This International Standard specifies the characteristics of 120 mm optical disks for information interchange between information processing systems and for information storage, called CD-ROM. The optical disk specified by this International Standard is of the type in which the information is recorded before delivery to the user and can only be read from the disk. Characteristics are specified for tracks recorded with digital data. According to this International Standard, a disk may also contain one or more tracks recorded with digital audio data. Such tracks shall be recorded according to IEC 908.