# rcs commands
ci file.c                      # check in, delete file.c
ci -u file.c                   # check in, leave file.c
ci -r2.1 file.c                # check in, as rev 2.1
ci -l                          # check in, leave file.c, lock

co file.c                      # check out
co -l file.c                   # check out, lock
co -r1.1 file.c                # check out, rev 1.1

rcsdiff file.c                 # diff active file.c to last rev
rcsdiff -r1.1 -r2.1 file.c     # diff 1.1 to 2.1 of file.c

rlog file.c                    # view log

rcs -u file.c                  # break lock