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COBOL - Conditional Statements
  • 时间：2024-11-03

COBOL - Conditional Statements

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Conditional statements are used to change the execution flow depending on certain conditions specified by the programmer. Conditional statements will always evaluate to true or false. Conditions are used in IF, Evaluate, and Perform statements. The different types of conditions are as follows −

    IF Condition Statement

    Relation Condition

    Sign Condition

    Class Condition

    Condition-Name Condition

    Negated Condition

    Combined Condition

IF Condition Statement

IF statement checks for conditions. If a condition is true, the IF block is executed; and if the condition is false, the ELSE block is executed.

END-IF is used to end the IF block. To end the IF block, a period can be used instead of END-IF. But it is always preferable to use END-IF for multiple IF blocks.

Nested-IF − IF blocks appearing inside another IF block. There is no pmit to the depth of nested IF statements.

Syntax

Following is the syntax of IF condition statements −

IF [condition] THEN
   [COBOL statements]
ELSE
   [COBOL statements]
END-IF.

Example

IDENTIFICATION DIVISION.
PROGRAM-ID. HELLO.

DATA DIVISION.
   WORKING-STORAGE SECTION.
   01 WS-NUM1 PIC 9(9).
   01 WS-NUM2 PIC 9(9).
   01 WS-NUM3 PIC 9(5).
   01 WS-NUM4 PIC 9(6).

PROCEDURE DIVISION.
   A000-FIRST-PARA.
   MOVE 25 TO WS-NUM1 WS-NUM3.
   MOVE 15 TO WS-NUM2 WS-NUM4.
   
   IF WS-NUM1 > WS-NUM2 THEN
      DISPLAY  IN LOOP 1 - IF BLOCK 
      
      IF WS-NUM3 = WS-NUM4 THEN
         DISPLAY  IN LOOP 2 - IF BLOCK 
      ELSE
         DISPLAY  IN LOOP 2 - ELSE BLOCK 
      END-IF
      
   ELSE
      DISPLAY  IN LOOP 1 - ELSE BLOCK 
   END-IF.
   
STOP RUN.

JCL to execute the above COBOL program −

//SAMPLE JOB(TESTJCL,XXXXXX),CLASS = A,MSGCLASS = C
//STEP1 EXEC PGM = HELLO

When you compile and execute the above program, it produces the following result −

IN LOOP 1 - IF BLOCK
IN LOOP 2 - ELSE BLOCK

Relation Condition

Relation condition compares two operands, either of which can be an identifier, pteral, or arithmetic expression. Algebraic comparison of numeric fields is done regardless of size and usage clause.

For non-numeric operands

If two non-numeric operands of equal size are compared, then the characters are compared from left with the corresponding positions till the end is reached. The operand containing greater number of characters is declared greater.

If two non-numeric operands of unequal size are compared, then the shorter data item is appended with spaces at the end till the size of the operands becomes equal and then compared according to the rules mentioned in the previous point.

Syntax

Given below is the syntax of Relation condition statements −

[Data Name/Arithmetic Operation]

   [IS] [NOT] 

[Equal to (=),Greater than (>), Less than (<), 
Greater than or Equal (>=), Less than or equal (<=) ]

[Data Name/Arithmetic Operation]

Example

IDENTIFICATION DIVISION.
PROGRAM-ID. HELLO.

DATA DIVISION.
   WORKING-STORAGE SECTION.
   01 WS-NUM1 PIC 9(9).
   01 WS-NUM2 PIC 9(9).

PROCEDURE DIVISION.
   A000-FIRST-PARA.
   MOVE 25 TO WS-NUM1.
   MOVE 15 TO WS-NUM2.
   
   IF WS-NUM1 IS GREATER THAN OR EQUAL TO WS-NUM2 THEN
      DISPLAY  WS-NUM1 IS GREATER THAN WS-NUM2 
   ELSE
      DISPLAY  WS-NUM1 IS LESS THAN WS-NUM2 
   END-IF.
   
STOP RUN.

