The first thing to do is to switch on RCS checking in PBMake. This
      is achieved by adding the RCSCHECKOUT directive in your make file.

      RCSCHECKOUT=co -M

      This directive switches on RCS checking, and also tells PBMake how
      to check out a source file from RCS if it doesn't exist in the
      current directory.

      If a SOURCE, INCLUDE or LIBRARY file already exists, PBMake will
      continue normally. If the source file doesn't exist then the RCS
      checking kicks in.

      After adding the RCSCHECKOUT directive you need to add the
      RCSTIDYUP directive, this directive tells PBMake how to delete the
      files that had to be checked out in order to continue with the
      make.

      RCSTIDYUP=rm -f 

      Remember, most RCS systems check out files with the READONLY file
      attribute set ... so you must use a DELETE function that can
      delete READONLY files. I use the GNU clone of the Unix program
      'rm', which has the -f flag to force the delete.  MS/DOS 6 ->
      allow you to use DEL /F, to force the delete.

      Once you've added the RCSCHECKOUT directive and the RCSTIDYUP
      directive, your PBMake script is RCS aware.

      This means that if PBMake looks in your source directory for
      <sourcefile> (which could also be a library or include file)
      and it is not found there, then PBMake will begin to look for
      <sourcefile> within the RCS system, and will check it out if
      necessary.