A Tablet Input Facility for an Interactive Graphics System

Effect ive man-machine communication in an interact ive graphics environment requires a natural and convenient way for the on-line user to input information and issue commands to the computer. Several applications have been described 1,2,3 in which such an interface has been achieved by allowing the user to draw symbols on a tab le t . In order to make th is mode of in ter action generally available to users of the TX-2 graphics f a c i l i t y , * we have augmented the TX-2 graphics programming language LEAP with constructs for handling tablet input and interfacing with a user-trainable symbol recognizer. These extensions to LEAP have made the incorporation of a f lex ib le input technique into a graphics appl i cation program as straightforward for the programmer as typewriter input. Experimentation with the man-machine interface has thereby been greatly s impl i f ied, resul t ing in the faster development of useful graphics applications. This paper i l l us t ra tes an application which uses the symbol recognition f a c i l i t y , and describes the language extensions through which the interact ive aspects of such an application are implemented.