COBOL COMP-6 (COMPUTATIONAL-6)

The COMP-6 usage clause in COBOL specifies unsigned packed decimal format, providing efficient storage for positive numeric values. By eliminating the sign nibble, COMP-6 maximizes storage utilization for applications dealing exclusively with non-negative numbers.

Overview and Purpose

COMP-6 represents an unsigned variant of packed decimal storage, similar to COMP-3 but without the sign nibble. This format packs two decimal digits into each byte, using all available nibbles for numeric data. The absence of sign information makes COMP-6 ideal for counters, quantities, identifiers, and other data that is inherently positive. This optimization provides slightly better storage efficiency compared to COMP-3 for unsigned numeric data.

Storage Comparison: COMP-3 vs COMP-6

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01  WS-COMP3-FIELD       PIC 9(5) COMP-3.
01  WS-COMP6-FIELD       PIC 9(6) COMP-6.
 
*> COMP-3: 5 digits + sign in 3 bytes (12345+)
*> COMP-6: 6 digits in 3 bytes (123456)
*> Same storage, more capacity with COMP-6

This comparison illustrates COMP-6's storage advantage. Both fields use 3 bytes, but COMP-6 can store 6 digits while COMP-3 stores 5 digits plus sign. This 20% increase in capacity makes COMP-6 valuable for applications with large volumes of unsigned numeric data where storage efficiency is critical.

Basic COMP-6 Declarations

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01  UNSIGNED-COUNTERS.
    05  WS-RECORD-COUNT     PIC 9(7) COMP-6.
    05  WS-SEQUENCE-NUM     PIC 9(9) COMP-6.
    05  WS-QUANTITY         PIC 9(5) COMP-6.
    05  WS-PRODUCT-ID       PIC 9(8) COMP-6.

COMP-6 fields are declared similarly to COMP-3 but without sign considerations. The PIC clause specifies the number of digits, and storage is calculated as (digits + 1) / 2 bytes. These fields are perfect for data that is conceptually unsigned, such as counts, quantities, and positive identifiers.

Efficient Counter Operations

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01  PROCESSING-COUNTERS.
    05  WS-RECORDS-PROCESSED    PIC 9(8) COMP-6.
    05  WS-ERRORS-FOUND         PIC 9(6) COMP-6.
    05  WS-BATCH-SIZE           PIC 9(5) COMP-6.
 
INCREMENT-COUNTERS.
    ADD 1 TO WS-RECORDS-PROCESSED
    
    IF ERROR-CONDITION
        ADD 1 TO WS-ERRORS-FOUND
    END-IF
 
RESET-BATCH-COUNTERS.
    MOVE ZERO TO WS-RECORDS-PROCESSED
    MOVE ZERO TO WS-ERRORS-FOUND

Counter operations with COMP-6 are highly efficient due to the packed decimal format's arithmetic optimization. The unsigned nature eliminates sign processing overhead, making increment and accumulation operations faster. This is particularly beneficial for high-frequency counting operations in batch processing environments.

Tutorial: Building an Inventory Management System

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01  INVENTORY-RECORD.
    05  INV-PRODUCT-ID      PIC 9(8) COMP-6.
    05  INV-QUANTITY-HAND   PIC 9(7) COMP-6.
    05  INV-REORDER-LEVEL   PIC 9(5) COMP-6.
    05  INV-UNITS-SOLD      PIC 9(8) COMP-6.
    05  INV-UNITS-RECEIVED  PIC 9(7) COMP-6.

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UPDATE-INVENTORY.
    IF TRANSACTION-TYPE = 'RECEIPT'
        ADD TRANS-QUANTITY TO INV-QUANTITY-HAND
        ADD TRANS-QUANTITY TO INV-UNITS-RECEIVED
    ELSE IF TRANSACTION-TYPE = 'SALE'
        IF TRANS-QUANTITY <= INV-QUANTITY-HAND
            SUBTRACT TRANS-QUANTITY FROM INV-QUANTITY-HAND
            ADD TRANS-QUANTITY TO INV-UNITS-SOLD
        ELSE
            PERFORM INSUFFICIENT-INVENTORY-ERROR
        END-IF
    END-IF

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CHECK-REORDER-STATUS.
    IF INV-QUANTITY-HAND <= INV-REORDER-LEVEL
        PERFORM GENERATE-REORDER-NOTICE
    END-IF
 
CALCULATE-REORDER-QUANTITY.
    COMPUTE WS-SUGGESTED-ORDER = 
        (INV-REORDER-LEVEL * 2) - INV-QUANTITY-HAND
    
    IF WS-SUGGESTED-ORDER < 0
        MOVE INV-REORDER-LEVEL TO WS-SUGGESTED-ORDER
    END-IF

Practical Exercises

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01  SALES-ANALYTICS.
    05  SA-TOTAL-SALES      PIC 9(10) COMP-6.
    05  SA-CUSTOMER-COUNT   PIC 9(7) COMP-6.
    05  SA-PRODUCT-COUNT    PIC 9(6) COMP-6.
    05  SA-REVENUE-CENTS    PIC 9(12) COMP-6.
    05  SA-ORDERS-PROCESSED PIC 9(8) COMP-6.
 
