The identity of the first electronic digital computer is a matter that is often debated by technology historians and computer enthusiasts. In 1937, John Atanasoff and Cliff Berry, a professor and graduate student at Iowa State College, invented and built the first electronic digital computing device. Known as the ABC computer, after the names of the two men, it was not a programmable device but was designed to solve simple equations. In 1946, two University of Pennsylvania researchers finished work on the Electronic Numerical Integrator And Computer (ENIAC), which received the first patent for a digital electronic computing device.
The ABC computer was about the size of a desk and could only solve a series of linear equations. It was not fully programmable in the way that the general purpose computers that came after it were, but was a purpose-built device capable of only one function. This leads some to deny its status as a true computer. Part of this controversy results from different definitions of the word "computer."
For many years, the work of Presper Echert and John Mauchly on the ENIAC computer was regarded as having produced the first electronic digital computer. ENIAC was certainly the first device of this type to be both programmable and to exhibit something called Turing completeness, a criterion of true logic-based multiple branching computing capability. In 1964, Echert and Mauchly received a patent for their device, which had been built for and financed by the United States Defense Department.
In 1973, after a lawsuit filed by the Honeywell corporation, A United States federal court issued a decision determining that the ENIAC patent was invalid and that it was derived from the earlier work by Atanasoff and Berry on the ABC computer. This made the ABC computer the first electronic digital computer, at least according to United States law. An earlier device, produced in Germany, was similar in capability, but operated on an electro-mechanical basis and was not a true digital device.
Historians recognize both the ABC computer and the ENIAC computer as the progenitors of modern computers. History shows, and the law has decided, that, technically, the ABC computer was the first electronic digital computer. Most modern technology and computer historians, however believe that its lack of programmability relegates it to a status of no more than the forerunner of what many consider, due to its programmability and operational history, to be the true first digital electronic computer, ENIAC.