Day 13: Mastering COBOL Loops and Iterations Using PERFORM for Repeated and Controlled Program Execution

 


1. Introduction: The Importance of Loops in COBOL Programming

In programming, loops are essential for performing repetitive tasks efficiently. Instead of writing the same code multiple times, you can use a loop to repeat an operation — such as processing multiple records, printing a list of employees, or calculating totals for several transactions.

In COBOL, looping is handled using the PERFORM statement, which provides flexible control for executing parts of your program repeatedly. Depending on your needs, COBOL supports:

  • Simple PERFORM (for one-time execution of a paragraph),

  • PERFORM UNTIL (for condition-based looping), and

  • PERFORM VARYING (for counter-based loops).

These looping mechanisms make COBOL highly efficient for batch processing and large-scale data management, which are common in enterprise and financial systems.

2. Simple and Conditional PERFORM Statements

The PERFORM statement executes a paragraph or section in your program. It helps organize your code into smaller, reusable parts.

Simple PERFORM

PERFORM DISPLAY-DETAILS.

DISPLAY-DETAILS.
    DISPLAY "WELCOME TO COBOL PROGRAMMING".

Here, DISPLAY-DETAILS runs once when called. This approach promotes modular and readable code.

PERFORM UNTIL

This version repeats code until a condition becomes true:

MOVE 1 TO I.
PERFORM UNTIL I > 5
    DISPLAY "VALUE OF I = " I
    ADD 1 TO I
END-PERFORM.

This loop prints numbers from 1 to 5.
The condition is checked before each iteration, so if it’s already true, the loop won’t execute at all.

3. Using PERFORM VARYING for Counter-Controlled Loops

The PERFORM VARYING statement is COBOL’s most flexible looping structure — similar to a “for loop” in modern languages. It automatically updates a counter variable after each iteration.

Example:

PERFORM VARYING I FROM 1 BY 1 UNTIL I > 10
    DISPLAY "EMPLOYEE NUMBER: " I
END-PERFORM.

Explanation:

  • FROM 1 → Starting value

  • BY 1 → Increment by 1 each time

  • UNTIL I > 10 → Stop when condition becomes true

You can also nest loops:

PERFORM VARYING I FROM 1 BY 1 UNTIL I > 3
    PERFORM VARYING J FROM 1 BY 1 UNTIL J > 3
        DISPLAY "I=" I " J=" J
    END-PERFORM
END-PERFORM.

This is perfect for matrix processing, tables, and record iteration in COBOL applications.

🧠 Key Takeaways

  • PERFORM allows modular and reusable program sections.

  • PERFORM UNTIL executes loops based on a condition.

  • PERFORM VARYING provides counter-based iteration.

  • Loops make COBOL efficient for repetitive and bulk operations.

  • Combining PERFORM with tables and conditions leads to robust business logic.

💻 Practice Task

  1. Create a COBOL program named LoopExample.cbl.

  2. Accept a number N from the user.

  3. Use PERFORM VARYING to display all numbers from 1 to N.

  4. Use PERFORM UNTIL to calculate the sum of numbers from 1 to N.

  5. Display both the list and the sum at the end.


"This Content Sponsored by SBO Digital Marketing.

Mobile-Based Part-Time Job Opportunity by SBO!

Earn money online by doing simple content publishing and sharing tasks. Here's how:

  • Job Type: Mobile-based part-time work
  • Work Involves:
    • Content publishing
    • Content sharing on social media
  • Time Required: As little as 1 hour a day
  • Earnings: ₹300 or more daily
  • Requirements:
    • Active Facebook and Instagram account
    • Basic knowledge of using mobile and social media

For more details:

WhatsApp your Name and Qualification to 9994104160

a.Online Part Time Jobs from Home

b.Work from Home Jobs Without Investment

c.Freelance Jobs Online for Students

d.Mobile Based Online Jobs

e.Daily Payment Online Jobs

Keyword & Tag: #OnlinePartTimeJob #WorkFromHome #EarnMoneyOnline #PartTimeJob #jobs #jobalerts #withoutinvestmentjob"


Comments

Post a Comment