If you have a project which you are maintaining with another version control system, such as RCS, you may wish to put the files from that project into CVS, and preserve the revision history of the files.
If you have been using RCS, find the RCS files—usually a file named foo.c will have its RCS file in RCS/foo.c,v (but it could be other places; consult the RCS documentation for details). Then create the appropriate directories in CVS if they do not already exist. Then copy the files into the appropriate directories in the CVS repository (the name in the repository must be the name of the source file with ‘,v’ added; the files go directly in the appropriate directory of the repository, not in an RCS subdirectory). This is one of the few times when it is a good idea to access the CVS repository directly, rather than using CVS commands. Then you are ready to check out a new working directory.
The RCS file should not be locked when you move it into CVS; if it is, CVS will have trouble letting you operate on it.
Many version control systems have the ability to export RCS files in the standard format. If yours does, export the RCS files and then follow the above instructions.
Failing that, probably your best bet is to write a script that will check out the files one revision at a time using the command line interface to the other system, and then check the revisions into CVS. The sccs2rcs script mentioned below may be a useful example to follow.
There is a script in the contrib directory of the CVS source distribution called sccs2rcs which converts SCCS files to RCS files. Note: you must run it on a machine which has both SCCS and RCS installed, and like everything else in contrib it is unsupported (your mileage may vary).
There is a script in the contrib directory of the CVS source distribution called pvcs_to_rcs which converts PVCS archives to RCS files. You must run it on a machine which has both PVCS and RCS installed, and like everything else in contrib it is unsupported (your mileage may vary). See the comments in the script for details.