First page of the English patent on ENIAC,
Creative Commons LicenseJeremy Norman Collection of Images - Creative Commons

First page of the English patent on ENIAC, which was granted in 1954, a full ten years for the U.S. patent was granted. The text of the U.S. and English patents is essentially identifical. The ENIAC patent was the patent on the electronic digital computer concept.

Physical layout of the various components of the ENIAC
Creative Commons LicenseJeremy Norman Collection of Images - Creative Commons

Physical layout of the various components of the ENIAC from the English version of the patent granted ten years before the American patent.

Detail map of Philadelphia, Pennsylvania, United States Overview map of Philadelphia, Pennsylvania, United States

A: Philadelphia, Pennsylvania, United States

Key Developments Concerning the ENIAC Patent, the Patent on the General Purpose Electronic Digital Computer

1/29/1944 to 10/19/1973
Text of Mauchley's "Disclosure of a Magnetic Calculating Machine" sent by Mauchly to Don Knuth in 1978

Text of the first page of Mauchley's "Disclosure of a Magnetic Calculating Machine" originally written by Mauchley in 1944, and sent by Mauchly to Don Knuth in 1978. Computer History Museum.

On January 29, 1944, while Pres Eckert and John Mauchly were working on making the ENIAC operational at the Moore School at the University of Pennsylvania, Eckert wrote a three-page typewritten document entitled Disclosure of a Magnetic Calculating Machine. This confidential document, which was not formally published until decades after it was written, very briefly and generally described a theoretical electronic computer that would store its program and data in an electronic memory— a type of magnetic disc or drum. Years later the document was unearthed in the trial over the ENIAC patent, to show that Eckert had conceived elements of the stored program concept before John von Neumann wrote down and distributed a complete theoretical description of a stored-program computer in his First Draft of a Report on the EDVAC

Mostly likely von Neumann and Eckert and Mauchly developed the stored-program computer concept jointly— Eckert from the engineering side and von Neumann from the theoretical side. Because von Neumann first described the design of the stored-program computer, its architecture has come to be known as the von Neumann architecture. In October 2013 I viewed the copy of Eckert's disclosure posted on the website of the Computer History Museum. This copy included an informative cover letter sent by John Mauchly to Donald Knuth on June 22, 1978.

About eight months after Eckert's "Disclosure," on September 27, 1944 Eckert and Mauchly declared that their conception of the ENIAC was complete. Eckert wrote a letter to other members of the project asking them to state written claims to inventions on the project. None was received. Also in September 1944, faced with mathematical computations regarding the Atomic bomb that were impossible for human computers, mathematician and physicist John von Neumann visited the ENIAC two-accumulator system for the first time, well before the computer was operational, and became deeply interested in the project. This visit represented the beginning of von Neumann's interest in electronic computing. As a result of his research, on June 30, 1945 von Neumann privately circulated copies of his First Draft on a Report on the EDVAC to twenty-four people connected with the EDVAC project. This document, written between February and June 1945, provided the first theoretical description of the basic details of a stored-program computer.

On April 8, 1947 Eckert and Mauchly learned from a patent lawyer that John von Neumann’s First Draft of a Report on the EDVAC was a publication barring their patenting the ENIAC because von Neumann's report, which described the theoretical principles of the machine, was issued more than a year before they planned to apply for a patent. Nevertheless, that knowledge did not, however, deter Eckert and Mauchly from applying for the patent. On June 26, 1947 Eckert and Mauchly applied for the broad ENIAC patent, essentially a patent on the stored-program electronic digital computer. They based their description of the machine to a large extent on the government report they issued on November 30, 1945.

While the ENIAC patent was being applied for, on August 21, 1956 Sperry Rand, to whom Eckert and Mauchly had transferred their patent rights, agreed to cross-license patents with IBM, thereby turning over strategic technology. On February 4, 1964 Eckert and Mauchly finally received U.S. patent no. 3,120,606 for the ENIAC—a general patent on the stored-program electronic computer, roughly 18 years after their application. Sperry Rand Univac, owner of the patent, charged a 1.5 percent royalty for all electronic computers sold by all companies except IBM, with which it had previously cross-licensed patents. Since IBM manufactured the majority of computers produced at this time, the royalties on the patent were not as large as they could have been.

On October 19, 1973 Eckert and Mauchly’s ENIAC patent was ruled invalid in the case of Honeywell Inc. v. Sperry Rand Corporation et al, largely because of John von Neumann's prior theoretical description of the machine that was circulated in his First Draft of a Report on the EDVAC. and evidence that John Mauchly obtained some of his key ideas for the design of the ENIAC from John Atanasoff's report of 1940.


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