7-1 Structured COBOL Programming Nancy Stern Hofstra University Robert A. Stern Nassau Community...

7-1

Structured COBOL Programming

Nancy Stern Hofstra University

Robert A. Stern Nassau Community College

James P. Ley University of Wisconsin-Stout

John Wiley & Sons, Inc.

PowerPoint Winifred J. Rex Presentation Bowling Green State University

10th edition

7-2

Computing in COBOL: The Arithmetic Verbs and Intrinsic Functions

Chapter 7

7-3

Chapter Objectives

To familiarize you with

• Ways in which arithmetic may be performed in COBOL

• Formats and options available with arithmetic verbs

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Chapter Contents

• Basic Arithmetic Verbs

• Options Available with Arithmetic Verbs

• COMPUTE Statement

• Signed Numbers in Arithmetic Operations

• Intrinsic Functions

7-5

Basic Arithmetic Verbs

• ADD, SUBTRACT, MULTIPLY, DIVIDE

• All require fields operated on to– Have numeric PICTURE clauses– Contain numeric data when statements

executed

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ADD … TO Statement

identifier-1ADD … TO identifier-2 ...

literal-1

• identifier-1 or literal-1 added to identifier-2

• Result stored in identifier-2

• What does the syntax tell you?

Format 1

7-7

ADD … TO Examples

Assume X, Y and Z are numeric fieldsX = 5, Y = 3 and Z = 7

ADD Statement ResultAdd X To Y Y = 8Add X, 9 To Y Y = 17Add X, 6, Y To Z Z = 21

7-8

ADD … TO Statement

• Identifiers preceding TO are unchanged• Value of identifier after TO

– Used in ADD operation– Original value replaced with ADD result

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ADD … GIVING Statement

identifier-1ADD … GIVING identifier-2 ...

literal-1

• Identifiers and literals preceding GIVING added together

• Result stored in identifier-2• Identifier-1 and literal-1 are unchanged!

Format 2

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ADD … GIVING Examples


ADD Statement ResultAdd X, Y Giving Z Z = 8Add X, 10 Giving Y Y = 15Add X, 4, Y Giving Z Z = 12 X, Y, 10, etc. are all unchanged!

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• Identifiers preceding GIVING are unchanged

• Value of identifier after GIVING – Not part of ADD operation– Original value replaced with ADD result May be report-item with edit symbols

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• TO may be included before last identifier or literal preceding GIVING

• For example: Add X, 4 To Y Giving Z– Adds values of X, 4 and Y together– Stores result in Z– X, 4, and Y are UNCHANGED!

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ADD Statement

• Comma followed by one space may be used to separate operands

Result of ADD always placed in field(s) after TO or GIVING

Result field must be data-name, not a literal

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Producing More Than One Sum• Several ADD operations can be done in single

statement• Assume X, Y and Z are numeric fields

X = 5, Y = 3 and Z = 7

ADD Statement ResultAdd X To Y, Z Y = 8, Z = 12

Value of X is added to Y and ZAdd X, 6 Giving Y, Z Y = 11, Z = 11

Result of the addition of X and 6 are MOVED to Y and Z. Former values of Y and Z do NOT participate in this operation.

7-15

ADD … TO vs ADD … GIVING

• Use ADD … TO when original contents of result operand – Need to be included in operation – But are not needed after operation– All operands must be numeric.

• Use ADD … GIVING when– Original contents of all operands except

result field are to be retained– Operands following the GIVI NG need NOT

be numeric and will frequently be report-item fields.

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SUBTRACT Statement

identifier-1SUBTRACT … FROM identifier-2 ...

literal-1

• identifier-1 or literal-1 subtracted from identifier-2


Format 1

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SUBTRACT Examples

Assume A, B and C are numeric fields A = 6, B = 2 and C = 18

SUBTRACT Statement ResultSubtract A From C C = 12Subtract B, 5 From C C = 11Subtract B From A, C A = 4, C = 16

7-18

SUBTRACT Statement Rules

• All identifiers and literals must be numeric

Data-name, not a literal, must follow FROM

• All fields, literals preceding FROM added together

• Sum subtracted from field after FROM

• Result stored in field after FROM

7-19

SUBTRACT … GIVING Statement

identifier-1 identifier-2SUBTRACT … FROM

literal-1 literal-2

GIVING identifier-3 ...

• identifier-1 or literal-1 subtracted from identifier-2 or literal-2

• Result stored in identifier-3• Only Operand changed is identifier-3!

