PURPOSE: To accelerate a data access processing by calculating a difference between the present location of the head of a floppy disk drive and the targeted cylinder number of each task, and selecting the optimum command to be executed next.

CONSTITUTION: A random access memory 21 to store command information and a task number from a central processing unit and the present location of the head of the floppy disk drive, a means 22 to calculate the difference between the present location of the floppy disk drive and the targeted cylinder number of each task to decide an execution command, and a means to send the optimum command to be executed next are provided. And the present head position of the floppy disk drive is compared with the targeted cylinder addresses of plural tasks requesting input/output simultaneously, and the task which requests the execution of the command with the minimum access time is selected, then, the command is executed. In such a way, the data access time of a floppy disk can be shortened.