7-1 cobol for the 21 st century nancy stern hofstra university robert a. stern nassau community...
TRANSCRIPT
7-1
COBOL for the 21st Century
Nancy Stern Hofstra University
Robert A. Stern Nassau Community College
James P. Ley University of Wisconsin-Stout (Emeritus)
John Wiley & Sons, Inc.11th edition
7-2
Chapter Contents
• Basic Arithmetic Verbs
• Options Available with Arithmetic Verbs
• COMPUTE Statement
• Signed Numbers in Arithmetic Operations
• Intrinsic Functions
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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
Format 1
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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
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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
Format 2
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ADD … GIVING Examples
Assume X, Y and Z are numeric fieldsX = 5, Y = 3 and Z = 7
ADD Statement ResultAdd X, Y Giving Z Z = 8Add X, 10 Giving Y Y = 15Add X, 4, Y Giving Z Z = 12
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ADD … GIVING Statement
• 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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ADD … GIVING Statement
• 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
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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 fieldsX = 5, Y = 3 and Z = 7
ADD Statement ResultAdd X To Y, Z Y = 8, Z = 12Add X, 6 Giving Y, Z Y = 11, Z = 11
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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
• Use ADD … GIVING when– Original contents of all operands except
result field are to be retained
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SUBTRACT Statement
identifier-1SUBTRACT … FROM identifier-2 ...
literal-1
• identifier-1 or literal-1 subtracted from identifier-2
• Result stored in 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
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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
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SUBTRACT … GIVING Statement
identifier-1 identifier-2
SUBTRACT … 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
Format 2
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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
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SUBTRACT … GIVING Rules
• All identifiers, literals before FROM must be numeric
• GIVING must be followed by data-name– May be numeric or report-item
• All fields, literals preceding FROM added together
• Sum subtracted from field after FROM
• Result stored in field after GIVING
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MULTIPLY Statement
identifier-1MULTIPLY BY identifier-2 ...
literal-1
• identifier-1 or literal-1 multiplied by identifier-2
• Result stored in identifier-2
Format 1
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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
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MULTIPLY … GIVING Statement
identifier-1 identifier-2
MULTIPLY BY literal-1 literal-2
GIVING identifier-3 ...
• identifier-1 or literal-1 multiplied by identifier-2 or literal-2
• Result stored in identifier-3
Format 2
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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 Statement
• Only 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
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DIVIDE Statement
identifier-1DIVIDE INTO identifier-2 ...
literal-1
• identifier-1 or literal-1 divided into identifier-2
• Result stored in identifier-2
Format 1
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DIVIDE Examples
Assume X, Y and Z are numeric fieldsX = 2, Y = 12 and Z = 8
DIVIDE Statement ResultDivide X Into Y Y = 6Divide 3 Into Y Y = 4 Divide 2 Into Y, Z Y = 6, Z = 4
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DIVIDE … GIVING Statement
identifier-1 INTO identifier-2
DIVIDE literal-1 BY literal-2
GIVING identifier-3 ...
• identifier-1 or literal-1 divided into or by identifier-2 or literal-2
• Result stored in identifier-3
Format 2
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DIVIDE … GIVING Examples
Assume X, Y and Z are numeric fieldsX = 2, Y = 12 and Z = 8
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 = 2
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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
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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
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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
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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
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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
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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
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SIZE ERROR Clauses
• When using one or both clauses, use scope terminator to end arithmetic operation– END-ADD, END-SUBTRACT – END-MULTIPLY, END-DIVIDE
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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
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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
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COMPUTE Statement
• General arithmetic statement using symbols in place of arithmetic verbs
Symbol Verb+ ADD- SUBTRACT* MULTIPLY/ DIVIDE** exponentiation
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COMPUTE Statement
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
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COMPUTE Examples
Assume X, Y and Z are numeric fieldsX = 9, Y = 4 and Z = 12
COMPUTE Statement ResultCompute Z = X * Y Z = 36Compute X = Z - Y + 2 X = 10Compute X = Y X = 4Compute Z = Y ** 2 Z = 16
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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 first
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COMPUTE Examples
Assume X, Y and Z are numeric fieldsX = 6, Y = 18 and Z = 5
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
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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
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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
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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
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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
Example
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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
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Intrinsic Functions
FUNCTION function-name (argument)
• Argument - input to function– May be numeric or alpha-numeric
depending on function – Functions may have 0, 1 or more
Format
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Intrinsic Functions
• Output of function - result returned after function performs its task
• Function returning alphanumeric result used in statements using alphanumeric data-items
• Function returning numeric result can be used only in arithmetic expressions
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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
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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
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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)
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