Format 2

7-20

SUBTRACT … GIVING Examples

Assume A, B and C are numeric fields A = 6, B = 2 and C = 18

SUBTRACT Statement ResultSubtract B From A Giving C C = 4Subtract A From 15 Giving C C = 9Subtract A, 4 From C Giving B B = 8

7-21

SUBTRACT … GIVING Rules• All identifiers, literals before FROM must be

numeric• GIVING must be followed by data-name

May be numeric or report-item remember, GIVING really is a Move results

here• All fields, literals preceding FROM added

together• Sum subtracted from field after FROM

– BUT ‘from field’ is NOT changed!!• Result stored in field after GIVING

7-22

MULTIPLY Statement

identifier-1MULTIPLY BY identifier-2 ...

literal-1

• identifier-1 or literal-1 multiplied by identifier-2


Format 1

7-23

MULTIPLY Examples

Assume Q, R and S are numeric fields Q = 4, R = 7 and S = 5

MULTIPLY Statement ResultMultiply Q By R R = 28Multiply 10 By S S = 50 Multiply 2 By R, S R = 14, S = 10

7-24

MULTIPLY … GIVING Statement

identifier-1 identifier-2MULTIPLY BY

literal-1 literal-2


• identifier-1 or literal-1 multiplied by identifier-2 or literal-2

Result stored in identifier-3• Must be careful here!!! (more ahead!)

Format 2

7-25

MULTIPLY … GIVING Examples

Assume Q, R and S are numeric fields Q = 4, R = 7 and S = 5

MULTIPLY Statement ResultMultiply Q By R Giving S S = 28Multiply Q By 3 Giving S S = 12Multiply 6 By Q Giving R, S R = 24

S = 24

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MULTIPLY StatementOnly two operands can be multiplied• To obtain product of 3 operands

requires two instructions

To find Price x Qty x Discount

Multiply Price By Qty Giving WS-AmtMultiply Discount By WS-Amt

7-27

DIVIDE Statement

identifier-1DIVIDE INTO identifier-2 ...

literal-1

• identifier-1 or literal-1 divided into identifier-2


Format 1

7-28

DIVIDE Examples


DIVIDE Statement ResultDivide X Into Y Y = 6Divide 3 Into Y Y = 4 Divide 2 Into Y, Z Y = 6, Z = 4

7-29

DIVIDE … GIVING Statement

identifier-1 INTO identifier-2

DIVIDE literal-1 BY literal-2


• identifier-1 or literal-1 divided into or by identifier-2 or literal-2


Format 2

7-30

DIVIDE … GIVING Examples


DIVIDE Statement ResultDivide X Into Y Giving Z Z = 6Divide Y By X Giving Z Z = 6Divide 16 By Z Giving X, Y X = 2

Y = 2Note: only receiving fields are changed!!

7-31

REMAINDER Clause

• Optional clause with DIVIDE used to store remainder of division

Assume Q and R have PICTUREs of 99

Divide 70 By 15

Giving Q Remainder R

• Stores quotient 4 in Q and integer remainder 10 in R

7-32

ROUNDED Option

• Arithmetic result truncated if room to store all decimal positions not available– Result of 3.89 stored in field with PIC 9V9

as 3^8

• Include ROUNDED to round result to PICTURE specification– Result of 3.89 stored as 3.9 if ROUNDED

option used

7-33

ROUNDED Option

01 Amt1 Pic 9V99 Value 2.25.

01 Amt2 Pic 999.

Arithmetic statement Result Value Stored

Multiply .3 By Amt1 .675 Amt1 = 0^67

Multiply .3 By Amt1 Rounded .675 Amt1 = 0^68

Divide 150 By 9Giving Amt2 Rounded 16.66… Amt2 = 017

Examples

7-34

Overflow or Size Error

• Occurs when result value too large to be stored in result field

• Result of this ADD statement is 1,075Add 350 To 725 Giving Num

• If Num has PICTURE of 999, only 3 digits can be stored

• High-order digits truncated so 075 stored in Num

7-35

Checking for Overflow

• Any arithmetic statement may include one or both size error clauses

• ON SIZE ERROR statement(s)– Specifies one or more statements to be

executed if overflow (size error) occurs

• NOT ON SIZE ERROR statement(s)– Specifies one or more statements to be

executed if overflow (size error) does not occur

7-36

SIZE ERROR Clause Example

Add X To Y Giving Z

On Size Error Display ' Result too large'

Not On Size Error Perform Calc-Para

End-Add

• If sum of X and Y too large to store in Z, Display statement executed

• If Z large enough for result, Calc-Para is performed

7-37

SIZE ERROR Clauses• When using one or both clauses, use scope

terminator to end arithmetic operation– END-ADD, END-SUBTRACT – END-MULTIPLY, END-DIVIDE

• If you do not?Multiply A by B

on size error………

end-multiply

7-38

Size of Receiving Fields

• Ensure receiving field has PICTURE large enough to store result

• Addition - define resultant field one position larger than largest field added

• Subtraction - define resultant field as large as number being subtracted from– Assumes positive numbers– Assumes smaller subtracted from larger

number

7-39

Size of Receiving Fields

• Multiplication - define resultant field equal to sum of lengths of operands begin multiplied

• Division - define resultant field equal to sum of number of digits in divisor and dividend

• Go through examples!!!

