Digital display system with refresh memory for storing character and

Abstract

A digital display system includes a refresh store containing character data for display on a raster scan video display device and field attribute data defining attributes of fields of the character data. The character data is stored as character bytes in sequential locations in the store for readout in groups to provide respective rows of displayed characters. The field attribute data comprises attribute bytes interspersed with the character bytes. Character bytes in a group read out following an attribute byte provide displayed characters with an attribute defined by that attribute byte until another attribute byte is accessed in the group. In order to maintain an attribute from one row of displayed characters to the next, the group of character bytes corresponding to the next row requires a copy attribute byte at the start of readout of that group. Instead of being stored with the character bytes, the copy attribute bytes are stored in a separate table in the refresh store, each entry of which contains a copy attribute byte for the start of a corresponding row of displayed characters.