Raster display apparatus

A raster display apparatus comprising a cathode ray tube adapted to display a picture formed as a plurality of character cells,

• a refresh buffer adapted to contain a plurality of pointers one for each character cell position on said tube,
• a loadable character generator adapted to contain bit patterns representing character cells to be displayed,
• means adapted to load said refresh buffer with pointers determined by the content of a picture to be displayed and to load said character generator with bit patterns representing the character cells constituting said picture,
• and refresh logic means adapted to access said refresh buffer to read said pointers and to cause said read-out pointers to access their associated bit patterns in said character generator for refreshing said tube,
• characterized in that said loading means is adapted to combine two or more adjacent character cells into a single character cell of lower resolution when said character generator is full thereby to create additional space in said generator for the storage of further bit patterns and to associate with the or each pointer respresenting a low resolution cell an indication that said cell is of lower resolution, said logic means being responsive to said indication to control clocking of the bit pattern for said lower resolution.