In order to edit a file in Emacs that is under RCS control, you can follow
these easy steps.

1. Bring up file in a buffer (control-x control-f)
2. Check out the file as follows: control-x control-q
3. Edit the file as usual.
4. Check the file in as follows: control-x control-q
5. Answer the query by typing in a log message in the indicated buffer
6. Hit control-c control-c to complete the check-in when log message
   is done

You can check what's been going on with, e.g.:

rlog file.txt