ummm...the DOS version requires you type a command line of information, best done (if you aren't using a frontend) from the run menu under START.(posted 8900 days ago)typical playback for a recording would go something like this
mame
<.inp name>
is fully described in the main MAME help file, which comes with any official version of MAME (not necessarily the stripped down versions available at MARP) so a typical playback line for, say, Tron, would look like this:
mame tron -playback tron
Hope this helps, but I would recommend you read the help files included with an official MAME release, also available at the MAME site www.mame.net