PURPOSE: To read data at a high speed by storing data, which indicates the state of characters, in a virtual VRAM provided on a main memory and reading in data indicating the state of characters from the virtual VRAM.

CONSTITUTION: BAT and CG indicating the background and SAT and SG indicating sprites are partially extracted and copied from a VRAM to the virtual VRAM. Only picture information to be frequently used is copied from the VRAM to the virtual VRAM and is managed in the virtual VRAM. In the case of detection of the position of a display material or the discriminating processing of collision between materials, it is necessary to read contents of the picture; and in this case, the virtual VRAM is used, and the VRAM is not directly read but the virtual VRAM is first read to discriminate the processing to be next executed. Consequently, this method copes with most processings with the virtual VRAM because principal picture information is equally stored in the VRAM and the virtual VRAM, and the read speed is considerably increased.