Specifies definitions of the essential concepts, the environment in which the characteristics are to be tested, the environments in which the cartridge is to be operated and stored, the mechanical, physical and dimensional characteristics of the case and of the optical disk, the magneto-optical characteristics and the recording characteristics, so as to provide physical interchangeability between data processing systems, the format for the physical disposition of the tracks and sectors, the error correction codes, the modulation method used for recording and the quality of the recorded signals.