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programming in basic - National Open University of Nigeria

1. arent NIVERSITY OF gt ie ee A NATIONAL OPEN UNIVERISITY OF NIGERIA SCHOOL OF SCIENCE AND TECHNOLOGY COURSE CODE CIT 132 COURSE TITLE PROGRAMMING IN BASIC COURSE GUIDE CIT 132 PROGRAMMING IN BASIC Course Team Course Writer Prof R O Ayeni Programme Leader Course Coordinator NATIONAL OPEN UNIVERSITY OF NIGERIA National Open University of Nigeria Headquarters 14 16 Ahmadu Bello Way Victoria Island Lagos Abuja Office 5 Dar es Salaam Street Off Aminu Kano Crescent Wuse II Abuja e mail centralinfo nou edu ng URL www nou edu ng Published by National Open University of Nigeria Printed 2014 ISBN 978 058 906 6 All Rights Reserved CONTENT PAGES A A iv What you will Learn in this Course oooooocccccccccncccnooo iv Working through this Course ca iv AASSESSINICHIO ti A a E o Sa iv COMO VERE O iv How to get most from this Course ceeeeeeeee v O E T vi INTRODUCTION CST Programming in BASIC is an introductory course in programming in BASIC The second part will cover all other essential topics The BASIC language was originally designed as a simplified version of FORTRAN for use in teaching programming From the simple beginnings the language has grown to become a very popular multi purpose language available on a wide variety of machines WHAT YOU LEARN IN THIS COURSE An electronic computer may be called an electronic brain but its functions
2. 10 15 20 25 10 LETS 0 15 FORK 1TO 50 20 LETS S A K B K 25 NEXTK Array Merge Ai Bi A2 Boy a could be used 10 LETK 1 15 FORI 1TO 10 20 LETC K A 25 LETK K 1 30 LETC K B I 30 LETK 1 FOR I 1 TO 20 STEP 2 LET C D A K LET C I 1 B K LETK K I 35 LETK K 1 35 NEXT I 40 NEXTI 10 FORI 1TO10 2 I 1 generates the odd entries of C 15 LETC 2 I 1 A I 2 I generates the even entries of C 20 LETC 2 i b 1 25 NEXTI Array Search Assume array A contains 10 grades and we want to know the number of grades over 60 The following code could be used 10 LETK 0 K is used to count grades over 60 15 FORI 1TO 100 20 IFA lt 60THEN 30 IfA D lt 60 skip the counting of grades over 60 but stay in the 25 LETK K 1 loop by connecting to the NEXT I statement 30 NEXT I 4 0 CONCLUSION Here you are introduced to array manipulation 5 0 SUMMARY Arrays could be manipulated in several ways 6 0 TUTOR MARKED ASSIGNMENT What will be the content of each element of the array Y after the following 10 DIMY 10 20 LETY 1 1 30 LETY Q 2 40 FORI 3TO10 50 LETY Y 1 Yd 2 60 NEXTI 7 0 REFERENCE FURTHER READING Boillot M and Horn L W BASIC aso Edition West Publishing Company New York UNIT 5 END OF FILE CONDITIONS CONTENTS 1 0 Introduction 2 0 Objectives 3 0 Main Contents 3 1 End of File Conditions 4 0 Conclusion 5 0 Summary 6 0
3. To debug a program means to take the bugs out of a program i e to correct it consider the following program 10 15 20 25 RUN 3 3 LET H 40 The user types letter O instead of zero LEM R 5 50 LEM is typed instead of LET LET P H R Also there is an error due to the omission of PRINT instruction END Number Representation Constants in BASIC can be expressed in two different notations l Decimal notation with or without decimak points Examples 45 67 12 3 11240 48216 3 Exponent notation where the character E is used to represent the decimal base 10 followed by a two digit with or without sign to represent the exponent power Examples 10 LET X 3 456 E 2 where 3 456 E 2 3 456x10 12 LET Y 3 E 3where 3 E 3 3 x 10 3 003 14 LETZ 1 23EO where 1 23 EO 1 23 x 10 1 23 On output as a result of the PRINT statement the BASIC will use E notation to represent a constant if the value of the constant is outside a certain range The range will vary from one computer to another Example 10 LET X 123456 20 LET Y 123456 789012345 30 LET T 0003245 35 LET Z 22 1 E3 45 LET V 001 48 LET W 01 49 PRINT X Y T Z V W RUN 123456 1 2345679E 14 3 245E 4 22100 1E 03 01 3 4 Programming Example Income Calculation Mr V is a widower with three children aged 12 10 and 19 His monthly salary is 1 523 36 His monthly contribution to a retirement plan is 6 6 perce
4. Xn 5 4X X n n 1 SELF ASSESSMENT EXERCISE 1 Write a program to input N grades and compute the grade average and the standard deviation a negative grade indicates the end of grades To compute the standard deviation it is necessary to l Accumulate the sum of grades A 1 X2 Xn Ze Accumulate the sum of the square of each grade Based on the above we can use the program below l LET N 0 N counts grades 5 LET Q 0 set variable to accumulate the sum of the square of each grade to 0 10 LETS 0 setvariable to accumulate sum of grades to 0 20 INPUTEG Read one grade each lime through the loop 24 IFG lt 0GOTO 40 25 LET S S G Accumulate sum of grades 30 LET Q Q Q G G Accumulate the sum of the square of each grade 34 LETN N 1 Count each grade 35 GOTO20 Go and accept next grade 37 REMCUMPUTE THE STANDARD DEVIATION D 40 LET D N Q S S N N 1 1 5 45 PRINT STANDARD DEVIATION D 50 PRINT AVERAGE GRADE S N 60 END SELF ASSESSMENT EXERCISE l To what depth or level can loops be rested 4 0 CONCLUSION Nested loops are useful in solving standard deviation 5 0 SUMMARY A good report is one which is self explanatory self contained and organized in a way that allows the reader to capture the essence of the report as well as the detail 6 0 TUTOR MARKED ASSIGNMENT Using the previous problem calculate i mean ii standard deviation of the following data X Marks 21 42 53 60 73 81 Fr
5. 25 GO TO 15 Unit 4 Exercise Write the BASIC code for the following Answer 10ifa gt B THEN 40 20 LET C C 30 PRINT A MODULE 3 UNITS 3 Exercise What output is expected from the following 10 FOR I 2 TO 10 STEP 2 20 FOR J 10 TO 1 STEP 1 30 FOR PRINT I J 40 NEXTJ SO NEXTI SOLUTION I J 2 10 Zo 9 2 1 4 10 4 9 4 1 10 10 10 9 10 1 OUTER LOOP Since 1 varies from 1 to 3 the loop will be processed three times INNER LOOP The inner loop will cause the PRINT statement to be processed 4 times Since the outer loop is processed altogether 12 times 10 FOR I 1 TO 3 FOR J 1TO4 PRINT LJ NEXT J 20 NEXTI The result produced by the above code I J l l First time through the inner loop 1 2 outer loop index I 4 l 3 l 4 2 1 2 2 Second time through the inner loop 2 3 outer loop index I 2 2 4 3 l 3 2 Third time through the inner loop 3 3 outer loop index I 3 3 4 Exercise State whether the following are valid or invalid FOR NEXT loops and give reasons if invalids 1 FOR I 1 TO 10 FOR I 1T0O 6 PRINT I NEXT I Answer Invalid nested loops may not use the same variable 2 FOR L 8 TO 1 STEP 1 FOR K 1 TO 3 FORL L 1 NEXT K NEXT L Answer Invalid synthax statement FOR L L 1 is incorrect L UNIT 4 Answer It depends on the manufacturer s BASIC It is safe to assume that all BASIC systems will allow a depth of three rested loops 2 What happen
6. UNIT 3 NESTED LOOPS CONTENT 10 Introduction 2 0 Objectives 3 0 Main Contents 3 1 Nested loops 40 Conclusion 5 0 Summary 6 0 Tutor Marked Assignment 7 0 Reference Further Reading 2 0 4 0 CONCLUSION Repeating a loop for a certain number of times is an example of a loop within a loop 5 0 SUMMARY In nested loops a complete loop is part of the body of another loop In such cases each pass in the outer loop causes the inner loop to run through its complete cycle Exercise see below another sheet 6 0 TUTOR MARKED ASSIGNMENT A DATA statement contains an unknown number of grades 0 100 with a maximum of 100 entries in the DATA statement including the trip record Write a program to determine the percentage of passing grades Passing grades are grades above 73 7 0 REFERENCE FURTHER READING M Boillot and L W Horn BASIC Third Edition West publishing Company New York UNIT 4 APPLICATION OF NESTED LOOPS IN STATIATICS CONTENT 1 0 Introduction 2 0 Objectives 3 0 Main Contents 3 1 Standard Deviation 40 Conclusion 5 0 Summary 6 0 Tutor marked Assignment 7 0 Reference Further Reading 1 0 NTRODUCTION Here you will solve the standard deviation problem using rested loops 2 0 OBJECTIVE At the end of the loop you would be able to write a program to compute the standard deviation of M grades 3 0 MAIN CONTENTS 3 1 Standard Deviation The general formula to compute the standard for n grades x1 Xn is SD Mx X
7. screen for visual display The memory control and arithmetic logical units are collectively called the central processing unit CPU 3 1 2 Computers Programs The set of instructors that control the computer is called a program A program can be executed by the computer only when it is stored in the computer s memory and is in machine language code Machine language is the only language the computer can understand It is a language in which arithmetic logical operations are represented by machine recognizable numeric codes and in which memory locations containing data and program instructions are represented by numeric addresses Machine language vary from one computer manufacturer to another and as such they are machine dependent other types of languages called high level languages have been developed to allow the user to formulate problems in a much more convenient and efficient manner High level languages are machine independent programs written in such languages can be processed on any type of computer However high level languages must be ultimately translated into machine language before they can be executed by the computer Special programs called language translators or compilers have therefore been developed to provide this translation service BASIC Beginner s All purpose Symbolic Instruction Code is an example of a high level language SELF ASSESSMENT EXERCISE 1 What is the name of the computer
