Editing Drum memory (section)

== History ==
Tauschek's original drum memory (1932) had a capacity of about 500,000 [[bit]]s (62.5 [[kilobyte]]s).<ref name="Tauschek" />

One of the earliest functioning computers to employ drum memory was the [[Atanasoff–Berry computer]] (1942). It stored 3,000 bits; however, it employed [[capacitance]] rather than [[magnetism]] to store the information.  The outer surface of the drum was lined with electrical contacts leading to [[capacitor]]s contained within.

Magnetic drums were developed for the [[U.S. Navy]] by [[Engineering Research Associates]] (ERA) in 1946 and 1947.<ref name="Daniel">{{cite book |author1=Eric D. Daniel |url=https://books.google.com/books?id=7WrCSCqMk5gC&pg=PA238 |title=Magnetic Recording: The First 100 Years |author2=C. Denis Mee |author3=Mark H. Clark |publisher=Wiley-IEEE |year=1998 |isbn=0-7803-4709-9 |pages=238, 241}} </ref>  An experimental ERA study was completed and reported to the Navy on June 19, 1947.<ref name="Daniel" /> Other early drum storage device development occurred at [[Birkbeck, University of London|Birkbeck College]] ([[University of London]]),<ref name="birkbeck">{{cite journal|last1=Campbell-Kelly|first1=Martin|title=The Development of Computer Programming in Britain (1945 to 1955)|journal=IEEE Annals of the History of Computing|date=April 1982|volume=4|issue=2|pages=121–139|doi=10.1109/MAHC.1982.10016|s2cid=14861159}}</ref> [[Harvard University]], [[IBM]] and the [[University of Manchester]]. An ERA drum was the internal memory for the ATLAS-I computer delivered to the U.S. Navy in October 1950 and later sold commercially as the ERA 1101 and [[UNIVAC 1101]]. Through [[Mergers and acquisitions|mergers]], ERA became a division of [[UNIVAC]] shipping the Series 1100 drum as a part of the [[UNIVAC]] File Computer in 1956; each drum stored 180,000 6-bit characters (135 kilobytes).<ref>{{cite journal
 | last1 = Gray | first1 = George T.| last2 = Smith| first2 = Ronald Q. | date = October 2004
 | title = Sperry Rand's First-Generation Computers, 1955–1960: Hardware and Software
 | journal = IEEE Annals of the History of Computing| page = 23
 | quote =There was a 1,070-word drum memory for data, stored as twelve 6-bit digits or characters per word}}</ref>

<!-- Using explicit numbers for decimal units to avoid reading the 650 sizes as 2 Kiwords and 4Kiwords. -->
The first mass-produced computer, the [[IBM_650#Main_memory|IBM 650]] (1954), initially had up to 2,000 10-digit words, about 17.5 [[kilobyte]]s, of drum memory (later doubled to 4,000 words, about 35 kilobytes, in the Model 4).

In [[Berkeley Software Distribution|BSD Unix]] and its descendants, {{mono|/dev/drum}} was the name of the default [[virtual memory]] (swap) device,<ref name="bsddrum">{{cite web|url=http://www.freebsd.org/cgi/man.cgi?query=drum&apropos=0&sektion=0&manpath=FreeBSD+3.5.1-RELEASE&format=html|title=FreeBSD drum(4) manpage|access-date=2013-01-27}}</ref> deriving from the historical use of drum secondary-storage devices as backup storage for [[Page (computer memory)|pages]] in [[virtual memory]].

Magnetic drum memory units were used in the [[LGM-30 Minuteman|Minuteman ICBM]] launch control centers from the beginning in the early 1960s until the [[Rapid Execution and Combat Targeting System|REACT]] upgrades in the mid-1990s.