What is FOR in COBOL programming?

FOR is a clause used in COBOL for loop control and iteration management. It's commonly used with PERFORM statements to specify the number of times a paragraph or section should be executed, providing controlled repetitive processing capabilities.

How do I use FOR with PERFORM statements?

Use FOR with PERFORM by specifying 'PERFORM paragraph-name FOR number-of-times TIMES' or with VARYING clauses for more complex iteration control. The FOR clause determines how many iterations the loop will execute.

What's the difference between FOR and other loop control methods?

FOR provides simple count-based iteration, VARYING offers variable-controlled loops with increment/decrement, UNTIL provides condition-based termination, and WHILE offers condition-based continuation. Each serves different loop control needs.

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COBOL Tutorial

COBOL FOR Clause

The FOR clause represents a fundamental iteration control mechanism in COBOL programming, serving as a precise specification for defining the number of times a particular operation, paragraph, or section should be executed within repetitive processing structures. This clause embodies the principles of controlled iteration by providing deterministic loop execution capabilities, enabling sophisticated repetitive processing patterns, and supporting efficient batch processing operations while maintaining program clarity and ensuring predictable execution behavior in enterprise applications and data processing systems that require precise iteration control and performance optimization.

Syntax and Usage

FOR Clause Syntax

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PERFORM paragraph-name FOR integer TIMES
 
PERFORM paragraph-name FOR identifier TIMES
 
PERFORM paragraph-name VARYING identifier 
    FROM initial-value BY increment-value
    UNTIL condition
    FOR maximum-iterations TIMES

Loop Control

Iteration

Count-Based

Basic FOR Examples

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IDENTIFICATION DIVISION.
PROGRAM-ID. FOR-CLAUSE-EXAMPLES.
 
DATA DIVISION.
WORKING-STORAGE SECTION.
01  LOOP-COUNTER            PIC 9(3) VALUE 0.
01  ITERATION-COUNT         PIC 9(3) VALUE 5.
01  TOTAL-PROCESSED         PIC 9(5) VALUE 0.
 
PROCEDURE DIVISION.
MAIN-PROCESSING.
    *> Basic FOR with literal count
    PERFORM SIMPLE-OPERATION FOR 10 TIMES
    
    *> FOR with variable count
    PERFORM VARIABLE-OPERATION FOR ITERATION-COUNT TIMES
    
    *> FOR with computed count
    COMPUTE ITERATION-COUNT = 3 * 4
    PERFORM COMPUTED-OPERATION FOR ITERATION-COUNT TIMES
    
    STOP RUN.
 
SIMPLE-OPERATION.
    ADD 1 TO LOOP-COUNTER
    DISPLAY 'Simple operation iteration: ' LOOP-COUNTER.
 
VARIABLE-OPERATION.
    ADD 1 TO TOTAL-PROCESSED
    DISPLAY 'Variable operation iteration: ' TOTAL-PROCESSED.
 
COMPUTED-OPERATION.
    DISPLAY 'Computed operation executed'.

Key Features and Benefits

Simple Loop Control

• Fixed iteration count
• Predictable execution
• Easy to understand and maintain
• Optimal for batch processing

Flexible Implementation

• Literal or variable counts
• Runtime count determination
• Computed iteration values
• Integration with other clauses

Interactive Tutorial

Hands-On Exercise: Loop Patterns

Practice using FOR clause for different iteration scenarios

Exercise 1: Array Processing

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01 DATA-ARRAY OCCURS 50 TIMES.
   05 ARRAY-VALUE PIC 9(5).
01 ARRAY-INDEX PIC 9(2) VALUE 1.
 
PROCEDURE DIVISION.
    *> Initialize array using FOR
    PERFORM INITIALIZE-ELEMENT FOR 50 TIMES
    
    *> Process array using FOR
    MOVE 1 TO ARRAY-INDEX
    PERFORM PROCESS-ELEMENT FOR 50 TIMES.
 
INITIALIZE-ELEMENT.
    COMPUTE ARRAY-VALUE(ARRAY-INDEX) = ARRAY-INDEX * 10
    ADD 1 TO ARRAY-INDEX.
 
PROCESS-ELEMENT.
    DISPLAY 'Element ' ARRAY-INDEX ': ' ARRAY-VALUE(ARRAY-INDEX)
    ADD 1 TO ARRAY-INDEX.

Exercise 2: Batch Processing

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01 BATCH-SIZE PIC 9(3) VALUE 100.
01 RECORD-COUNT PIC 9(5) VALUE 0.
 
PROCEDURE DIVISION.
    *> Process records in batches
    PERFORM PROCESS-BATCH FOR 10 TIMES.
 
PROCESS-BATCH.
    DISPLAY 'Starting batch processing...'
    PERFORM PROCESS-RECORD FOR BATCH-SIZE TIMES
    DISPLAY 'Batch completed. Records processed: ' RECORD-COUNT.
 