8. 107 values one might visualize the elements of X Z and J as follows Array X X 1 X 2 X 3 X 4 XS X 6 Array Z Z 1 Z 2 Z 19 Z 20 Array J Jd JQ abn 4 0 CONCLUSION Here you learn how to use the DIM Statement 5 0 SUMMARY Subscripts are used with array names to locate specific elements of an array 6 0 TUTOR MARKED ASSIGNMENT What will be the content of each of element of the array Y after each of the following l 10 DIM Y 10 20 FORI ITO10 30 LET Y I I 40 NEXT I 2 10 DIM Y 10 20 FOR I I TO 10 30 LETY 11 1 40 NEXTI 7 0 REFERENCE FURTHER READING Boillot M and Horn L W BASIC 3BD Edition West Publishing Company New York UNIT 4 ARRAY MANIPULATION CONTENTS 1 0 Introduction 2 0 Objectives 3 0 Main Contents 3 1 DIM Statement 4 0 Conclusion 5 0 Summary 6 0 Tutor Marked Assignment 7 0 Reference Further Readings 1 0 INTRODUCTION Here you will be introduced to manipulation of arrays 2 0 OBJECTIVES At the end of this unit you would be able to manipulate arrays 3 0 MAIN CONTENTS 3 1 Arrays Manipulation When working with arrays it is often necessary to initialize arrays to certain values to create duplicate arrays to inter change elements within arrays to merge two or more arrays into one to search or to accumulate array entries to sort arrays etc In this section you will be introduced to certain commonly used
9. Expressions and the AND OR Logical Operators Unit 5 The Counting Process and Basic Statements Module 3 Unit 1 The Accumulation Process and Statement FOR NEXT Unit 2 The Accumulation Process Unit 3 Nested Loops Unit 4 Application of Nested Loops in Statistics Unit 5 Project Module 4 Unit 1 One dimensional Arrays Unit 2 Use of Arrays Unit 3 DIM Statement Unit 4 Array Manipulation Unit 5 End of File Conditions HOW TO GET MOST FROM THIS COURSE In distance learning study units replace the University lecture This is one of the great advantages of distance learning you can read and work through specially designed study materials at your own pace and at a time and place that suit you best Think of it as reading the lecture instead of listening to the lecture Just as a lecturer might give you in class exercise your study units provide exercises for you to do at appropriate points The following hints are useful L Read this course guide schedule Za Organize a study schedule 3 Once you have created you own study schedule do everything you can to stick to it The major reason that students fail is that they get behind their course work 4 Turn to a unit and read the introduction and the objectives of the unit 5 Use the order of the units 6 Practice the exercises on a computer Jx Debug your programs 8 Review the objectives for each unit at the end of the unit 9 Do the Tutor Marked Assignments 10 Start
10. Tutor Marked Assignment 7 0 Reference Further Readings 1 0 INTRODUCTION Sometimes data may have to be read into arrays from an unknown number of records Here you will learn how to handle such cases 2 0 OBJECTIVES At the end of this unit you would be able to read data into array from unknown courses 3 0 MAIN CONTENTS 3 1 End of File Conditions Sometimes data may have to be read into arrays from an unknown number of records For example someone may give you a large data file to read into an array A since the DIM statement must specify an integer constant for the size of the array the programmer must decide ahead of time what he thinks is the maximum number of locations he will need for the array Consider the following problems Each record of data file contains a student s number and two test scores Read into an array N the student s number and store in array the average of each student s score Print the number of records processed and the average of all grades not more than 100 students records are expected A negative value for the student s number terminates the data file A program to solve the problem is as follows 10 15 20 25 30 35 40 42 45 50 55 65 70 75 80 85 90 92 95 4 0 DIM S 100 N 100 REM LETSI 0 LETI 0 REM READ N1 T1 T2 IF N1 lt 0 THEN 70 LETI 1 1 LETN D n1 LET S I T1 T2 2 LET S1 S1 S I GO TO 35
11. and problem solving ability depend on the intelligence of a human being who directs and controls the machine This person is called a programmer and is responsible for giving the computer a set of instructions consisting of the necessary steps required to derive a solution to a given problem The set of instructions that control the computer is called a program The purpose of this course is to teach you how to program in BASIC The course will i Introduce you to basic hardware and software il Teach you how to program in BASIC to a certain level iii Teach you how to use computer to process information WORKING THROUGH THIS COURSE The major components of the course are l Course Guide 2 Modules 3 Study Units 4 Further Reading which is recommended ASSESSMENT There are two aspects to the assessment of the course continuous assessment and final examination The tutor marked assignments will form the continuous assessment So you must do all and submit all to your tutor for grading The date and place of final examination will be communicated to you by NOU COURSE OVERVIEW Module 1 Unit 1 Computers Hardware and Software Unit 2 Computing Arithmetic and Logical Operation Unit 3 Basic Statements Unit 4 Basic Statements Continued Unit 5 Listing and Debugging Programmes Module 2 Unit 1 Flowcharting and Basic Statements Unit 2 The Decision Statement Unit 3 The IF Statement the REM Unit 4 Logical
12. be evaluated If S 1 AND M 1 lt gt 0 OR S 3 AND M1 gt 4 THEN PRINT S M1 3 2 On Go To Statement The ON GO TO statement is a useful and convenient statement that allows transfer to many different points in a program Line number ON expression GO TO line number line Another form of the If statement is line number on expression GO TO line number 1 line number n The rule is the following If the value of the expression is 1 control is transferred to line number 1 If the value of the expression is 2 control is transferred to the line number 2 Examples 20 ON N GO TO 3 57 100 4 IF N 3 control is transferred to 100 15 ON J 2 K GO TO 30 10 IF J 2 K 1 go to statement 30 300N Y 1 GOTO 10 20 60IFY 4 1 2 3 go to 10 20 and 60 respectively 4 0 CONCLUSION A complete program is useful in understanding how to use ON GO TO as we shall show later 5 0 SUMMARY Here you learn how to use AND OR Logical operators and ON GO TO 6 0 TUTOR MARKED ASSIGNMENT Final grades in a course are determined by adding scores obtained on there tests Ti T2 and T3 students get a PASS grade if the sum of the three scores is above 186 and a FAIL otherwise write a program to enter three scores and determine the grade Print the input scores the average and the final letter grade 7 0 REFERENCE FURTHER READING Boillot and Horn BASIC 3 Editor UNIT 5 THE COUNTING PROCESS AND BASIC STATEMENTS READ DATA REST 0 RE PRINT USI
13. instruction Calculations Perform calculations using the arithmetic unit and place results in desired memory location For example the instruction Let M 5 F will cause the control unit to fetch the value contained in the memory location F and activate the arithmetic unit to multiply that value by 5 The final result is then stored in memory location P product Unconditional branding Take the next instruction from a specified memory location For example the instruction Go to 700 cause the control units to fetch the next instruction from location 70 rather than from the next sequentially numbered location Unconditional branding then simply means transfer directly to a particular instruction in memory Output Copy a value fro a memory location onto the output medium For example the instruction PRINT F P will cause the contents of F and P to be written out on the output pad Termination Cease execution of instructions for this program and wait for a new program to be loaded into memory For example the instruction END causes the program to terminate No more instructions in this program are executed Sample Program Here we wish to calculate and write out an amount of pay owed an employee who is paid N 50 per hour with time and N 100 for all hours in excess of 40 INPUT F IFF gt 40GOTO 5 Let P 50 F GOTO6 LET P 2000 100 F 40 PRINT P F END AA E Oe 4 0 CONCLUSION Here you have been introduced to the wo
14. presses the RETURN key This 30 PRINT ENTER RATE causes the name entered on the screen to 35 INPUT R be stored in memory location N 40 REM 45 IF H gt 40 GO TO 65 If condition is true transfer to 65 to 50 LETP H R compute overtime otherwise H lt 40 the computer automatically goes to the 2 PTOS next instruction 50 60 REM 65 LETP1 40 R 70 LET V H 40 The transfer to line 65 is made only if the condition H gt at line 45 is true 75 LEEPZSV RPS 80 LET P P1 P2 P1 is the first 40 hours at regular rate 85 PRINT OVERTIME HOURS V Vis the overtime pay 90 PRINT OVERTIME PAY P2 D is the final pay 95 PRINT PAY TO N P Line 90 or as aresult of line 55 98 GO TO 10 When the input instruction is executed run the following happens l The computer types a question mark on the terminal The computer stops the user at this pint should enter a value for each of the variables specified by the INPUT statement These values are then stored in the computer memory in the specified memory locations when the ENTER RETURN key is pressed 10 PRINT ENTER AGE PLEASE Note that when the input Instruction is typed and the user presses ENTER key to get to the next instruction 20 the computer does not display a and it does not stop This only happens when RUN is typed 15 INPUT X 20 PRINT YOU FIBBER YOUR ARE NOT 25 PRINT X YEARS OLD RUN ENTER AGE PLEASE 41 entered by user Output produ
