PURPOSE: To make direct size compact and to rapidly execute directory search by making it unnecessary to include file information preceding up-to-date file in a directory.

CONSTITUTION: A communication interface part 13 is an interface part for transmitting/receiving data to be stored in an optical disk. A system disk 15 is a memory for storing program data and is controlled by a system disk controller 14. A memory 16 is a system memory. Consequently, a system provided with large capacity storage media such as an additional type optical disk device and a rewritable optical disk device and capable of updating records to be used for information registration and retrieval can refer a version in a generation preceding k generations from the current generation in a file including n generations.