Editing Revision Control System (section)

=== Usage ===
RCS revolves around the usage of "revision groups" or sets of files that have been checked-in via the <code>co</code> (checkout) and <code>ci</code> (check-in) commands. By default, a checked-in file is removed and replaced with a ",v" file (so foo.rb when checked in becomes foo.rb,v) which can then be checked out by anyone with access to the revision group.  RCS files (again, files with the extension ",v") reflect the main file with additional metadata on its first lines.  Once checked in, RCS stores revisions in a tree structure that can be followed so that a user can revert a file to a previous form if necessary.<ref name=":1" />