COBOL COMP-4

Native binary format for optimized integer storage.

Overview and Purpose

COMP-4 represents integers in the native binary format of the target hardware platform, ensuring optimal performance for arithmetic operations. Unlike other computational formats that may require conversion, COMP-4 data can be processed directly by the processor's arithmetic logic unit. This makes it the preferred choice for high-performance applications, intensive calculations, array processing, and any scenario where computational speed is critical.

Basic COMP-4 Declaration and Storage

1
2
3
4
01  WS-COUNTER           PIC 9(4) COMP-4.
01  WS-ARRAY-INDEX       PIC 9(5) COMP-4.
01  WS-RECORD-COUNT      PIC 9(9) COMP-4.
01  WS-LARGE-NUMBER      PIC 9(18) COMP-4.

COMP-4 fields require a PIC clause to specify the maximum number of digits. The storage allocation follows platform-specific rules: typically 1-4 digits use 2 bytes, 5-9 digits use 4 bytes, and 10-18 digits use 8 bytes. This alignment with native word sizes ensures optimal memory access and arithmetic performance on the target hardware.

Signed and Unsigned COMP-4 Fields

1
2
3
4
01  WS-SIGNED-COUNTER     PIC S9(7) COMP-4.
01  WS-UNSIGNED-COUNTER   PIC 9(7) COMP-4.
01  WS-BALANCE            PIC S9(11)V99 COMP-4.
01  WS-POSITIVE-ONLY      PIC 9(8) COMP-4.

Signed COMP-4 fields (using the S in the PIC clause) can store both positive and negative values, while unsigned fields store only positive values. The sign reduces the effective range by half but allows for negative number representation. The V99 notation indicates implied decimal places for fixed-point arithmetic, though COMP-4 stores only the integer portion.

High-Performance Array Processing

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
01  PERFORMANCE-ARRAYS.
    05  WS-DATA-ARRAY       PIC 9(7) COMP-4 OCCURS 10000 TIMES.
    05  WS-INDEX            PIC 9(5) COMP-4.
    05  WS-SUM              PIC 9(12) COMP-4.
    05  WS-MAX-VALUE        PIC 9(7) COMP-4.
 
PROCESS-LARGE-ARRAY.
    MOVE ZERO TO WS-SUM
    MOVE ZERO TO WS-MAX-VALUE
    PERFORM VARYING WS-INDEX FROM 1 BY 1 
        UNTIL WS-INDEX > 10000
        ADD WS-DATA-ARRAY(WS-INDEX) TO WS-SUM
        IF WS-DATA-ARRAY(WS-INDEX) > WS-MAX-VALUE
            MOVE WS-DATA-ARRAY(WS-INDEX) TO WS-MAX-VALUE
        END-IF
    END-PERFORM

This example demonstrates COMP-4's efficiency in array processing operations. Using COMP-4 for both array elements and loop indices maximizes performance by eliminating data conversion overhead. The native binary format allows the processor to perform arithmetic operations directly, making this approach ideal for large-scale data processing and mathematical computations.

Tutorial: Building a High-Performance Counter System

1
2
3
4
5
01  COUNTER-SYSTEM.
    05  WS-TRANSACTION-COUNT    PIC 9(9) COMP-4.
    05  WS-ERROR-COUNT          PIC 9(7) COMP-4.
    05  WS-SUCCESS-COUNT        PIC 9(9) COMP-4.
    05  WS-BATCH-NUMBER         PIC 9(5) COMP-4.

1
2
3
4
5
6
7
8
INCREMENT-COUNTERS.
    ADD 1 TO WS-TRANSACTION-COUNT
    
    IF TRANSACTION-SUCCESSFUL
        ADD 1 TO WS-SUCCESS-COUNT
    ELSE
        ADD 1 TO WS-ERROR-COUNT
    END-IF

1
2
3
4
5
6
7
8
9
10
CHECK-COUNTER-LIMITS.
    IF WS-TRANSACTION-COUNT > 999999999
        PERFORM RESET-COUNTERS
        ADD 1 TO WS-BATCH-NUMBER
    END-IF
 
RESET-COUNTERS.
    MOVE ZERO TO WS-TRANSACTION-COUNT
    MOVE ZERO TO WS-ERROR-COUNT  
    MOVE ZERO TO WS-SUCCESS-COUNT

Practical Exercises

1
2
3
4
5
6
7
8
9
10
11
01  PERFORMANCE-METRICS.
    05  WS-OPERATIONS-PER-SEC   PIC 9(7) COMP-4.
    05  WS-TOTAL-OPERATIONS     PIC 9(12) COMP-4.
    05  WS-START-TIME           PIC 9(8) COMP-4.
    05  WS-END-TIME             PIC 9(8) COMP-4.
    05  WS-ELAPSED-SECONDS      PIC 9(6) COMP-4.
 
