The Digi-Comp I is a functioning, mechanical digital computer

Computer

A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...

 sold in kit form. It was originally manufactured from polystyrene

Polystyrene

Polystyrene ) also known as Thermocole, abbreviated following ISO Standard PS, is an aromatic polymer made from the monomer styrene, a liquid hydrocarbon that is manufactured from petroleum by the chemical industry...

 parts by E.S.R., Inc. starting in 1963 and sold as an educational toy for $5.95.

In essence the Digi-Comp I contains three mechanical flip-flops

Flip-flop (electronics)

In electronics, a flip-flop or latch is a circuit that has two stable states and can be used to store state information. The circuit can be made to change state by signals applied to one or more control inputs and will have one or two outputs. It is the basic storage element in sequential logic...

 and provides 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

Boolean logic

Boolean algebra is a logical calculus of truth values, developed by George Boole in the 1840s. It resembles the algebra of real numbers, but with the numeric operations of multiplication xy, addition x + y, and negation −x replaced by the respective logical operations of...

 operations. With a three binary digit (3-bit) readout of the state of the flip-flops, it can 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

Nim

Nim is a mathematical game of strategy in which two players take turns removing objects from distinct heaps. On each turn, a player must remove at least one object, and may remove any number of objects provided they all come from the same heap....

.

The Digi-Comp I version 2.0 was made available by Minds-On Toys in 2005 as a relatively inexpensive cardboard

Paperboard

Paperboard is a thick paper based material. While there is no rigid differentiation between paper and paperboard, paperboard is generally thicker than paper. According to ISO standards, paperboard is a paper with a basis weight above 224 g/m2, but there are exceptions. Paperboard can be single...

 version of the original Digi-Comp with a much enhanced instruction manual.

A successor, the Digi-Comp II

Digi-Comp II

The Digi-Comp II was a toy computer manufactured by E.S.R., Inc. that used marbles rolling down a ramp to perform basic calculations. A two-level masonite platform with guides served as the medium for a supply of marbles that rolled down an inclined plane moving plastic cams as they went...

, is much more elaborate. A two-level masonite platform with guides serves as the medium for a supply of marbles that roll down an inclined plane moving plastic cams as they go.

External links

• The Old Computer Museum - Collection of old analog, digital and mechanical computers
• Friends of Digi-Comp - Discussion of this toy. Images, links, manuals and programming information
• Digi-Comp I v2.0 - Online vendor of working replica kit; historical details
• Digi-Comp I Emulator - Emulator for the original Digi-Comp I written in JavaScript