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CPAN 320 COBOL
Lecture 9
Decision Making
Basic conditional statements:
A conditional statement will perform a certain operation if a given condition is
met. The Basic format of IF statement is:
IF CONDITION-1
[THEN]
IMPERATIVE STATEMENT-1 …
[ELSE
IMPERATIVE STATEMENT-2 ….]
[END-IF]
THEN and END-IF are COBOL 85 options.
As we studied before, an imperative statement performs an operation
regardless of any existing condition, and it is not a condition by itself.
The following are simple relational conditions that may be used with IF
statement:
 IS EQUAL TO
 IS LESS THAN
 IS GREATER THAN
Ex 1:
Following is a simple IF statement without ELSE option:
IF ITEM-1 IS EQUAL TO ITEM-2
THEN
MOVE ‘EQUAL ITEMS WAS FOUND’ TO WS-MESSAGE
END-IF
Ex 2:
Following is a simple IF statement with ELSE option:
IF AMNT-1 IS LESS THAN AMNT-2
THEN
SUBTRACT AMNT-1 FROM AMNT-2 GIVING AMNT-3
ELSE
SUBTRACT AMNT-2 FROM AMNT-1 GIVING AMNT-3
END-IF
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Ex 3:
More than one imperative statements can be executed within the same IF
statement:
IF AMNT-1 IS LESS THAN AMNT-2
THEN
SUBTRACT AMNT-1 FROM AMNT-2 GIVING AMNT-3
MOVE AMNT-3 TO OUT-FIELD
ELSE
SUBTRACT AMNT-2 FROM AMNT-1 GIVING AMNT-3
MOVE AMNT-3 TO OUT-FIELD
END-IF
In COBOL 85 when we use a scope terminator (such as END-IF,END-READ,
etc), a period at the end of the line is optional except for the last statement in
a paragraph. COBOL 74 users should omit the END-IF and terminate the IF
sentence by placing a period on the previous line.
Ex 4:
Using a period instead of END-IF option:
IF PRICE-1 > PRICE-LIMIT
ADD PRICE-1 TO AMNT GIVING TOTAL
SUBTRUCT 1 FROM UNITS-IN
ELSE
MOVE ZERO TO TOTAL.
MOVE TOTAL TO TOT-OUT.
Note: The last statement is not part of ELSE option, it will be executed all the
time.
Field used in comparison:
Fields used in any conditional statement must be of the same data types in
order to obtain proper results.
Numeric fields are compared algebraically. For example the following values
are all considered equal in COBOL:
12, 12.0, +12.0, 0012
When we compare non-numeric fields the following are considered
equivalent:
ABC , ABC b , ABCbb
The rightmost blanks do not affect the comparison. However leftmost blanks
affect the comparison. For example: bABC and ABC are not equivalent.
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Using Relational Operators in place of Verbs:
We can use the following simple relational operators symbols within COBOL
code instead of verbs:
Operator symbol
Meaning
<
IS LESS THAN
>
IS GREATER THAN
=
IS EQUAL TO
<= (COBOL 85 only)
IS LESS THAN OR EQUAL TO
>= (COBOL 85 only)
IS GREATER THAN OR EQUAL TO
Most COBOL compilers require a blank on each side of the relational
operators symbols.
Ex 5:
IF INV-IN < DEM-IN
PERFOM ADD-SUPPLY
END-IF
Ex 6:
IF AMNT-IN <= ZERO
DISPLAY ‘ NEGATIVE VALUE’
END-IF
Ex 7:
To code the preceding example using COBOL 74 we write:
IF AMNT-IN < ZERO OR AMNT-IN = ZERO
DISPLAY ‘NEGATIVE VALUE’.
CONTINUE or NEXT Sentence:
COBOL 85 expression CONTINUE or COBOL 74 NEXT SENTENCE enable
to:
1- Avoid performing any operation if a condition is met
2- Execute instructions only if ELSE condition is met.
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Ex 8: COBOL 85
IF AMNT-1 = AMNT-2
CONTINUE
ELSE
ADD 1 TO TOTAL
END-IF
In this example if AMNT-1 equals to AMNT-2 then nothing is done, otherwise
1 will be added to TOTAL.
Ex 9: COBOL 74
The same above example using COBOL 74
IF AMNT-1 = AMNT-2
NEXT SENTENCE
ELSE
ADD 1 TO TOTAL.
Ex 10:
In the following example we add 1 to counter if TOTAL-1 is equals to TOTAL2 ,otherwise nothing is done.
IF TOTAL-1 = TO TATAL-2
ADD 1 TO COUNTER
ELSE
CONTINUE
END-IF
Nested conditional:
A nested conditional is a condition in which an IF statement can contain
additional IF statements, for example:
IF CONDITION-1
STATEMENT-1
ELSE
IF CONDITION-2
STATEMENT-2
ELSE
STATEMENT-3
[END-IF]
[END-IF]
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Ex 11:
IF AMNT > ZERO
IF UNITS-IN > ZERO
PERFORM ORDER-1
ELSE
PERFORM ADD-SUPPLY
END-IF
ELSE
PERFORM START-OVER
ENDIF
In this example if AMNT is positive then another condition is tested for UNITSIN field. If AMNT-IN is not positive then START-OVER procedure is executed.
Compound conditional using (OR, AND):
With compound conditional, several conditions can be tested with one
statement.
When we have two or more conditions and at least one must be met we use
OR operator to separate them.
AND operator is used to separate two or more conditions when all must be
met.
