PURPOSE: To recognize the data transfer system at the side of an electronic equipment main body by displaying the data transfer system of an external equipment on a display device when this external equipment is loaded into the electronic equipment.

CONSTITUTION: An interface mode request is inputted from a keyboard 10 and an external logic 5 is connected to an I/O interface circuit 4. Then a request for data transfer style of the logic 5 is informed to the circuit 4 from a CPU1 via a data bus 7. Thus the circuit 4 transfers the signal to the CPU1 to show the transfer style of the logic 5. The CPU1 decides the data transfer style and reads the data transfer style data out of a ROM2 to send it to a display device controller 9. Then the transfer style is displayed on a display device 8.