Like mime, CSV has no provision for structures with more than one level.
A text file can contain any stream of characters, including possible control characters, and is encoded in one of various character encoding schemes.
The hexadecimal number FF5 is "aliased" to PoScript, representing a PostScript file.
An important design criterium for this program is simplicity.
Many formats still use three-character extensions even though modern operating systems and application programs no longer have this limitation.