15. print results Example 3 Write the code to input a code with value either 1 or 2 If the code equals 1 compute the circumference of a circle of radius 1 34 if the code has value 2 compute the area of a circle of radius 3 2 Print results 10 INPUT K NO 20IFK 1GOTO 50 Es A 3 14 3 212 Line 25 is executed if K is not equal to 1 30 PRINT AREA A 40 GO TO GO YES IfK 1 computer circumference of circle 50 C 2 3 13 1 344 55 PRINT CIRC C 90 END Write the BASIC code for the following flowcharts Eu Yes No PRINT Vb 4ac Answers l 10 If x gt 0 GO TO 99 20 PRINT X 99 END 2 10IFa Xx12 b X gt C 0THEN 99 20 PRINT B12 4 A 5 99 END 4 0 CONCLUSION If the condition specified is true control will be transferred to a block code that does not immediately follow the if statement 5 0 SUMMARY The line number specified by the GO TO statement in the If instruction need not physically follow the If statement 6 0 TUTOR MARKED ASSIGNMENT l Explain what would happen in example 3 above if at line 20 we had If K 1 THEN 25 Ze Write the BASIC code for the following flowcharts YES E 7 0 REFERENCE FURTHER READING Boillot and Horn BASIC 3 Edition UNIT 3 THE IF STATEMENT REVISITED THE REM STATEMENT CONTENTS 1 0 Introduction 2 0 Objectives 3 0 Main Contents 3 1 If Statement Revisited 3 2 The Rem Statement 4 0 Conclusion 5 0 Summary 6 0 Further reading 7
16. the next unit SUMMARY CST is the first two semester course in BASIC programming At the end of the first course you will be able to use the computer to do some exercises in the course and hope that you will find the course interesting and useful MAIN COURSE ONTENT odule 1 nit 1 nit 2 nit 3 nit 4 nit 5 odule 2 nit 1 nit 2 nit 3 nit 4 nit 5 odule 3 nit 1 nit 2 nit 3 nit 4 nit 5 odule 4 nit 1 nit 2 nit 3 nit 4 nit 5 eeccocococoooooooococooooooooooooooooooooooooooooooooooooo Computers Hardware and Software Computing Arithmetic and Logical Operation Basic Statements cc cece eee cece en Basic Statements Continued 68 Listing and Debugging Programmes Flowcharting and Basic Statements The Decision Statement cece cece cee ees The IF Statement the REM Logical Expressions and the AND OR Logical PEO ir The Counting Process and Basic Statements The Accumulation Process and Statement FORINEX Tano Des The Accumulation Process ooomoocccmooooo Nested oops is Application of Nested Loops in Statistics PLOT E rra One dimensional Arrays 00oooocccccccnncccnnos A ETERA DIM Statement asociado Array Manipulation oooocccncccocconconcconcnnnnnns End of File Conditions 0 PAGES jua
17. the two represent no new programming concepts They are used primarily for loop control The usual procedure for loop control is to initialize a counter to a certain value then increment that counter by a constant and finally compare the counter to the terminal value for loop exiting Using the FOR NEXT statements the user specifies in the FOR statement the initial incremental and terminal value of the counter index and identifies the range of the loop by making the NEXT statement the last statement of the procedure to be repeated The general form of the FOR statement is Line number FOR index e Toe STEP e The FOR statement must always be used in conjunction with l The NEXT statement WITHOUT FOR NEXT WITH FOR NEXT 05 DATA 60 70 80 05 DATA 60 70 80 06 DATA 20 100 06 DAPO 20 100 10 LETS 0O 10 LETS 0 15 LETI 1 20 FOR1 1T0O5 20 If 1 gt 5 then 45 25 READG 25 Reading 30 LETS S G 30 LETS STG 40 NEXT 35 LET 1 1 1 45 LETA S 5 40 GOTO 20 45 LETA S 5 50 PRINTA 50 PRINTA 55 STOP 55 STOP 99 END 99 END S is used as an accumulation to add to all grades It is set to zero initially Process the next two statements 5 times as I ranges from to 5 is initially 1 As long as it does not exceed 5 read a grack and add to it to 5 thereby forming a running sum of grades s added to 1 automatically and the loop is repeated until 1 gt 5 at which time the average is computed and printed SELF ASSESSMENT EXER
18. 0 Reference Further Reading 1 0 INTRODUCTION The main different between counting and accumulating is that instead of repeat adding a constant example 1 to a counter a variable is added repeatedly to an accumulator 2 0 OBJECTIVE At the end of the unit you would be able to perform an accumulation process 3 0 MAIN CONTENTS 3 1 The Accumulation Process You now know how counting in BASIC is made possible by repeated execution of such statements as 1 1 1 Where 1 is initial set a beginning value Each line 1 1 1 is executed The value 1 is added is added to the counter 1 which then takes a successive value 1 2 3 4 and so on if it is initially set to zero Counting Accumulating DATA 60 70 80 20 100 Each time 1 is added to the previous count C Each time a new Grade G is added to the current sum S We consider an example on accumulation process and statements for next 10 LET S OInitialize sum to 0 8 um is as an accumulator to accumulate all grades 20 FOR 1 1 TO 5 Process statements 25 to 30 five times 25 READ G Read a grade G 30 LETS STG The new sum is equal to the old sum plus the grade just read The first time around the loop sum plus grade 0 60 hence new sum 60 The second time around sum plus grade 60 70 130 Each time through the loop we are adding the grade just read to form a running or partial sum of grades When five grades have been read the sum of five grades will have b
19. 0 Tutor marked assignment 1 0 INTRODUCTION In many BASIC systems the If statement is some what more powerful than has been previously shown as gen will learn here 2 0 OBJECTIVES At the end of this unit you would be able to use IF statement further use REM statement 3 0 MAIN CONTENTS 3 1 The If Statement Revisited Another form of the If statement is line number if condition THEN statement Where the statement can be an input output instruction a replacement statement or a STOP If the condition is met the statement and only one is executed and the control is transferred to the condition is not met control is transferred to the statement following the If This If statement can be visualized as follows Condition true Next statement Statement IF condition THEN statement 15 next statement Q Example 1 10 IfA lt B THEN K K 1 If A gt B the statement K K 1 will executed after which statement 15 If A 4 GO TO 67 15 will be executed If A gt B 15 will be processed next Example 2 10 If C lt gt 0 THEN PRINT A IF C 0 print the value A and stop otherwise C 15 STOP 0 stop Since only one statement is permissible after the THEN keyword the following code would be needed to account for the following flowchart 10 IF A gt B GO TO 25 20 PRINT A 25K 5 3 2 The REM Statement The general form of REM statement is line number REM literal characters Where REM remar
20. 4 0 CONCLUSION 5 0 SUMMARY 6 0 TUTOR MARKED ASSIGNMENT Modify Figure 3 to handle 10 100 grades 7 0 REFERENCE FURTHER READING Boillot M and Horn L W BASIC chars Edition West Publishing Company New York UNIT 3 DIM STATEMENT CONTENTS 1 0 Introduction 2 0 Objectives 3 0 Main Contents 3 1 DIM Statement 4 0 Conclusion 5 0 Summary 6 0 Tutor Marked Assignment 7 0 Reference Further Readings 1 0 INTRODUCTION Here you will be introduced the DIM statement 2 0 OBJECTIVES At the end of this unit you would be able to use the DIM Statement 3 0 MAIN CONTENTS 3 1 DIM Statement The general from of the DIM statement is Line number DIM variable limit variable limit Where DIM is a BASIC keyword variablel variable 2 Are names of the various arrays any valid variable name and limit 1 limit 2 Are unsigned integer constants representing the desired number of memory locations reserved for each array This does not mean that the reserved locations must be used when processing the array Array subscripts may vary from 1 to the limit declared in the DIM statement and may not exceed that limit Any array used in a program must first be declared in a DIM statement Any number of arrays may be declared in a DIM list For example DIM X 10 Z 1 20 J 107 declares X and 21 and J as arrays In this case the array X may contain up to 10 elements the array Z1 up to 20 elements and the array J up to
21. CISE i How would you modify the program to compute the average of 10 grades ii Answer Change line 20 to 20 If 1 gt 10 then 45 or 20 FOR 1 1 TO 10 Change line 45 to 45 LET A 5 10 3 1 1 The General Form of NEXT Statement Line number NEXT index Where NEXT is the key word and index is a variable name that must be the same name as the variable specified for the index in the corresponding FOR statement It is used to indicate the physical end of a loop initiated by a FOR statement 10 FOR 1 El TO E2 STEP E3 90 NEXT1 To make your program more readable it is a good idea to indent all statements between the FOR and NEXT statements 4 0 CONCLUSION Any BASIC program can be written without the FOR NEXT statement The purpose of these two statements 1s one convenience to the programmer 5 0 SUMMARY For next are used primarily for loop control 6 0 TUTOR MARKED ASSIGNMENT What is the expected output of each of the following program Tabulate the Program 10 DATA 20 40 70 90 15 LET A 0 20 FOR 1 1TO4 30 READX 40 LET A A X 50 NEX 1 60 PRINT A 70 END 7 0 REFERENCE FURTHER READING M Boillot and L W Horn BASIC Third Edition West publishing company New York UNIT 2 THE ACCUMULATION PROCESS CONTENT 1 0 Introduction 2 0 Objectives 3 0 Main Contents 3 1 The accumulation Process 3 2 Accumulation and FOR NEXT 3 3 The FOR NEXT Revisited 40 Conclusion 5 0 Summary 6 0 Tutor Marked Assignment 7
