An interactive graphics terminal for a large computer system



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Graphic input and output Is becoming increasingly common for use with medium and large computer systems in the form of plotters, storage cathode ray tubes, and non-storage cathode ray tubes requiring periodic refreshing of the display. Although graphic output and input makes greater demands upon a computer system, both in terms of memory and computing time, it is extremely valuable to the user, since it permits more rapid analysis of data and permits more natural input. Problems, for example, in Mechanical Engineering can be presented in the form of sketches of structures under stress analysis or in the form of objects in motion in systems under force and velocity analysis. Using an IMLAC PDS-1 Graphic Computer, an interactive graphic input/output terminal is developed which is capable of operation with any computer system equipped with highspeed data transmission. The interface with the computer system is via a fixed message protocol which makes the terminal operation relatively independent of the driving computer system. The terminal itself is capable of maintaining a display without assistance once display specifications have been transmitted by the driving computer. In addition, the terminal can assemble and transmit information from its keyboard and screen location information from a keyboard-controlled location pointer. A sample application for the graphic terminal is implemented and system performance is examined in operation with the University of Houston UNIVAC 1108/EXEC 8 computer system.