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$50 in 2023).

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] 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.

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.