from
The Free On-line Dictionary of Computing (8 July 2008)
copybook
copy member
copy module
<programming, library> (Or "copy member", "copy module") A
common piece of {source code} designed to be copied into many
source programs, used mainly in {IBM} {DOS} {mainframe}
programming.
In {mainframe} {DOS} (DOS/VS, DOS/{VSE}, etc.), the copybook
was stored as a "book" in a {source} library. A library was
comprised of "books", prefixed with a letter designating the
language, e.g., A.name for Assembler, C.name for Cobol, etc.,
because {DOS} didn't support multiple libraries, private
libraries, or anything. This term is commonly used by {COBOL}
programmers but is supported by most {mainframe} languages.
The {IBM} {OS} series did not use the term "copybook", instead
it referred to such files as "libraries" implemented as
"partitioned data sets" or {PDS}.
Copybooks are functionally equivalent to {C} and {C++}
{include} files.
(1997-07-31)