PURPOSE: To attain continuous scroll screen display regardless of the number of displayed scroll screens by writing data in an upper corresponding area at the time of writing data in a lower overlap writing range with the prescribed number of lines in a video RAM which has larger number of lines than a display screen.

CONSTITUTION: At the time of writing overlap data in a lower overlap writing range with the number of lines N -1=7 of a video RAM with large number of lines, for example, 32 in contrast to a display screen with the number of lines N=8, the similar overlap data are written in an upper area with the number of lines N -1=7. Then, when each line is instructed by a pointer, and the RAM is read, the RAM can be successively used from the uppermost even when the RAM is used until the lowermost. Thus, scroll display can continuously be operated regardless of the number of scroll screens without rewiring the RAM.