Digi-Comp I

The Digi-Comp I is a functioning, mechanical digital computer sold in kit form. It was originally manufactured from polystyrene parts by E.S.R., Inc. starting in 1963 and sold as an educational toy for US$4.99 (equivalent to US$51 in 2024).^[1]

The original DigiComp I

The Digi-Comp I has been referred to as the first home computer.^[2]

A successor, the Digi-Comp II, is not programmable, but in effect a visible calculator. A two-level Masonite platform with guides serves as the medium for a supply of marbles that rolled down an inclined plane, moving plastic cams as they fell.^[3]

Operation

The Digi-Comp I contains three mechanical flip-flops, providing an ability to connect them together in a programmable way using thin vertical wires that are either pushed, or blocked from moving, by a number of cylindrical pegs. The whole arrangement is "clocked" by moving a lever back and forth. Different configurations of these cylinders cause the Digi-Comp to compute different Boolean logic operations. With a three binary digit (3-bit) readout of the state of the flip-flops, it could be programmed to demonstrate binary logic, to perform various operations such as addition and subtraction, and to play some simple logic games such as Nim.^[4]

Although promotional materials described it as an "actual working digital computer," the device is more accurately described as a finite-state machine, one of the underpinning concepts used to build computers.

Reproductions

A front view of the Digi-Comp I version 2.0.

Starting in 2005, Minds-On Toys has made available the Digi-Comp I version 2.0 as a relatively inexpensive binder's board version of the original Digi-Comp, albeit with a much enhanced instruction manual.^[5]

See also

• Dr. Nim - game based on the computer
• Geniac
• WDR paper computer
• CARDboard Illustrative Aid to Computation
• Turing Tumble, a 2019 mechanical computer inspired by it
• Robert C. Martin, who credits playing with this toy at the age of 12 as being what made him decide to become a programmer for the rest of his life.^[6]
• Little man computer