Emulate RCS version n, where n can be 3, 4, or 5. This can be useful when interchanging RCS files with others who are running older versions of RCS. To see which version of RCS your correspondents are running, have them invoke rcs -V; this works with newer versions of RCS. If it doesn't work, have them invoke rlog on an RCS file; if none of the first few lines of output contain the string branch: it is version 3; if the dates' years have just two digits, it is version 4; otherwise, it is version 5. An RCS file generated while emulating version 3 loses its default branch. An RCS revision generated while emulating version 4 or earlier has a time stamp that is off by up to 13 hours. A revision extracted while emulating version 4 or earlier contains abbreviated dates of the form yy/mm/dd and can also contain different white space and line prefixes in the substitution for $Log$.