This article is from the Final-Fantasy and other Square Soft Games FAQ, by firstname.lastname@example.org (Nick Zitzmann) with numerous contributions by others.
Ever wonder what happens if you finish the game using all seven
characters on the same system data? Doing this unlocks the Programmer's
Room, which is the "secret ending" mentioned briefly in the game's
To get the Programmer's Room, you need to finish the game with all seven
characters, taking one quest at a time. Playing multiple quests at the
same time on the same system data supposedly destroys any chances of
receiving this ending, but this has yet to be confirmed in the USA
The Programmer's Room includes a sound test feature, as well as battles
against all seven of the game's final bosses.