What are control groups in COBOL?

Hierarchical groupings of data records based on key fields, used for generating subtotals and summaries at different levels.

How do I process hierarchical data?

Sort data by hierarchical keys, then process control breaks at each level to generate subtotals and summaries.

What is the difference between control groups and control breaks?

Control groups define the hierarchical structure, while control breaks detect changes and trigger processing at each group level.

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COBOL Control Groups

Control groups organize data hierarchically for processing and reporting. Learn to define hierarchical structures, process multi-level groups, and generate comprehensive reports with subtotals and summaries.

Defining Control Groups

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       WORKING-STORAGE SECTION.
       01 CONTROL-GROUP-STRUCTURE.
           05 REGION-GROUP.
               10 REGION-CODE PIC X(3).
               10 REGION-TOTAL PIC 9(9)V99 VALUE 0.
           05 DEPARTMENT-GROUP.
               10 DEPT-CODE PIC X(5).
               10 DEPT-TOTAL PIC 9(9)V99 VALUE 0.
           05 EMPLOYEE-GROUP.
               10 EMP-ID PIC 9(6).
               10 EMP-SALARY PIC 9(7)V99.
       
       01 PREVIOUS-VALUES.
           05 PREV-REGION PIC X(3) VALUE SPACES.
           05 PREV-DEPT PIC X(5) VALUE SPACES.

Define control group structures with hierarchical levels. Each level represents a different grouping (region, department, employee). Include totals for each level and previous values for break detection.

Hierarchical Data Processing

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       PROCESS-CONTROL-GROUPS.
           PERFORM UNTIL EOF
               READ EMPLOYEE-FILE AT END SET EOF TO TRUE
               NOT AT END
                   MOVE EMP-REGION TO REGION-CODE
                   MOVE EMP-DEPT TO DEPT-CODE
                   MOVE EMP-ID TO EMP-ID
                   MOVE EMP-SALARY TO EMP-SALARY
                   
                   *> Check for control breaks in hierarchical order
                   IF REGION-CODE NOT = PREV-REGION
                       PERFORM REGION-BREAK
                   ELSE IF DEPT-CODE NOT = PREV-DEPT
                       PERFORM DEPT-BREAK
                   END-IF
                   
                   *> Process current record
                   PERFORM PROCESS-EMPLOYEE-RECORD
                   
                   *> Update previous values
                   MOVE REGION-CODE TO PREV-REGION
                   MOVE DEPT-CODE TO PREV-DEPT
               END-READ
           END-PERFORM
           PERFORM FINAL-BREAKS.

Process data hierarchically by checking control breaks in order from highest to lowest level. Each break triggers subtotal processing and formatting. Process the current record and update previous values for next iteration.

Multi-Level Break Processing

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

Process breaks at each hierarchical level. Higher-level breaks call lower-level breaks to ensure proper subtotal processing. Print headers, footers, and reset totals for each level.

Group-Level Calculations

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       PROCESS-EMPLOYEE-RECORD.
           DISPLAY EMP-ID ' ' EMP-NAME ' ' EMP-SALARY
           ADD EMP-SALARY TO DEPT-TOTAL
           ADD EMP-SALARY TO REGION-TOTAL
           ADD EMP-SALARY TO GRAND-TOTAL
           ADD 1 TO EMP-COUNT
           ADD 1 TO DEPT-COUNT
           ADD 1 TO REGION-COUNT.

Perform calculations at all group levels simultaneously. Add values to department, region, and grand totals. Count records at each level for comprehensive reporting and analysis.

Control Group Initialization

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       INITIALIZE-CONTROL-GROUPS.
           MOVE SPACES TO PREV-REGION
           MOVE SPACES TO PREV-DEPT
           MOVE 0 TO REGION-TOTAL
           MOVE 0 TO DEPT-TOTAL
           MOVE 0 TO GRAND-TOTAL
           MOVE 0 TO REGION-COUNT
           MOVE 0 TO DEPT-COUNT
           MOVE 0 TO EMP-COUNT
           DISPLAY 'Employee Report by Region and Department'
           DISPLAY '========================================'
           DISPLAY 'Region Dept  Employee ID  Name           Salary'
           DISPLAY '------ ----- -----------  ----           ------'.

Initialize all control group variables before processing. Set previous values to spaces, totals to zero, and counters to zero. Print report headers with column titles for clear formatting.

Final Break Processing

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       FINAL-BREAKS.
           IF PREV-REGION NOT = SPACES
               PERFORM DEPT-BREAK  *> Process final dept break
               DISPLAY 'Region Total: ' PREV-REGION ' = ' REGION-TOTAL
               DISPLAY 'Employees in region: ' REGION-COUNT
               DISPLAY '========================================'
           END-IF
           DISPLAY 'GRAND TOTAL: ' GRAND-TOTAL
           DISPLAY 'Total employees: ' EMP-COUNT
           DISPLAY '========================================'.

Process final breaks to complete the last group's processing. Print final subtotals, counts, and grand totals. This ensures all data is properly summarized and reported.

Control Group Validation

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       VALIDATE-CONTROL-GROUPS.
           IF REGION-CODE < PREV-REGION
               DISPLAY 'Error: Data not sorted by region'
               PERFORM ERROR-HANDLING
           ELSE IF REGION-CODE = PREV-REGION
               AND DEPT-CODE < PREV-DEPT
               DISPLAY 'Error: Data not sorted by department'
               PERFORM ERROR-HANDLING
           END-IF.

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

Dynamic Control Groups

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       *> Process variable number of group levels
       EVALUATE GROUP-LEVEL
           WHEN 1
               PERFORM SINGLE-LEVEL-PROCESSING
           WHEN 2
               PERFORM TWO-LEVEL-PROCESSING
           WHEN 3
               PERFORM THREE-LEVEL-PROCESSING
           WHEN OTHER
               PERFORM MULTI-LEVEL-PROCESSING
       END-EVALUATE.

Handle variable numbers of control group levels based on configuration or data characteristics. Use EVALUATE to select appropriate processing logic for different hierarchical structures.

Define hierarchical group structures with appropriate totals.
Sort data by all group key fields before processing.
Process breaks in hierarchical order (highest to lowest).
Calculate totals and counts at all group levels.
Validate data sorting to ensure proper group processing.

Control Breaks

Report processing and group totals

Control Flow

Program flow control