Simon | 1950

 

Simon is a relay-based electromechanical computer described in a series of 13 construction articles written by Edmund Berkeley, published in Radio-Electronics magazine starting in October 1950. It was designed to educationally demonstrate the concept of digital computers but had only 2 bits of memory, making it impractical for actual computation. The first working model was built by two graduate students at Columbia University using parts costing less than $300 (approximately $3,650 in 2022). Some describe it as the "first personal computer," but this classification is controversial due to its extremely limited capacity and unsuitability for purposes beyond educational demonstration.

The "Simon Project" began with Berkeley's book, Giant Brains, or Machines That Think, published in November 1949. In it, he stated:

"We will now consider how to design a very simple machine. Let’s call this machine ‘Simon.’ This is named after an earlier machine called Simple Simon... Simon is so simple and small that it could actually occupy less space than a grocery store box; it is only about 4 cubic feet... This simple model of a mechanical brain might seem to have no practical value. However, Simon has the same value for educational purposes as a simple chemical experiment set: it stimulates thinking and understanding, and generates training and skills. The course on mechanical brains can include building a simple model mechanical brain as practice."

In November 1950, Berkeley wrote an article titled "Simple Simon" for Scientific American, explaining the principles of digital computing to the general public. Despite its extremely limited resources (it could only represent the numbers 0, 1, 2, and 3), Berkeley claimed in 40 pages that this machine possessed "two unique properties that define all true mechanical brains": it could "automatically transfer information from one 'register' to another and perform reasoning tasks of infinite length." He concluded the article with predictions about the future:

"Someday we might have small computers that can draw electric energy from our homes, just like refrigerators or radios... They could help us recall facts that are difficult to remember, and calculate accounts or taxes. Students doing homework might seek their assistance. We might even envision mechanical brains around us capable of listing the combinations of possibilities needed for important decisions."

Simon's architecture was relay-based. Programs ran on standard punched paper tape, which had a row with five holes for data. Both the register and ALU could store only 2 bits. Users input data using a paper punch or five keys on the front panel. The machine output data through five lamps.

The punched tape served not only for data input but also as a memory storage. The machine executed commands read from the tape sequentially. It could perform four operations: addition, negation, comparison, and selection.