Loop Statements

There are some tasks that need to be done over and over again like reading each record of a file till its end. The loop statements used in COBOL are −

• Perform Thru
• Perform Until
• Perform Times
• Perform Varying

Perform Thru

Perform Thru is used to execute a series of paragraph by giving the first and last paragraph names in the sequence. After executing the last paragraph, the control is returned back.

In-line Perform

Statements inside the PERFORM will be executed till END-PERFORM is reached.

Syntax

Following is the syntax of In-line perform −

PERFORM 
   DISPLAY 'HELLO WORLD'
END-PERFORM.

Out-of-line Perform

Here, a statement is executed in one paragraph and then the control is transferred to other paragraph or section.

Syntax

Following is the syntax of Out-of-line perform −

PERFORM PARAGRAPH1 THRU PARAGRAPH2

Example

IDENTIFICATIONDIVISION.PROGRAM-ID. HELLO.PROCEDUREDIVISION.
   A-PARA.PERFORMDISPLAY'IN A-PARA'END-PERFORM.PERFORM C-PARA THRU E-PARA.
   
   B-PARA.DISPLAY'IN B-PARA'.STOPRUN.
   
   C-PARA.DISPLAY'IN C-PARA'.
   
   D-PARA.DISPLAY'IN D-PARA'.
   
   E-PARA.DISPLAY'IN E-PARA'.

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 A-PARA
IN C-PARA
IN D-PARA
IN E-PARA
IN B-PARA

Perform Until

In perform until, a paragraph is executed until the given condition becomes true. With test before is the default condition and it indicates that the condition is checked before the execution of statements in a paragraph.

Syntax

Following is the syntax of perform until −

PERFORM A-PARA UNTILCOUNT=5PERFORM A-PARA WITHTESTBEFOREUNTILCOUNT=5PERFORM A-PARA WITHTESTAFTERUNTILCOUNT=5

Example

IDENTIFICATIONDIVISION.PROGRAM-ID. HELLO.DATADIVISION.WORKING-STORAGESECTION.01 WS-CNT PIC9(1)VALUE0.PROCEDUREDIVISION.
   A-PARA.PERFORM B-PARA WITHTESTAFTERUNTIL WS-CNT>3.STOPRUN.
   
   B-PARA.DISPLAY'WS-CNT : 'WS-CNT.ADD1TO WS-CNT.

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-CNT : 0
WS-CNT : 1
WS-CNT : 2
WS-CNT : 3

Perform Times

In perform times, a paragraph will be executed the number of times specified.

Syntax

Following is the syntax of perform times −

PERFORM A-PARA 5 TIMES.

Example

IDENTIFICATIONDIVISION.PROGRAM-ID. HELLO.PROCEDUREDIVISION.
   A-PARA.PERFORM B-PARA 3TIMES.STOPRUN.
   
   B-PARA.DISPLAY'IN B-PARA'.

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 B-PARA
IN B-PARA
IN B-PARA

Perform Varying

In perform varying, a paragraph will be executed till the condition in Until phrase becomes true.

Syntax

Following is the syntax of perform varying −

PERFORM A-PARA VARYING A FROM 1 BY 1 UNTIL A = 5.

Example

IDENTIFICATIONDIVISION.PROGRAM-ID. HELLO.DATADIVISION.WORKING-STORAGESECTION.01 WS-A PIC9VALUE0.PROCEDUREDIVISION.
   A-PARA.PERFORM B-PARA VARYING WS-A FROM1BY1UNTIL WS-A=5STOPRUN.
   
   B-PARA.DISPLAY'IN B-PARA ' WS-A.

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 B-PARA 1
IN B-PARA 2
IN B-PARA 3
IN B-PARA 4

GO TO Statement

GO TO statement is used to change the flow of execution in a program. In GO TO statements, transfer goes only in the forward direction. It is used to exit a paragraph. The different types of GO TO statements used are as follows −

Unconditional GO TO

GO TO para-name.

Conditional GO TO

GO TO para-1 para-2 para-3 DEPENDING ON x.

If ‘x’ is equal to 1, then the control will be transferred to the first paragraph; and if ‘x’ is equal to 2, then the control will be transferred to the second paragraph, and so on.

Example

IDENTIFICATIONDIVISION.PROGRAM-ID. HELLO.DATADIVISION.WORKING-STORAGESECTION.01 WS-A PIC9VALUE2.PROCEDUREDIVISION.
   A-PARA.DISPLAY'IN A-PARA'GOTO B-PARA.
   
   B-PARA.DISPLAY'IN B-PARA '.GOTO C-PARA D-PARA DEPENDINGON WS-A.
   
   C-PARA.DISPLAY'IN C-PARA '.
   
   D-PARA.DISPLAY'IN D-PARA '.STOPRUN.

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 A-PARA
IN B-PARA 
IN D-PARA