Editing ORDVAC

{{short description|Ordnance Discrete Variable Automatic Computer}}
[[File:Ordvac.jpg|ORDVAC|thumb]]

The '''ORDVAC''' ('''''Or'''dnance '''D'''iscrete '''V'''ariable '''A'''utomatic '''C'''omputer)'', is an early [[computer]] built by the [[University of Illinois at Urbana–Champaign|University of Illinois]] for the [[Ballistic Research Laboratory]] at [[Aberdeen Proving Ground]].<ref>{{cite web|title=The History of Computing at BRL|url=http://chimera.roma1.infn.it/SPENG/COMMON/ftp.arl.mil/mike/comphist/hist.html|access-date=2021-12-03|website=chimera.roma1.infn.it}}</ref> It was a successor to the [[ENIAC]] (along with [[EDVAC]] built earlier). It was based on the [[IAS machine|IAS]] architecture developed by [[John von Neumann]], which came to be known as the [[von Neumann architecture]]. The ORDVAC was the first computer to have a [[compiler]]{{citation needed|date=January 2025}}. ORDVAC passed its acceptance tests on March 6, 1952, at Aberdeen Proving Ground in Maryland.<ref>{{Cite book|url=https://books.google.com/books?id=AsvSBQAAQBAJ&q=ORDVAC+1952&pg=PA359 |title=History of Computing in the Twentieth Century|last=Metropolis|first=Nicholas|date=2014-06-28|publisher=Elsevier|isbn=9781483296685 |pages=359–360|language=en}}</ref><ref name="mv1" />{{Rp|IV}}<ref>{{cite journal|title=The ORDVAC|journal=Digital Computer Newsletter|date=1952|volume=4|issue=3|page=4 |url=http://www.dtic.mil/docs/citations/AD0694605|language=en|others=In use from 9 March}}{{dead link|date=June 2022|bot=medic}}{{cbignore|bot=medic}}</ref> Its purpose was to perform ballistic trajectory calculations for the US Military. In 1992, the [[Ballistic Research Laboratory]] became a part of the [[U.S. Army Research Laboratory]].

Unlike the other computers of its era, the ORDVAC and [[ILLIAC I]] were twins and could exchange programs with each other. The later [[SILLIAC]] computer was a copy of the ORDVAC/ILLIAC series. J. P. Nash of the University of Illinois was a developer of both the ORDVAC and of the university's own identical copy, the [[ILLIAC I|ILLIAC]], which was later renamed the ILLIAC I. Abe Taub, Sylvian Ray, and [[Donald B. Gillies]]<ref>{{cite web|title=About Abraham Haskel Taub|url=https://campuscluster.illinois.edu/hardware/about_taub.html|access-date=2017-03-14|archive-date=2017-03-14|archive-url=https://web.archive.org/web/20170314153315/https://campuscluster.illinois.edu/hardware/about_taub.html|url-status=dead}}</ref> assisted in the checkout of ORDVAC at Aberdeen Proving Ground. After ORDVAC was moved to Aberdeen, it was used remotely by telephone by the University of Illinois for up to eight hours per night. It was one of the first computers to be used remotely and probably the first to routinely be used remotely.

The ORDVAC used 2178 [[vacuum tube]]s. Its addition time was 72 [[microseconds]] and the multiplication time was 732 microseconds. Its [[Primary storage|main memory]] consisted of 1024 [[Word (data type)|words]] of 40 [[bit]]s each, stored using [[Williams tube]]s. It was a rare [[asynchronous circuit|asynchronous]] machine, meaning that there was no central clock regulating the timing of the instructions. One instruction started executing when the previous one finished.

Among the ORDVAC programmers were [[Martin Davis (mathematician)|Martin Davis]]<ref>{{cite web| title=Interview with Martin Davis|publisher=American Mathematical Society |url=https://www.ams.org/notices/200805/tx080500560p.pdf|first=Allyn|last=Jackson |access-date=2021-05-20|date=2008-05-01}}</ref> and [[Elsie Shutt]].

ORDVAC and its successor at Aberdeen Proving Ground, [[BRLESC]], used their own unique notation for [[hexadecimal]] numbers. Instead of the sequence A B C D E F universally used today, the digits ten to fifteen were represented by the letters K S N J F L (King Sized Numbers Just For Laughs), corresponding to the [[teleprinter]] characters on five-track [[punched tape|paper tape]]. The manual that was used by the military in 1958  used the name sexadecimal for the base 16 number system.

==Commissioning==
When ORDVAC was completed, it was tested at the University of Illinois and then disassembled and shipped to [[Aberdeen Proving Ground]] in [[Maryland]]. Three faculty members including Sylvian Ray and Abe Taub drove to Maryland to help assemble the machine, which was reconstructed and passed its validation tests in just a week. It was expected that assembly and testing would take over a month. When some military officers came to check on the progress of Ordvac assembly, they asked, "Who is in charge here?", and were told, "It's the guy who is holding the broom!", as Abe Taub—the head of The University of Illinois Digital Computer Laboratory—was sweeping up after having completed all the necessary tasks.<ref>{{cite web| title=No Boundaries:University of Illinois Vignettes - Chapter 15, by Sylvian Ray|publisher=University of Illinois Press |url=http://www.press.uillinois.edu/books/catalog/35mtc3nd9780252029578.html |access-date=2008-07-24}}</ref>

==Details==
* Memory uses 40 cathode ray tubes and 800 vacuum tubes,<ref name=mv1>[http://bitsavers.informatik.uni-stuttgart.de/pdf/univOfIllinoisUrbana/ordvac/ORDVAC_Manual_Volume_1_1952.pdf manual Vol 1]</ref>{{RP|1}}
* Arithmetic unit uses 1100 vacuum tubes,<ref name=mv1 />{{RP|2}}
* Control, uses about 500 vacuum tubes,<ref name=mv1 />{{RP|3}}
Total of 2718 vacuum tubes,<ref name=mv1 />{{RP|4}} weight {{convert|3000|lb|ST MT}}.<ref>{{cite web|url=http://ed-thelen.org/comp-hist/BRL-o-s.html#ORDVAC|title=ORDVAC|last1=Weik |first1=Martin H.|date=December 1955|website=ed-thelen.org|series=A Survey of Domestic Electronic Digital Computing Systems}}</ref>

==See also==
* [[ILLIAC II]]
* [[ILLIAC III]]
* [[ILLIAC IV]]
* [[History of computing hardware]]
* [[List of vacuum tube computers]]

==References==
{{reflist}}

==External links==
*[http://bitsavers.informatik.uni-stuttgart.de/pdf/univOfIllinoisUrbana/ordvac/  ORDVAC documentation] at bitsavers.org
{{Mainframes}}
[[Category:IAS architecture computers]]
[[Category:United States Army equipment]]
[[Category:Vacuum tube computers]]