JCL to execute the above COBOL program −

//SAMPLE JOB(TESTJCL,XXXXXX),CLASS = A,MSGCLASS = C
//STEP1 EXEC PGM = HELLO

When you compile and execute the above program it produces the following result −

WS-NUM1 IS GREATER THAN WS-NUM2

Sign Condition

Sign condition is used to check the sign of a numeric operand. It determines whether a given numeric value is greater than, less than, or equal to ZERO.

Syntax

Following is the syntax of Sign condition statements −

[Data Name/Arithmetic Operation] 

   [IS] [NOT] 

[Positive, Negative or Zero]

[Data Name/Arithmetic Operation]

Example

IDENTIFICATION DIVISION.
PROGRAM-ID. HELLO.

DATA DIVISION.
   WORKING-STORAGE SECTION.
   01 WS-NUM1 PIC S9(9) VALUE -1234.
   01 WS-NUM2 PIC S9(9) VALUE 123456.

PROCEDURE DIVISION.
   A000-FIRST-PARA.
   IF WS-NUM1 IS POSITIVE THEN
      DISPLAY  WS-NUM1 IS POSITIVE .
      
   IF WS-NUM1 IS NEGATIVE THEN
      DISPLAY  WS-NUM1 IS NEGATIVE .
      
   IF WS-NUM1 IS ZERO THEN
      DISPLAY  WS-NUM1 IS ZERO .
      
   IF WS-NUM2 IS POSITIVE THEN
      DISPLAY  WS-NUM2 IS POSITIVE .

STOP RUN.

JCL to execute the above COBOL program −

//SAMPLE JOB(TESTJCL,XXXXXX),CLASS = A,MSGCLASS = C
//STEP1 EXEC PGM = HELLO

When you compile and execute the above program it produces the following result −

WS-NUM1 IS NEGATIVE
WS-NUM2 IS POSITIVE

Class Condition

Class condition is used to check if an operand contains only alphabets or numeric data. Spaces are considered in ALPHABETIC, ALPHABETIC-LOWER, and ALPHABETIC-UPPER.

Syntax

Following is the syntax of Class condition statements −

[Data Name/Arithmetic Operation>]

   [IS] [NOT] 

[NUMERIC, ALPHABETIC, ALPHABETIC-LOWER, ALPHABETIC-UPPER]

[Data Name/Arithmetic Operation]

Example

IDENTIFICATION DIVISION.
PROGRAM-ID. HELLO.

DATA DIVISION.
   WORKING-STORAGE SECTION.
   01 WS-NUM1 PIC X(9) VALUE  ABCD  .
   01 WS-NUM2 PIC 9(9) VALUE 123456789.

PROCEDURE DIVISION.
   A000-FIRST-PARA.
   
   IF WS-NUM1 IS ALPHABETIC THEN
      DISPLAY  WS-NUM1 IS ALPHABETIC .
      
   IF WS-NUM1 IS NUMERIC THEN
      DISPLAY  WS-NUM1 IS NUMERIC .
      
   IF WS-NUM2 IS NUMERIC THEN
      DISPLAY  WS-NUM2 IS NUMERIC .
   
STOP RUN.

JCL to execute the above COBOL program −

//SAMPLE JOB(TESTJCL,XXXXXX),CLASS = A,MSGCLASS = C
//STEP1 EXEC PGM = HELLO

When you compile and execute the above program, it produces the following result −

WS-NUM1 IS ALPHABETIC
WS-NUM2 IS NUMERIC

Condition-name Condition

A condition-name is a user-defined name. It contains a set of values specified by the user. It behaves pke Boolean variables. They are defined with level number 88. It will not have a PIC clause.

Syntax

Following is the syntax of user-defined condition statements −

88 [Condition-Name] VALUE [IS, ARE] [LITERAL] [THRU LITERAL].

Example

IDENTIFICATION DIVISION.
PROGRAM-ID. HELLO.

DATA DIVISION.
   WORKING-STORAGE SECTION.
   01 WS-NUM PIC 9(3).
   88 PASS VALUES ARE 041 THRU 100.
   88 FAIL VALUES ARE 000 THRU 40.

