PURPOSE: To select the commands with high operability by selecting a command corresponding to an identifier when the key input of the identifier is detected by an identifier input detecting part.

CONSTITUTION: When a list of commands is displayed on a screen, an identifier input detecting part 14 detects the presence or absence of the key input of an identifier that is assigned by an identifier assigning part 13 through a keyboard 3. When this key input is detected, the part 14 selects a command corresponding to the identifier of the key input and informs it to a data processing part 11. Receiving the information of the command type, the part 11 processes the data. Thus it is not required to move a cursor each time nor to operate alternately the keys and a mouse at the time of selecting command from the list of commands on screen. As a result, the commands can be selected with high operability.