Editing ENIAC (section)

==Programming==
ENIAC could be programmed to perform complex sequences of operations, including loops, branches, and subroutines. However, instead of the [[stored-program computer]]s that exist today, ENIAC was just a large collection of arithmetic machines, which originally had programs set up into the machine<ref>{{Cite journal |last=Grier |first=David |s2cid=7822223 |date=July–September 2004 |title=From the Editor's Desk |journal=IEEE Annals of the History of Computing |volume=26 |issue=3 |pages=2–3 |doi=10.1109/MAHC.2004.9}}</ref> by a combination of [[plugboard]] wiring and three portable function tables (containing 1,200 ten-way switches each).<ref>{{cite web |url=http://www.columbia.edu/cu/computinghistory/eniac.html |title=Programming the ENIAC |last=Cruz |first=Frank |date=2013-11-09 |website=Programming the ENIAC |publisher=Columbia University |access-date=2016-05-16}}</ref> The task of taking a problem and mapping it onto the machine was complex, and usually took weeks. Due to the complexity of mapping programs onto the machine, programs were only changed after huge numbers of tests of the current program.<ref>{{Cite journal |last=Alt |first=Franz |date=July 1972 |title=Archaeology of computers: reminiscences, 1945-1947 |journal=Communications of the ACM |volume=15 |issue=7 |pages=693–694 |doi=10.1145/361454.361528 |s2cid=28565286|doi-access=free }}</ref> After the program was figured out on paper, the process of getting the program into ENIAC by manipulating its switches and cables could take days. This was followed by a period of verification and debugging, aided by the ability to execute the program step by step. A programming tutorial for the modulo function using an ENIAC simulator gives an impression of what a program on the ENIAC looked like.<ref>{{cite web |url=http://placebo.hpi.uni-potsdam.de/webhome/matthieu.schapranow/eniac/modulo/ |archive-url=https://web.archive.org/web/20140107125516/http://placebo.hpi.uni-potsdam.de/webhome/matthieu.schapranow/eniac/modulo/ |url-status=dead |archive-date=7 January 2014 |title=ENIAC tutorial - the modulo function |first=Matthieu-P. |last=Schapranow |date=1 June 2006 |access-date=2017-03-04}}</ref><ref>Description of Lehmer's program computing the exponent of modulo 2 prime</ref><ref>{{harvnb|De Mol|Bullynck|2008}}</ref>

ENIAC's six primary programmers, [[Kathleen Antonelli|Kay McNulty]], [[Jean Bartik|Betty Jennings]], [[Betty Holberton|Betty Snyder]], [[Marlyn Meltzer|Marlyn Wescoff]], [[Frances Spence|Fran Bilas]] and [[Ruth Teitelbaum|Ruth Lichterman]], not only determined how to input ENIAC programs, but also developed an understanding of ENIAC's inner workings.<ref>{{cite web |url=http://eniacprogrammers.org/eniac-programmers-project/ |title=ENIAC Programmers Project |publisher=eniacprogrammers.org |access-date=2015-03-29}}</ref><ref>{{cite web |last=Donaldson James |first=Susan |title=First Computer Programmers Inspire Documentary |url=https://abcnews.go.com/Technology/story?id=3951187&page=1&singlePage=true |work=[[ABC News (United States)|ABC News]] |access-date=2015-03-29 |date=2007-12-04}}</ref> The programmers were often able to narrow bugs down to an individual failed tube which could be pointed to for replacement by a technician.<ref>{{cite journal |last=Fritz |first=W. Barkley |title=The Women of ENIAC |journal=IEEE Annals of the History of Computing |date=1996 |volume=18 |issue=3 |pages=13–28 |url=http://www.eg.bucknell.edu/~csci203/2012-fall/hw/hw06/assets/womenOfENIAC.pdf |access-date=2015-04-12 |doi=10.1109/85.511940 |url-status=dead |archive-url=https://web.archive.org/web/20160304052225/http://www.eg.bucknell.edu/~csci203/2012-fall/hw/hw06/assets/womenOfENIAC.pdf |archive-date=2016-03-04}}</ref>

