Editing ENIAC (section)

==Development and design==
<!-- Deleted image removed: [[File:Screen Shot 2020-09-06 at 8.43.44 AM.png|thumb|Text of the first page of Eckert's "Disclosure of a Magnetic Calculating Machine" originally written by Eckert in January 1944, and sent by Mauchly to Don Knuth in 1978. [[Computer History Museum]].]] -->

ENIAC's design and construction was financed by the United States Army, Ordnance Corps, Research and Development Command, led by Major General [[Gladeon M. Barnes]]. The total cost was about $487,000, {{Inflation|US-GDP|487000|1943|fmt=eq|r=-5}}.<ref>{{cite web |url=http://history-computer.com/ModernComputer/Electronic/ENIAC.html |title=ENIAC |last=Dalakov |first=Georgi |website=History of Computers |publisher=Georgi Dalakov |access-date=2016-05-23}}</ref> The conception of ENIAC began in June 1941, when Friden calculators and [[differential analyzer]]s were used by the [[United States Army Ordnance Department]] to compute firing tables for artillery, which was done by graduate students under John Mauchly's supervision. Mauchly began to wonder if electronics could be applied to mathematics for faster calculations. He partnered up with research associate [[J. Presper Eckert]], as Mauchly wasn't an electronics expert, to draft an electronic computer that could work at an excellent pace. Later, in August 1942, Mauchly proposed an all-electronic calculating machine that could help the U.S. Army calculate complex ballistics tables.<ref>{{cite web|url=https://www.computerhistory.org/revolution/birth-of-the-computer/4/78|title=ENIAC - CHM Revolution|work=[[Computer History Museum]]|access-date=November 9, 2024}}</ref><ref name="ENIAC DEV">{{cite web|url=https://www.historyofinformation.com/detail.php?id=636|title=Key Events in the Development of the ENIAC|work=History of Information|access-date=November 29, 2024}}</ref> The U.S. Army Ordnance accepted their plan, giving the [[University of Pennsylvania]] a six-months research contract for $61,700.<ref name="UNIVAC">{{cite video|url=https://www.youtube.com/watch?v=h4wQJfdhOlU|date=August 15, 2008|title=UNIVAC - Information Age: Then and Now|author=[[Computer History Museum]]|work=[[YouTube]]|access-date=November 6, 2024}}</ref> The construction contract was signed on June 5, 1943; work on the computer began in secret at the [[University of Pennsylvania]]'s [[Moore School of Electrical Engineering]]<ref>{{Harvnb|Goldstine|Goldstine|1946}}</ref> the following month, under the code name "Project PX", with [[John Grist Brainerd]] as principal investigator. [[Herman H. Goldstine]] persuaded the Army to fund the project, which put him in charge to oversee it for them.<ref>{{cite web |author=Gayle Ronan Sims |date=June 22, 2004 |title=Herman Heine Goldstine |work=[[The Philadelphia Inquirer]] |url=http://www.princeton.edu/mudd/finding_aids/mathoral/pmcxgoldstine.htm |access-date=2017-04-15 |archive-url=https://web.archive.org/web/20151130170611/http://www.princeton.edu/mudd/finding_aids/mathoral/pmcxgoldstine.htm |archive-date=2015-11-30 |url-status=dead |via=www.princeton.edu}}</ref> Assembly for the computer began in June 1944.<ref name="UNIVAC"/> Later, in September of that year, Eckert and Mauchly completed their conception on the computer.<ref name="ENIAC PAT">{{cite web|url=https://www.historyofinformation.com/detail.php?id=639|title=Key Developments Concerning the ENIAC Patent|work=History of Information|access-date=November 29, 2024}}</ref> Construction for the computer was complete in May 1945, and testing for it began at the Moore School. Later, in November of that year, the duo, along with [[John Brainerd]] and [[Herman Goldstine]], issued the first confidential published report on the computer, which talks about how it worked and the methods by which it was programmed.<ref name="ENIAC DEV"/>

ENIAC was designed by [[Ursinus College]] physics professor [[John Mauchly]] and [[J. Presper Eckert]] of the University of Pennsylvania.<ref name="Wilkes">{{cite book |last=Wilkes |first=M. V. |author-link=Maurice Wilkes |title=Automatic Digital Computers |publisher=[[John Wiley & Sons]] |date=1956 |location=New York |id=QA76.W5 1956}}</ref> The team of design engineers assisting the development included Robert F. Shaw (function tables), [[Jeffrey Chuan Chu]] (divider/square-rooter), Thomas Kite Sharpless (master programmer), Frank Mural (master programmer), [[Arthur Burks]] (multiplier), [[Harry Huskey]] (reader/printer) and Jack Davis (accumulators).<ref name="eniac-on-trial">{{cite web |title=ENIAC on Trial |url=https://www.ushistory.org/more/eniac/inventors.htm |website=USHistory.org |publisher=Independence Hall Association |access-date=9 November 2020 |archive-url=https://web.archive.org/web/20190812225517/https://www.ushistory.org/more/eniac/inventors.htm |archive-date=12 August 2019}}</ref> Significant development work was undertaken by the female mathematicians who handled the bulk of the ENIAC programming: [[Jean Bartik|Jean Jennings]], [[Marlyn Wescoff]], [[Ruth Lichterman]], [[Betty Snyder]], [[Frances Bilas]], and [[Kay McNulty]].{{sfn|Light|1999}} In 1946, the researchers resigned from the University of Pennsylvania and formed the [[Eckert–Mauchly Computer Corporation]].

