Lays down 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 is of the type in which the information is recorded before delivery to the user and can only be read from the disk. It specifies some definitions, the environments in which the characteristics of the disk shall be tested and in which it shall be used and stored; the mechanical physical, and dimensional characteristics, the recording characteristics, the format of the tracks, the error-detecting and the error-correcting characters and the coding of the information; and the optical characteristics for reading the information.