Editing Analog computer (section)

{{Short description|Computation machine that uses continuously varying data technology}}
{{For|the Atari 8-bit computer magazine|ANALOG Computing}}
{{Use American English|date=July 2020}}
{{Use dmy dates|date=July 2020}}
[[File:Bifnordennomenclature.jpg|thumb|A page from the ''Bombardier's Information File'' (BIF) that describes the components and controls of the [[Norden bombsight]], a highly sophisticated optical/mechanical analog computer used by the United States Army Air Force during [[World War II]], the [[Korean War]], and the [[Vietnam War]] to aid the pilot of a [[bomber]] aircraft in dropping [[bomb]]s accurately.|alt=|356x356px]]
[[File:PACE-TR-10 analog computer - National Cryptologic Museum - DSC07908.JPG|thumb|TR-10 desktop analog computer of the late 1960s and early 1970s|alt=|347x347px]]

An '''analog computer''' or '''analogue computer''' is a type of [[computation]] machine (computer) that uses physical phenomena such as [[Electrical network|electrical]], [[Mechanics|mechanical]], or [[Hydraulics|hydraulic]] quantities behaving according to the mathematical principles in question (''[[analog signal]]s'') to [[Scientific modelling|model]] the problem being solved. In contrast, [[digital computer]]s represent varying quantities symbolically and by discrete values of both time and amplitude ([[digital signal]]s).

Analog computers can have a very wide range of complexity. [[Slide rule]]s and [[nomogram]]s are the simplest, while naval gunfire control computers and large hybrid digital/analog computers were among the most complicated.<ref name="9HtsB">{{cite web|url=https://arstechnica.com/information-technology/2014/03/gears-of-war-when-mechanical-analog-computers-ruled-the-waves/|title=Gears of war: When mechanical analog computers ruled the waves|first1=Sean|last1=Gallagher|date=2014-03-17|access-date=2017-06-14|archive-url=https://web.archive.org/web/20180908173957/https://arstechnica.com/information-technology/2014/03/gears-of-war-when-mechanical-analog-computers-ruled-the-waves/|archive-date=2018-09-08|url-status=live|website=ARS Technica}}</ref> Complex mechanisms for [[process control]] and [[protective relay]]s used analog computation to perform control and protective functions.

Analog computers were widely used in scientific and industrial applications even after the advent of digital computers, because at the time they were typically much faster, but they started to become obsolete as early as the 1950s and 1960s, although they remained in use in some specific applications, such as aircraft [[flight simulator]]s, the [[flight computer]] in [[aircraft]], and for teaching [[control system]]s in universities. Perhaps the most relatable example of analog computers are [[mechanical watch]]es where the continuous and periodic rotation of interlinked gears drives the second, minute and hour needles in the clock. More complex applications, such as aircraft flight simulators and [[synthetic-aperture radar]], remained the domain of analog computing (and [[Hybrid computer|hybrid computing]]) well into the 1980s, since digital computers were insufficient for the task.<ref name="Johnston">{{cite book | url=https://books.google.com/books?id=iPfU_powAgAC&q=%22through%20the%201980s%22&pg=PA90 | title=Holographic Visions: A History of New Science | publisher=OUP Oxford | author=Johnston, Sean F. | year=2006 | pages=90 | isbn=978-0191513886}}</ref>