To construct an I/O bus capable of connecting plural I/O ports, for directly operating input and output control from the CPU of a personal computer outside the personal computer.

Each independent address register write signal, extended data register write signal, and port data write signal is generated by using the interface signal of a printer port, and a general I/O bus 14 constituted of 8 output data buses, 6 address buses, 4 input data buses, and 1 interrupt control signal is constructed, and plural quickly controllable I/O ports can be directly connected from the CPU of a personal computer.