A standard file naming system for CD-ROM media, published by the International Organization for Standardization. It provides cross-platform support for many different computer operating systems such as Microsoft Windows, Mac OS, and systems that follow the Unix specification, so that data may be exchanged. Almost all computers – and most hardware synths and samplers – with CD-ROM drives can read files from an ISO 9660-compliant CD-ROM.
The ISO 9660 specification has been around for many years. It was originally issued in 1988, developed by an industry group named High Sierra. There are different levels to the standard. Level 1 restricts file names to eight characters with a 3-character extension (the “XXXXXXXX.XXX” format commonly used since the days of DOS). Level 1 also specifies the use of upper-case letters, numbers, and underscore as the only accepted characters.
Level 2 allows file names to be up to 31 characters long. Level 3 files can be fragmented (mainly to allow packet writing, or track-at-once CD recording).
The restrictions on file name length have been seen by many as a serious limitation of the ISO 9660 system. Many CD authoring applications attempt to work around this by truncating filenames automatically, but risk “breaking” applications that rely on a specific file structure.