A function designate method for designating a variety of functions to be performed by a control unit. The method includes the step of displaying graphic icons under ordinary circumstances, which are for designating a variety of functions to the control unit on a display device. The method further includes displaying character icons, each of which includes one of the graphic icons and one character for designating a key on a keyboard, when a predetermined control key has been pressed. Also, the method includes a graphic icon by a cursor or simultaneously pressing the control key and a key corresponding to a character displayed together therewith. Finally, the method includes designating a function that has been allocated to the graphic icon to the control unit.