Transcript Lecture Notes from Authors - Chapter 7, Arithmetic Operations.

Structured COBOL Programming
10th edition
John Wiley & Sons, Inc.
Nancy Stern
Hofstra University
Robert A. Stern
Nassau Community College
James P. Ley
University of Wisconsin-Stout
PowerPoint
Presentation
Winifred J. Rex
Bowling Green State University
7-1
Chapter 7
Computing in COBOL: The
Arithmetic Verbs and Intrinsic
Functions
7-2
Chapter Objectives
To familiarize you with
• Ways in which arithmetic may be
performed in COBOL
• Formats and options available with
arithmetic verbs
7-3
Chapter Contents
•
•
•
•
Basic Arithmetic Verbs
Options Available with Arithmetic Verbs
COMPUTE Statement
Signed Numbers in Arithmetic
Operations
• Intrinsic Functions
7-4
Basic Arithmetic Verbs
• ADD, SUBTRACT, MULTIPLY, DIVIDE
• All require fields operated on to
– Have numeric PICTURE clauses
– Contain numeric data when statements
executed
7-5
ADD … TO Statement
Format 1
identifier-1
ADD
… 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?
7-6
ADD … TO Examples
Assume X, Y and Z are numeric fields
X = 5, Y = 3 and Z = 7
ADD Statement
Add X To Y
Add X, 9 To Y
Add X, 6, Y To Z
Result
Y=8
Y = 17
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
Format 2
identifier-1
ADD
… GIVING identifier-2 ...
literal-1
• Identifiers and literals preceding GIVING
added together
• Result stored in identifier-2
• Identifier-1 and literal-1 are unchanged!
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ADD … GIVING Examples
Assume X, Y and Z are numeric fields
X = 5, Y = 3 and Z = 7
ADD Statement
Result
Add X, Y Giving Z
Z=8
Add X, 10 Giving Y
Y = 15
Add X, 4, Y Giving Z
Z = 12
X, Y, 10, etc. are all unchanged!
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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
– 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
Result
Add X To Y, Z
Y = 8, Z = 12
Value of X is added to Y and Z
Add X, 6 Giving Y, ZY = 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.
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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
– 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 reportitem fields.
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SUBTRACT Statement
Format 1
identifier-1
SUBTRACT
… FROM identifier-2 ...
literal-1
• identifier-1 or literal-1 subtracted from
identifier-2
• Result stored in identifier-2
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 SUBTRACT Examples
Assume A, B and C are numeric fields
A = 6, B = 2 and C = 18
SUBTRACT Statement
Subtract A From C
Subtract B, 5 From C
Subtract B From A, C
Result
C = 12
C = 11
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
Format 2
identifier-1
SUBTRACT
… FROM
literal-1
identifier-2
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!
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 SUBTRACT … GIVING Examples
Assume A, B and C are numeric fields
A = 6, B = 2 and C = 18
SUBTRACT Statement
Subtract B From A Giving C
Subtract A From 15 Giving C
Subtract A, 4 From C Giving B
Result
C=4
C=9
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
–  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
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MULTIPLY Statement
Format 1
identifier-1
MULTIPLY
BY identifier-2 ...
literal-1
• identifier-1 or literal-1 multiplied by
identifier-2
• Result stored in identifier-2
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 MULTIPLY Examples
Assume Q, R and S are numeric fields
Q = 4, R = 7 and S = 5
MULTIPLY StatementResult
Multiply Q By R
Multiply 10 By S
Multiply 2 By R, S
R = 28
S = 50
R = 14, S = 10
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MULTIPLY … GIVING Statement
Format 2
identifier-1
MULTIPLY
identifier-2
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
• Must be careful here!!! (more ahead!)