CALCULATE-THROUGHPUT.
    SUBTRACT WS-START-TIME FROM WS-END-TIME GIVING WS-ELAPSED-SECONDS
    DIVIDE WS-TOTAL-OPERATIONS BY WS-ELAPSED-SECONDS 
        GIVING WS-OPERATIONS-PER-SEC

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
01  SORT-VARIABLES.
    05  WS-ARRAY-SIZE           PIC 9(5) COMP-4.
    05  WS-I                    PIC 9(5) COMP-4.
    05  WS-J                    PIC 9(5) COMP-4.
    05  WS-MIN-INDEX            PIC 9(5) COMP-4.
    05  WS-TEMP-VALUE           PIC 9(9) COMP-4.
 
SELECTION-SORT.
    PERFORM VARYING WS-I FROM 1 BY 1 UNTIL WS-I >= WS-ARRAY-SIZE
        MOVE WS-I TO WS-MIN-INDEX
        PERFORM VARYING WS-J FROM WS-I + 1 BY 1 
            UNTIL WS-J > WS-ARRAY-SIZE
            IF WS-DATA-ARRAY(WS-J) < WS-DATA-ARRAY(WS-MIN-INDEX)
                MOVE WS-J TO WS-MIN-INDEX
            END-IF
        END-PERFORM
        IF WS-MIN-INDEX NOT = WS-I
            MOVE WS-DATA-ARRAY(WS-I) TO WS-TEMP-VALUE
            MOVE WS-DATA-ARRAY(WS-MIN-INDEX) TO WS-DATA-ARRAY(WS-I)
            MOVE WS-TEMP-VALUE TO WS-DATA-ARRAY(WS-MIN-INDEX)
        END-IF
    END-PERFORM

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
01  MATH-VARIABLES.
    05  WS-NUMBER               PIC 9(7) COMP-4.
    05  WS-RESULT               PIC 9(18) COMP-4.
    05  WS-COUNTER              PIC 9(7) COMP-4.
    05  WS-TEMP                 PIC 9(18) COMP-4.
 
CALCULATE-FACTORIAL.
    MOVE 1 TO WS-RESULT
    PERFORM VARYING WS-COUNTER FROM 2 BY 1 
        UNTIL WS-COUNTER > WS-NUMBER
        MULTIPLY WS-COUNTER BY WS-RESULT
    END-PERFORM
 
FIBONACCI-SEQUENCE.
    IF WS-NUMBER <= 2
        MOVE 1 TO WS-RESULT
    ELSE
        MOVE 1 TO WS-PREV-1
        MOVE 1 TO WS-PREV-2
        PERFORM VARYING WS-COUNTER FROM 3 BY 1 
            UNTIL WS-COUNTER > WS-NUMBER
            ADD WS-PREV-1 TO WS-PREV-2 GIVING WS-RESULT
            MOVE WS-PREV-2 TO WS-PREV-1
            MOVE WS-RESULT TO WS-PREV-2
        END-PERFORM
    END-IF

Advanced COMP-4 Optimization Techniques

Memory Alignment and Performance

1
2
3
4
5
01  ALIGNED-STRUCTURE.
    05  WS-HALFWORD-1       PIC 9(4) COMP-4.
    05  WS-HALFWORD-2       PIC 9(4) COMP-4.
    05  WS-FULLWORD-1       PIC 9(9) COMP-4.
    05  WS-FULLWORD-2       PIC 9(9) COMP-4.

Proper alignment of COMP-4 fields can improve performance by ensuring optimal memory access patterns. Group similar-sized fields together and consider the target platform's alignment requirements when designing data structures for maximum efficiency.

Range Validation and Overflow Prevention

1
2
3
4
5
6
7
VALIDATE-COMP4-RANGE.
    IF WS-INPUT-VALUE > 999999999
        MOVE "OVERFLOW ERROR" TO WS-ERROR-MESSAGE
        PERFORM ERROR-HANDLING
    ELSE
        MOVE WS-INPUT-VALUE TO WS-COMP4-FIELD
    END-IF

Always validate input values before storing them in COMP-4 fields to prevent overflow conditions. Implement proper error handling and consider using larger field sizes when dealing with potentially large values to maintain data integrity.

Conversion Performance Considerations

1
2
3
4
5
6
7
8
9
10
EFFICIENT-CONVERSION.
    *> Fast: Direct COMP-4 to COMP-4 operations
    MOVE WS-COMP4-SOURCE TO WS-COMP4-TARGET
    
    *> Slower: COMP-4 to display conversion
    MOVE WS-COMP4-VALUE TO WS-DISPLAY-FIELD
    
    *> Optimize by minimizing conversions
    PERFORM CALCULATIONS-IN-COMP4
    MOVE WS-COMP4-RESULT TO WS-DISPLAY-RESULT

Minimize conversions between COMP-4 and other formats to maintain optimal performance. Perform calculations entirely in COMP-4 format when possible, converting to display format only when necessary for output or external interface requirements.