Copybooks and COPY

The COPY statement

COPY inserts the text of another file at compile time, like include in C. Copybooks usually hold shared data layouts so every program sees the same record:

DATA DIVISION. WORKING-STORAGE SECTION. COPY EMPLOYEE-REC.

REPLACING

REPLACING renames text as the copybook is included, so one copybook can serve several record prefixes:

COPY EMPLOYEE-REC REPLACING ==EMP== BY ==CUST==.

Copybook hygiene

Keep copybooks small and free of procedure code: data layouts only, with a clear prefix on every field name. A copybook that changes one program should be recompiled into all of its users before the next release.

Next: OO COBOL: classes and objects

Article author: Arthur Isaev