PROCEDURE DIVISION.
   A000-FIRST-PARA.
   MOVE 65 TO WS-NUM.
   
   IF PASS 
      DISPLAY  Passed with   WS-NUM   marks .
      
   IF FAIL 
      DISPLAY  FAILED with   WS-NUM  marks .
      
STOP RUN.

JCL to execute the above COBOL program −

//SAMPLE JOB(TESTJCL,XXXXXX),CLASS = A,MSGCLASS = C
//STEP1 EXEC PGM = HELLO

When you compile and execute the above program, it produces the following result −

Passed with 065 marks

Negated Condition

Negated condition is given by using the NOT keyword. If a condition is true and we have given NOT in front of it, then its final value will be false.

Syntax

Following is the syntax of Negated condition statements −

IF NOT [CONDITION] 
   COBOL Statements
END-IF.

Example

IDENTIFICATION DIVISION.
PROGRAM-ID. HELLO.

DATA DIVISION.
   WORKING-STORAGE SECTION.
   01 WS-NUM1 PIC 9(2) VALUE 20.
   01 WS-NUM2 PIC 9(9) VALUE 25.

PROCEDURE DIVISION.
   A000-FIRST-PARA.
   
   IF NOT WS-NUM1 IS LESS THAN WS-NUM2 THEN
      DISPLAY  IF-BLOCK 
   ELSE
      DISPLAY  ELSE-BLOCK 
   END-IF.
   
STOP RUN.

JCL to execute the above COBOL program −

//SAMPLE JOB(TESTJCL,XXXXXX),CLASS = A,MSGCLASS = C
//STEP1 EXEC PGM = HELLO

When you compile and execute the above program, it produces the following result −

ELSE-BLOCK

Combined Condition

A combined condition contains two or more conditions connected using logical operators AND or OR.

Syntax

Following is the syntax of combined condition statements −

IF [CONDITION] AND [CONDITION]
   COBOL Statements
END-IF.

Example

IDENTIFICATION DIVISION.
PROGRAM-ID. HELLO.

DATA DIVISION.
   WORKING-STORAGE SECTION.
   01 WS-NUM1 PIC 9(2) VALUE 20.
   01 WS-NUM2 PIC 9(2) VALUE 25.
   01 WS-NUM3 PIC 9(2) VALUE 20.

PROCEDURE DIVISION.
   A000-FIRST-PARA.
   
   IF WS-NUM1 IS LESS THAN WS-NUM2 AND WS-NUM1=WS-NUM3 THEN
      DISPLAY  Both condition OK 
   ELSE
      DISPLAY  Error 
   END-IF.
   
STOP RUN.

JCL to execute the above COBOL program −

//SAMPLE JOB(TESTJCL,XXXXXX),CLASS = A,MSGCLASS = C
//STEP1 EXEC PGM = HELLO

When you compile and execute the above program, it produces the following result −

Both condition OK

Evaluate Verb

Evaluate verb is a replacement of series of IF-ELSE statement. It can be used to evaluate more than one condition. It is similar to SWITCH statement in C programs.

Example

IDENTIFICATION DIVISION.
PROGRAM-ID. HELLO.

DATA DIVISION.
   WORKING-STORAGE SECTION.
   01 WS-A PIC 9 VALUE 0.
   
PROCEDURE DIVISION.
   MOVE 3 TO WS-A.
   
   EVALUATE TRUE
      WHEN WS-A > 2
         DISPLAY  WS-A GREATER THAN 2 

      WHEN WS-A < 0
         DISPLAY  WS-A LESS THAN 0 

      WHEN OTHER
         DISPLAY  INVALID VALUE OF WS-A 
   END-EVALUATE.
   
STOP RUN.

JCL to execute the above COBOL program −

//SAMPLE JOB(TESTJCL,XXXXXX),CLASS = A,MSGCLASS = C
//STEP1 EXEC PGM = HELLO

When you compile and execute the above program, it produces the following result −

WS-A GREATER THAN 2
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