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Simon, the First Personal Computer (May – November 1950)


Edmund Berkeley's "Simon," which has been called the first personal computer, developed out of his book, Giant Brains, or Machines That Think, published in November 1949, in which he wrote,

 “We shall now consider how we can design a very simple machine that will think.. Let us call it Simon, because of its predecessor, Simple Simon... Simon is so simple and so small in fact that it could be built to fill up less space than a grocery-store box; about four cubic feet. . . . It may seem that a simple model of a mechanical brain like Simon is of no great practical use. On the contrary, Simon has the same use in instruction as a set of simple chemical experiments has: to stimulate thinking and understanding, and to produce training and skill. A training course on mechanical brains could very well include the construction of a simple model mechanical brain, as an exercise."

One year later in an article published in Scientific American about “Simon,” in November 1950 Berkeley predicted that “some day we may even have small computers in our homes, drawing energy from electric power lines like refrigerators or radios.”

"Who built "Simon"? The machine represents the combined efforts of a skilled mechanic, William A. Porter, of West Medford, Mass., and two Columbia University graduate students of electrical engineering, Robert A. Jensen . . . and Andrew Vall . . . . Porter did the basic construction, while Jensen and Vall took the machine when it was still not in working order and engineered it so that it functioned. Specifically, they designed a switching system that made possible the follow-through of a given problem; set up an automatic synchronizing system; installed a system for indicated errors due to loss of synchronization; re-designed completely the power supply of themachine" (Fact Sheet on "Simon." Public Information Office, Columbia University, May 18, 1950).

"The Simon's architecture was based on relays. The programs were run from a standard paper tape with five rows of holes for data. The registers and ALU could store only 2 bit. The data entry was made through the punched paper or by five keys on the front panel of the machine. The output was provided by five lamps. The punched tape served not only for data entry, but also as a memory for the machine. The instructions were carried out in sequence, as they were read from the tape. The machine was able to perform four operations: addition, negation, greater than, and selection" (Wikipedia article on Simon (computer) accessed 10-10-2011).

In his 1956 article, "Small Robots-Report," Berkeley stated that he had spent $4000 developing Simon. The single machine that was constructed is preserved at the Computer History Museum, Mountain View, California. Berkeley also marketed engineering plans for Simon, of which 400 copies were sold.