RCS (revision control system) is a project management tool. RCS uses a number of commands to manage source file. It works by tracking source file as its changed by maintaining a single file with list of changes in sufficient detail to recreate the previous version. It also allows you to store comment with every change , which can be very useful to look back in the history of changes that has made to the files. To RCS a file following commands are used.
1. rcs -i filename
this creates a rcs file with name filenamec,v.
2. ci filename
3 . co -l filename
this locks the previous version of file and allow you to do further changes into it.