A Computer Graphics System for Block Diagram Problems

DESIGNPAD, it consists of a small computer with graphic display equipment connected to a time-sharing computer and includes the necessary programming support for the equipment. The system is designed to accept problems covering a broad spectrum of applications in the form of labeled block diagrams. The input/output medium, the man-machine interface, and the supporting data structures, particularly the cellular structure, are discussed. Generally it is easier to express complex ideas symbolically by sketching them on paper rather than by using other means of communication. When such two-dimensional representations were applied to computer output, they resulted in the development of computer graphics.' But they are only now being applied to the input. We anticipate an evolution in input from one-dimensional character strings to two-dimensional methods occurring similarly to the one in which programming languages evolved from machine code and assembly language to such higher level languages as PL/1. To further this evolution, the construction of an experimental system called DESIGNPAD was started with the major single objective to explore the potential of two-dimensional man-machine interfaces for both computer input and output. Frequent need for total reprogramming to reflect even slight variations in functional specifications has been an unfortunate attribute of computer graphics. For example, the case of a program for graphical electrical network analysis' being incompatible with a system for graphical programming using flowcharts3 is 'a manifestation of this difficulty, although there are commonalities between these two problem-solving areas. DESIGNPAD is a single, integrated graphics system that can handle both these applications and similar ones. First outlined by Baskin and be lad^,^ it is an extension of the