===Programmers===
[[Image:Two women operating ENIAC (full resolution).jpg|thumb|250px|Programmers [[Jean Bartik|Betty Jean Jennings]] (left) and [[Frances Spence|Fran Bilas]] (right) operating ENIAC's main control panel at the [[Moore School of Electrical Engineering]], {{c.}} 1945 (U.S. Army photo from the archives of the ARL Technical Library)]]
{{Listen|type=speech|pos=right|filename=The ENIAC Programmers (As Told By U.S. Chief Technology Officer Megan Smith).ogg|title=The ENIAC Programmers (As Told By U.S. Chief Technology Officer Megan Smith)|description=}}

During [[World War II]], while the [[U.S. Army]] needed to compute ballistics trajectories, many women were interviewed for this task. At least 200 women were hired by the [[Moore School of Engineering]] to work as "[[computer (occupation)|computer]]s"{{sfn|Light|1999}} and six of them were chosen to be the programmers of ENIAC. [[Betty Holberton]], [[Kathleen Antonelli|Kay McNulty]], [[Marlyn Meltzer|Marlyn Wescoff]], [[Ruth Teitelbaum|Ruth Lichterman]], [[Jean Bartik|Betty Jean Jennings]], and [[Frances Spence|Fran Bilas]] programmed the ENIAC to perform calculations for ballistics trajectories electronically for the Army's [[Ballistic Research Laboratory]].<ref name="SWE-Spr19">{{cite news |last1=McCabe |first1=Seabright |title=The Programming Pioneers of ENIAC |url=https://drive.google.com/file/d/11_csuKxT-rprQO1CvlGEP0pBl1-1TcRT/view |url-status=live |archive-date=2023-12-25 |archive-url=https://web.archive.org/web/20231225110455/https://drive.google.com/file/d/11_csuKxT-rprQO1CvlGEP0pBl1-1TcRT/view |access-date=July 8, 2020 |work=All Together |issue=Spring 2019 |publisher=Society of Women Engineers |date=June 3, 2019}}</ref> While men having the same education and experience were designated "professionals", these women were designated "subprofessionals", though they had professional degrees in mathematics and were highly trained mathematicians.<ref name="SWE-Spr19" />

These women were not "refrigerator ladies", i.e., models posing in front of the machine for press photography, as then computer scientist undergrad [[Kathryn Kleiman]] discovered in her own research as opposed to what she was told by a historian in computing.<ref name=":1">{{Cite web |date=2013-10-13 |title=Meet the 'Refrigerator Ladies' Who Programmed the ENIAC |url=https://www.mentalfloss.com/article/53160/meet-refrigerator-ladies-who-programmed-eniac |access-date=2024-05-30 |website=Mental Floss |language=en-US}}</ref> However, some of the women did not receive recognition for their work on the ENIAC in their entire lifetimes.{{sfn|Light|1999}} After the war ended, the women continued to work on the ENIAC. Their expertise made their positions difficult to replace with returning soldiers.<ref>{{cite web |title=ENIAC Programmers: A History of Women in Computing |url=https://spin.atomicobject.com/2016/07/31/eniac-programmers/ |website=Atomic Spin |date=31 July 2016}}</ref> Later in the 1990s, Kleiman learned that most of the ENIAC programmers were not invited to the ENIAC’s 50th anniversary event. So she made it her mission to track them down and record their oral histories. "They were shocked to be discovered," Kleiman says. "They were thrilled to be recognized, but had mixed impressions about how they felt about being ignored for so long."<ref name=":1" /> Kleiman released a book on the six female ENIAC programmers in 2022.<ref>{{cite book |title=Proving Ground |first=Kathy |last=Kleiman |isbn=9781787388628 |year=2022 |publisher=Hurst |location=London}}</ref>

