Page "History of computing hardware" Paragraph 61

In 1939, John Vincent Atanasoff and Clifford E. Berry of Iowa State University developed the Atanasoff – Berry Computer ( ABC ), The Atanasoff-Berry Computer was the world's first electronic digital computer.

The design used over 300 vacuum tubes and employed capacitors fixed in a mechanically rotating drum for memory.

Though the ABC machine was not programmable, it was the first to use electronic tubes in an adder.

ENIAC co-inventor John Mauchly examined the ABC in June 1941, and its influence on the design of the later ENIAC machine is a matter of contention among computer historians.

The ABC was largely forgotten until it became the focus of the lawsuit Honeywell v. Sperry Rand, the ruling of which invalidated the ENIAC patent ( and several others ) as, among many reasons, having been anticipated by Atanasoff's work.