Copybook
Noun · Development
Definitions
A COBOL source code file that defines data structures and is included into other programs at compile time via the COPY statement. Functionally equivalent to header files in C, copybooks ensure consistent record layouts across programs in mainframe environments.
In plain English: A reusable template file in COBOL that defines data formats and gets pasted into multiple programs, like a shared form everyone fills out the same way.