PURPOSE: To shorten the access waiting time of a floppy disk by providing a means to produce or renew the data set information to each floppy disk.

CONSTITUTION: When a rise request is given for a floppy disk operating device, a loader is driven by the functions of a CPU1 and an FDC2. Thus the directories of the data sets of floppy disks FD0WFD3 set to floppy disk drivers FDD0W FDD3 are read, and then catalogs are produced for drivers FDD0WFDD3. These catalogs are transferred and stored to a main memory MM3 from the CPU1. Then the data is initialized to start the FDD0WFDD3, and the information is produced for each data set from the catalog data which is produced by the loader and stored in the MM3. Thus the data set information which is used by the floppy disk operating device is produced. Thus it is possible to give an access to the desired data set with no detection given to all floppy disk drivers.