Main Page | See live article | Alphabetical index

Atanasoff Berry Computer

Atanasoff Berry Computer is the name applied, long after the fact, to an experimental machine for solving systems of simultaneous linear equations, developed in 1938-42 at Iowa State University by John Vincent Atanasoff and Clifford E. Berry.

Because of the machine's innovative use of electronics for arithmetical calculation, it has been described as the first "electronic digital computer". However, it was a special-purpose, non-programmable "hard wired" machine, which distinguishes it from later, more general machines, such as ENIAC, the Harvard Mark I, EDVAC, the University of Manchester designs, or Turing's post-War designs at NPL and elsewhere.

The machine was, however, the first to implement three ideas that are still part of every modern computer:

  1. Using binary digits to represent all numbers and data
  2. Performing all calculations using electronics rather than wheels, rachets, or mechanical switches
  3. Organizing a system in which computation and memory are separated.

The machine was seen by John Mauchly in 1941, and is alleged to have influenced his later work on ENIAC. Mauchly denied this, but it was the basis for a court decision invalidating the ENIAC patents.

The memory was a pair of drums, each containing 1600 capacitors that rotated on a common shaft once per second. The capacitors on each drum were organized into 32 "bands" of 50 (30 active bands and 2 spares in case a capacitor failed), giving the machine a speed of 30 additions/subtractions per second.

See also: History of computing hardware


  1. The Birth of the ABC:
  2. Rebuilding the ABC: