The invention provides an improved image memory device including an image processing memory unit incorporated into a universal image processing device and an address switching control circuit connected thereto, wherein an address data for raster display and an address data fed from an external input-output device are periodically selected by an address switching control circuit for supply to the image processing memory unit so that the memory unit may be accessed by an external input-output device without intercepting the raster display with remarkably reduced data transfer time.

A digital data display in which each display unit includes a random access, read/write character definition buffer store and a screen buffer. The character definitions and screen buffer for each picture to be displayed are constructed in a remote host central processing unit. In order to minimize the time that a user has a blank screen while new character definition and screen buffer data is sent from the c.p.u. to the display unit, this information is sent in groups relating to rows of character cells on the screen and a coherent picture is displayed growing from the top downwards, giving a roller blind effect. Data relating to the first significant row is sent initially followed by groups of character definitions and screen buffer data, the size of the groups dependent upon the characteristics of the transmission buffer.

A circuit realizable on a single substrate, for interfacing between a digital processor and a raster scanned, video display particularly suitable for games, or the like. In the presently preferred embodiment, up to thirty-two objects may be simultaneously displayed. Content addressable memories (CAMs) which compare beam location with desired object location are employed to locate objects on the display. Fewer than thirty-two CAMs are employed to locate thirty-two objects with the circuit's "grouped major system". The display circuit includes another subsystem ("minor system") for displaying patterns with a minimum of control by the processor.

Hardware duplication at each of a plurality of CRT key stations is minimized and centralized control is maintained by performing many traditional CRT key station operations under software control by a central processing unit. Simplified CRT key stations include circuitry providing automatic key stroke repeat for continuously actuated keys only after receipt of a repeat enable signal from the central processing unit for each separate repeat and a tone generator responsive to commands from the central processing unit. The tone generator includes a key click circuit to audibly indicate each completion of a key activation. CRT key station circuitry inserts a configuration code with each key stroke data word which indicates one of a plurality of available key switch arrangements for the CRT key station. The configuration code permits a single key station hardware design to be included in a data entry system with different keyboard configurations such as typewriter, calculator, keypunch or even foreign language to be selected without need for a conversion system at each CRT key station to convert key stroke information to a common code. Instead, a central processing unit may utilize the configuration code to identify an appropriate conversion table stored in memory.

A stand-alone, interactive processor and display system for displaying, performing positioning, sizing, and performing supportive composition functions for newspaper ad layout. Interactive work stations position copy, edit and correct text, adjust style and point sizes, to accomplish accurate composition functions. A Bit Image Memory digitally stores all displayed patterns directly to minimize the response time of the system to operator inputs. An arithmetic unit and character generator are disclosed which produce lines and character which accurately represent the final copy.