This International Standard specifies the mechanical, physical and optical characteristics of a 120 mm optical disk to enable interchange of such disks. It specifies the quality of the recorded signals, the format of the data and the recording method, thereby allowing for information interchange by means of such disks. The data can be written, read and overwritten many times using the phase change method. This disk is identified as DVD-RAM. This International Standard specifies — two related but different Types of this disk (see clause 7), — the conditions for conformance, — the environments in which the disk is to be tested, operated and stored, — the mechanical, physical and dimensional characteristics of the disk, so as to provide mechanical interchange between data processing systems, — the format of the information on the disk, including the physical disposition of the tracks and sectors, the error correcting codes and the coding method, — the characteristics of the signals recorded on the disk, thus enabling data processing systems to read the data from the disk. This International Standard provides for the interchange of disks between optical disk drives. Together with a standard for volume and file structure, it provides for full data interchange between data processing systems. The optical disks specified by this International Standard may be enclosed in cases according to ISO/IEC 16825 as specified therein.