the compiler files the linker and run time library files on one logical drive The compiler files are as follows e MT68 68K e MT68 000 e MTERRS TXT optional The linker and run time libraries are as follows e LINK68 68K e PASLI B L68 e BCDREALS L68 e FPREALS L68 e FULLHEAP 0 System with Floppy disk Drives If your system has two floppy disk drives you can use one disk for compiling and another disk for linking You can use other disks for the programming tools assorted source code and examples To configure separate disks for compiling and linking perform the following steps 1 Install the CP M 68K operating system the PIP utility and a text editor on two blank disks Label one disk as the compiler and the other as the linker Put the following files on the compiler disk e MT68 68K e MT68 000 e MTERRS TXT optional 2 Put the following files on the linker disk e LINK68 68K e PASLIB L68 e BCDREALS L68 e FPREALS L68 e FULLHEAP O This suggestion is one way of configuring your disks All the compiler modules must be on one disk For simplicity put all the related relocatable files on the same disk Note that compiler can run without the error message file MTERRS TXT If your compiler disk is short of space you can eliminate this file Pascal MT Programmer s Guide Compi
93. uced by any CP M 68K language processor including AS68 CB68K and the Digital Research C compiler LINK68 resolves all references to external symbols and concatenates the object code files in the order you specify in the command line The entry point of the resulting command file is the first instruction in the first object code file Figure 4 1 illustrates LINK68 operation Object file 1 Object file n PASLIB Link68 Command file Or OtherLibraries Overlay file Input Command file Figure 4 1 LINK68 Operation Run time Libraries Although the Pascal MT compiler generates native machine code each implementation requires a library of run time routines to handle file processing and other features that are not supported by the native hardware PASLIB The main run time library is called PASLIB for Pascal Library All I O is per formed and all set variables are manipulated with PASLIB routines Console I O is assumed by the initialization routine _INL so the I O routines are always loaded You can avoid this by writing a replacement _INI routine and linking it before linking PASLIB to resolve the INI reference Other Libraries Other libraries contain routines that are required by any program using real numbers in either BCD or floating point format or per forming calculations with transcendental functions or random access I O operations Table 4 1 summarizes these libraries Appendix C contains a complete list of the routi
94. y in each of the chained Pascal MT Programmer s Guide Chaining programs so that they have the same location and size Using the absolute variable method you typically define a record that is used as a communication area then place the record at the same absolute location in each module Maintaining the Heap No special facilities are needed to maintain the heap across the chain However files cannot remain open across a chain If you want to leave something open you must use overlays not chaining Listings 7 3a and 7 3b list two example programs that communicate with each other using absolute variables The first program chains to the second program which prints the results of the first program s execution Listing 7 3 Chain Demonstration Program 1 PROGRAM chain_1 Program 1 in chain demonstration TYPE comm_area RECORD igk INTEGER END VAR globals ABSOLUTE 8000 comm area this address is arbitrary it may not work on your system chain file FILE title string BEGIN Main program 41 title F CHAIN2 68K WITH globals DO BEGIN i 3 j 3 k i 3 END IF IORESULT 255 THEN BEGIN WRITELN Unable to open CHAIN2 68K EXIT END CHAIN chain file END End chain_1 Pascal MT Programmer s Guide Chaining Listing 7 3b chain Demonstration Program 2 PROGRAM chain_2 Program 2 in chain demonstration TYPE comm_area RECORD i j k INTEGER END VA
95. y of a program called PPRIME which counts prime numbers Pascal MT Programmer s Guide Sample Disassembly Listing 5 1 PPRIME PAS PROGRAM pprime Uses sieve of Eratosthenes CONST size 8190 VAR flags ARRAY O size OF BOOLEAN i k INTEGER prime INTEGER count INTEGER iteration INTEGER BEGIN Main Program count 0 writeln Do 10 iterations FOR iteration 1 TO 10 DO BEGIN count 0 FILLCHAR flags SIZEOF flags CHR TRUE FOR i 0 TO size DO IF flags i THEN BEGIN prime i i 3 k i prime WHILE k lt size DO BEGIN flags k FALSE k k prime END count count 1 END END WRITELN count Primes END Main Program Pascal MT Programmer s Guide Sample Disassembly Listing 5 2 PPRIME DIS Address Opcode Mneumonic Operands 00000000 globl _win external 00000000 globl _crl external 00000000 globl _sfb external 00000000 globl ini external 00000000 globl _wrs external 00000000 globl _hlt external 00000000 globl flags external 00004000 globl 1 external 00003FFE globl k external 00004002 globl prime external 00004006 globl iteratio external 00004004 globl count external 00000000 globl output external 00000000 globl fillchar external 00000000 6000 bra 0004 00000004 4EB9 jsr ini 1 0 PROGRAM pprime Uses sieve of Eratosthenes zi 2 0 3 0 CONST 4 1 size 8190 5 1 6 1 V

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