The following rules apply for using (AND) and (OR):
 If both (OR) and (AND) are used in the same compound conditional
then conditions surrounding the word AND are evaluated first then
conditions surrounding the word OR are evaluated last.
 Several AND or Several OR can be used in the same compound
conditional.
 To override the sequence of evaluation, parentheses should be used.
Ex 12:
IF AMNT-1 = AMNT-2 OR AMNT-2 > AMNT-3
PERFORM TOTAL-CALCULATION
END-IF
Ex 13:
IF AMNT-1 = AMNT-2 AND AMNT-3 >ZERO
PERFORM TOTAL-CALCULATION
END-IF
Sign Test:
It is used to test whether a field is POSITIVE, NEGATIVE or ZERO.
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Ex 14:
IF AMNT IS POSITIVE
PERFORM CALCULATION
END-IF
Class test:
It is used to test the type of a data in a field by coding:
IF identifier-1 IS NUMERIC
Or
IF identifier-1 IS ALPHABETIC
COBOL 85 offers two extra class tests that are:
ALPHABETIC-UPPER and ALPHABETIC-LOWER
Negating conditional:
All simple relational, class and sign tests may be coded using a negated
conditional (NOT).
Ex 15:
IF AMNT IS NOT EQUAL TO AMNT-2
PERFORM DISPLAY-TOTAL
ELSE
PERFORM ORDER-DETAILS
END-IF
Condition-names:
A condition name is a user-defined word established in the DATA DIVISION.
It gives a name to a specific value that an identifier can assume.
An 88-level entry coded in the DATA DIVISION is a condition-name that
denotes a possible value of an identifier. It has the following format:
88 condition-name VALUE literal.
Ex 16:
We can code in the DATA DIVISION
05 MARITAL-STATUS
88 SINGLE
PIC X.
VALUE
‘S’
In the PROCEDURER DIVISION we can code:
IF SINGLE
PERFORM SINGLE-RTN
END-IF
Instead of
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IF MARITAL-STATUS IS EQUAL TO ‘S’
PERFORM SINGLE-RTN
END-IF
Ex 17:
05 MARITAL-STATUS PIC X .
88
SINGLE
VALUE ‘S’
88
DEVORCED VALUE ‘D’.
88
MARRID
VALUE ‘M’.
Ex 18:
05 STATUS PIC 9.
88 STATUS-VALU 1 THRU 5.
Ex 19:
05 CODE
PIC X.
88 CODE-VAL ‘A’ ‘B’ ‘F’.
Ex 20:
05 CODE
PIC X(5).
88 STYLE VALUE ALL ‘A’.
EVALUATE Statement (COBOL 85):
EVALUATE verb is used to test a series of conditions. It implements the case
structure. This statement has the following format:
EVALUATE {identifier-1 or expression-1 }
WHEN condition-1 imperative statement-1
…
[WHEN OTHER imperative statement-2]
[END-EVALUATE]
Ex 21:
EVALUATE MENU-SELECTION
WHEN 1 PERFORM ENTER-DATA
WHEN 2 PERFORM PRINT-REPORT
WHEN OTHER
PERFORM INCORRECT-SELECTION
END-EVALUATE
Instead of
IF MENU-SELECTION IS EQUAL TO 1
PERFORM ENTER-DATA
END-IF
IF MENU-SELECTION IS EQUAL TO 2
PERFORM PRINT-REPORT
END-IF
IF MENU-SELECTION IS NOT EQUAL TO 1 AND NOT EQUAL TO 2
PERFORM ENTER-DATA
END-IF
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Ex 22:
EVALUATE TRUE
WHEN MENU-SELECTION = 1 PERFORM ENTER-DATA
WHEN MENU-SELECTION = 2 PERFORM PRINT-REPORT
WHEN OTHER
PERFORM INCORRECT-SELECTION
END-EVALUATE
Ex 23:
DATA DIVISION
5 LEVEL
PIC 9.
88 FIRST
88 SECOND
88 THIRD
VALUE 1.
VALUE 2.
VALUE 3.
In the PROCEDURE DIVISION we can code:
EVALUATE LEVEL
WHEN FIRST
PERFORM
WHEN SECOND PERFORM
WHEN THIRD
PERFORM
WHEN OTHER
PERFORM
END-EVALUATE
FIRST-PROCEDURE
SECOND-PROCEDURE
THIRD-PROCEDURE
ERROR-PROCEDURE
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Accessing segment of a field using COCOL 85:
It is possible to reference a portion of an elementary field with COBOL 85.
Assume that the field WS-PHONE-NO is defined in the WORKINGSTORAGE SECTION as follow:
WS-PHONE-NO
PIC X(10) VALUE ‘4161112222’
To test the area code part of this field we can code the following in the
PROCEDURE DIVISION:
IF WS-PHONE-NO (1:3) = ’416’
DISPLAY ‘ TORONTO’
END-IF
The result of this IF statement is ‘TORONTO’.
The first integer in the parentheses represents the starting position of the field
segment; the second integer represents the field segment length.
Ex 24:
IDENTIFICATION DIVISION.
PROGRAM-ID. YearSegment.
DATA DIVISION.
WORKING-STORAGE SECTION.
01 YEAR-IN-4 PIC 9999.
01 YEAR-IN-2 PIC 99.
PROCEDURE DIVISION.
MOVE 1900 TO YEAR-IN-4
MOVE YEAR-IN-4(3:2) TO YEAR-IN-2
DISPLAY YEAR-IN-2
STOP RUN.
Reference: textbook Ch 8.
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