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A '''computer''' is a machine that is designed to perform a wide variety of information-processing tasks, depending on the program it has stored in its memory.  It processes (computes) everything as mathematical problems, although many non-mathematical functions can be ultimately performed. Digital computers manipulate all data in the form of numbers, and encode all numbers in either [[binary|binary code]], which is base 2, or in the case of quantum computers, ternary code which is base 3. Binary means that there can only be a 1 or a 0 in any data.  This makes it possible to process data electronically, since one voltage can be used to represent a zero and another voltage for a one.  Ternary systems are far more complicated, and still in development.  Most computers use binary.

A '''computer''' is a [[machine]] that is designed to perform a wide variety of information-processing tasks, depending on the program it is running.  It processes (computes) everything as mathematical problems, although many non-mathematical functions can be ultimately performed. Digital computers manipulate all data in the form of numbers, and encode all numbers in either [[binary|binary code]], which is base 2, or in the case of quantum computers, ternary code which is base 3. Binary means that each value can only be a 1 or a 0.  This makes it possible to process data electronically, since one voltage can be used to represent a zero and another voltage for a one.  Ternary systems are far more complicated, and still in development.  Most computers use binary.

==History==

==History==

==Hardware Classifications==

==Hardware Classifications==

===Mainframe===

===Mainframe===

[[File:NASAComputerRoom-1962.gif|250px|thumbnail|NASA's Mainfram computer (1962)]]

[[File:NASAComputerRoom-1962.gif|250px|thumbnail|NASA's Mainframe computer (1962)]]

Mainframes were the first kind of commercially used digital computers, and always used to be the fastest option.  They had the ability to process much more information at a faster rate than any other kind.<ref name="WorldBook01"/> However, with the rapid advancement of technology in recent years, these have fallen behind somewhat.  They consume an enormous amount of space, and use much more electricity than modern computers.  In many cases, they have since been replaced with the client-server architecture.<ref>"mainframe." Encyclopaedia Britannica. Britannica Academic. Encyclopædia Britannica Inc., 2016. Web. 31 May. 2016. <http://0-academic.eb.com.www.consuls.org/EBchecked/topic/358715/mainframe>.</ref> However, mainframes (mainly the IBM System Z) are still used by a number of companies.  Although an older technology, they are still powerful, durable, and reliable systems.  Some have been in fault-tolerant operation for at least forty years.<ref name="interview with DavidB4">Personal interview of an anonymous individual with [[User:DavidB4]]</ref><br />

Mainframes were the first kind of commercially used digital computers, and always used to be the fastest option.  They had the ability to process much more information at a faster rate than any other kind.<ref name="WorldBook01"/> However, with the rapid advancement of technology in recent years, these have fallen behind somewhat.  They consume an enormous amount of space, and use much more electricity than modern computers.  In many cases, they have since been replaced with the client-server architecture.<ref>"mainframe." Encyclopaedia Britannica. Britannica Academic. Encyclopædia Britannica Inc., 2016. Web. 31 May. 2016. <http://0-academic.eb.com.www.consuls.org/EBchecked/topic/358715/mainframe>.</ref> However, mainframes (mainly the IBM System Z) are still used by a number of companies.  Although an older technology, they are still powerful, durable, and reliable systems.  Some have been in fault-tolerant operation for at least forty years.<ref name="interview with DavidB4">Personal interview of an anonymous individual with [[User:DavidB4]]</ref><br />

Manufacturers of mainframes included Burroughs, CDC, Univac, and IBM.  IBM mainframes were the most commonly used mainframes in the world, and are still being manufactured today.<br />

Manufacturers of mainframes included Burroughs, CDC, Univac, and IBM.  IBM mainframes were the most commonly used mainframes in the world, and are still being manufactured today.<br />

==Architecture==

==Architecture==

All digital computer systems, regardless of classification or usage, consist of the following components:

All digital computer systems, regardless of classification or usage, consist of the following components:

* <b>Processing.</b> Provided by one or more [[Central processing unit|CPU]]s, sometimes with ancillary processors, such as [[floating-point]] processors (now usually included as part of the CPU), and array processors (in mainframes and [[supercomputer]]s).

* '''Processing.''' Provided by one or more [[Central processing unit|CPU]]s, sometimes with ancillary processors, such as [[floating-point]] processors (now usually included as part of the CPU), and array processors (in mainframes and [[supercomputer]]s).

* <b>Memory.</b> High-speed local storage, such as [[Random-access memory]]

* '''Memory.''' High-speed local storage, such as [[Random-access memory]]

* <b>Software.</b> Each unique computer hardware environment needs [[software]] that works with the model of processor used in that computer.

* '''Software.''' Each unique computer hardware environment needs [[software]] that works with the model of processor used in that computer.

* <b>Input/Output.</b> Computers are only useful if they can generate output.  Output can vary from control lines for engine components to characters on a video screen.  Input also varies in form, but most computers need input to process, which then drives the output.

* '''Input/Output.''' Computers are only useful if they can generate output.  Output can vary from control lines for engine components to characters on a video screen.  Input also varies in form, but most computers need input to process, which then drives the output.

Most modern computer systems also have peripheral devices:

Most modern computer systems also have peripheral devices:

* <b>Storage.</b> Large amounts of lower-speed, less-expensive hardware where data can be stored for later retrieval.  Storage can be local or it can be remotely accessed via a network.  The most typical form of local storage are hard disks, SSDs, thumb drives, and DVDROMs.  Older mass storage devices include punch cards, paper tapes, magnetic tapes, and CDROMs.

* '''Storage.''' Large amounts of lower-speed, less-expensive hardware where data can be stored for later retrieval.  Storage can be local or it can be remotely accessed via a network.  The most typical form of local storage are hard disks, SSDs, thumb drives, and DVDROMs.  Older mass storage devices include punch cards, paper tapes, magnetic tapes, and CDROMs.

* <b>Other I/O devices.</b> Any number of optional peripheral devices are available for computers, including [[Computer mouse|mice]], scanners, card readers, [[network]] interfaces, [[terminals]], and [[printers]].

* '''Other I/O devices.''' Any number of optional peripheral devices are available for computers, including [[Computer mouse|mice]], scanners, card readers, [[network]] interfaces, [[terminals]], and [[Printer (computing)|printers]].

==Binary and ternary==

==Binary and ternary==

*[[Apple Computer|Apple]] [[iOS]] for [[iPhone]]-[[iPod]]-[[iPad]]

*[[Apple Computer|Apple]] [[iOS]] for [[iPhone]]-[[iPod]]-[[iPad]]

*[[Acorn computers]]

*[[Acorn computers]]

*[[ZX Spectrum]]

*[[ZX Spectrum]]