RCS

RCS is 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.

Because it operates only on single files, and has no way of working with an entire project, or allowing multiple users to work on a file at once, it has been superseded by CVS for more complex projects. CVS is built upon RCS.