22. If the value s greater than or equatu4 the block X 4 is executed and transfer is made to the entry point labeled B if X is not greater than or equal to 4 the block Y x z is executed and transfer is made 15 the entry point 25 which contains the PRINT instruction 40 CONCLUSION In a flowchart it is possible to have many connectors 5 0 SUMMARY Here you are introduced to BASIC statements INPUT and GO TO You also learn how to write flowcharts 6 0 TUTOR MARKED ASSIGNMENT Determine the output produced by each of the following flowcharts 7 0 REFERENCE FURTHER READING Boilot and Horn BASIC 3 Edition UNIT 2 BASIC STATEMENTS THE DECISION STATEMENT CONTENTS 1 0 Introduction 2 0 Objectives 3 0 Main Contents 3 1 If then 4 0 Conclusion 5 0 Summary 6 0 Further reading 7 0 Tutor marked assignment 1 0 INTRODUCTION The central processing unit CPO has a logical unit which allows the computer to compare one number with another as well as one alphanumeric string with another This decision making capability is available to BASIC through the If statement which allows the computer to transfer to a nonsequentral instruction 2 0 OBJECTIVES At the end of this unit you would be able to use IF THEN statement 3 0 MAIN CONTENTS 3 1 If Then Then general form of the If statement is line number if condition GO TO THEN transfer line number Where the condition consists of two arithmetic express
23. K Cost in watts per kilo watt hour 7 0 REFERENCE FURTHER READING Boillot and Horn BASIC 3 Edition MODULE 2 Unit 1 Unit 2 Unit 3 Unit 4 Unit 5 Flowcharting and Basic Statements The Decision Statement The IF Statement the REM Logical Expressions and the AND OR Logical Operators The Counting Process and Basic Statements UNIT 1 FLOWCHARTING AND BASIC STATEMENTS CONTENTS 1 0 Introduction 2 0 Objectives 3 0 Main Contents 1 0 3 1 Input statement 3 2 The unconditional transfer statement go to 3 3 Flowcharting Conclusion Summary Further reading Tutor marked assignment INTRODUCTION Flowchart is a set of symbols linked by directed lines which represent a sequence of operations for flowchart is essentially a pictorials representation as sort of visual outline of the sequence of steps that must be taken in order to solve a particular problem 2 0 OBJECTIVES At the end of this unit you would be able to use input statement go to statement draw a flowchart of simple programs 3 0 MAIN CONTENTS 3 1 Input Statement Below is the program to compute each employee of a company s gross pay 05 REM PAYROLL PROGRAM The REM instruction is to document the 10 PRINT ENTER NAME program when the program is Ron the INPUT instruction line 15 will cause the 20 PRINT ENTER HOURS computer to stop and display a question 25 INPUT H mark on the screen The user enters a name and
24. LETA SI PRINT AVERAGE A Array S is reserved for the scores N for student numbers SI is used to accumulate all grades I counts all students records exclusive of the trip Read student number and two scores If last record compute average etc Increase student counter by 1 State student number in array N Compute each student average Accumulate sum of grades Go back and read a new student s record Compute average PRINT NO SUTDENTS I DATA III 60 50 DATA 222 60 40 DATA 3 0 0 END CONCLUSION Data file student number and two grades Here you are introduced to End of File conditions and how to handle such cases 5 0 SUMMARY End of File Conditions could be handled as stated in the example above 6 0 TUTOR MARKED ASSIGNMENT Devise a code to search an array G to print the largest grade 7 0 REFERENCE FURTHER READING Boillot M and Horn L W BASIC 3RD Edition West Publishing Company New York MODULE 1 UNIT 1 Exercise How would the execution of the program be affected by replacing statement in location 7 by GO To 1 Answer After procession one record the system will input another MODULE 2 UNIT 1 Exercise What is a flow chart Answer A flowchart is a pictorial representation of the logic used to solve a particular problem UNIT 3 Exercise Predict the output of the suit six line of the following 10I 1 15 PRINT TAB D 201I I A
25. NG CONTENTS 1 0 Introduction 2 0 Objectives 3 0 Main Contents 3 1 Read Statement 32 Data Statement 4 0 Conclusion 5 0 Summary 6 0 Tutor marked assignment 7 0 Reference Further Reading 1 0 INTRODUCTION This unit introduces a new programming concept counting which is of great importance in writing programs 2 0 OBJECTIVES At the end of this unit you would be able to use the programming concept counting THE COUNTING PROCESS AND BASIC STATEMENTS 10 REM THE RESPONSES ARE 11 REM RECORDED ON THE 12 REM DATA STATEMENTS 15 LETI 0 20 READ C 25 IF C 9 THEN 50 30 PRINTC 35 IF C lt gt 2 THEN 20 40 45 47 48 50 99 LETI I 1 GO TO 20 DATA 0 1 1 0 2 0 0 1 DATA 2 2 0 0 0 1 2 9 PRINT ISOLATION ISTS I END y READ CODE PRINT CODE is used to count number of isolationist students Read Code Is 1t the last ON Yes go and write out total of isolationists No print code Is it an isolationist response No go read another code Yes count it and read more codes Print total of isolationists students SELF ASSESSMENT EXERCISE l Modify the program to determine the number of students for isolationism neutral against isolationism 2 Modify the program to determine the percentage of students in each category 3 0 MAIN CONTENTS 3 1 Data Statement The general form of the DATA Statement is line number DATA constant list Where DAT
26. array manipulation techniques Array Initialization and Duplication The following code sets all elements of array A to zeros sets each element of array B equal to the variable X and the duplicates array D into array S 10 DIM A 100 B 100 S 100 D 100 12 LET X 5 15 INPUTN Read a value for N This value must not exceed the size of the arrays declared in the DIM statement 20 FORI 1TON 25 LET A 1 0 A D AQ A N are set to O one at a time as I ranges from 1 to N 30 LETB I xX Similarly B 1 B 2 B N are set to the value in X Finally S I D D 40 NEXTI S 2 D 2 0 000 SN D N Sometimes it might be necessary to set an array C equal to the sum of two other arrays A and B in such a way that C I A 1 B 1 CO A 2 BQ ee e 100 A 100 B 100 The following code might be used 10 DIMA 100 B 100 C 100 15 FORJ 1TO 100 20 LETC N A B0 25 NEXTJ A 1 B 1 A 2 B 2 A 100 4 5 B100 4 5 C 100 Suppose it is desired to initialize two arrays A and B as follows A D B 10 1 10 DIMA 910 B 10 A 2 B 9 2 15 FORI 1T010 A 3 B 8 3 20 LETA D I 23 LETK 10 I 1 The code on the right could 30 LETB K I be used 35 NEXTI A 10 B 1 10 The variable K generates the numbers 10 9 8 l as I ranges from 1 to 10 If I ranged from 1 to N the formula K N I 1 would generate the numbers N N 1 N DA cits Back take R
27. by a computer A constant is made up of any of the digits through a and may be preceded by the or symbol Examples of valid constants 300 2 31 62504 0 3 14 Imbedded blanks blanks between first and last digit do not affect the value of the constant Example 6 32 632 63 2 Examples of invalid constant 1 634 123 No comma is allowed 23 24 Only one decimal point is allowed 40 42 Character is invalid 127 423 Character is invalid 3 2 2 Alphanumeric Constants Alphanumeric constants are generally words messages captions column headings titles names addresses etc that are endorsed within quotation marks Examples of valid alphanumeric constants 1425 ADEYI ST 1425 ADEYI ST IT IS HER S Note The maximum number of characters allowed in an alphanumeric string varies from one system to another Constants may be used in BASIC as follows e LET T1 P 1 T1 7N 15 e PRINT 10 36 4 6 5 93 005 e LET N CHARLES e PRINT A 3 3 Variables Unlike a constant a variable may assume different values They are two types of variable l Variables that contain numeric data can be processed arithmetically added subtracted etc 2 Variables that contain alphanumeric data cannot be processed arithmetically The specifications for standard BASIC variable names are as follows Numeric Variables A single letter of the alphabet such as A B Z P or a single letter fol
28. ced by instruction above You FIBBER YOU ARE NOT 41 YEARS OLD Remark Note the GO TO 10 statements at the line program repeatedly The process of repeating a sequence of instructions is called a Loop In this case the loop is infinite and the only way the user can escape from it is by pressing a special key on the keyboard see your user s manual The unconditional Transfer Statement GO TO The General form of the Go to Statement is line number Go TO transfer line number A BASIC program consists of a sequence of BASIC STATEMENTS Basic will process these statements one after another in sequential order When BASIC encounters a GO TO statement it will transfer control to the statement specified that is processing will continue at the transfer number It also allows the program to branch back to repeat reprocess certain instructions or certain procedures this is called looping Examples 1 20 GOT TO 50 This code is by passed SOLETY 3 Z Example 2 20 INPUT H R B MN This block of code is processed repeatedly 50 GO TO 20 variables is used The contents value of each location are to be printed on some output device For example the Block Indicates that values in locations P and H are to be displayed written on some device PRINT P H a The Processing Block A rectangular symbol po used for processing instructions The most common form for expressing these instructions is the replacement statement A repla
