PURPOSE: To improve the operability and the work efficiency by displaying a guidance to explain menu items simultaneously with operator's menu display.

CONSTITUTION: A client process (a) is the user application for window operation request or the like, and a server process (b) is the process for the processing of window operation request from the client process (a) and the resource manage ment. When the button of a mouse as an input device (c) is depressed, the event of button depression is transferred to the client process (a) through the server process (b). The client process (a) receives the event to transfer informa tion of menu window generation and information of guidance window generation to the server process (b), and they are displayed on a display device (e). Thus, the inconvenience for operator's operation is resolved to improve the operability and the work efficiency.