Iterative Statements in COBOL

Introduction

• Iterative statements are also known as loop statements.
• The loop statements are required for repeated execution of the same task based on some requirement.

Loop statement

Following loop statements are used in COBOL:

1. PERFORM THRU

• Using PERFORM THRU, a series of paragraph is executed by giving the first and last paragraph names in the sequence.
• The function is returned after executing the last paragraph.

In-line perform
The statements inside the PERFORM are executed till the END-PERFORM  is reached.

Syntax for In-line perform:

Out-of-line Perform
In Out-of-line Perform, a statement in one paragraph is executed and then the control is transferred to another paragraph.

Syntax for Out-of-line perform:
PERFORM PARAGRAPH1 THRU PARAGRAPH2


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

2. PERFORM UNTIL

• Until the given condition becomes true, a paragraph is executed in PERFORM UNTIL.
• TEST BEFORE is the default condition. Before the execution of statements in a paragraph, the given condition will be tested.
• TEST BEFORE is similar to DO WHILE statement in other programming language.
• TEST AFTER is tested after the execution of the program.

Syntax:


Output:
CNT : 1
CNT : 2
CNT : 3
CNT : 4

3. PERFORM TIMES

'PERFORM TIMES' tells the number of times a paragraph should be executed.

Syntax:
PERFORM A-PARA 5 TIMES


Output:
This is para B
This is para B
This is para B
This is para B

4. PERFORM VARYING

In PERFORM VARYING, a statement in paragraph will be executed till the condition in UNTIL is true.

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


Output:
IN PARA-B 02
IN PARA-B 04
IN PARA-B 06
IN PARA-B 08
IN PARA-B 10