This International Standard specifies the characteristics of 90 mm Optical Disk Cartridges (ODC) with a capacity of 650 Mbytes per Cartridge. The Standard specifies three related, but different implementations of such cartridges, viz.

• Type R/W Provides for data to be written and read many times over the recording surface of the disk using the thermo-magnetic and magneto-optical effects.
• Type P-ROM Provides for a part of the recording surface of the disk to be embossed by stamping or other means. This part of the disk is read without recourse to the magneto-optical effect. The part which is not embossed provides for data to meet the requirements of Type R/W.
• Type O-ROM Provides for the recording surface of the disk to be embossed and reproduced by stamping or other means. This type of disk is read without recourse to the magneto-optical effect.

Type R/W, Type P-ROM and Type O-ROM are also referred to as “fully rewritable”, “partially embossed” and “fully embossed”, respectively.

This International Standard specifies

• the conditions for conformance testing and the Reference Drive;
• the environments in which the cartridges are to be operated and stored;
• the mechanical and physical characteristics of the cartridge, so as to provide mechanical interchangeability between data processing systems;
• the format of the information on the disk, called HS-1 (HS stands for “Hyper-Storage”), including the physical disposition of the tracks and sectors, the error correction codes, and the recording method used;
• the characteristics of the embossed information on the disk;
• the magneto-optical characteristics of the disk, enabling processing systems to write data onto the disk;
• the minimum quality of user-written data on the disk, enabling data processing systems to read data from the disk.

This International Standard provides for interchange between optical disk drives. Together with a standard for volume and file structure, it provides for full data interchange between data processing systems.