If you're doing any development work on your Unix environment (or in fact any platform) it is recommended to make use of some form of source code control system to manage software version s (especially useful if you have large development projects).

SCCS is the source control system most often found on Unix platforms, and attached are some training notes for a session we prepared for one of our customers. 

The notes are very much geared around the requirements of the client (including the setup of their SCCS directory structure) but feel free to use them.

SCCS Notes