PROCESS-RECORD.
    ADD 1 TO RECORD-COUNT
    *> Simulate record processing
    IF FUNCTION MOD(RECORD-COUNT, 25) = 0
        DISPLAY 'Processed ' RECORD-COUNT ' records'
    END-IF.

Advanced FOR Patterns

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IDENTIFICATION DIVISION.
PROGRAM-ID. ADVANCED-FOR-PATTERNS.
 
DATA DIVISION.
WORKING-STORAGE SECTION.
01  DYNAMIC-COUNT           PIC 9(3).
01  NESTED-COUNTER          PIC 9(2) VALUE 0.
01  MATRIX OCCURS 10 TIMES.
    05  MATRIX-ROW OCCURS 10 TIMES.
        10  MATRIX-CELL     PIC 9(3).
 
PROCEDURE DIVISION.
MAIN-PROCESSING.
    *> Dynamic count based on conditions
    COMPUTE DYNAMIC-COUNT = FUNCTION CURRENT-DATE(7:2)
    IF DYNAMIC-COUNT < 5
        MOVE 5 TO DYNAMIC-COUNT
    END-IF
    
    PERFORM DYNAMIC-OPERATION FOR DYNAMIC-COUNT TIMES
    
    *> Nested FOR loops for matrix processing
    PERFORM PROCESS-MATRIX-ROW FOR 10 TIMES
    
    STOP RUN.
 
DYNAMIC-OPERATION.
    ADD 1 TO NESTED-COUNTER
    DISPLAY 'Dynamic operation ' NESTED-COUNTER.
 
PROCESS-MATRIX-ROW.
    ADD 1 TO NESTED-COUNTER
    DISPLAY 'Processing matrix row ' NESTED-COUNTER
    PERFORM PROCESS-MATRIX-CELL FOR 10 TIMES.
 
PROCESS-MATRIX-CELL.
    COMPUTE MATRIX-CELL(NESTED-COUNTER, 1) = NESTED-COUNTER * 10.

Best Practices

Knowledge Check

Test Your Understanding

Question 1: Basic Syntax

What's the correct syntax to execute a paragraph 15 times?

Answer: PERFORM PARAGRAPH-NAME FOR 15 TIMES

Question 2: Variable Usage

How do you use a variable to control FOR loop iterations?

Answer: PERFORM PARAGRAPH-NAME FOR variable-name TIMES, where variable-name contains the iteration count.

Question 3: Best Practice

What should you check before using a variable in a FOR clause?

Answer: Validate that the variable contains a positive numeric value and is within acceptable range to prevent infinite loops or performance issues.

Common Patterns

Array Initialization

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01 DATA-TABLE OCCURS 100 TIMES.
   05 TABLE-VALUE PIC 9(5).
01 INDEX-VAR PIC 9(3) VALUE 1.
 
PROCEDURE DIVISION.
    PERFORM INIT-TABLE-ELEMENT FOR 100 TIMES.
 
INIT-TABLE-ELEMENT.
    MOVE ZEROS TO TABLE-VALUE(INDEX-VAR)
    ADD 1 TO INDEX-VAR.

Report Generation

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01 LINES-PER-PAGE PIC 9(2) VALUE 60.
01 CURRENT-LINE PIC 9(2) VALUE 1.
 
PROCEDURE DIVISION.
    PERFORM PRINT-REPORT-LINE FOR LINES-PER-PAGE TIMES.
 
PRINT-REPORT-LINE.
    DISPLAY 'Report line ' CURRENT-LINE
    ADD 1 TO CURRENT-LINE.

COBOL Tutorial

COBOL FOR Clause

Syntax and Usage

Basic FOR Examples

Key Features and Benefits

Interactive Tutorial

Exercise 1: Array Processing

Exercise 2: Batch Processing

Advanced FOR Patterns

Best Practices

Knowledge Check

Question 1: Basic Syntax

Question 2: Variable Usage

Question 3: Best Practice

Common Patterns

Frequently Asked Questions

Related Concepts

Loop Control

PERFORM Statement

Iteration Patterns

Related Pages

COBOL Tutorial

COBOL FOR Clause

Syntax and Usage

Basic FOR Examples

Key Features and Benefits

Interactive Tutorial

Exercise 1: Array Processing

Exercise 2: Batch Processing

Advanced FOR Patterns

Best Practices

Count Validation

Performance Considerations

Error Handling

Knowledge Check

Question 1: Basic Syntax

Question 2: Variable Usage

Question 3: Best Practice

Common Patterns

Frequently Asked Questions

Can I modify the count variable during FOR loop execution?

What happens if the FOR count is zero or negative?

How does FOR compare to VARYING for loop control?

Can I nest FOR loops?

Related Concepts

Loop Control

PERFORM Statement

Iteration Patterns

Related Pages