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These computers include:
#* [[Desktop computer]]s – A case put under or on a desk. The display may be optional, depending on use. The case size may vary, depending on the required expansion slots. Very small computers of this kind may be integrated into the monitor.
#* Rackmount computers – The cases of these computers fit into [[19-inch rack]]s, and maybe space-optimized and very flat. A dedicated display, keyboard, and mouse may not exist, but a [[KVM switch]] or built-in remote control (via LAN or other means) can be used to gain console access. Many [[server (computing)|servers]] are rackmount computers and [[data center]]s may have dozens or hundreds of racks with hundreds or thousands of rackmount computers acting as servers.
#* In-car computers ([[carputer]]s) – Built into automobiles, for [[In car entertainment|entertainment]], [[Automotive navigation system|navigation]], etc.
#* [[Laptop]]s and [[notebook computer]]s – Portable and all in one case.
#* [[Tablet computer]] – Like laptops, but with a [[touch-screen]], entirely replacing the physical keyboard.
#* [[Smartphone]]s, [[smartbook]]s, and [[palmtop computer]]s – Small handheld personal computers with limited hardware specifications.
#* [[Programmable calculator]]– Like small handhelds, but specialized in mathematical work.
#* [[Game console|Video game console]]s – Fixed computers built specifically for entertainment purposes.
#* [[Handheld game console]]s – The same as game consoles, but small and portable.
===Minicomputers (mid-range computers)===
[[computer server|Server]] usually refers to a computer that is dedicated to providing one or more services. A server is expected to be reliable (e.g. error-correction of RAM; redundant cooling; self-monitoring, RAID), fit for running for several years, and giving useful diagnosis in case of an error. For even increased security, the server may be mirrored. Many smaller servers are actually personal computers that have been dedicated to provide services for other computers.
#* A [[database server]] is a server which uses a [[database application]] that provides [[database]] services to other computer programs or to [[computer]]s. [[Database|Database management systems]] (DBMSs) frequently provide database-server functionality, and some database management systems (such as [[MySQL]]) rely exclusively on the [[client–server model]] for database access while others (such as [[SQLite]]) are meant for using as an [[embedded database]]. Users access a database server either through a "[[Front and back ends|front end]]" running on the user's computer – which displays requested data – or through the "[[Front and back ends|back end]]", which runs on the server and handles tasks such as data analysis and storage.
#* A [[file server]] does not normally perform computational tasks or run programs on behalf of its client workstations but manage and store a large collection of [[computer file]]s. The crucial function of a file server is storage. File servers are commonly found in schools and offices, where users use a [[local area network]] to connect their client computers and use [[Network-attached storage|Network-attached storage (NAS)]] systems to provide data access.
#* A [[web server]] is a server that can satisfy [[Client (computing)|client]] requests on the [[World Wide Web]]. A web server can, in general, contain one or more [[website]]s. A web server processes incoming [[Computer network|network]] requests over [[Hypertext Transfer Protocol|HTTP]] and several other related [[Communication protocol|protocols]]. The primary function of a web server is to store, process and deliver [[web page]]s to clients. The communication between client and server takes place using the [[Hypertext Transfer Protocol|Hypertext Transfer Protocol (HTTP)]]. Pages delivered are most frequently [[HTML|HTML documents]], which may include [[image]]s, [[Style sheet (web development)|style sheets]] and [[JavaScript|scripts]] in addition to the text content.
#* A [[terminal server]] enables organizations to connect devices with an [[RS-232]], [[EIA-422|RS-422]] or [[EIA-485|RS-485]] serial interface to a [[local area network]] (LAN). Products marketed as terminal servers can be very simple devices that do not offer any security functionality, such as [[data encryption]] and user authentication. These provide GUI sessions that can be used by client PCs that work someway like a remote control. Only the screen (and audio) output is shown on the client. The GUI applications run on the server, data (like in files) would be stored in the same LAN, thus avoiding problems, should a client PC be damaged or stolen.
A server may run several [[virtual machine]]s (VMs) for different activities, supplying the same environment to each VM as if it ran on dedicated hardware. Different operating systems (OS) can therefore be run at the same time. This technology approach needs special hardware support to be useful and was first the ___domain of mainframes and other large computers. Nowadays, most personal computers are equipped for this task, but for long-term operation or critical systems, specialized server hardware may be needed.<br />
==Classed by generation of computer technology==
{{Main|History of computing hardware}}The history of computing hardware is often used to reference the different generations of computing devices:
#*First generation computers (1940-1955): It used [[vacuum tube]]s such as the [[List of vacuum tubes#6 volt heater.2Ffilament tubes|6J6]]<ref>{{cite book|last1=Dyson|first1=George|title=Turing's Cathedral - The origins of the Digital Universe|url=https://archive.org/details/turingscathedral0000dyso|url-access=registration|date=2012|publisher=Pantheon Books|___location=New York|isbn=978-0-375-42277-5|page=[https://archive.org/details/turingscathedral0000dyso/page/124 124]|chapter=7}}</ref> or specially designed tubes - or even mechanical arrangements, and were relatively slow, energy-hungry and the [[First generation computer|earliest computer]]s were less flexible in their programmability.
#*Second generation computers (1956-1963): It used [[Discrete device|discrete]] [[Transistor computer|transistors]], and so were smaller and consumed less power.
#*Third generation computers (1964-1970): It used [[Integrated Circuits|Integrated Circuits (ICs)]], the main difference between hardware in computers of the 1960s and today being the density of transistors in each IC (beginning with [[Small Scale Integration]] chips like the [[Transistor-transistor logic]] (TTL) [[7400 series|SN7400]] [[logic gates|gates]] with 20 transistors, through [[Medium Scale Integration]] and [[Large Scale Integration]] to [[Very-large-scale integration|Very-large-scale integration (VLSI)]] with over ten billion transistors in a single silicon-based IC "chip".
#*Fourth generation computers(1971–present): It uses [[Microprocessor]]s, as millions of ICs were built onto a single silicon-based chip. Since then form factor of computers reduced, task processing & graphic rendering improved and it became more battery-powered with the advent of personal mobile devices such as laptops, tablets, smartphones etc.
==See also==
#*[[List of computer size categories]]
#*[[Bell's law of computer classes]]
#*[[Analog computers]]
#* [[Feng's classification]]
#* [[Flynn's taxonomy]]
== References ==
==External links==
#* [http://www.byte-notes.com/four-types-computers Four types of Computers]
{{Computer sizes}}
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