Graphics display terminal and method of storing alphanumeric data therein

Abstract

The specification describes a method of storing alphanumeric characters in a graphics display terminal comprising a raster-scan display device and a refresh buffer including a plurality of bit planes each having a respective bit storage location corresponding to each addressable pel position on the screen of the display device. In the method, a first bit plane stores high resolution luminance data defining alphanumeric characters each as a selection of 'on' bits within a respective n.times.m array where n is the width of the character box in the scan line direction, and at least one further bit plane stores low resolution color data for the characters. The attribute plane comprises a respective n-bit set of storage locations which corresponds to each n-bit wide by one pel deep portion of a character box in the luminance plane and defines at least the color and/or intensity of the foreground and background of the character for the width of the character box in respect of a single scan line. The specification also describes a graphics display terminal in which data in the luminance and attribute planes may be selectively decoded either as alphanumeric data stored as above, or as bit-mapped graphics data.