identified as DVD Rewritable Disk (DVD-RAM), 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. Two Types are specified that differ only by their diameter of 120 mm and 80 mm, and the resulting difference of capacity. 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.