ENIAC, short for Electronic Numerical Integrator And Computer, although earlier computers had been built with some of these properties. ENIAC was designed and built to calculate artillery firing tables for the U.S. Army's Ballistics Research Laboratory. The first problems run on the ENIAC however, were related to the design of the hydrogen bomb.
The contract was signed on June 5, 1943 and Project PX was constructed by the University of Pennsylvania's Moore School of Electrical Engineering from July, 1943. It was unveiled on February 14, 1946 at Penn, having cost almost $500,000. ENIAC was shut down on November 9, 1946 for a refurbishment and a memory upgrade, and was transferred to Aberdeen Proving Ground, Maryland in 1947. There, on July 29 of that year, it was turned on and would be in continuous operation until 11:45 p.m. on October 2, 1955.
ENIAC was conceived and designed by John Mauchly and J. Presper Eckert of the University of Pennsylvania. The team of design engineers assisting the development included Bob Shaw (function tables), Chuan Chu (divider/square-rooter), Kite Sharpless (master programmer), Arthur Burks (multiplier), Harry Huskey (reader/printer), and Jack Davis (accumulators).

Reliability
The six women who did most of the programming of ENIAC by manipulating its switches and cables were inducted in 1997 into the Women in Technology International Hall of Fame ([1]). As they were called by each other in 1946, they were Kay McNulty, Betty Jennings, Betty Snyder, Marlyn Wescoff, Fran Bilas and Ruth Lichterman.
Eckert and Mauchly took the experience they gained and founded the Eckert-Mauchly Computer Corporation, producing their first computer, BINAC, in 1949 before being acquired by Remington Rand in 1950 and renamed as their UNIVAC division.
ENIAC was a one-of-a-kind design and was never repeated. The freeze on design in 1943 meant that the computer had a number of shortcomings which were not solved, notably the inability to store a program. But the ideas generated from the work and the impact it had on people such as John von Neumann were profoundly influential in the development of later computers, initially EDVAC, EDSAC and SEAC.
A number of improvements were also made to ENIAC from 1948, including a primitive read-only stored programming mechanism [2] using the Function Tables as program ROM, an idea proposed by John von Neumann. Three digits of one accumulator (6) was used as the program counter, another accumulator (15) was used as the main accumulator, another accumulator (8) was used as the address pointer for reading data from the function tables, and most of the other accumulators (1-5,7,9-14,17-19) were just used for data memory. It was first demonstrated as a stored-program computer on September 16, 1948, running a program by Adele Goldstine for John von Neumann. This modification reduced the speed of ENIAC by a factor of six and eliminated the ability of parallel computation, but as it also reduced the reprogramming time to hours instead of days, it was considered well worth the loss of performance. Also analysis had shown that due to differences between the electronic speed of computation and the electromechanical speed of input/output, almost any practical real world problem was completely I/O bound even without making use of the original machine's parallelism and most would still be I/O bound even after the speed reduction from this modification. Early in 1952, a high speed shifter was added, which improved the speed for shifting by a factor of five. In July 1953, a 100-word expansion core memory was added to the system, using binary coded decimal, excess-3 number representation. To support this expansion memory, the ENIAC was equipped with a new Function Table selector, a memory address selector, pulse-shaping circuits, and three new orders were added to the programming mechanism.

Programmability

Main article: History of computing hardware Comparison with other early computers
The Colossus and ENIAC were developed independently and in secret as part of each country's war effort in World War II. The Z3 was destroyed by Allied bombing of Berlin in 1944. The Colossus machines were destroyed in 1945 on Winston Churchill's orders and their existence remained classified until the 1970s, though knowledge of their capabilities remained among the UK staff and invited Americans. The ABC was dismantled by Iowa State University, after John Atanasoff was called to Washington, D.C. to do physics research for the U.S. Navy. ENIAC, by contrast, was put through its paces for the press in 1946, "and captured the world's imagination". For these reasons, histories of computing formerly mentioned only ENIAC and the Harvard Mark I from this period.

Priority

Main article: Honeywell v. Sperry Rand Patent
The School of Engineering and Applied Science at the University of Pennsylvania has four of the original forty panels and one of the three function tables of the ENIAC. The Smithsonian has five panels in the National Museum of American History in Washington D.C. The Computer History Museum in Mountain View, California has a single panel on display. The University of Michigan in Ann Arbor has four panels, salvaged by Arthur Burks. The U.S. Army Ordnance Museum at Aberdeen Proving Ground (Aberdeen, Maryland), where ENIAC was used, has one of the function tables.
As of 2004, a chip of silicon measuring 0.02 inches (0.5 mm) square holds the same capacity as the ENIAC, which occupied a large room.

See also

H. H. Goldstine, A. Goldstine, The Electronic Numerical Integrator and Computer (ENIAC), 1946 (reprinted in The Origins of Digital Computers: Selected Papers, Springer-Verlag, New York, 1982, pp. 359-373)
J. Presper Eckert, The ENIAC (in Nicholas Metropolis, J. Howlett, Gian-Carlo Rota, (editors), A History of Computing in the Twentieth Century, Academic Press, New York, 1980, pp. 525-540)
John W. Mauchly, The ENIAC (in A History of Computing in the Twentieth Century, pp. 541-550)
Arthur W. Burks, Alice R. Burks, The ENIAC: The First General-Purpose Electronic Computer (in Annals of the History of Computing, Vol. 3 (No. 4), 1981, pp. 310-389; commentary pp. 389-399)
W. Barkley Fritz, The Women of ENIAC (in IEEE Annals of the History of Computing, Vol. 18, 1996, pp. 13-28)
J. Presper Eckert, John Mauchly, Outline of plans for development of electronic computers (The founding document in the electronic computer industry.)
Raúl Rojas and Ulf Hashagen, editors, The First Computers: History and Architectures, 2000, MIT Press, ISBN 0-262-18197-5.