PURPOSE: To transfer data at a high speed by simple constitution, by directly switching an address or a command as hardware by a control signal from an input/output device controlling part.

CONSTITUTION: An address or a command is switched directly as hardware by a control signal from an input/output device controlling part. For instance, an address signal is sent out to a decoder part 6 of an input/output device interface 2, an input/output device controlling part 7 and a storage part 4 through an address bus from a CPU 1, and also a control signal is sent out to the decoder part 6 and the input/output device controlling part 7 through a control bus. Subsequently, a select signal is sent out to the input/output device controlling part 7, a buffer part 5 and the storage part 4 from the decoder part 6. Subsequently, a control program of an input/output device 3 is switched as hardware by sending out a control signal to the storage part 4 from the input/output device controlling part 7.