OPTICAL DISK FILE DEVICE

PURPOSE:To retrieve and read the large quantity of file, to write in addition and to form a chart at high speed by dividing a user area on an optical disk into an index recording area and a file recording area. CONSTITUTION:At the time of inputting and outputting data to the optical disk, the file consisting of the header 51 of MH bytes as the input and output unit of data and a data part 52 is used, and the user recording area on the optical disk is divided into the index recording area 41 and the file recording area 42. Then, at the time of recording the data, the data is written sequentially from the leading part of the file area 42 and when MH is written in the file, the data of the header part 51 of the file of MH is sequentially synthesized, defined to be the data of one sector, sequentially written from the leading part of the area 41, and a leading sector address, a final sector address and a file name on an area 42 are included in the header part 51. Thereby, at the time of retrieving by the file name, the file of the maximum MH-1 of the areas 41, and 42 can be retrieved.