The Rock Ridge extensions to ISO 9660 define a way for UNIX file system features like long mixed-case filenames and symbolic links to be supported by CD-ROMs. Because it's still an ISO-9660 filesystem, the files can still be read by machines that don't support Rock Ridge; they just won't see the long forms of the names. Rock Ridge is supported by *NIX systems and the Mac OS. Neither DOS nor Windows NT/9x support it, however.