Ivan Sutherland demonstrating Sketchpad (UVC via IA: video and thumbnails) |
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| Original author(s) | Ivan E. Sutherland |
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| Initial release | 1963 |
| Platform | Lincoln TX-2 |
| Type | animation, drawing, drafting, CAD |
Sketchpad (aka Robot Draftsman) was a revolutionary computer program written by Ivan Sutherland in 1963 in the course of his PhD thesis, for which he received the Turing Award in 1988. It helped change the way people interact with computers. Sketchpad is considered to be the ancestor of modern computer-aided drafting (CAD) programs as well as a major breakthrough in the development of computer graphics in general. For example, the Graphic User Interface was derived from the Sketchpad as well as modern object oriented programming. Ivan Sutherland demonstrated with it that computer graphics could be used for both artistic and technical purposes in addition to showing a novel method of human-computer interaction.
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Sutherland was inspired by the Memex from 'As We May Think' by Vannevar Bush. Sketchpad inspired Douglas Engelbart to design and develop oN-Line System at the Augmentation Research Center (ARC) at the Stanford Research Institute (SRI) during the 1960s. Sketchpad was the first program ever to utilize a complete graphical user interface, using an x-y point plotter display and the recently invented light pen. The clever way the program organized its geometric data pioneered the use of "objects" and "instances" in computing and pointed forward to object oriented programming. The main idea was to have master drawings which one could instantiate into many duplicates. If the user changed the master drawing, all the instances would change as well. Another major invention in Sketchpad was that it let the user easily constrain geometric properties in the drawing—for instance, the length of a line or the angle between two lines could be fixed. Bolt, Beranek and Newman had a "similar program"[1] and T-Square was developed by Peter Samson and one or more fellow MIT students in 1962, both for the PDP-1.[2]
Sketchpad ran on the Lincoln TX-2 (1958) computer at MIT, which had 64k of 36-bit words. Of the 36 bits available to store each display spot in the display file, 20 gave the coordinates of that spot for the display system and the remaining 16 gave the address of the n-component element responsible for adding that spot to display. In 1963 most computers ran jobs in batch job mode only, using punched cards or magnetic tape reels submitted by professional programmers or engineering students. A considerable amount of work was required to make the TX-2 operate in interactive mode with a large CRT screen. When Sutherland had finished with it, it had to be reconverted to run in batch mode again.
The Sketchpad program was part and parcel of Sutherland's Ph.D. thesis at MIT. It was reprinted in 1980 under the title Sketchpad: A Man-Machine Graphical Communication System. It is now out of print, but several university libraries have copies and it is also present on the rare book market. A new electronic editionPDF (3.90 MiB) was published in 2003.