Editing Naming and Coding Standards (section)

== 6. Procedure Division Coding Rules ==

<span id="structured-programming"></span>
=== 6.1 Structured programming ===

All control flow must use structured constructs:

{|
!width="50%"| Construct
!width="50%"| Use for
|-
| <code>PERFORM &lt;paragraph&gt;</code>
| Single call to a named paragraph
|-
| <code>PERFORM &lt;paragraph&gt; UNTIL &lt;condition&gt;</code>
| Loops with pre-test condition
|-
| <code>EVALUATE TRUE … WHEN … END-EVALUATE</code>
| Multi-way branch (preferred over nested IF)
|-
| <code>IF … ELSE … END-IF</code>
| Two-way branch
|-
| <code>NEXT SENTENCE</code>
| Skip remainder of sentence (used sparingly; prefer END-IF)
|}

'''Never use:''' - <code>GO TO</code> (except structured skip idiom in legacy contexts) - <code>ALTER</code> - <code>PERFORM … THRU</code> (couples paragraphs; prefer explicit PERFORM chains)

<span id="evaluate-true-convention"></span>
=== 6.2 EVALUATE TRUE convention ===

The method-dispatch EVALUATE always takes this form:

<syntaxhighlight lang="cobol">EVALUATE TRUE
  WHEN <condition-name-1>
    PERFORM <paragraph>
  WHEN <condition-name-2>
    PERFORM <paragraph>
  WHEN OTHER
    MOVE 1 TO <result-field>
END-EVALUATE.</syntaxhighlight>
* Every EVALUATE must have a <code>WHEN OTHER</code> clause.
* The <code>WHEN OTHER</code> must set a meaningful error indicator; it must never be a no-op.

<span id="perform-until"></span>
=== 6.3 PERFORM … UNTIL ===

* The loop condition is checked '''before''' the first iteration (test-before / DO-WHILE reversed).
* Infinite loops are not permitted. Every PERFORM UNTIL must have a reachable exit condition.
* Loop termination must be tested and documented in the program logic guide.

<span id="call-conventions"></span>
=== 6.4 CALL conventions ===

* All inter-program calls use <code>CALL &quot;literal&quot; USING &lt;data-block&gt;</code>.
* The called program name must be a string literal, not a data name (for static linkage and security).
* Always check the result field of the called program’s control block immediately after the CALL.

<span id="arithmetic"></span>
=== 6.5 Arithmetic ===

* Use <code>COMPUTE</code> for complex expressions: <code>COMPUTE x = a ** 0.5</code>.
* Use <code>ADD … TO</code>, <code>SUBTRACT … FROM</code>, <code>MULTIPLY … BY</code>, <code>DIVIDE … BY … GIVING … REMAINDER</code> for simple operations.
* Always use <code>GIVING</code> and <code>REMAINDER</code> clauses to avoid in-place modification of source operands.
* Always check for zero divisor before DIVIDE.
* Declare intermediate results with sufficient precision to avoid truncation: <code>PIC 9(9)V9(9)</code> for square-root results.


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<span id="sql-embedding-conventions"></span>