To construct the class libraries of plural hierarchies, thus allowing the respective class libraries to be independently used with an application program.

In the class library of graphic plotting, an abstract basic layer, a basic graphic layer, a composite graphic layer and an application graphic operation layer are made into hierarchies and the respective hierarchies can independently construct an application. The respective hierarchies realize differential programming by permitting the succeeded low-order class to call the similar function of a high-order class so as to transmit it. The respective hierarchies output objects in a block unit and read them in the block unit, generate the corresponding object and read data into the generated object itself.