Version Control and the Mode Line
When you visit a file that is under version control, Emacs indicates this on the mode line. For example, RCS-1.3 says that RCS is used for that file, and the current version is 1.3.
The character between the back-end name and the version number indicates the version control status of the file. - means that the work file is not locked (if locking is in use), or not modified (if locking is not in use). : indicates that the file is locked, or that it is modified. If the file is locked by some other user (for instance, jim), that is displayed as RCS:jim:1.3.
