Sketchpad

Sketchpad, the first interactive computer-graphics program, originated as a graduate student's thesis project in the early 1960s. It became a foundation for graphical sciences, computer operating system (OS) interfaces, and software applications that are used in many facets of today's computer work.

At the Massachusetts Institute of Technology (MIT), Ivan Sutherland published his 1963 doctoral thesis, titled “Sketchpad: A Man-Machine Graphical Communications System,” which described a program that was capable of drawing simple geometrical shapes on the screen of a computer. The software's functionality was unique, and required the use of a rather complex hardware system.

In 1961, Sutherland had developed a primitive application that would run on one of the first programmable computers. During that time period, it was difficult to find computers to work with, due to their size and cost. With the Sketchpad idea in mind, Sutherland found a computer that he could use at MIT's Lincoln Laboratory, and began to develop the program. MIT's Lincoln Laboratory computer was a TX-2 machine, a huge computer whose capacity was twice that of the largest commercial machines. Impressive for its programmable capabilities, the TX-2 possessed 320KB (kilobytes) of memory for fast storage, magnetic tape storage, and a feeding mechanism for paper-tape programs—long strips of paper with holes punched into them that communicated instructions to the computer.

The TX-2 also powered a nine-inch Cathode Ray Tube (CRT) display, an essential component that allowed the computer user to view the graphics created with Sketchpad. A light pen allowed drawings to be represented on the screen, and was used to manipulate the line objects, similar to the way that the mouse selects and moves files and windows on today's computers. When used in collaboration with the light pen, several switches located on the computer were used to control certain aspects of the graphics, such as size and ratio.

Sketchpad's process for drawing lines, shapes, and corners was quite complicated. The Research [Page 413]Laboratory of Electronics (RLE) at MIT reported the system's functionality to be heavily electrical, and described Sketchpad's drawing process as electronic pulses that are shared between the photoelectric cell of the light pen and an electronic gun fired from the CRT. The timing of the pulse displayed a cursor, representing the light pen's position on the screen, thus converting the computer screen into a sketchpad upon which objects could be drawn.

Sketchpad permitted precise drawings to be fashioned, copied, and stored. In fact, the concept of graphical computing originated from the way that objects created using Sketchpad could be visualized and modeled on a screen. This inaugurated the new research field of computer-graphical sciences. In 1964, Sutherland collaborated with Dr. David Evan at the University of Utah to initiate one of the first educational computer-graphics labs. With a foundation created, computer graphics was able to evolve into its current roles in advertising, business, entertainment, architecture, and Web design, among many other fields.

Sketchpad's performance in computer-graphics representation also led to the advanced development of other imaging software. One such example is computer-aided drafting (CAD), used by engineers to create architectural designs for new products and buildings. Sketchpad demonstrated a way in which graphics can be drawn to exact scale, and models can be changed quicker than by hand.

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