29. cement statement specifies the arithmetic operations to be performed on constants or variables and the location variable into which the value computed is to be placed For example the block specifies that the contents value of H is to be multiplied by 2 and dl p 2 H be placed into P b The Decision Block The diamond shaped symbol amp is used to denote decisions A common means of expressing a decision is in terms of a 46 question that can be answered Yes or No The question must involve only mathematical relations such as equality less than lt Flowchart is on the logic required for solving a problem rather than on the mechanics or specifics of a programming language c The Terminal Block An oval shaped symbol Ce used to mark the point at which execution of instructions is to begin and end The instruction START may be used to mark the beginning point the instruction END or STOP may be used to mark the ending point A flowchart may have only one starting point entry point but may have many ending points d The Input Output Block A parallelogram shaped symbol s used for input and output operation the instruction command READ OR INPUT followed by a list of names variables separated by commas is used These names or variables can be thought of as symbolic names given to memory locations in which the data read is to be stored Variables names should be chosen to covey the nature of the data to be
30. d in order from left to right according to the rule of precedence Exponentiation is performed in order from right to left If parenthesis is nested the operation in the innermost set of parenthesis is performed first 7 Consider the expression 3 2 213 4 1 2 3 a 8 be ABE pp AE 5 6666 A A 7 3333 A B C B is subtracted from A and the result is added to C 3 2 5 32 5 1 5 6 A B C Since multiplication has priority B C is computed the result is then added to A giving A B C SRLS 3 2 3 3 6 9 A B C Since multiplication and division have the same priority B is first divided into A B and the result of the division is multiplied by C 9 4 2 9 4 2 2 25 2 4 50 A B C First A B is performed and the result is then divided by C 8 4 2 8 4 2 2 2 1 A B C D A B C D So 3 6 3 6 3 6 3 6 3 6 18 A B C72 A B C12 343 232 3 3 2 3 3 4 3 12 15 At B C 4A 1B 7 C37273 6 12 73 C 7 H 9 709 SELF ASSESSMENT EXERCISE Evaluate the following expressions for X 8 Y 4 Z 5 A a XIY 2 X 2 Y Z 1 EQ XP VEL ED 3 2 The Replacement Statement LET A replacement statement evaluates an expression and stores the value of the expression in a memory location identified by a variable name The general form of a replacement statement 1s Ooo In most BASIC systems the key word LET is optional and need not be specified by the user When the particular statement is carried ou
31. ded to preserve grades 6 0 TUTOR MARKED ASSIGNMENT Compute the average of 50 72 74 81 87 Input Output of Arrays Arrays can be read and printed out by indexing the arrays with the index of a FOR NEXT Loop Example I To read 10 data from a DATA statement the following code might be used 10 DIM 10 15 FORI 1 to 10 20 READ A D 25 READA I 30 DATAS 559 corrio 15 Array A 15 A 10 The first time through the loop I is 1 and A I is read from the DATA statement The second time through the loop I is 2 and the next data item is read into A 10 7 0 REFERENCE FURTHER READING Boillot M and Horn L W BASIC akD Edition West Publishing Company New York UNIT 2 USE OF ARRAYS CONTENTS 1 0 Introduction 2 0 Objectives 3 0 Main Contents 3 1 Use of Arrays to Store the Grades 3 1 1 Definition 3 1 2 An Array Storage 4 0 Conclusion 5 0 Summary 6 0 Tutor Marked Assignment 7 0 Reference Further Readings 1 0 INTRODUCTION Here you will learn another method that is not as cumbersome as the first 2 0 OBJECTIVES At the end of this unit you would be able to compute average of grades and compare each grade with the average 3 0 MAIN CONTENTS 3 1 1 Use of Arrays to Store the Grades 3 1 1 Definition An array is a sequence of consecutive memory locations in which data elements are stored 56 79 89 45 80 G 1 G 2 G 3 G 4 G5 3 1 2 An Array Storage All g
32. der a simple model computer that operates conceptually as its real life counter parts The input is a terminal where numbers have been entered typed The memory unit consists of a group of sequentially numbered pigeonholes Locations can be referred to either by name or by address The arithmetic logical unit is represented by a desk calculator capable of performing arithmetic and logical operations The role of the control unit played by a human operator who can fetch instructions from the memory one at a time and execute them The type of instructions the operator is capable of executing includes 3 3 Input Read a value from the input medium and store that value in a specified memory location e g INPUT F will cause one value on the input medium to be read and stored in a memory location called F Conditional branding Perform a comparison test between two values using the logical unit and brands to a specified memory location if the test condition is met If the condition is not met no transfer occurs and the following instruction is taken from the next memory location For example the instruction IF F lt 50 Go To 20 Cause the control to fist fetch F from memory and then request the logical unit to compare the value with 50 If the logical unit reports that the value F is less than 50 the control unit fetched the next instruction is taken from the next sequentially numbered location If F is not less than 50 it processes the next
33. een computed 40 NEXT 1 Go back to statement 25 until the loop has been processed five times 45 LETA S S Now that all the grades have been read that is the loop has gone through the full cycle 50 PRINTA We can compute the average and print it out 55 DATA 20 100 90 END The above shows accumulating process SELF ASSESSMENT EXERCISE What is the expected output of each of the following program 10 DATA 1 5 17 2 15 LET P 1 20 FOR 1 1 TO 4 30 READ X 40 LETP P X 50 NEXT 1 60 PRINT P 70 END Answer Expected output 170 3 2 The For Next Revisited The FOR NEXT statement can be quite convenient when it is desired to execute one or more statements at a specific number of times 5 FOR Index J Initial value 1 to terminal 303 STEP 1 increment for index 10 READ X 15 PRINT X 20 NEXT J 25 LET K 5 2 4 Here you learn the difference between counting and accumulating 4 0 CONCLUSION 5 0 SUMMARY FOR NEXT is very useful when you wish to execute one or more statements specific number of times 6 0 TUTOR MARKED ASSIGNMENT Examine the following program how many times will the loop be repeated 5 FOR 1 2 TO 2 5 STEP 5 37 EXT 1 7 0 REFERENCE FURTHER READING M Boillot and L W Horn BASIC Third Edition West publishing Company New York TMA Solution 5 FOR 1 2 to 2 3 STEP 5 37 NEXT 1 The values assumed by the index 1 are 2 1 5 1 0 5 0 0 5 1 0 1 5 2 3 It will be executed 9 times
34. equency 2 4 5 5 3 1 7 0 REFERENCE FURTHER READING Boillot and L W Horn BASIC 3 Edition UNIT5 PROJECT CONTENT 1 0 Introduction 2 0 Objectives 3 0 Main Contents 3 1 Projects 4 0 Conclusion 5 0 Summary 6 0 Tutor Marked Assignments 7 0 Reference Further Reading 1 0 INTRODUCTION Here you will use your knowledge of programmes to solve the following problems 2 0 OBJECTIVES At the end of this Unit you would be able to give a report of the assigned projects 6 0 TUTOR MARKED ASSIGNMENTS Write a program to compute the area under a curve TN Y f x X X2 Your program should approximate the area under the curve y e X 2 2 Write a program to compute the following sequence of sums Si 1 So 1 1 2 S3 1 1 2 1 3 S 1 1 2 1 3 1 4 How many different sums would you have to compute before the sum exceed 3 9 For X between I and 2 for three values of h 0 1 h 0 01 h 0 001 7 0 REFERENCE FURTHER READING M Boillot and L W Horn BASIC 3 Edition MODULE 4 Unit 1 Unit 2 Unit 3 Unit 4 Unit 5 One dimensional Arrays Use of Arrays DIM Statement Array Manipulation End of File Conditions UNIT 1 ONE DIMENSIONAL ARRAYS CONTENTS 1 0 Introduction 2 0 Objectives 3 0 Main Contents 3 1 One Dimensional Arrays 4 0 Conclusion 5 0 Summary 6 0 Tutor Marked Assignment 7 0 Reference Further Readings 1 0 INTRODUCTION You will learn here how to calculate the average of f
35. er Solution l 2 3 4 5 6 7 8 9 10 Y 1 Y 2 Y 10 l 2 3 4 5 6 7 8 9 10 YD YO YG Y 10 Unit 4 Exercise L 2 Array X Write DIM statement s to create an array O containing 10 elements and an array R containing 25 elements Suppose an array X has the following content 2 2 3 0 3 2 6 10 XI X XG XA X6 X6 X And suppose 3 and j 2 Evaluate each of the following expressions a X 3 b X 4 coe X I X 4 d XM amp p E XOU s XAA Answers 1 10DIMQ 10 R 25 OR 2 a 0 by 2 co 3 3 10 DIM Q 10 20 DIM R 25 f 0 2 3 2 3 g X 3 0 Solution Y 1 Y 2 Y 10 UNIT 5 Trip Record Exercise Modify the code of the code above example to include a listing of each student s number and his her initial test scores Answer 71 FOR J 1TOI 72 PRINT N J SV 73 NEXTJ