These early programmers were drawn from a group of about two hundred women employed as [[Computer (occupation)|computers]] at the [[Moore School of Electrical Engineering]] at the University of Pennsylvania. The job of computers was to produce the numeric result of mathematical formulas needed for a scientific study, or an engineering project. They usually did so with a mechanical calculator. The women studied the machine's logic, physical structure, operation, and circuitry in order to not only understand the mathematics of computing, but also the machine itself.{{sfn|Light|1999}} This was one of the few technical job categories available to women at that time.<ref>{{cite book |last=Grier |first=David |title=When Computers Were Human |publisher=Princeton University Press |date=2007 |isbn=9781400849369 |url=https://archive.org/details/whencomputerswer00davi |access-date=2016-11-24}}</ref> [[Betty Holberton]] (née Snyder) continued on to help write the first generative programming system ([[Mainframe sort merge|SORT/MERGE]]) and help design the first commercial electronic computers, the [[UNIVAC]] and the [[BINAC]], alongside Jean Jennings.<ref name="beyer">{{cite book |title=Grace Hopper and the Invention of the Information Age |last1=Beyer |first1=Kurt |date=2012 |publisher=MIT Press |isbn=9780262517263 |location=London, Cambridge |page=198}}</ref> McNulty developed the use of [[subroutine]]s in order to help increase ENIAC's computational capability.<ref name=":4">{{cite web |url=http://fortune.com/2014/09/18/walter-isaacson-the-women-of-eniac/ |title=Walter Isaacson on the Women of ENIAC |last=Isaacson |first=Walter |date=18 September 2014 |website=Fortune |archive-url=https://web.archive.org/web/20181212003245/http://fortune.com/2014/09/18/walter-isaacson-the-women-of-eniac/ |archive-date=12 December 2018 |access-date=2018-12-14}}</ref>

[[Herman Goldstine]] selected the programmers, whom he called operators, from the computers who had been calculating ballistics tables with mechanical desk calculators and a differential analyzer prior to and during the development of ENIAC.{{sfn|Light|1999}} Under Herman and [[Adele Goldstine]]'s direction, the computers studied ENIAC's blueprints and physical structure to determine how to manipulate its switches and cables, as [[programming language]]s did not yet exist. Though contemporaries considered programming a clerical task and did not publicly recognize the programmers' effect on the successful operation and announcement of ENIAC,{{sfn|Light|1999}} McNulty, Jennings, Snyder, Wescoff, Bilas, and Lichterman have since been recognized for their contributions to computing.<ref name="invisible"/><ref name="secret"/><ref name="siff"/> Three of the current (2020) Army supercomputers, ''Jean'', ''Kay'', and ''Betty,'' are named after [[Jean Bartik]] (Betty Jennings), [[Kathleen Antonelli|Kay McNulty]], and [[Betty Holberton|Betty Snyder]] respectively.<ref>{{cite web |url=https://www.army.mil/article/242062/army_researchers_acquire_two_new_supercomputers |title=Army researchers acquire two new supercomputers |website=U.S. Army DEVCOM Army Research Laboratory Public Affairs |date=December 28, 2020 |access-date=March 1, 2021}}</ref>

The "programmer" and "operator" job titles were not originally considered professions suitable for women. The labor shortage created by World War II helped enable the entry of women into the field.{{sfn|Light|1999}} However, the field was not viewed as prestigious, and bringing in women was viewed as a way to free men up for more skilled labor. Essentially, women were seen as meeting a need in a temporary crisis.{{sfn|Light|1999}} For example, the National Advisory Committee for Aeronautics said in 1942, "It is felt that enough greater return is obtained by freeing the engineers from calculating detail to overcome any increased expenses in the computers' salaries. The engineers admit themselves that the girl computers do the work more rapidly and accurately than they would. This is due in large measure to the feeling among the engineers that their college and industrial experience is being wasted and thwarted by mere repetitive calculation."{{sfn|Light|1999}}

