PURPOSE: To use the application programs specialized in a computer system for various computer systems by changing the setting mode at the present point in time to a mode corresponding to the change operation in the case of a change operation by the use of a specified key and displaying the display contents corresponding to the changed mode.

CONSTITUTION: When a user performs change by using a specific key, for example, a key 21b0 for English/figure/KANA (Japanese syllabary writing), a control part changes the mode at the present point of time to the one according to the change operation and the display contents corresponding to the changed mode is displayed on a display part 21b1. At the same time, an operation signal showing the control content of the change operation is outputted to the computer system. On the other hand, when a display signal is outputted from the computer system, the control part displays the display contents on the display part 21b1 and the mode corresponding to the displayed contents is set. At the same time, an operation signal is outputted to the computer system.