Revision Control System
(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].