Following the initial six programmers, an expanded team of a hundred scientists was recruited to continue work on the ENIAC. Among these were several women, including [[Gloria Gordon Bolotsky|Gloria Ruth Gordon]].<ref name="wapobit">{{cite news |newspaper=[[The Washington Post]] |url=https://www.washingtonpost.com/wp-dyn/content/article/2009/07/25/AR2009072502045.html |title=Gloria Gordon Bolotsky, 87; Programmer Worked on Historic ENIAC Computer |last=Sullivan |first=Patricia |date=2009-07-26 |access-date=2015-08-19}}</ref> Adele Goldstine wrote the original technical description of the ENIAC.<ref>{{cite web |url=https://arl.devcom.army.mil/who-we-are/ |title=ARL Computing History |publisher=Arl.army.mil |access-date=2019-06-29}}</ref>

=== Programming languages ===

Several language systems were developed to describe programs for the ENIAC, including:

{|
|-
! Year
! Name
! Chief developers
|-
| 1943–46
| ENIAC coding system
| [[John von Neumann]], [[John Mauchly]], [[J. Presper Eckert]], [[Herman Goldstine]] after [[Alan Turing]].
|-
| 1946
| ENIAC Short Code
| Richard Clippinger, [[John von Neumann]] after [[Alan Turing]]
|-
| 1946
| Von Neumann and Goldstine graphing system (Notation)
| [[John von Neumann]] and [[Herman Goldstine]]
|-
| 1947
| ARC Assembly
| [[Kathleen Booth]]<ref>{{cite journal|last=Booth|first=Kathleen|title=Machine Language for Automatic Relay Computer|journal=Birkbeck College Computation Laboratory|publisher=University of London}}</ref><ref>Campbell-Kelly, Martin "The Development of Computer Programming in Britain (1945 to 1955)", The Birkbeck College Machines, in (1982) Annals of the History of Computing 4(2) April 1982 IEEE</ref>
|-
| 1948
| Curry notation system
| [[Haskell Curry]]
|}

===Role in the hydrogen bomb===
Although the Ballistic Research Laboratory was the sponsor of ENIAC, one year into this three-year project [[John von Neumann]], a mathematician working on the [[hydrogen bomb]] at [[Los Alamos National Laboratory]], became aware of the ENIAC.<ref>{{Harvnb|Goldstine|1993|page=182}}</ref> In December 1945, the ENIAC was used to calculate [[thermonuclear reaction]]s using [[equation]]s. The data was used to support research on building a hydrogen bomb.<ref>{{cite book |first=Jeffrey R. |last=Yost |title=Making IT Work: A History of the Computer Services Industry |publisher=MIT Press |year=2017 |page=19 |isbn=9780262036726}}</ref><ref>{{harvnb|Rhodes|1995|loc=chapter 2}}</ref>

===Role in development of the Monte Carlo methods===
{{See also|Monte Carlo method#History|label 1=History of Monte Carlo method}}
Related to ENIAC's role in the hydrogen bomb was its role in the [[Monte Carlo method]] becoming popular. Scientists involved in the original nuclear bomb development used massive groups of people doing huge numbers of calculations ("computers" in the terminology of the time) to investigate the distance that neutrons would likely travel through various materials. [[John von Neumann]] and [[Stanislaw Ulam]] realized the speed of ENIAC would allow these calculations to be done much more quickly.<ref name="mbv01">{{Cite book |last1=Mazhdrakov |first1=Metodi |last2=Benov |first2=Dobriyan |last3=Valkanov |first3=Nikolai |year=2018 |title=The Monte Carlo Method. Engineering Applications |publisher=ACMO Academic Press |page=250 |isbn=978-619-90684-3-4 |url=https://books.google.com/books?id=t0BqDwAAQBAJ&q=the+monte+carlo+method+engineering+applications+mazhdrakov}}</ref> The success of this project showed the value of Monte Carlo methods in science.<ref>{{Cite book |title=The Disappearing Spoon |last=Kean |first=Sam |publisher=Little, Brown and Company |date=2010 |isbn=978-0-316-05163-7 |location=New York |pages=109–111}}</ref>