MainframeMaster

COBOL Control Breaks

Control breaks detect changes in key fields and trigger subtotal calculations and report formatting. Learn to process grouped data hierarchically for business reports and summaries.

Basic Control Break Logic

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       WORKING-STORAGE SECTION.
       01 PREVIOUS-DEPT PIC X(10) VALUE SPACES.
       01 CURRENT-DEPT PIC X(10).
       01 DEPT-TOTAL PIC 9(9)V99 VALUE 0.
       01 GRAND-TOTAL PIC 9(9)V99 VALUE 0.
       
       PROCEDURE DIVISION.
       PERFORM UNTIL EOF
           READ EMPLOYEE-FILE AT END SET EOF TO TRUE
           NOT AT END
               MOVE EMP-DEPT TO CURRENT-DEPT
               IF CURRENT-DEPT NOT = PREVIOUS-DEPT
                   PERFORM DEPT-BREAK
               END-IF
               ADD EMP-SALARY TO DEPT-TOTAL
               ADD EMP-SALARY TO GRAND-TOTAL
               MOVE CURRENT-DEPT TO PREVIOUS-DEPT
           END-READ
       END-PERFORM
       PERFORM FINAL-BREAK.

Compare current record key fields with previous values to detect changes. When a change occurs, process the control break (subtotals, headers, footers) before continuing with new group processing.

Control Break Processing

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       DEPT-BREAK.
           IF PREVIOUS-DEPT NOT = SPACES
               DISPLAY 'Department Total: ' PREVIOUS-DEPT ' = ' DEPT-TOTAL
               DISPLAY '----------------------------------------'
           END-IF
           DISPLAY 'Department: ' CURRENT-DEPT
           DISPLAY 'Employee Name        Salary'
           DISPLAY '-------------------  -------'
           MOVE 0 TO DEPT-TOTAL.
       
       FINAL-BREAK.
           IF PREVIOUS-DEPT NOT = SPACES
               DISPLAY 'Department Total: ' PREVIOUS-DEPT ' = ' DEPT-TOTAL
               DISPLAY '========================================'
               DISPLAY 'Grand Total: ' GRAND-TOTAL
           END-IF.

Process control breaks by printing subtotals, headers, and footers. Reset counters for the new group. Handle the final break to print the last group's totals and grand totals.

Multi-Level Control Breaks

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       WORKING-STORAGE SECTION.
       01 PREVIOUS-REGION PIC X(10) VALUE SPACES.
       01 PREVIOUS-DEPT PIC X(10) VALUE SPACES.
       01 CURRENT-REGION PIC X(10).
       01 CURRENT-DEPT PIC X(10).
       01 REGION-TOTAL PIC 9(9)V99 VALUE 0.
       01 DEPT-TOTAL PIC 9(9)V99 VALUE 0.
       01 GRAND-TOTAL PIC 9(9)V99 VALUE 0.
       
       *> Check for breaks in hierarchical order
       IF CURRENT-REGION NOT = PREVIOUS-REGION
           PERFORM REGION-BREAK
       ELSE IF CURRENT-DEPT NOT = PREVIOUS-DEPT
           PERFORM DEPT-BREAK
       END-IF.

Implement multi-level control breaks for hierarchical reporting. Check breaks in order from highest to lowest level (region, then department). Process each level's subtotals and formatting.

Control Break Procedures

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       REGION-BREAK.
           IF PREVIOUS-REGION NOT = SPACES
               PERFORM DEPT-BREAK  *> Process final dept break
               DISPLAY 'Region Total: ' PREVIOUS-REGION ' = ' REGION-TOTAL
               DISPLAY '========================================'
           END-IF
           DISPLAY 'REGION: ' CURRENT-REGION
           DISPLAY '========================================'
           MOVE 0 TO REGION-TOTAL.
       
       DEPT-BREAK.
           IF PREVIOUS-DEPT NOT = SPACES
               DISPLAY 'Department Total: ' PREVIOUS-DEPT ' = ' DEPT-TOTAL
               DISPLAY '----------------------------------------'
           END-IF
           DISPLAY 'Department: ' CURRENT-DEPT
           DISPLAY '----------------------------------------'
           MOVE 0 TO DEPT-TOTAL.

Create separate procedures for each control break level. Higher-level breaks should call lower-level breaks to ensure proper subtotal processing. Reset counters and print appropriate headers/footers.

Control Break Initialization

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       INITIALIZE-CONTROL-BREAKS.
           MOVE SPACES TO PREVIOUS-REGION
           MOVE SPACES TO PREVIOUS-DEPT
           MOVE 0 TO REGION-TOTAL
           MOVE 0 TO DEPT-TOTAL
           MOVE 0 TO GRAND-TOTAL
           DISPLAY 'Sales Report by Region and Department'
           DISPLAY '====================================='
           DISPLAY 'Region    Department  Employee        Salary'
           DISPLAY '------    ----------  --------        ------'.

Initialize control break variables and print report headers before processing data. Set previous values to spaces and totals to zero. Print column headers for the report.

Control Break with Page Control

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       WORKING-STORAGE SECTION.
       01 LINES-PER-PAGE PIC 9(3) VALUE 50.
       01 LINE-COUNT PIC 9(3) VALUE 0.
       01 PAGE-COUNT PIC 9(3) VALUE 0.
       
       DEPT-BREAK.
           ADD 3 TO LINE-COUNT  *> Account for header lines
           IF LINE-COUNT > LINES-PER-PAGE
               PERFORM NEW-PAGE
           END-IF
           DISPLAY 'Department: ' CURRENT-DEPT
           DISPLAY 'Employee Name        Salary'
           DISPLAY '-------------------  -------'.
       
       NEW-PAGE.
           ADD 1 TO PAGE-COUNT
           DISPLAY 'Page ' PAGE-COUNT
           DISPLAY '========================================'
           MOVE 0 TO LINE-COUNT.

Combine control breaks with page control for professional reports. Track line counts and trigger page breaks when limits are exceeded. Print page numbers and maintain proper formatting.

Control Break Error Handling

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       *> Validate data is sorted properly
       IF CURRENT-REGION < PREVIOUS-REGION
           DISPLAY 'Error: Data not sorted by region'
           PERFORM ERROR-HANDLING
       ELSE IF CURRENT-REGION = PREVIOUS-REGION
           AND CURRENT-DEPT < PREVIOUS-DEPT
           DISPLAY 'Error: Data not sorted by department within region'
           PERFORM ERROR-HANDLING
       END-IF.

Validate that input data is properly sorted for control break processing. Check that higher-level keys don't decrease and that lower-level keys are properly ordered within higher levels.

Control Flow

Program flow control

Report Writing

Report generation techniques