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ENIAC

ENIAC, short for Electronic Numerical Integrator And Computer, was the first purely electronic, Turing-complete, digital computer capable of being reprogrammed to solve a full range of computing problems, 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 Ballistic Research Laboratory.

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.

John Mauchly Presper Eckert

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).

ENIAC's physical size was massive compared to modern PC standards. It contained 17,468 vacuum tubes, 7,200 crystal diodes, 1,500 relays, 70,000 resistors, 10,000 capacitors and around 5 million hand-soldered joints. It weighed 30 short tons (27 t), was roughly 8.5 feet by 3 feet by 80 feet (2.6 m by 0.9 m by 26 m), took up 680 square feet (63 m²), and consumed 150 kW of power.

Input was possible from an IBM card reader, while an IBM card punch was used for output. These cards could be used to produce printed output offline using an IBM accounting machine, probably the IBM 405. ENIAC used common octal-base radio tubes of the day.

Some electronics experts predicted that tube failures would occur so frequently that the machine would never be useful. This prediction turned out to be partially correct: several tubes burned out almost every day, leaving it nonfunctional about half the time. Special high-reliability tubes were not available until 1948.


 

 

Most of these failure, however, occurred during the warm-up and cool-down periods, when the tube heaters and cathodes were under the most thermal stress. The the simple )if expensive) expedient of never turning the machines off, the engineers reduced ENIAC's tube failures to the more acceptable rate of one tube every two days.

According to a 1989 interview with Eckert the continuously failing tubes story was therefore mostly a myth: "We had a tube fail about every two days and we could locate the problem within 15 minutes."  In 1954, the longest continuous period of operation without a failure was 116 hours (close to five days).

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 included in the design, notably the inability to store a program. John von Neumann, who was consulting for the Moore School on the EDVAC (the ENIAC's successor computer for the BRL) and sat in on the Moore School meetings at which the stored program concept was elaborated, wrote up an incomplete set of notes (First Draft of a Report on the EDVAC) intended to be used as an internal memorandum describing, elaborating, and couching in formal logical language the ideas developed in the meetings.

Herman Goldstine distributed copies of the First Draft to a number of government and educational institutions, spurring widespread interest in the construction of a new generation of electronic computing machines, including EDSAC and SEAC.

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.