Editing ENIAC (section)

==Later developments==
A press conference was held on February 1, 1946,{{sfn|Light|1999}} and the completed machine was announced to the public the evening of February 14, 1946,<ref>{{cite news |title=Electronic Computer Flashes Answers | last=Kennedy | first=T. R. Jr. |date=1946-02-15 |newspaper=New York Times |url=http://learn.fi.edu/learn/case-files/eckertmauchly/design.html |access-date=2015-03-29 |archive-url=https://web.archive.org/web/20150710220137/http://learn.fi.edu/learn/case-files/eckertmauchly/design.html |archive-date=2015-07-10 |url-status=dead}}</ref> featuring demonstrations of its capabilities. Elizabeth Snyder and Betty Jean Jennings were responsible for developing the demonstration trajectory program, although Herman and Adele Goldstine took credit for it.{{sfn|Light|1999}} The machine was formally dedicated the next day<ref>{{cite court |litigants=Honeywell, Inc. v. Sperry Rand Corp. |vol=180 |reporter=U.S.P.Q. (BNA) |opinion=673 |pinpoint=p. 20, finding 1.1.3 |court=U.S. District Court for the District of Minnesota, Fourth Division |date=1973 |url=http://www.ushistory.org/more/eniac/public.htm |quote=The ENIAC machine which embodied 'the invention' claimed by the ENIAC patent was in public use and non-experimental use for the following purposes, and at times prior to the critical date: ... Formal dedication use February 15, 1946 ...}}</ref> at the University of Pennsylvania. None of the women involved in programming the machine or creating the demonstration were invited to the formal dedication nor to the celebratory dinner held afterwards.<ref>{{Cite book |title=Broad Band: The Untold Story of the Women Who Made the Internet |last=Evans |first=Claire L. |date=2018-03-06 |publisher=Penguin |isbn=9780735211766 |page=51 |url=https://books.google.com/books?id=C8ouDwAAQBAJ&q=broad%20band%20evans&pg=PP1}}</ref>

The original contract amount was $61,700; the final cost was almost $500,000 (approximately {{Inflation|US|487000|1943|fmt=eq|r=-6}}). It was formally accepted by the U.S. Army Ordnance Corps in July 1946. 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, 1947, it was turned on and was in continuous operation until 11:45&nbsp;p.m. on October 2, 1955, when it was retired in favor of the more efficient [[EDVAC]] and [[ORDVAC]] computers.<ref name="ENIACstory" />

===Role in the development of the EDVAC===
A few months after ENIAC's unveiling in the summer of 1946, as part of "an extraordinary effort to jump-start research in the field",<ref name="Mac">{{harvnb|McCartney|1999|p=140}}</ref> [[the Pentagon]] invited "the top people in electronics and mathematics from the United States and Great Britain"<ref name="Mac"/> to a series of forty-eight lectures given in Philadelphia, Pennsylvania; all together called ''The Theory and Techniques for Design of Digital Computers''—more often named the [[Moore School Lectures]].<ref name="Mac"/> Half of these lectures were given by the inventors of ENIAC.<ref>{{harvnb|McCartney|1999|p=140}}: "Eckert gave eleven lectures, Mauchly gave six, Goldstine gave six. von Neumann, who was to give one lecture, didn't show up; the other 24 were spread among various invited academics and military officials."</ref>

ENIAC was a one-of-a-kind design and was never repeated. The freeze on design in 1943 meant that it lacked some innovations that soon became well-developed, notably the ability to store a program. Eckert and Mauchly started work on a new design, to be later called the [[EDVAC]], which would be both simpler and more powerful. In particular, in 1944 Eckert wrote his description of a memory unit (the mercury [[delay-line memory|delay line]]) which would hold both the data and the program. John von Neumann, who was consulting for the Moore School on the EDVAC, sat in on the Moore School meetings at which the stored program concept was elaborated. Von Neumann wrote up an incomplete set of notes (''[[First Draft of a Report on the EDVAC]]'') which were intended to be used as an internal memorandum—describing, elaborating, and couching in formal logical language the ideas developed in the meetings. ENIAC administrator and security officer [[Herman Goldstine]] distributed copies of this ''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 [[Electronic Delay Storage Automatic Calculator]] (EDSAC) at Cambridge University, England and [[SEAC (computer)|SEAC]] at the U.S. Bureau of Standards.<ref name=":2" />

