FILENAME.EXT
The BIOS seems to support only (max) 8-letter filenames with 3-letter
extension, typically all uppercase, eg. "FILENAME.EXT". Eventually, once when
the executable has started, some programs might install drivers for long
filenames(?)
The PSX uses the standard CDROM ISO9660 filesystem without any encryption (ie.
you can put an original PSX CDROM into a DOS/Windows computer, and view the
content of the files in text or hex editors without problems).
Note
MagDemoNN is short for "Official U.S. Playstation Magazine Demo Disc NN"