Editing COBOL Std 5 Program Structure (section)

== 5. Program Structure ==

=== 5.1 Division Order ===

Every program must contain all four divisions in this sequence:

# IDENTIFICATION DIVISION — program identity and metadata.
# ENVIRONMENT DIVISION — platform bindings, file assignments, special names (e.g. <code>CONSOLE IS scherm</code>).
# DATA DIVISION — FILE SECTION, WORKING-STORAGE SECTION, LINKAGE SECTION (if a subprogram).
# PROCEDURE DIVISION — all executable logic.

=== 5.2 Mandatory IDENTIFICATION DIVISION Entries ===

<syntaxhighlight lang="cobol">
       IDENTIFICATION DIVISION.
       PROGRAM-ID.      PROG-NAME.
       AUTHOR.          Developer Name.
       DATE-WRITTEN.    YYYY-MM-DD.
       DATE-COMPILED.   YYYY-MM-DD.
       SECURITY.        INTERNAL USE ONLY.
</syntaxhighlight>

The PROGRAM-ID must match the source file name exactly (without extension).

=== 5.3 Working-Storage Layout Order ===

Organise WORKING-STORAGE in this sequence:

# Program identification filler (version string, program name).
# Database connection parameters (if a DAL program).
# Switch / flag fields (<code>SW-</code> prefix).
# Counter fields (<code>CTR-</code> prefix).
# Error-handling fields (<code>ERR-</code> prefix).
# Business data fields.
# SQL host variable groups (<code>DB-</code> prefix, via <code>EXEC SQL INCLUDE</code> or <code>COPY</code>).

=== 5.4 PROCEDURE DIVISION Structure ===

The procedure division must follow this paragraph-series order:

# '''A000''' — entry paragraph; EVALUATE on method verb or input flag; dispatches to lower series.
# '''R-series''' — business logic (algorithm, loop bodies, report formatting).
# '''S-series''' — database and system routines (connect, cursor, fetch, insert, disconnect).
# '''D-series''' — validation sub-routines.
# '''E-series''' — error handling.
# '''Z000''' — termination / cleanup; always the last paragraph; contains EXIT PROGRAM or STOP RUN.

=== 5.5 Three-Tier Architecture ===

For any application accessing a database, adopt the following tier separation. Each tier communicates through a shared copybook control block passed by reference.

{| class="wikitable" style="width:100%"
! Tier !! Program Role !! Responsibilities
|-
| Orchestrator || <code>*main</code> || Accept command-line arguments; initialise UI; dispatch to business logic; manage session lifecycle.
|-
| Business Logic || <code>*gen / *proc</code> || Implement algorithms, loops, and decision logic. Call DAL and UI. '''Never contain SQL.'''
|-
| Data Access (DAL) || <code>*dal / *db</code> || All SQL statements. One EXEC SQL per paragraph. Exposes a method-dispatch interface. '''Never contains presentation logic.'''
|-
| Presentation (UI) || <code>*ui / *rpt</code> || All file I/O and console output. Manages print-file lifecycle. '''Never contains SQL or business rules.'''
|}

=== 5.6 Method-Dispatch Pattern ===

Inter-tier calls use a method-dispatch pattern: the caller places a verb string into a control-block method field, invokes the subprogram, and inspects the result code on return.

<syntaxhighlight lang="cobol">
           MOVE 'connect'   TO DAL-METHODS
           CALL 'primes'    USING PRIMES-DAL
           IF dal-method-ok
               CONTINUE
           ELSE
               PERFORM E000-HANDLE-ERROR
           END-IF
</syntaxhighlight>

The called program must implement an A000 EVALUATE block on its method field and set the result code before EXIT PROGRAM. Valid result codes are defined in [[#7.1 Return-Code Standard|§7.1]].

{{Ambox
| type  = stop
| text  = '''Prohibited''' — Direct SQL in business-logic or presentation programs. All database access must go through the DAL tier.
}}

=== 5.7 Paragraph Size ===

Each paragraph should perform a single, named function. Aim for 20–80 lines. Paragraphs exceeding 100 lines must be subdivided. Paragraphs under 5 lines are acceptable for dispatch stubs and result-setting.

=== 5.8 Use of Sections ===

Avoid PROCEDURE DIVISION sections, except where required by the compiler: DECLARATIVES, SORT/MERGE INPUT/OUTPUT PROCEDURE. Use paragraph-level PERFORM for all other control flow. Section fall-through is a common source of subtle bugs.

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