Parametric graphical computer display system using analogue storage

A cathode-ray-tube graphical display system for use as a digital-computer output terminal has been developed The display employs analogue function-generation circuits to produce line drawings composed of straight-line and curved-line segments which are specified by parameters transferred from the computer in analogue form. To maintain a flicker-free image, while also imposing a minimal demand on the computer to which it is connected, the display incorporates an analogue memory composed of capacitors and field-effect-transistor switches. The displayed image may then be refreshed at the required rate by cyclically reading the line and curve control parameters from this memory. The computer need only access the memory to insert fresh data to be displayed or, infrequently, to refresh the stored information. The paper includes discussions of the specification of the overall display system, of the design of the analogue storage system and of two methods used to produce the required picture segments for display. Some results obtained with the display connected online to a small digital computer are shown.