36. eversing Arrays Suppose A is an array of size N where N has been previously defined and it is desired to interchange A1 with A N A 2 with A N 1 A 3 with A N 2 etc The following code could be sued 10 DIM A 100 Since each interchange step involves a pair of array elements 15 INPUT N Ay An Ad Ayn etc the interchange process needs be 20 FOR I 1 TO N 2 repeated only N 2 times If N is odd the median element 25 LET T A 1 remains unchanged K generates the number N N 1 30 LETK N I 1 N 2 1 T is a temporary location needed to save A 1 35 LETA A K before A 1 A N is executed otherwise A 1 40 LETA K T would be destroyed 45 NEXT I If we used N instead of N in statement 20 the array would reverse itself and end up as if nothing had changed Accumulation of Array Elements To compute the product of the elements of the array A 10 20 30 40 50 The following code could be used 10 15 20 25 LETS 1 FORK 1T0O5 LET S S A k NEXT K S initially set to 1 before the loop is entered The first time through the loop S S A 1 1 10 10 The second time through the loop S S A 1 To compute the sum of two arrays S A 1 B 1 A 2 B 2 A 50 B 50 we could use Suppose A and B are two arrays of size 10 and we want the array C to contain the data Ajo Bio arranged in that order Any of the following codes
37. hat operation is to be prformed It is not necessary to express the instructions used in a flowchart block in any particular computer language The emphasis in the less than or equal to lt greater than gt greater than or equal to gt or nhot equal to gt The decision blow is the only block from which two different logical paths may be selected follows indicate the path to be taken depending on the decision block No If the value of H is greater than 40 the path marked YES is taken other wise the NO path is taken c Flowlines The sequence of instructions to be executed in a flowcharted algorithm is denoted by straight lines with an arrowhead such as or The direction of flow is always in the direction pointed by the arrowhead d Connector Blocks When it is convenient to draw flowlines to connect one area of the flowchart to another connectors are often used Conncetors serve two pupose l To identify a block by a label for refence purposes 2 To indicate transfer to another labeled block The symbol used for a connector is a ircle A label is placed in the connector block when the flow line points away from the connector such as xe onnector is being used to denote an entry point that is a block to which transfer will be made from some point in the flowchat when the flow line points toward the connectorl as in the connector is being used to indicate a transfer gt O a PRINT X Y ep
38. hehe JJ ar on 22 31 36 39 41 46 46 49 54 55 57 58 58 62 65 67 72 MODULE 1 PROGRAMMING IN BASIC Unit 1 Computers Hardware and Software Unit 2 Computing Arithmetic and Logical Operation Unit 3 Basic Statements Unit 4 Basic Statements Continued Unit 5 Listing and Debugging Programmes INTRODUCTION Basic was created in 1964 by J G Kemeny and T E Kurtz at Dartmonth College USA The language was originally designed as a simplified version of FORTRAN for use in Teaching programming From the simple beginnings the language has grown to become a very popular multi purpose language available on a wide variety of machines in particular microcomputers and minicomputers This course is therefore devoted to BASIS because of its usefulness UNIT 1 COMPUTERS HARDWARE AND SOFTWARE CONTENTS 1 0 Introduction 2 0 Objectives 3 0 Main Contents 3 1 Computers what are they 3 1 1 Organization of a computer Hardware 3 1 1 Computer Program Software 4 0 Conclusion 5 0 Summary 6 0 Tutor Marked Assignment 7 0 Reference Further Reading 1 0 INTRODUCTION In this unit you will be introduced to the components of a computer and their function You will also learn what a program is 2 0 OBJECTIVES At the end of this unit you would be able to define a computer define a program 3 0 MAIN CONTENT 3 1 Computers what are they Computers are automatic machines that can accept data store vast amounts of
39. his unit we introduce to BASIC expressions We shall also discover further Basic statements LET PRINT STOP END 2 0 OBJECTIVES At the end of this unit you would be able to work with BASIC expressions e use BASIC statements LET PRINT STOP and END 3 0 MAIN CONTENTS 3 1 Expressions An expression may be a constant a variable or any combination of constants and or variables linked by the five arithmetic operators shown below Note that no two arithmetic operators may be typed side by side Parenthesis may be included to denote the order of computations The allowable arithmetic operators are F Addition Subtraction Multiplication Division or or Exponentiation raising to a power p g p Valid Expressions Algebraic Expressions BASIC Expressions 3 5 3 5 c c a b 30 A B 30 a C A B c Ax2 bx c A X1T2 B x c a by A B 72 c 1 4 d c 1 4 D Vx Xt 5 a b A B 13 25 Cost salvage Years c s Y Bonus hours x rate B H R 1 1 F 1 r2 F 1 r3 1 R a 1 R gt F 1 R3 3 1 1 Precedence in Expressions Operations within expression are performed according to the following rules of precedence Operation Precedence high precedence or or or low precedence Operations with high precedence are performed before operations with lower precedence The operations addition subtraction multiplication division are performe
40. information and perform arithmetic at high speeds to solve complex machines 3 1 1 Organization of a Computer The computer may be thought of as a system composed of five components The components and their functions are as follows l The Input Unit This unit feeds information from the outside world to the computer Input units are capable of reading information recorded on such different mediums as punched cards or magnetic tape or from terminals The information read from these devices is placed into appropriate memory locations 2 The Memory Unit The memory unit stores information It holds the sequence of instructions necessary to solve particular problem and any additional data required The memory is divided into locations that each have an address are addressable Instructions are stored in these cells 3 The Control Unit The control unit fetches the instructions and data from memory and executes the instructions one at a time with logical unit All of the other components operate as directed by the control unit 4 The Arithmetic Logical Unit The arithmetic logical unit consists of the electronic circuitry that performs arithmetic operations such as comparison of numbers de The Output Unit The output unit transfers or copies the contents of certain memory locations onto some external medium such as punched cards punched paper tape magnetic tape a printed page produced by a teletype or line printer or a cathode ray tube CRT
41. ions or character string variables linked together by one of the relational operations shown in figure 1 below BASIC Relational Mathematical symbol Meaning Operators Equal to A A Less than lt 0r lt lt Less than or gt gt Equal to gt or gt gt Greater than lt gt or gt lt 4 Nor equal to Figure 1 BASIC relational Operators The If statement can be flowcharted as follows If condition GO TO 200 z E What to do if FAL E Skip Code 80 What to do if TRUE Example 1 Write the code to input an age and print the message OLD if the age gt 50 and print YOUNG otherwise then stop 10 INPUT A NO 20IF A gt 50 GO TO Transfer to statement 80 de PRINT YOUNG if the age is gt 50 otherwise print YOUNG 40 GO TO GO than go to go is stop if 80 PRINT OLD age gt 50 skip over lines 30 40 and print OLD 90 END Note the importance of statement 40 IF line 40 had been omitted than if the age were less than or equal to 50 not only would the message YOUNG be printed but also the message OLD Example 2 Write the code to input a persons name and a corresponding pay If the name read happens to be LUCKY add 100 to the pay In any event print the persons name and the pay 10 INPUT NS P If the name is not NO 20 1d lt gt LUNCKY GO TO 40 LUCKY go and print 30 P P 100 name and pay otherwise if its 40 PRINT N P LUCKY add 100 to pay and
42. is the keyword The constant list consists of numeric or character constants Items in the list must be separated by commas DATA is a non executable statement unlike all other BASIC statements except REM encountered so far The DATA statement inform the BASIC system that the numbers specified in its constant list are to be stored in memory until the user decides to process these numbers during program execution Example 1 DATA1 3 1 5 READX Y Z W 10 PRINT X Y Z WS 15 DATA3 HI 20 END RUN l 3 1 3 HI l 3 1 3 HI Data Block Memory Example 2 l DATA 1 3 1 3 HI 5 READ X 10 READ Y 15 READ Z W 20 PRINT X Y Z W 25 END 1 3 1 3 HI Example 3 l DATA 1 5 DATA 3 1 10 READ X Y Z W 15 DATA 3 HI 20 PRINT X Y Z W 25 END RUN 1 31 3 HI 2 Parentheses may be used to devote the order in which the expressions are to be evaluated If S 1 AND M 1 lt gt 0 OR S 3 AND MI gt 4 THEN PRINT S M1 3 2 Read Statement The general form of the READ statement is Line number READ variable list Where READ is a key word The variable list consists of variables separated from one another by commas The READ statement causes as many values to be fetched from the DATA block as there are variables in the READ list Data block 5 READ X Y 10 DATA 1 3 15 READ 2 20 DATA WE 4 6 25 READ W 4 0 CONCLUSION The assignment of values to
