PURPOSE: To greatly shorten an access processing time by transferring ≥2 continuous blocks continuously to a main memory via a DMA controller if a file contains ≥2 continuous blocks.

CONSTITUTION: When an I/O request is delivered from a CPU 10 for a file covering plural blocks, the block information contained in the index table 151 of an auxiliary memory device 15 is retrieved by an OS controller 13. Thus a DMA controller 11 transfers continuously ≥2 continuous blocks to a main memory 12 based on the block information of the table 151 if a desired file contains ≥2 continuous blocks. Therefore it is not required to deliver a file I/O request via the CPU 10 at every block and the access time is greatly shortened.