ENIAC was a large, modular computer, composed of individual panels to perform different functions. Twenty of these modules were accumulators that could not only add and subtract, but hold a ten-digit [[decimal]] number in memory. Numbers were passed between these units across several general-purpose [[Bus (computing)|buses]] (or ''trays'', as they were called). In order to achieve its high speed, the panels had to send and receive numbers, compute, save the answer and trigger the next operation, all without any moving parts. Key to its versatility was the ability to ''branch''; it could trigger different operations, depending on the sign of a computed result.

===Components===
By the end of its operation in 1956, ENIAC contained 18,000 [[vacuum tube]]s, 7,200 [[crystal diode]]s, 1,500 [[relay]]s, 70,000 [[resistor]]s, 10,000 [[capacitor]]s, and approximately 5,000,000 hand-[[solder]]ed joints. It weighed more than {{cvt|30|short ton|t|lk=in}}, was roughly {{cvt|8|feet|0}} tall, {{cvt|3|feet|0}} deep, and {{cvt|100|feet|0}} long, occupied {{cvt|300|sqft|m2}} and consumed 150&nbsp;kW of electricity.<ref>{{cite web |title=ENIAC |url=http://encyclopedia2.thefreedictionary.com/ENIAC |website=The Free Dictionary |access-date=2015-03-29}}</ref><ref name="BRLreport">{{cite book |last1=Weik |first1=Martin H. |title=Ballistic Research Laboratories Report No. 971: A Survey of Domestic Electronic Digital Computing Systems |date=December 1955 |publisher=United States Department of Commerce Office of Technical Services |location=Aberdeen Proving Ground, MD |page=41 |url=http://ed-thelen.org/comp-hist/BRL-e-h.html#ENIAC |access-date=2015-03-29}}</ref> Input was possible from an IBM [[Card reader (punched card)|card reader]] and an IBM [[card punch]] was used for output. These cards could be used to produce printed output offline using an [[IBM]] accounting machine, such as the [[IBM 405]]. While ENIAC had no system to store memory in its inception, these punch cards could be used for external memory storage.<ref>{{cite web |url=http://www.seas.upenn.edu/about-seas/eniac/operation.php |title=ENIAC in Action: What it Was and How it Worked |website=ENIAC: Celebrating Penn Engineering History |publisher=University of Pennsylvania |access-date=2016-05-17}}</ref> In 1953, a 100-[[Word (computer architecture)|word]] [[magnetic-core memory]] built by the [[Burroughs Corporation]] was added to ENIAC.<ref>{{cite web |url=https://www.cs.umd.edu/class/fall2001/cmsc411/projects/ramguide/pastandfuture/pastandfuture.html |title=Past and Future Developments in Memory Design |last=Martin |first=Jason |date=1998-12-17 |website=Past and Future Developments in Memory Design |publisher=University of Maryland |access-date=2016-05-17}}</ref>

ENIAC used [[Serial decimal|ten-position]] [[ring counter]]s to store digits; each digit required 36 vacuum tubes, 10 of which were the dual triodes making up the [[Flip-flop (electronics)|flip-flops]] of the ring counter. Arithmetic was performed by "counting" pulses with the ring counters and generating carry pulses if the counter "wrapped around", the idea being to electronically emulate the operation of the digit wheels of a mechanical [[adding machine]].<ref>{{Cite book |last=Peddie |first=Jon |url=https://books.google.com/books?id=6a8_AAAAQBAJ&q=ENIAC+used+ten-position+ring+counters+to+store+digits;+each+digit+required+36+vacuum+tubes,&pg=PA147 |title=The History of Visual Magic in Computers: How Beautiful Images are Made in CAD, 3D, VR and AR |date=2013-06-13 |publisher=Springer Science & Business Media |isbn=978-1-4471-4932-3 |language=en}}</ref>

ENIAC had 20 ten-digit signed [[accumulator (computing)|accumulators]], which used [[ten's complement]] representation and could perform 5,000 simple addition or subtraction operations between any of them and a source (e.g., another accumulator or a constant transmitter) per second. It was possible to connect several accumulators to run simultaneously, so the peak speed of operation was potentially much higher, due to parallel operation.{{sfn|Goldstine|Goldstine|1946}}<ref>{{Cite book |last1=Igarashi |first1=Yoshihide |url=https://books.google.com/books?id=58ySAwAAQBAJ&q=ENIAC+had+20+ten-digit+signed+accumulators,+which+used+ten's+complement+representation&pg=PA154 |title=Computing: A Historical and Technical Perspective |last2=Altman |first2=Tom |last3=Funada |first3=Mariko |last4=Kamiyama |first4=Barbara |date=2014-05-27 |publisher=CRC Press |isbn=978-1-4822-2741-3 |language=en}}</ref>