===Improvements===
A number of improvements were made to ENIAC after 1947, including a primitive read-only stored programming mechanism using the function tables as program [[Read-only memory|ROM]],<ref name=":2" />{{sfn|Goldstine|1947}}<ref>{{harvnb|Goldstine|1993|pp=233–234, 270|loc=search string: "eniac Adele 1947"}}</ref><ref>By July 1947 von Neumann was writing: "I am much obliged to Adele for her letters. Nick and I are working with her new code, and it seems excellent."</ref><ref>{{harvnb|Clippinger|1948|loc=Section IV: Summary of Orders}}</ref><ref>{{harvnb|Haigh|Priestley|Rope|2014b|pp=44–48}}</ref> after which programming was done by setting the switches.<ref>{{cite book |last1=Pugh |first1=Emerson W. |title=Building IBM: Shaping an Industry and Its Technology |date=1995 |publisher=MIT Press |isbn=9780262161473 |page=353 |chapter-url=https://books.google.com/books?id=Bc8BGhSOawgC&q=eniac%20rewiring&pg=PA353 |chapter=Notes to Pages 132-135}}</ref> The idea has been worked out in several variants by Richard Clippinger and his group, on the one hand, and the Goldstines, on the other,{{sfn|Haigh|Priestley|Rope|2014b|pp=44-45}} and it was included in the ENIAC [[#Patent|patent]].{{sfn|Haigh|Priestley|Rope|2014b|p=44}} Clippinger consulted with von Neumann on what instruction set to implement.<ref name=":2" />{{sfn|Clippinger|1948|loc=INTRODUCTION}}{{sfn|Goldstine|1993|p=|loc=233-234, 270; search string: ''eniac Adele 1947''}} Clippinger had thought of a three-address architecture while von Neumann proposed a one-address architecture because it was simpler to implement. Three digits of one accumulator (#6) were used as the program counter, another accumulator (#15) was used as the main accumulator, a third 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 used for data memory.

In March 1948 the converter unit was installed,{{sfn|Haigh|Priestley|Rope|2014b|pp=47-48}} which made possible programming through the reader from standard IBM cards.{{sfn|Clippinger|1948|loc=Section VIII: Modified ENIAC}}<ref>{{cite journal |last1=Fritz |first1=W. Barkley |title=Description and Use of the ENIAC Converter Code |journal=Technical Note |date=1949 |issue=141 |url=http://eniacinaction.com/the-articles/2-engineering-the-miracle-of-the-eniac-implementing-the-modern-code-paradigm/ |at=Section 1. – Introduction, p. 1 |quote=At present it is controlled by a code which incorporates a unit called the Converter as a basic part of its operation, hence the name ENIAC Converter Code. These code digits are brought into the machine either through the Reader from standard IBM cards*or from the Function Tables (...). (...) *The card control method of operation is used primarily for testing and the running of short highly iterative problems and is not discussed in this report.}}</ref> The "first production run" of the new coding techniques on the [[Monte Carlo method|Monte Carlo]] problem followed in April.{{sfn|Haigh|Priestley|Rope|2014b|pp=47-48}}<ref>{{Cite journal |url=http://eniacinaction.com/the-articles/3-los-alamos-bets-on-eniac-nuclear-monte-carlo-simulations-1947-8/ |title=Los Alamos Bets On ENIAC: Nuclear Monte Carlo Simulations 1947-48 |last1=Haigh |first1=Thomas |last2=Priestley |first2=Mark |last3=Rope |first3=Crispin |date=July–September 2014c |volume=36 |issue=3 |pages=42–63 |journal=IEEE Annals of the History of Computing |access-date=2018-11-13 |doi=10.1109/MAHC.2014.40 |s2cid=17470931}}</ref> After ENIAC's move to Aberdeen, a register panel for memory was also constructed, but it did not work. A small master control unit to turn the machine on and off was also added.{{sfn|Haigh|Priestley|Rope|2016|pp=113–114}}

The programming of the stored program for ENIAC was done by Betty Jennings, Clippinger, Adele Goldstine and others.<ref>{{harvnb|Clippinger|1948|loc=INTRODUCTION}}</ref><ref>{{harvnb|Haigh|Priestley|Rope|2014b|p=44}}</ref>{{sfn|Goldstine|1947}}<ref name=":2" /> It was first demonstrated as a [[stored-program computer]] in April 1948,{{sfn|Haigh|Priestley|Rope|2016|p=153}} running a program by [[Adele Goldstine]] for John von Neumann. This modification reduced the speed of ENIAC by a factor of 6 and eliminated the ability of parallel computation, but as it also reduced the reprogramming time{{sfn|Goldstine|1993|p=|loc=233-234, 270; search string: ''eniac Adele 1947''}}<ref name=":2" /> 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 real-world problem was completely [[I/O bound]], even without making use of the original machine's parallelism. Most computations would still be I/O bound, even after the speed reduction imposed by 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 [[Magnetic-core memory|core memory]] was added to the system, using [[binary-coded decimal]], [[excess-3]] number representation. To support this expansion memory, 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.<ref name=":2">{{cite web |url=http://epictechnologyforgreatjustice.weebly.com/eniac.html |title=Eniac |website=Epic Technology for Great Justice |access-date=2017-01-28}}</ref>