COBOL Std 5 Program Structure

5. Program Structure

5.1 Division Order

Every program must contain all four divisions in this sequence:

1. IDENTIFICATION DIVISION — program identity and metadata.
2. ENVIRONMENT DIVISION — platform bindings, file assignments, special names (e.g. CONSOLE IS scherm).
3. DATA DIVISION — FILE SECTION, WORKING-STORAGE SECTION, LINKAGE SECTION (if a subprogram).
4. 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:

1. Program identification filler (version string, program name).
2. Database connection parameters (if a DAL program).
3. Switch / flag fields (SW- prefix).
4. Counter fields (CTR- prefix).
5. Error-handling fields (ERR- prefix).
6. Business data fields.
7. SQL host variable groups (DB- prefix, via EXEC SQL INCLUDE or COPY).

5.4 PROCEDURE DIVISION Structure

The procedure division must follow this paragraph-series order:

1. A000 — entry paragraph; EVALUATE on method verb or input flag; dispatches to lower series.
2. R-series — business logic (algorithm, loop bodies, report formatting).
3. S-series — database and system routines (connect, cursor, fetch, insert, disconnect).
4. D-series — validation sub-routines.
5. E-series — error handling.
6. 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.

Tier	Program Role	Responsibilities
Orchestrator	*main	Accept command-line arguments; initialise UI; dispatch to business logic; manage session lifecycle.
Business Logic	*gen / *proc	Implement algorithms, loops, and decision logic. Call DAL and UI. Never contain SQL.
Data Access (DAL)	*dal / *db	All SQL statements. One EXEC SQL per paragraph. Exposes a method-dispatch interface. Never contains presentation logic.
Presentation (UI)	*ui / *rpt	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.

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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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