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MULTIPLY … GIVING Examples
Assume Q, R and S are numeric fields
Q = 4, R = 7 and S = 5
MULTIPLY Statement
Multiply Q By R Giving S
Multiply Q By 3 Giving S
Multiply 6 By Q Giving R, S
Result
S = 28
S = 12
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-Amt
Multiply Discount By WS-Amt
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DIVIDE Statement
Format 1
identifier-1
DIVIDE
INTO identifier-2 ...
literal-1
• identifier-1 or literal-1 divided into
identifier-2
• Result stored in identifier-2
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DIVIDE Examples
Assume X, Y and Z are numeric fields
X = 2, Y = 12 and Z = 8
DIVIDE Statement
Divide X Into Y
Divide 3 Into Y
Divide 2 Into Y, Z
Result
Y=6
Y=4
Y = 6, Z = 4
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 DIVIDE … GIVING Statement
Format 2
DIVIDE
identifier-1
literal-1
INTO
BY
identifier-2
literal-2
GIVING identifier-3 ...
• identifier-1 or literal-1 divided into or by
identifier-2 or literal-2
• Result stored in identifier-3
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DIVIDE … GIVING Examples
Assume X, Y and Z are numeric fields
X = 2, Y = 12 and Z = 8
DIVIDE Statement
Divide X Into Y Giving Z
Divide Y By X Giving Z
Divide 16 By Z Giving X, Y
Result
Z=6
Z=6
X=2
Y=2
Note: only receiving fields are changed!!
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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
7-31
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
7-32
ROUNDED Option
Examples
01 Amt1
01 Amt2
Pic 9V99
Pic 999.
Value 2.25.
Arithmetic statement
Multiply .3 By Amt1
Multiply .3 By Amt1 Rounded
Divide 150 By 9
Giving Amt2 Rounded
Result
.675
.675
Value Stored
Amt1 = 0^67
Amt1 = 0^68
16.66… Amt2 = 017
7-33
 Overflow or Size Error
• Occurs when result value too large to
be stored in result field
• Result of this ADD statement is 1,075
Add 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
• If you do not?
Multiply A by B
on size error
…
…
…
end-multiply
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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
• Go through examples!!!
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COMPUTE Statement
• General arithmetic statement using
symbols in place of arithmetic verbs
Symbol
Verb
+
ADD
SUBTRACT
*
MULTIPLY
/
DIVIDE
**
exponentiation
7-40
COMPUTE Statement – simple
format
Format
COMPUTE identifier-1 … =
arithmetic-exp-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
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COMPUTE Examples
Assume X, Y and Z are numeric fields
X = 9, Y = 4 and Z = 12
COMPUTE Statement
Result
Compute Z = X * Y
Z = 36
Compute X = Z - Y + 2
X = 10
Compute X = Y
X=4
Compute Z = Y ** 2
Z = 16
Resultant field need NOT be numeric!!!!!
May use both: Computer X, X-Out = …
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 Order of Evaluation
• Arithmetic expression may include any
combination of symbols +, -, *, / or **
• Order of operations
1.
2.
3.
4.
**
* or /
+ or ()
all exponentiation performed first
in order or appearance left to right
in order or appearance left to right
override rules 1-3, all operations
in ( ) performed first
Know these rules; Practice examples!!!
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COMPUTE Examples
Assume X, Y and Z are numeric fields
X = 6, Y = 18 and Z = 5
What are the order of operations???
COMPUTE Statement
Compute Z = Y / X + 3
Compute Z = Y / (X + 3)
Compute Y = Z + X * 10
Compute Y = Z * X / 10
Result
Z=6
Z=2
Y = 65
Y=3
7-44
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.
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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
Example
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)
7-48
Intrinsic Functions
Example
Convert More-Data to uppercase
Move Function Upper-Case(More-Data)
To Up-More-Data
• If More-Data = "Yes", function UpperCase returns value "YES"
• Value "YES" moved to Up-More-Data
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Intrinsic Functions – format!!
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.
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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 (like UpperCase)
•  Function returning numeric result
can be used only in arithmetic
expressions like SQRT( )
7-51
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
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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
7-53
Chapter Summary
• COMPUTE used for any combination of
arithmetic operations
• Order of evaluation of operators
1.
2.
3.
4.
**
* or / in sequence left to right
+ or - in sequence left to right
( ) override normal hierarchy rules
7-54
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)
7-55
Chapter Summary
• Intrinsic functions added as COBOL
extensions in 1989
– Calendar
– Numerical analysis
– Statistical
– Trigonometric
– Financial
– Character and String
7-56
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7-57