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Sketchpad

Sketchpad: A Man-Machine Graphical Communication System / Sketchpad thesis
2026-09-11 add · 425 words

Sketchpad refers to the interactive drawing program that Ivan Sutherland developed for his doctoral thesis at MIT, and to the 1963 thesis that described it, "Sketchpad: A Man-Machine Graphical Communication System". It was a system in which lines were drawn directly on the screen with a light pen and the drawn figures could be pointed at and edited, allowing a person and a computer to exchange line drawings quickly. It is regarded as the ancestor of CAD, and is also counted among the origins of the GUI and of object-oriented programming.

The thesis

  • Title: Sketchpad: A Man-Machine Graphical Communication System
  • Author: Ivan E. Sutherland
  • Submitted: January 1963, to MIT as a Ph.D. thesis
  • Supervision: Claude Shannon agreed to supervise, and Marvin Minsky and Steven Coons joined the examining committee

In the same year, 1963, Sutherland presented Sketchpad at the Spring Joint Computer Conference. In September 2003, the University of Cambridge Computer Laboratory reissued the thesis as a technical report (UCAM-CL-TR-574), with a new preface by Alan Blackwell and Kerry Rodden.

The system

It ran on the TX-2, a large computer at MIT Lincoln Laboratory (36-bit words, 64k words of memory). For input it used a light pen, which detected the scanning light of the cathode-ray tube to determine a position on the screen, and the user manipulated figures by pointing at them directly on the screen.

Ideas it introduced

  • Constraints: geometric conditions such as the length of a line or the angle between lines could be specified, and figures could be handled while those conditions were maintained
  • Master and instance: multiple copies (instances) could be made from an original figure (master), and changing the master was reflected in all copies
  • Type-specific behavior: it had a mechanism for switching processing according to the kind of figure through pointers to functions, anticipating the idea of later virtual functions

Influence

It is the ancestor of modern CAD software and is regarded as a major turning point for computer graphics as a whole. The method of directly pointing at and manipulating objects on the screen influenced the development of the GUI, and the idea of master and instance influenced object-oriented programming. For these achievements Sutherland received the Turing Award in 1988 and the Kyoto Prize in 2012.

To verify

  • Whether the thesis was also issued as an MIT Lincoln Laboratory technical report (No. 296), and its date
  • The differences in content between the paper presented at the Spring Joint Computer Conference and the doctoral thesis

References

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