ISO9660 is a file system that was designed with the aim of creating a file system that is as system-independent and so as compatible as possible. CDs with ISO9660 as the file system can be read on all operating systems.
ISO9660 supports filenames in 8.3 format in Level 1 (8 characters for the filename and 3 for the extension) and directory names 8 characters long. Only characters A-Z, 0-9 and the underscore (_) are allowed. The maximum interleaf depth is restricted to 8 levels (including root directory).
A total of 31 characters are allowed in Level 2 and can be read by Windows 95 and higher, whereas DOS and Windows 3.1 usually have trouble handling the long filenames.