The logical data organisation on CDs is independent of the underlying physical structure. As a consequence, there exist CD implementations of all major operating system file systems, e.g. UNIX, DOS, and Macintosh.
Furthermore, a common file system has been defined in ISO 9660 (also called the High Sierra format), which is supported by all major operating systems. It follows the DOS file system structure closely by allowing only the legal DOS file names, i.e. eight capital letters plus a three capital letter extension (and an optional version number). The directory structure may be eight levels deep. An important extension of the ISO 9660 format is the Rock Ridge Extension, which allows symbolic links and nesting deeper than 8 levels.
Finally, due to the independence of physical structure and logical data organisation, hybrid CDs can contain different file systems in different tracks on one CD. This reduces the amount of space available to each file system, but results in a CD that has a native file system for more than one operating system.