Editing Analog computer (section)

===Precursors===
{{See also|Timeline of computing hardware before 1950}}

This is a list of examples of early computation devices considered precursors of the modern computers. Some of them may even have been dubbed 'computers' by the press, though they may fail to fit modern definitions.

[[File:Antikythera Fragment A (Front).webp|thumb|The [[Antikythera mechanism]], dating from between 200 BC and 80 BC, was an early analog computer.|alt=|260x260px]]
The [[Antikythera mechanism]], a type  of device used to determine the positions of [[Astronomical object|heavenly bodies]] known  as an [[orrery]], was  described as an early mechanical analog computer by British physicist, information scientist, and historian of science [[Derek J. de Solla Price]].<ref name="djclP">{{cite web|archiveurl=https://web.archive.org/web/20080428070448/http://www.antikythera-mechanism.gr/project/general/the-project.html|archivedate=28 April 2008|url-status=dead|url=http://www.antikythera-mechanism.gr/project/general/the-project.html|date=28 April 2008|title=The Antikythera Mechanism Research Project|accessdate=1 July 2007}}</ref> It was discovered in 1901, in the [[Antikythera wreck]] off the Greek island of [[Antikythera]], between [[Kythera]] and [[Crete]], and has been dated to {{circa|150~100 BC}}, during the [[Hellenistic period]]. Devices of a level of complexity comparable to that of the Antikythera mechanism would not reappear until a thousand years later.

Many mechanical aids to calculation and measurement were constructed for astronomical and navigation use.
The [[planisphere]] was first described by [[Ptolemy]] in the 2nd century AD. The [[astrolabe]] was invented in the [[Hellenistic civilization|Hellenistic world]] in either the 1st or 2nd centuries BC and is often attributed to [[Hipparchus]]. A combination of the planisphere and [[dioptra]], the astrolabe was effectively an analog computer capable of working out several different kinds of problems in [[spherical astronomy]].

The [[Sector (instrument)|sector]], a calculating instrument used for solving problems in proportion, trigonometry, multiplication and division, and for various functions, such as squares and cube roots, was developed in the late 16th century and found application in gunnery, surveying and navigation.

The [[planimeter]] was a manual instrument to calculate the area of a closed figure by tracing over it with a mechanical linkage.

[[File:Sliderule 2005.png|thumb|A [[slide rule]]. The sliding central slip is set to 1.3, the cursor to 2.0 and points to the multiplied result of 2.6.|alt=|260x260px]]
The [[slide rule]] was invented around 1620–1630, shortly after the publication of the [[history of logarithms|concept of the logarithm]]. It is a hand-operated analog computer for doing multiplication and division. As slide rule development progressed, added scales provided reciprocals, squares and square roots, cubes and cube roots, as well as [[transcendental function]]s such as logarithms and exponentials, circular and hyperbolic trigonometry and other [[Function (mathematics)|functions]]. Aviation is one of the few fields where slide rules are still in widespread use, particularly for solving time–distance problems in light aircraft.

In 1831–1835, mathematician and engineer [[Giovanni Plana]] devised a [[Cappella dei Mercanti (Turin)#Perpetual calendar|perpetual-calendar machine]], which, through a system of pulleys and cylinders, could predict the [[perpetual calendar]] for every year from AD&nbsp;0 (that is, 1&nbsp;BC) to AD&nbsp;4000, keeping track of leap years and varying day length.<ref name="1eYEV">{{Cite web|title=An Amazing Perpetual Calendar, Hidden in an Italian Chapel|first1=A J|last1=Oliveira|url=http://www.atlasobscura.com/places/planas-perpetual-calendar|access-date=2020-09-07|website=Atlas Obscura|language=en}}</ref>

The [[tide-predicting machine]] invented by [[William Thomson, 1st Baron Kelvin|Sir William Thomson]] in 1872 was of great utility to navigation in shallow waters. It used a system of pulleys and wires to automatically calculate predicted tide levels for a set period at a particular location.

The [[differential analyser]], a mechanical analog computer designed to solve [[differential equation]]s by [[integral|integration]], used wheel-and-disc mechanisms to perform the integration. In 1876 [[James Thomson (engineer)|James Thomson]] had already discussed the possible construction of such calculators, but he had been stymied by the limited output torque of the [[ball-and-disk integrator]]s. Several systems followed, notably those of Spanish [[engineer]] [[Leonardo Torres Quevedo]], who built various [[Leonardo Torres Quevedo#Analogue calculating machines|analog machines]] for solving real and complex roots of [[polynomial]]s;<ref>{{Cite journal |last=Torres |first=Leonardo |author-link=Leonardo Torres Quevedo |date=1895-10-10 |title=Memória sobre las Máquinas Algébricas |url=https://quickclick.es/rop/pdf/publico/1895/1895_tomoI_28_01.pdf |journal=Revista de Obras Públicas |language=es |issue=28 |pages=217–222}}</ref><ref name="MaquinasAlgebricasLTQ">Leonardo Torres. ''[https://books.google.com/books?id=Eo0NAQAAIAAJ Memoria sobre las máquinas algébricas: con un informe de la Real academia de ciencias exactas, fisicas y naturales]'', Misericordia, 1895.</ref><ref name="Gomez-JaureguiGutierrez-GarciaGonzález-RedondoIglesiasManchadoOtero2022">{{Cite journal |last1=Gomez-Jauregui |first1=Valentin |last2=Gutierrez-Garcia |first2=Andres |last3=González-Redondo |first3=Francisco A. |last4=Iglesias |first4=Miguel |last5=Manchado |first5=Cristina |last6=Otero |first6=Cesar |date=2022-06-01 |title=Torres Quevedo's mechanical calculator for second-degree equations with complex coefficients|journal=[[Mechanism and Machine Theory]] |publisher=[[International Federation for the Promotion of Mechanism and Machine Science|IFToMM]] |volume=172 |issue=8|page=104830 |doi=10.1016/j.mechmachtheory.2022.104830|s2cid=247503677 |doi-access=free |hdl=10902/24391 |hdl-access=free }}</ref> and Michelson and Stratton, whose Harmonic Analyser performed Fourier analysis, but using an array of 80 springs rather than Kelvin integrators. This work led to the mathematical understanding of the [[Gibbs phenomenon]] of overshoot in Fourier representation near discontinuities.<ref name="GdfNz">Ray Girvan, [http://www.scientific-computing.com/scwmayjun03computingmachines.html "The revealed grace of the mechanism: computing after Babbage"] {{webarchive |url=https://web.archive.org/web/20121103094710/http://www.scientific-computing.com/scwmayjun03computingmachines.html |date=November 3, 2012}}, ''Scientific Computing World'', May/June 2003</ref> In a differential analyzer, the output of one integrator drove the input of the next integrator, or a graphing output. The [[torque amplifier]] was the advance that allowed these machines to work. Starting in the 1920s, [[Vannevar Bush]] and others developed mechanical differential analyzers.