emacs(1) Version Control.The Version Control facility of emacs(1) works as a front end to RCS. This information applies specifically to Version 19.34 of GNU Emacs, which is provided with the major Linux distributions. When editing a file with emacs(1) which is registered with RCS, the command vc-toggle-read-only (bound to C-x C-q by default) will check a file in to the emacs's Version Control, and then into RCS. Emacs will open a buffer where you can type a log message to be included in the RCS log. When you are finished typing a log entry, type C-c C-c to terminate your input and proceed with the check-in process.
If you have selected strict locking for the file with RCS, you must re-lock the file for editing by emacs(1). You can check the file out for emacs's Version Control with the command % in buffer-menu mode.
For more information, see the GNU Emacs Manual and the Emacs info pages.