Editing COBOL Std 8 Data Definition Rules

== 8. Data Definition Rules ==

=== 8.1 Numeric Usage ===

* Signed arithmetic fields must use the S prefix: <code>PIC S9(9)</code>.
* Packed-decimal (COMP-3) is the preferred internal numeric type for arithmetic fields — smaller footprint and faster on most platforms.
* Binary (COMP-5) for SQL Communications Area fields (SQLCODE etc.) to match GixSQL generated C types.
* DISPLAY numeric only for print-output or host-variable character-format copybooks.

{| class="wikitable" style="width:100%"
! Use Case !! Recommended PIC !! Notes
|-
| Integer counter || <code>S9(9) COMP-3</code> || Handles values to ±999,999,999.
|-
| Currency / amount || <code>S9(9)V99 COMP-3</code> || Odd digit count for packed efficiency.
|-
| Square root / remainder || <code>9(9)V9(9) DISPLAY</code> || 18-digit decimal for precision comparisons.
|-
| DB identity / sequence || <code>S9(9) COMP-3</code> || Match PostgreSQL INTEGER type.
|-
| SQLCODE / SQLERRD || <code>S9(9) COMP-5</code> || Required by GixSQL SQLCA layout.
|}

=== 8.2 88-Level Condition Names ===

* Define 88-level conditions for every significant state a field can hold; never test magic numbers directly in procedural code.
* 88-level names must be self-documenting: <code>SW-END-OF-FILE</code> rather than <code>SW-FLAG-1</code>.
* Comment the business meaning of each 88 at its definition.

<syntaxhighlight lang="cobol">
       03 DAL-RESULT            PIC 9(2) VALUE ZERO.
          *-- 0 = operation succeeded
          88 DAL-METHOD-OK      VALUE 0.
          *-- 1 = operation failed; caller should log and stop
          88 DAL-METHOD-NOK     VALUE 1.
          *-- 2 = end of data / not found; not an error
          88 DAL-METHOD-EOF     VALUE 2.
</syntaxhighlight>

=== 8.3 Host Variable Copybooks ===

* SQL host variables must be defined in a dedicated copybook (suffix <code>-TAB</code>) included via <code>EXEC SQL INCLUDE</code>.
* Do not define host variables inline in WORKING-STORAGE outside a designated include.
* Character-format and packed-decimal versions are separate copybooks if both are needed; name them unambiguously (e.g. <code>PRIMES-TAB-PKD.cpy</code> vs <code>PRIMES-TAB.cpy</code>).

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