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COBOL Tutorial

COBOL VARYING - Quick Reference

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Overview

VARYING is a COBOL clause used with PERFORM statements to create controlled loops that automatically modify variables during iteration. It provides a convenient way to implement counting loops, array processing, and other iterative operations with automatic variable management.

Key Features

  • Automatic variable modification - Variables are incremented/decremented automatically
  • Range-based loops - Execute loops within specified ranges
  • Condition-based termination - Stop loops when conditions are met
  • Multiple variable control - Control multiple variables simultaneously

Syntax and Usage

VARYING clause syntax and usage patterns for different loop control scenarios.

Basic VARYING Loop

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       IDENTIFICATION DIVISION.
       PROGRAM-ID. VARYING-EXAMPLE.
       DATA DIVISION.
       WORKING-STORAGE SECTION.
       01  COUNTER PIC 9(3) VALUE 1.
       01  TOTAL   PIC 9(5) VALUE 0.
       
       PROCEDURE DIVISION.
           PERFORM VARYING COUNTER FROM 1 BY 1 UNTIL COUNTER > 10
               ADD COUNTER TO TOTAL
           END-PERFORM
           
           DISPLAY "Total: " TOTAL
           STOP RUN.

Basic VARYING loop that counts from 1 to 10 and accumulates the total.

VARYING with Range

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       IDENTIFICATION DIVISION.
       PROGRAM-ID. VARYING-RANGE.
       DATA DIVISION.
       WORKING-STORAGE SECTION.
       01  INDEX-VAR PIC 9(2) VALUE 1.
       01  ARRAY-DATA.
           05  ARRAY-ELEMENT PIC 9(3) OCCURS 10 TIMES.
       
       PROCEDURE DIVISION.
           PERFORM VARYING INDEX-VAR FROM 1 TO 10
               MOVE INDEX-VAR TO ARRAY-ELEMENT(INDEX-VAR)
               DISPLAY "Element " INDEX-VAR ": " ARRAY-ELEMENT(INDEX-VAR)
           END-PERFORM
           
           STOP RUN.

VARYING loop with range specification to process array elements.

VARYING with Multiple Variables

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       IDENTIFICATION DIVISION.
       PROGRAM-ID. VARYING-MULTIPLE.
       DATA DIVISION.
       WORKING-STORAGE SECTION.
       01  ROW-INDEX    PIC 9(2) VALUE 1.
       01  COL-INDEX    PIC 9(2) VALUE 1.
       01  MATRIX-DATA.
           05  MATRIX-ROW OCCURS 5 TIMES.
               10  MATRIX-ELEMENT PIC 9(3) OCCURS 5 TIMES.
       
       PROCEDURE DIVISION.
           PERFORM VARYING ROW-INDEX FROM 1 TO 5
               AFTER COL-INDEX FROM 1 TO 5
               MOVE ROW-INDEX TO MATRIX-ELEMENT(ROW-INDEX, COL-INDEX)
               DISPLAY "Matrix[" ROW-INDEX "," COL-INDEX "]: " 
                       MATRIX-ELEMENT(ROW-INDEX, COL-INDEX)
           END-PERFORM
           
           STOP RUN.

Nested VARYING loops to process a two-dimensional matrix.

Loop Types

Range Loops

Loops that execute within a specified range.

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PERFORM VARYING var FROM start TO end

Condition Loops

Loops that execute until a condition is met.

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PERFORM VARYING var UNTIL condition

Increment Loops

Loops with custom increment values.

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PERFORM VARYING var FROM start BY increment

Nested Loops

Loops within loops for complex iteration.

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PERFORM VARYING var1 FROM 1 TO 5
    AFTER var2 FROM 1 TO 3

Best Practices

  • Use meaningful variable names - Choose descriptive names for loop control variables
  • Ensure proper termination - Make sure loops will eventually terminate
  • Consider performance - Avoid excessive nesting or large iteration counts
  • Document loop logic - Add comments explaining complex loop behavior
  • Validate loop bounds - Ensure start and end values are appropriate

VARYING Quick Reference

Loop TypeSyntaxUse Case
RangeVARYING var FROM start TO endFixed iteration count
ConditionVARYING var UNTIL conditionCondition-based termination
IncrementVARYING var FROM start BY incrementCustom step values
NestedVARYING var1 AFTER var2Multi-dimensional processing

Test Your Knowledge

1. What is the primary purpose of VARYING in COBOL?

  • To define data types
  • To control loop iteration and modify variables during execution
  • To perform file operations
  • To handle exceptions

2. Which statement is VARYING most commonly used with?

  • MOVE
  • PERFORM
  • IF
  • STOP

3. What happens to the VARYING variable after each iteration?

  • It remains unchanged
  • It is automatically incremented or decremented
  • It is reset to zero
  • It becomes undefined

4. What is the syntax for VARYING in a PERFORM statement?

  • PERFORM VARYING variable FROM start TO end
  • PERFORM VARYING variable BY increment
  • PERFORM VARYING variable FROM start BY increment UNTIL condition
  • All of the above

5. When does a VARYING loop terminate?

  • When the variable reaches the end value
  • When a condition becomes true
  • Both A and B depending on the loop structure
  • After a fixed number of iterations

Frequently Asked Questions

Related Concepts

PERFORM Statement

Loop control and iteration.

Iteration Control

Loop control structures.

Array Processing

Processing arrays and tables.

Procedure Division

Program logic and control.

Data Manipulation

Data processing techniques.

VALUEWAIT