ISO 9660 (CDFS Compact Disc File System) is a file system for optical disc media. Being published by the International Organization for Standardization (ISO) the file system is considered an international technical standard. Since the specification is available for anybody to purchase, implementations have been written for many operating systems.
ISO 9660 traces its roots to the High Sierra Format file system. High Sierra arranged file information in a dense, sequential layout to minimize nonsequential access by using a hierarchical (eight levels of directories deep) tree file system arrangement, similar to UNIX and FAT. To facilitate cross platform compatibility, it defined a minimal set of common file attributes (directory or ordinary file and time of recording) and name attributes (name, extension, and version), and used a separate system use area where future optional extensions for each file may be specified.
High Sierra was adopted in December 1986 (with changes) as an international standard by Ecma International as ECMA-119 and submitted for fast tracking to the ISO, where it was eventually accepted as ISO 9660:1988.
In 2013, ISO published Amendment 1 to the ISO 9660 standard, introducing new data structures and relaxed file name rules intended to “bring harmonization between ISO 9660 and widely used ‘Joliet Specification’.” In December 2017, a 3rd Edition of ECMA-119 was published that is technically identical with ISO 9660, Amendment 1.