43. ive grades read on a DATA statement and the difference of each grade and the average Up till now it has been possible to compute an average of grades imply by reading one grade at a time into a variable using the statement READ G and accumulating the grades as they are read This procedure cannot be used in this case however since each new grade destroys the previous grade stored in G thereby making it impossible to compare each grade with average once the average has been computed 2 0 At the OBJECTIVES end of this unit you would be able to print the difference between each grade and the average 3 0 MAIN CONTENTS 3 1 One Dimensional Array Each grade must be preserved and for that reason five distinct memory locations variables are needed as shown in the figure below 1 0 ARRAY 15 20 30 PRINT 35 PRINT 40 PRINT 50 PRINT 60 DATA 99 END Figure 2 Gl G2 G3 56 89 45 78 a 80 UE ENTE ME G5 Figure I Five Memory Locations REM DEVIATION OF FIVE GRADES IWTHOUT AN READG G2 G3 G4 G5 LET A Gl G2 G3 G4 G5 5 Gl G1 1 G3 G3 A G5 G5 A G5 G5 A 56 78 89 45 80 One method for solving the problem is shown in Figure 2 We shall consider another method in the next unit 4 0 CONCLUSION To compare grades with the average of the grades each grade must be preserved 5 0 SUMMARY Distinct memory locations variables are nee
44. k is a key word and the literal characters are supplied by the programmer Although the REM statement requires a line number it is not an executable statement 40 CONCLUSION REM statement help understand the overall program structure 5 0 SUMMARY The If statement should be used with care 6 0 TUTOR MARKED ASSIGNMENT l Write a program to determine the roots of the quadratic equation ax bx c 0 if there are no real roots print the message NO REAL ROOTS 2 If the roots are unequal print message ROOT 1 xx ROOT 2 xx 7 0 REFERENCE FURTHER READING Boillot and Hon BASIC 3 Editor UNIT 4 LOGICAL EXPRESSIONS AND THE AND OR LOGICAL OPERATORS CONTENTS 1 0 Introduction 2 0 Objectives 3 0 Main Contents 3 1 And 3 2 On Go To Statement 4 0 Conclusion 5 0 Summary 6 0 Tutor Marked Assignment 7 0 Further Reading 1 0 INTRODUCTION A logical expression can be thought of as a proposition A proposition is a statement that is either true or false 2 0 OBJECTIVES At the end of this unit you would be able to use AND OR 3 0 MAIN CONTENTS 3 1 And Examples l To determine whether A lies between 7 and 14 the following statement could be used If A gt gt AND A lt 14 THEIR PRINT YES Note that the statement If A gt gt ABD lt 14 is invalided No logical operator may be side by side with a relational operator 2 Parentheses may be used to devote the order in which the expressions are to
45. lowed by one digit 0 9 such as B4 Z2 DO Alphanumeric Variables Same as numeric variables except that a is appended to the variable name Example A B Z5 The following are invalid variables as indicated I the notes 2B Does not start with letter KRB Too many letters B Invalid character C 2 Invalid character BA B2 would be valid HELLO Is a constant SELF ASSESSMENT EXERCISE Which of the following are invalid variable names di A34 2 B 3 B4 4 4 0 CONCLUSION A BASIC instruction is made up of different elements constants variables etc 5 0 SUMMARY Here you learn some BASIC statements LET PRINT and what a BASIC instruction is made up of 6 0 TUTOR MARKED ASSIGNMENT l Specify which of the following are valid numeric constants if invalid specify the reasons a 42 93 b 45 C 45 25 CR d 124 000 e 7 3 f 27 Za Which of the following are invalid variable names Why 1 B43 ii C iii B1 iv B4 v vi MIS 7 0 REFERENCES FURTHER READING Boillot and Horn BASIC 3 Edition UNIT 4 BASIC STATEMENTS Continued CONTENTS 1 0 Introduction 2 0 Objectives 3 0 Main Contents 3 1 Expressions 3 1 1 Precedence in Expressions 3 2 The Replacement statement LET 3 3 Line Numbers 3 4 The PRINT statement 3 5 The termination statements STOP and END 4 0 Conclusion 5 0 Summary 6 0 Tutor Marked Assignment 7 0 Further Reading 1 0 INTRODUCTION In t
46. mining whether one value is less than equal to or greater than another value BASIC instruction is made up of different elements BASIC keywords constants variables expressions arithmetic operators relational operators etc which when combined together under a proper grammatical structure yielded a valid BASIC instruction We consider the following problem the investment T is given by the formula T P 1 DP Where I is the interest rate N is the number of years and P is the Principal Mr Ojo wants to deposit N 1 500 at a savings institution He considers a bank and a credit union The credit union requires a non refundable membership fee of N 15 Deposits earn 12 25 percent at the credit union and 11 75 percent in the bank Mr Ojo will need the money in 2 years We wish to determine which institution that Mr Ojo should use The program is as follows 10 LET p 1500 15 LET T1 1225 20 LET T2 1175 25 LET N 2 5 30 LET TI P 1 T1 IN 15 35 LET T2 p 1 T2 1N 40 PRINT CREDIT AMOUNT TI 50 PRINT BANK AMOUNT T2 55 END The output CREDIT AMOUNT 1987 43 BANK AMOUNT 1980 20 So Mr Ojo will be advised to use credit union 3 2 Constants A constant is a quantity whose value is fixed and explicitly stated constants may either be numeric or alphanumeric 3 2 1 Numeric Constants Numeric constants are positive or negative numbers they can be added subtracted multiplied divided and raised to a pointer
47. nt of his first 9 month s salary retirement deductions are spread over a 12 month period for each child support for social security His monthly social security deduction is 6 7 percent of his monthly income and his federal income tax is 15 6 percent of his yearly gross deducted on monthly basis Monthly payments for life insurance equal 9 6 percent of his monthly salary after social security and federal tax deductions Write a program to compute his monthly spendable income LET C 119 25 Support per child LET I 1523 36 Monthly salary LET R 9 J 066 12 Monthly retirement plan deduction LET S 067 I Monthly social security deduction LET F 156 I Monthly federal income tax LET T I R S F Net after deductions LET L 096 I F S Monthly life insurance payments LET T1 T L Net minus life insurance payments LET T1 T1 2 C Plus child support 2 less than 18 years PRINT SPENDABLE INCOME IS T1 END SPENDABLE INCOME IS 1233 11 4 0 CONCLUSION Errors are called bugs Debugging means correcting errors 5 0 SUMMARY They are four varieties of errors and you learn here how to correct them The program example i e useful and should be studied in detail 6 0 TUTOR MARKED ASSIGNMENT Write a program to produce report on cost of operating electrical devices COST ANALYSIS WATTS HOURS COST W COST 60 6 087 100 6 08 The formula is C W T K 100 Where W number of watts T line in hours
48. processed INPUT N For an output operation the instruction 47 PRINT followed by a list of memory locations Enter the name into memory cell N Enter the hours into memory location H Enter the rate into R If the number of hours gt 40 Do the following Computer pay for first 40 hours compute over time hours compute overtime pay compute final pay Print overtime hours Print overtime pay otherwide do the following compute regular pay and Print the name and pay in P1 40 R either case And then go back to V H 40 process another record P2 V R 1 YROLL PRO P25 R his is for REM P LOWCHARTIN A flowchart is essentually a picto prinry sual outline of the sequence of steps hat must be taken ip order to sov a parucpar problem PRINT P2 logical orga Flowchart Definition nization and requring of program instructions Z program without first expressing the program a complex problem the tool is the flowchart although for a ne of steps required may suffice A flowchart is a pictorial ethod used to solve a particular problem representatjo gt 484 las STOP A flowchart is particularly useful for visualizing paths through the logic of a program b Flowchart symbols In program flowcharts the symbols shown in the figure below is normally used Each symbol or block represents a different type of operation written within the blocks are instructions to indicate in general terms w
49. r PRINT expression List Where the expression list can be alternatively A constant PRINT 7 6 A variable PRINT X An expression PRINT H 50 R 2 5 H R A character string PRINT PAY HOURS RATE A combination of the above separated by commas or semi colons PRINT PAY P HOURS H 3 5 The Termination Statements STOP and END The last BASIC statement in a BASIC program should always be the END statement For this reason the END statement should always have the highest line number in your program If you type BASIC statements after the END statement these will not be processed by BASIC The STOP statement tells BASIC where in your program you want to stop processing instructions The general form of termination statements are Line number STOP Line number END Any program can be written without a STOP statement 4 0 CONCLUSION It is important to follow BASIC instruction correctly 5 0 SUMMARY Here you learn what expressions are and the order of precedence You are now in a position to use BASIC statements LET PRINT STOP and END correctly 6 0 TUTOR MARKED ASSIGNMENT Write a program to compute and print the area and perimeter of each of the following 12cm a 6cm 4cm 9cm 7 0 REFERENCES FURTHER READING Boillot and Horn BASIC 3 Edition UNIT 5 LISTING AND DEBUGGING PROGRAMS NUMBER REPRESENTATION AND PROGRAMMING EXAMPLES CONTENTS 1 0 Introduction 2 0 Objectives 3 0 Main Contents 3 1 Bug
