An early standard for CD ROM data based on the Yellow Book disc format. High Sierra was defined by a group of 12 manufacturers dubbed the High Sierra Group back in 1985. The group included Apple, Microsoft, Sony, Phillips, etc. The idea was to provide a single CD ROM format that could be read by Macintosh, DOS, Unix, and VMS computers. The ISO 9660 format often used today is based on a modified version of the High Sierra format.