Notification is sent to an upper layer via a control device 2 (a device for managing operation buttons) provided between operation buttons “A-1”, “A-2” and the like and devices for operation input “Device A”, “Device B” and the like such as a pointing device for executing application processing. Function assignment and the like are put under management by the control device 2, so that any modification or change is not required in the OS, drivers, and applications in association with change in key assignment, which is advantageous and effective for reduction of cost and time for product development.