This International Standard specifies the mechanical@ physical and optical characteristics of a 60 mm@ readonly ODC having a maximum capacity of 1@8 Gbytes. It specifies the physical format@ the quality of the recorded signals@ the format of the data and its modulation method@ thereby allowing for information interchange by means of such ODCs. This International Standard specifies two types of ODCs@ Type A and Type B: Type A: Single layer disk with maximum recorded capacity of 0@9 G-bytes; Type B: Dual layer disk with maximum recorded capacity of 1@8 G-bytes. Information interchange between systems also requires@ at a minimum@ agreement between the interchange parties upon the interchange code(s) and the specifications of the structure and labeling of the information on the interchanged ODCs. UMD? is the trade mark of Sony Computer Entertainment Inc.