PURPOSE: To easily perform the retrieval processing of display processing data and a display change operation by forming one menu classified by every display processing function at every classified display processing function, and selecting a corresponding display processing program from the menu classified by every display processing function by a display processing designation code.

CONSTITUTION: Processing information to display the symbols, the numeric values, and the characters, etc., of a various kinds of equipments which constitute an instrumental monitor control picture is classified to a fixed picture element and a display change element. And the processing information of the fixed picture element is stored in an auxiliary memory device 28 in advance as a data base via an auxiliary memory controller. Next, the display designation code is attached on the processing information classified at every display processing function. Furthermore, the display processing program required for every display processing function is allocated, then, the menu classified by every display processing function is generated. By employing such method, a display processing requested based on the attribute of a classified equipment is always included in each program. Therefore, it is possible to facilitate the retrieval processing of the display processing data and to eliminate the complexity of the display change operation.