Log messages accumulate rather than being overwritten. The assigned revision number. The RCS filename, including its pathname. The state assigned by the -s option of ci or rcs . Unless told otherwise, RCS commands typically operate on the latest revision.
Some commands have a -r option that is used to specify a revision number.
In addition, many options accept a revision number as an optional argument. When you check it in again, the new revision will be marked as 1.5. But suppose the edited copy needs to be checked in as the next release. This creates revision 2.1. You can also create a branch from an earlier revision.