7-40

COMPUTE Statement

• General arithmetic statement using symbols in place of arithmetic verbs

Symbol Verb+ ADD- SUBTRACT* MULTIPLY/ DIVIDE** exponentiation

7-41

COMPUTE Statement – simple format

arithmetic-exp-1COMPUTE identifier-1 … = literal-1

identifier-2

• Identifier to left of equal sign set to value of arithmetic-expression, literal or identifier on right of equal sign

Format

7-42

COMPUTE Examples


COMPUTE Statement ResultCompute Z = X * Y Z = 36Compute X = Z - Y + 2 X = 10Compute X = Y X = 4Compute Z = Y ** 2 Z = 16Resultant field need NOT be numeric!!!!!May use both: Computer X, X-Out = …

7-43

Order of Evaluation• Arithmetic expression may include any

combination of symbols +, -, *, / or ** • Order of operations

1. ** all exponentiation performed first2. * or / in order or appearance left to right3. + or - in order or appearance left to right4. ( ) override rules 1-3, all operations

in ( ) performed firstKnow these rules; Practice examples!!!

7-44

COMPUTE Examples


What are the order of operations???

COMPUTE Statement ResultCompute Z = Y / X + 3 Z = 6Compute Z = Y / (X + 3) Z = 2Compute Y = Z + X * 10 Y = 65Compute Y = Z * X / 10 Y = 3

7-45

COMPUTE Statement• COMPUTE can include same optional

clauses used with other arithmetic verbs• ROUNDED follows result field (identifier

preceding equal sign)• If ON SIZE ERROR or NOT ON SIZE

ERROR clauses used, include scope terminator END-COMPUTE

• When you add ON Size Error or Not On Size Error, you are making an imperative statement a ‘conditional statement’ and thus the scope terminator needs to show the scope of the condition.

7-46

Signed Numbers

• Use S in PIC clause of result field if– Numbers used in calculation may be

negative– Calculation may produce negative results

• PIC clause without S assumed to be unsigned– If negative result stored in unsigned

field, sign not retained

7-47

Intrinsic Functions

• Built-in procedures to perform particular task like– Find square root of number– Convert letters to uppercase– Get current date

• Approved as extensions to COBOL standard in 1989

• Now included in many compilers

7-48

Intrinsic Functions

Find square root of X and place result in Y

Compute Y = Function Sqrt(X)

• Value of X passed to function called Sqrt

• Code in function finds square root of X

• Result returned by Sqrt assigned to Y

• Used to have to say (…) ** (.5)

Example

7-49

Intrinsic Functions

Convert More-Data to uppercase

Move Function Upper-Case(More-Data) To Up-More-Data

• If More-Data = "Yes", function Upper-Case returns value "YES"

• Value "YES" moved to Up-More-Data

Example

7-50

Intrinsic Functions – format!!

FUNCTION function-name (argument)

• Argument - input to function– May be numeric or alpha-numeric

depending on function – Functions may have 0, 1 or more

arguments.

Format

7-51

Intrinsic Functions

• Output of function - result returned after function performs its task

Function returning alphanumeric result used in statements using alphanumeric data-items (like Upper-Case)

Function returning numeric result can be used only in arithmetic expressions like SQRT( )

7-52

COBOL 2002+ Changes

• Spaces around arithmetic operators will no longer be required

• COMPUTE statement will yield same results on all compilers– Will make precision or number of decimal

places in each intermediate calculation fixed

7-53

Chapter Summary

• ADD, SUBTRACT, MULTIPLY, and DIVIDE verbs – format without GIVING

• Receiving field is part of arithmetic• May not be report-item

– with GIVING format• Receiving field is not part of arithmetic• May be report-item

7-54

Chapter Summary

• COMPUTE used for any combination of arithmetic operations

• Order of evaluation of operators1. **

2. * or / in sequence left to right

3. + or - in sequence left to right

4. ( ) override normal hierarchy rules

7-55

Chapter Summary

• ROUNDED can follow receiving field in any arithmetic verb

• ON SIZE ERROR, NOT ON SIZE ERROR– Can be used with any arithmetic verb– Include scope terminator (e.g., END-ADD)

7-56

Chapter Summary

• Intrinsic functions added as COBOL extensions in 1989– Calendar– Numerical analysis– Statistical– Trigonometric– Financial– Character and String

7-57

Copyright © 2003 John Wiley & Sons, Inc. All rights reserved. Reproduction or translation of this work beyond that permitted in Section 117 of the 1976 United States Copyright Act without the express written permission of the copyright owner is unlawful. Request for further information should be addressed to the Permissions Department, John Wiley & Sons, Inc. The purchaser may make back-up copies for his/her own use only and not for distribution or resale. The Publisher assumes no responsibility for errors, omissions, or damages, caused by the use of these programs or from the use of the information contained herein.

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