Atanasoff-Berry Computer (ABC)

The Atanasoff-Berry Computer, sometimes referred to by its initials, ‘ABC’ was invented in 1938-42 at Iowa State University, by Dr.John Vincent Atanasoff and Clifford E.Berry. It was used to solve simultaneous linear equations. This computer weighed about 320kg and contained about 16 km of wire, 280 dual-triode vacuum tubes and 31 thyratrons, and was about the size of a desk.

This machine was described as the first electronic digital computer because of its use of electronics for arithmetic calculations, and featured the main characteristics of a modern computer: the use of binary digits to represent data, performing all calculations by using electronics, having a system in which computations and memory were separated, and it also used regenerative capacitor memory. The capacitor’s memory consisted of a pair of drums, each containing 1,600 capacitors, which rotated on a shaft once per second. The machine had a speed of 30 additions/ subtractions per second. To represent the data, 50 bit binary fixed point numbers were used. It was capable of storing and operating on 300 bits at any given time. The logic functions which were implemented with vacuum tubes were fully electronic. The logic gates used ranged from inverters to two and three input gates.

The Atanasoff-Berry Computer was a step ahead of the previously invented machine. But it was not a stored program computer. An operator was required to set up its program. Front panel switches and jumpers were used to select the operation, read, write, conventions between binary to decimal, etc. Two forms of input and output were used as primary and an intermediate result input and output.Primary user input was handed by standard punch card and output was set through a front panel display. Later this helped to solve very large problems within the electronic memory.