A CD-ROM may be mastered with any kind of information on it. For example, Sun Microsystems uses the Berkeley UNIX UFS file systems on many CD-ROMs. This make them only usable on Sun equipment, which is no big deal for a bootable CD-ROM with an operating system on it. But for distributing general information it's a big limitation.

However, because CD-ROMs are especially suited to volume publishing of information, a standard file system useful across many kinds of architecture is very desirable. Before there was a standard on this matter some were using the High Sierra format on CD-ROM, which arranged file information in a dense, sequential layout to minimise nonsequential access.

The High Sierra file system format uses a hierarchical (eight levels of directories deep) tree file system arrangement, similar to UNIX and MS-DOS.

High Sierra has a minimal set of file attributes (directory or ordinary file and time of recording) and name attributes (name, extension, and version). The designers realised they could never get people to agree on a unified definition of file attributes, so the minimum common information was encoded, and a place for future optional extensions (system use area) was defined for each file.

The ISO 9660 File System →