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 differentiates it from later, more general machines, such as ENIAC.

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 rapidly 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.

See also: History of computing hardware

Links:

1. The Birth of the ABC: http://www.cs.iastate.edu/jva/jva-archive.shtml/
2. Rebuilding the ABC: http://www.scl.ameslab.gov/ABC/