Abstract: In the present invention, an information processing apparatus includes a host device and other external devices connected to the host device. When a memory that has stored a new control program of updated version is installed in the host device, the host device replaces the current control program that is stored in a memory of each external device with the new control program. As rewriting of control programs in the external device can be carried out by simply installing the new memory in the host device, the rewriting operation of control programs of the external devices becomes very simple. The present invention is especially effective when a plurality of the external devices is connected to the host device.