[[File:Classic shot of the ENIAC.jpg|thumb|250px|Cpl. Irwin Goldstein (foreground) sets the switches on one of ENIAC's function tables at the Moore School of Electrical Engineering. (U.S. Army photo, 1946)<ref>The original photo can be seen in the article: {{cite journal |last1=Rose |first1=Allen |title=Lightning Strikes Mathematics |journal=Popular Science |pages=83–86 |date=April 1946 |url=https://books.google.com/books?id=niEDAAAAMBAJ&pg=PA83 |access-date=2015-03-29}}</ref>]]

It was possible to wire the carry of one accumulator into another accumulator to perform arithmetic with double the precision, but the accumulator carry circuit timing prevented the wiring of three or more for even higher precision. ENIAC used four of the accumulators (controlled by a special multiplier unit) to perform up to 385 multiplication operations per second; five of the accumulators were controlled by a special divider/square-rooter unit to perform up to 40 division operations per second or three [[square root]] operations per second.

The other nine units in ENIAC were the initiating unit (started and stopped the machine), the cycling unit (used for synchronizing the other units), the master programmer (controlled loop sequencing), the reader (controlled an IBM punch-card reader), the printer (controlled an IBM card punch), the constant transmitter, and three function tables.{{sfn|Clippinger|1948|loc=Section I: General Description of the ENIAC – The Function Tables}}{{sfn|Goldstine|1946}}

===Operation times===
The references by Rojas and Hashagen (or Wilkes)<ref name="Wilkes"/> give more details about the times for operations, which differ somewhat from those stated above.

The basic machine cycle was 200 [[microsecond]]s (20 cycles of the 100&nbsp;kHz clock in the cycling unit), or 5,000 cycles per second for operations on the 10-digit numbers. In one of these cycles, ENIAC could write a number to a register, read a number from a register, or add/subtract two numbers.

A multiplication of a 10-digit number by a ''d''-digit number (for ''d'' up to 10) took ''d''+4 cycles, so the multiplication of a 10-digit number by 10-digit number took 14 cycles, or 2,800 microseconds—a rate of 357 per second. If one of the numbers had fewer than 10 digits, the operation was faster.

Division and square roots took 13(''d''+1) cycles, where ''d'' is the number of digits in the result (quotient or square root). So a division or square root took up to 143 cycles, or 28,600 microseconds—a rate of 35 per second. (Wilkes 1956:20<ref name="Wilkes"/> states that a division with a 10-digit quotient required 6 milliseconds.) If the result had fewer than ten digits, it was obtained faster.

ENIAC was able to process about 500 [[FLOPS]],<ref>{{Cite web |date=2019-03-18 |title=The incredible evolution of supercomputers' powers, from 1946 to today |url=https://www.popsci.com/supercomputers-then-and-now/ |access-date=2022-02-08 |website=Popular Science |language=en-US}}</ref> compared to [[Supercomputer#Performance metrics|modern supercomputers']] [[Petascale computing|petascale]] and [[Exascale computing|exascale]] computing power.

===Reliability===
ENIAC used common [[Octal tube|octal-base]] [[radio tube]]s of the day; the decimal [[accumulator (computing)|accumulators]] were made of [[6SN7]] [[flip-flop (electronics)|flip-flops]], while 6L7s, 6SJ7s, 6SA7s and 6AC7s were used in logic functions.<ref>{{Harvnb|Burks|1947|pp=756–767}}</ref> Numerous [[6L6]]s and [[6V6]]s served as line drivers to drive pulses through cables between rack assemblies.

Several tubes burned out almost every day, leaving ENIAC nonfunctional about half the time. Special high-reliability tubes were not available until 1948. Most of these failures, however, occurred during the warm-up and cool-down periods, when the tube heaters and cathodes were under the most thermal stress. Engineers reduced ENIAC's tube failures to the more acceptable rate of one tube every two days. According to an interview in 1989 with Eckert, "We had a tube fail about every two days and we could locate the problem within 15 minutes."<ref>{{cite web |url=http://www.computerworld.com/s/article/108568/Q_A_A_lost_interview_with_ENIAC_co_inventor_J._Presper_Eckert |title=A lost interview with ENIAC co-inventor J. Presper Eckert |first=((Alexander 5th)) |last=Randall|publisher=Computer World |date=2006-02-14 |access-date=2015-03-29}}</ref>
In 1954, the longest continuous period of operation without a failure was 116 hours—close to five days.