Editing ENIAC (section)

===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}}