PROCESS-SALES-TRANSACTION.
    ADD 1 TO SA-ORDERS-PROCESSED
    ADD SALE-AMOUNT-CENTS TO SA-REVENUE-CENTS
    
    IF NEW-CUSTOMER
        ADD 1 TO SA-CUSTOMER-COUNT
    END-IF
    
    PERFORM VARYING WS-I FROM 1 BY 1 
        UNTIL WS-I > ORDER-LINE-COUNT
        ADD ORDER-QTY(WS-I) TO SA-TOTAL-SALES
    END-PERFORM

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01  PRODUCTION-METRICS.
    05  PM-UNITS-PRODUCED   PIC 9(8) COMP-6.
    05  PM-DEFECTS-FOUND    PIC 9(6) COMP-6.
    05  PM-MACHINE-HOURS    PIC 9(7) COMP-6.
    05  PM-SETUP-COUNT      PIC 9(5) COMP-6.
    05  PM-BATCH-NUMBER     PIC 9(6) COMP-6.
 
RECORD-PRODUCTION.
    ADD BATCH-QUANTITY TO PM-UNITS-PRODUCED
    ADD SETUP-TIME-MINUTES TO PM-MACHINE-HOURS
    ADD 1 TO PM-SETUP-COUNT
    
    PERFORM VARYING WS-I FROM 1 BY 1 
        UNTIL WS-I > BATCH-QUANTITY
        IF QUALITY-CHECK(WS-I) = 'DEFECT'
            ADD 1 TO PM-DEFECTS-FOUND
        END-IF
    END-PERFORM
 
CALCULATE-EFFICIENCY.
    COMPUTE WS-EFFICIENCY-PCT = 
        ((PM-UNITS-PRODUCED - PM-DEFECTS-FOUND) * 100) / 
        PM-UNITS-PRODUCED

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01  TRAFFIC-COUNTERS.
    05  TC-PAGE-VIEWS       PIC 9(10) COMP-6.
    05  TC-UNIQUE-VISITORS  PIC 9(8) COMP-6.
    05  TC-SESSION-COUNT    PIC 9(8) COMP-6.
    05  TC-BOUNCE-COUNT     PIC 9(7) COMP-6.
    05  TC-CONVERSION-COUNT PIC 9(6) COMP-6.
 
PROCESS-WEB-REQUEST.
    ADD 1 TO TC-PAGE-VIEWS
    
    IF NEW-SESSION
        ADD 1 TO TC-SESSION-COUNT
    END-IF
    
    IF NEW-VISITOR
        ADD 1 TO TC-UNIQUE-VISITORS
    END-IF
    
    IF SINGLE-PAGE-SESSION
        ADD 1 TO TC-BOUNCE-COUNT
    END-IF
 
CALCULATE-CONVERSION-RATE.
    COMPUTE WS-CONVERSION-RATE = 
        (TC-CONVERSION-COUNT * 10000) / TC-UNIQUE-VISITORS

Advanced COMP-6 Techniques

Range Validation and Overflow Prevention

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VALIDATE-COMP6-INPUT.
    IF INPUT-VALUE < 0
        MOVE "Negative values not allowed" TO ERROR-MSG
        PERFORM ERROR-HANDLER
    END-IF
    
    IF INPUT-VALUE > 9999999
        MOVE "Value exceeds field capacity" TO ERROR-MSG
        PERFORM ERROR-HANDLER
    END-IF
    
    MOVE INPUT-VALUE TO WS-COMP6-FIELD

Always validate that input values are non-negative before storing in COMP-6 fields. Implement appropriate range checking based on the field size to prevent overflow conditions and data corruption.

Efficient Batch Processing

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BATCH-ACCUMULATION.
    MOVE ZERO TO WS-BATCH-TOTAL
    
    PERFORM VARYING WS-I FROM 1 BY 1 
        UNTIL WS-I > BATCH-SIZE
        ADD ITEM-QUANTITY(WS-I) TO WS-BATCH-TOTAL
        
        IF WS-BATCH-TOTAL > 999999999
            PERFORM PROCESS-BATCH-SEGMENT
            MOVE ITEM-QUANTITY(WS-I) TO WS-BATCH-TOTAL
        END-IF
    END-PERFORM

Design batch processing routines that take advantage of COMP-6's efficient arithmetic while handling potential overflow conditions. Segment large accumulations to prevent exceeding field capacity.

Data Conversion Strategies

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CONVERT-TO-DISPLAY.
    MOVE WS-COMP6-VALUE TO WS-DISPLAY-VALUE
    
CONVERT-FROM-SIGNED.
    IF SIGNED-INPUT >= 0
        MOVE SIGNED-INPUT TO WS-COMP6-FIELD
    ELSE
        MOVE "Cannot store negative value" TO ERROR-MSG
        PERFORM ERROR-HANDLER
    END-IF

Implement proper conversion routines when moving data between COMP-6 and other formats. Handle sign conversion carefully when interfacing with signed numeric formats to prevent data loss or corruption.