PURPOSE: To eliminate the need of a space for displaying the other kind of information data and to immediately recognize logical connection by connecting alphabetic and numeric information and/or graphics or those parts displayed on a display screen with a soft key by reference lines.

CONSTITUTION: The alphabetic and numeric information and/or graphics or one part of those information reproduced on a display screen 2 are logically connected with a soft key 3 by a reference line 4 displayed by software dependence extending on the display screen 2. Thus, the space necessary for displaying the other kind of information data is unnecessitated for the instructions of each soft key on the display screen 2, and the logical connection of the alphabetic and numeric instructions or graphics on the display screen 2 with the soft key 3 can be immediately recognized. Also, parts extremely close to each other on the display screen 2 can be driven separately by each soft key 3.