PURPOSE: To display even an unregistered character on the screen of a display device by reading out font data corresponding to the character code of the unregistered character at the time of finding this character in a designated position to not only write this data in a private memory area of a character generator but also display it on the screen.

CONSTITUTION: When the character code is written in a display memory VRAM, a first display control means VDP 1 reads out a font pattern from a character generator C/G to display a character corresponding to the character code on the screen of a display device CRT. When this unregistered character is designate don the screen with a cursor, a second display control means VDP2 reads out font data from a font data holding means FDM, where font data of the unregistered character is held, to write it in the private memory area of the character generator C/G. As the result, the font pattern of the unregistered character is displayed on the screen. Thus, the unregistered character is displayed on the screen at any time when being designated on the screen.