From The Free On-line Dictionary of Computing (19 January 2023):
Revision Control System
RCS
<software, tool> (RCS) A version control system that
automates the storing, retrieval, logging, identification, and
merging of revisions. RCS is useful for text that is revised
frequently, for example programs, documentation, graphics,
papers, and form letters.
Unix manual page: rcs(1).
["RCS -- A System for Version Control", Walter F. Tichy,
Software--Practice & Experience 15, 7, July 1985, 637-654].
[Features? Availability? URL?]
(1994-12-23)