50. rades G 1 Figure 1 G1 a TE 78 89 45 80 DATA 56 89 45 G 1 through the statement READ G 1 as I varies from 1 to 5 80 G 5 are stored into the array one at a time staring with REM DEVIATION FOR FIVE GRADES USING ARRAYS Figure 2 10 15 DIM G 5 20 LETS 0 25 FORI 1TOS5 G 1 30 READG 35 LETS s G 40 NEXTI 45 LETA S 5 50 FORI 1TOS5 Reserve 5 memory locations For array G S will accumulate grades When I is 1 read 1 grade in When l is 2 read 2 grade in G 2 Add grades one at a time to the accumulator Compute the average 55 PRINT G D GU A Print each grade and the difference between each grade and average 60 NEXTI When I is 1 T and G T A is printed 65 STOP 70 DATA 56 78 89 45 80 When is 5 G 5 and G 5 A is printed 9 END Figure 3 Through the use of indexing accumulation logic can be used to calculate the sum of the grades The statement LET S S G I Figure 3 accomplishes the accumulation process The suit line through the loop I 1 and S S G 0 g I 56 The first grade in the array is added to the sum which is initially zero The second time through the loop I 2 and S S G I 56 G 2 56 78 134 Finally when I 5 the fifth grade in the array is added to the sum of the four previous grades Output can be handled in a loop by using a variable subscript on the array G in much the same way as the input
51. rkings of a computer 5 0 SUMMARY The term software is generally used to describe the set of programs that causes the computer hardware to function 6 0 TUTOR MARKED ASSIGNMENT How would the execution of the example 2 5 be affected by replacing the statement in location 7 by GO To 1 What would be the advantages and disadvantages of doing this 7 0 REFERENCES FURTHER READING Boillot and Horn BASIC 3 Edition UNIT 3 BASIC STATEMENTS LET PRINT TERMINATION SYSTEM COMMANDS CONTENTS 1 0 Introduction 2 0 Objectives 3 0 Main Contents 3 1 Elements of BASIC Language 3 2 Constants 3 2 1 Numeric Constants 3 2 2 Alphanumeric Constants 33 Variables 40 Conclusion 5 0 Summary 6 0 Tutor Marked Assignment 7 0 Further Reading 10 INTRODUCTION Here you will learn some elements of BASIC the character set and constants 2 0 OBJECTIVES At the end of this unit you would be able to use some key words LET PRINT END use characters which are used to define create BASIC instructions define constants 3 0 MAIN CONTENTS 3 1 Elements of BASIC Language BASIC is a set of instructions telling the computer what actions operations to carry out to solve a particular problem There are three types of BASIC operations that the computer can carry out These are l Arithmetic operations add subtract multiply divide raise to the power 2 Input Output operations entering data and printing results 3 Comparison deter
52. s 3 2 Listing and Debugging Programs 3 3 Number Representative 3 4 Programming Example Conclusion Summary Tutor Marked Assignment Reference Further Reading INTRODUCTION By now you may have realized how easily one can make errors on a computer Errors commonly called bugs come in essentially four varieties typographical syntactical logical and system related D Typographical Errors These errors are due to mistypes and they are interpreted by the computer as syntax errors E g letter O is typed instead of digit 0 Sy ntactical Errors Syntax error reflects the programmer s inability to observe correctly the grammatical rules of the BASIC language Examples 10 LETP 1 Typographical error should be 20 LETX A B C 3 2 20 LETX A B C 30 PRINT HELLO S1 S2 Punctuation missing between items 40 LET Z 3 X 4 T Missing right parenthesis Logical Error Logical errors are the most difficult errors to detect because they are very well camouflaged Example LET Y T N Although it is a perfect instruction Yet it could be a time bomb during the execution if N O Also a programmer may wish to print the result stored in memory location R but instead write the instruction PRINTS System Errors Systems errors relate t the computer system itself for example a printer may not be turned on when the CPU needs it thereby causing a special error message to appear Listing and Debugging Programs
53. s to the FOR NEXT loop in the following cases a FORI 5TOS5 b FPRJ 100 T0 1 E FOR K 2 10 1 In most cases the following actions will be taken a The loop is executed only once b The loop is not executed and the control is passed to the statement following the NEXT statement G Same as b since value K is less than test value and the increment is negative 3 How can I determine whether an integer N is even or odd Answer W e use the integer function INI by computing the expression 2 INT N 2 N If N is even the result of the expression is always zero If N is odd the result of the expression is always negative MODULE 4 UNIT 1 Exercise Which of the following code segments will compute the average A of 10 grades a LetS 0 For I 1 to 10 READG LetS S G NEXT I Let A S I PRINT A b LETS 0 For I 1 to 10 READG LETS S G NEXT I PRINT A Answer A and B Unit 2 Exercise Modify statements 50 60 of the programme Figure 3 to print the grades in reverse order ie G 5 G 4 ricos G 1 Solution Charge the following statements 15 DIM G 10 15 DIM G 100 25 FOR I 1 TO 10 25 FOR I 1 TO 100 45 LET A S 10 45 LET A S 100 50 FOR I 1 TO 10 50 FOR I 1 TO 100 UNIT 3 Linear Arrays Exercise Discuss the validity of the following DIM statements DIM A 3 2 DIM A N Answer Not valid Invalid limit should be an integer constant Not valid N is not a constant N must be a positive Integ
54. t RUN the value of the expression is first computed and the result is placed stored in the variable memory location0 specified on the left hand side of the equal sign When we write 10 X 2 X 1 We are looking at the expression and saying find out what is in X multiply 1t by 2 add l and store the result in memory location X the equal sign must be understood as a replacement sign Thus if the memory location contains 4 then 2 X 1 9 and the value 9 is stored in X i e the value X is replaced by 9 Examples of valid replacement statements are 10 LET X 0 07 Store value 07 in X 12 X1l A B C 1_ Evaluate the expression and store the result in X1 14 LET C GROSS PROFIT Store the string GROSS PROFIT in C 15 I I 1 Computer I 1 and store result in I 3 3 Line Numbers Each BASIC line must be numbered Line numbers must be unsigned integers not exceeding five digits In most systems statements or lines may be entered in any desired order the system will sort the statements in order when the program is list or executed Statements will be processed by the computer in ascending order under a decision statement IF or unconditional transfer Go To is encountered Example 10 LETX 3 20 PRINT X Y 15 LETY X 3 BASIC would store these statements in its memory in the following orders 10 LETX 3 15 LETY xf3 20 PRINT X Y 3 4 The Print Statement The general form of the PRINT statement is Line numbe
55. variables is made in order in which variables appear in the READ list 50 SUMMARY Counting is an essential technique in programming 6 0 TUTOR MARKED ASSIGNMENT hi What will be the values assigned to each variable in the following program 10 READQ R 20 READSS T 30 DATA 25 6 T S 40 END 2 What output will be produced by the following program 10 DATA 6 9 20 DATA 1 0 13 30 READX 40 PRINT X 50 IF X lt gt 0 THEN 10 60 END 7 0 REFERENCE FURTHER READING Boillot and Horn BASIC 3 Edition MODULE 3 ACCUMULATION PROCESS Unit 1 Unit 2 Unit 3 Unit 4 Unit 5 STATEMENTS FOR NEXT The Accumulation Process and Statement FOR NEXT The Accumulation Process Nested Loops Application of Nested Loops in Statistics Project UNIT 1 THE ACCUMULATION PROCESS AND FOR NEXT CONTENTS 1 0 Introduction 2 0 Objectives 3 0 Main Contents 3 1 For Next Statements 3 1 1 The General form of Next Statement 40 Conclusion 5 0 Summary 6 0 Tutor Marked Assignment 7 0 Further Reading 1 0 INTRODUCTION STATEMENT The statement FOR NEXT represent no new programming concept that have not been already been discussed The purpose of these two statements is strictly one of convenience to the parameter 2 0 OBJECTIVES At the end of this unit you would be able to use 3 0 3 1 FOR NEXT Statements for loop control MAIN CONTENTS For Next Statements Any BASIC program can be written without FOR NEXT statements because
56. you will be using ii What procedure is needed to begin programming in BASIC 4 0 CONCLUSION A computer is a problem solving machine 5 0 SUMMARY A computer is composed of five components The CPU may be thought of as the seat of intelligence of the entire system The input and output functions may be performed by devices located at some distance from CPU 6 0 TUTOR MARKED ASSIGNMENT l List the five components of a computer system and explain the functions of each define the following 1 CPU i CRT iii Program iv Data 7 0 REFERENCES FURTHER READING M Boillot and L W Horn BASIC Third Edition West Publishing Company New York UNIT 2 COMPUTING CONTENTS 1 0 Introduction 2 0 Objectives 3 0 Main Contents 3 1 Arithmetic Operations 3 2 Types of Instructions 3 3 Sample Program 40 Conclusion 5 0 Summary 6 0 Tutor Marked Assignment 7 0 Reference Further Reading 1 0 INTRODUCTION In this unit you will learn how arithmetic operations are written You will also be exposed to some basic instructions 2 0 OBJECTIVES At the end of this unit you would be able to determine the symbols of arithmetic operations in BASIC explain how a computer carries out some simple instructions 3 0 MAIN CONTENTS 3 1 Arithmetic Operations In BASIC programs arithmetic operations are indicated by the symbols addition subtraction x multiplication or fexponentiation 3 2 Types of Instruction We consi

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