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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 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 to represent 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 to represent a one.  Ternary systems are far more complicated and still in development.  Most computers use binary.

==History==

==History==

[[File:Babbage Difference Engine.jpg|right|thumb|200px|The modern (1991) construction of the "difference engine 2" in the British Science Museum.]]

[[File:Babbage Difference Engine.jpg|right|thumb|200px|The modern (1991) construction of the "difference engine 2" in the British Science Museum.]]

Prior to the advent of computing machines, the definition for ''computer'' was a human being who performed complex mathematical calculations. This was accomplished with the aid of a manual counting device, such as an [[abacus]] or a [[slide rule]], and was mainly performed by traders and early bankers to keep a reliable record of funds.

Prior to the advent of computing machines, the definition of ''computer'' was a human being who performed complex mathematical calculations. This was accomplished with the aid of a manual counting device, such as an [[abacus]] or a [[slide rule]], and was mainly performed by traders and early bankers to keep a reliable record of funds.

Charles Babbage, a [[British]] scientist who lived in the 19th century, has been credited as the designer of the first digital computer, the Difference Engine, a machine set to do calculations reliably up to six decimal places.  It was entirely mechanical. However, the Engine was never constructed, being deemed "had derived no emolument whatsoever from the government" by a member of parliament. He also designed an even more sophisticated "Analytical Engine", that would actually have been a programmable computer in the modern sense; it, too, was mechanical.  Though it was never built, [[Ada Lovelace|Augusta Ada]] wrote some programs for it (to compute Bernoulli polynomials), making her the world's first computer programmer.  A small version of the Difference Engine was built after his death by his son.<ref>http://ei.cs.vt.edu/~history/Babbage.html</ref>

Charles Babbage, a [[British]] scientist who lived in the 19th century, has been credited as the designer of the first digital computer, the Difference Engine, a machine set to do calculations reliably up to six decimal places.  It was entirely mechanical. However, the Engine was never constructed, since it "had derived no emolument whatsoever from the government" by a member of parliament. He also designed an even more sophisticated "Analytical Engine," which would actually have been a programmable computer in the modern sense; it, too, was mechanical.  Though it was never built, [[Ada Lovelace|Augusta Ada]] wrote some programs for it (to compute Bernoulli polynomials), making her the world's first computer programmer.  A small version of the Difference Engine was built after his death by his son.<ref>http://ei.cs.vt.edu/~history/Babbage.html</ref>

Babbage later designed a simpler and even more clever "Difference Engine Number 2", which was also not completed in his lifetime.  But in 1991, the bicentennial of Babbage's birth, this computer was built in the British Science Museum from Babbage's original plans.  It operates flawlessly, though a few billion times slower than modern electronic computers.  It is operated by turning a crank.

Babbage later designed a simpler and even more clever "Difference Engine Number 2", which was also not completed in his lifetime.  But in 1991, the bicentennial of Babbage's birth, this computer was built in the British Science Museum from Babbage's original plans.  It operates flawlessly, though a few billion times slower than modern electronic computers.  It is operated by turning a crank.

[[File:SSEM Replica.jpg|thumb|left|The Manchester Small-Scale Experimental Machine is considered  the world's first stored-program computer, 1948.]]

[[File:SSEM Replica.jpg|thumb|left|The Manchester Small-Scale Experimental Machine is considered  the world's first stored-program computer, 1948.]]

The first computer comparable to the modern day computer, an electronic calculation machine, was the [[ENIAC]]. Built as an artillery support machine, it was unveiled in early 1946.<ref>http://ftp.arl.army.mil/~mike/comphist/</ref>

The first computer comparable to the modern-day computer, an electronic calculation machine, was the ENIAC. Built as an artillery support machine, it was unveiled in early 1946.<ref>http://ftp.arl.army.mil/~mike/comphist/</ref>

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===Mainframe===

===Mainframe===

[[File:NASAComputerRoom-1962.gif|250px|thumbnail|NASA's Mainframe 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 />

Most mainframes, including the IBM System Z, use the [[Cobol|COBOL]] language (short for COmmon Business-Oriented Language).  This is a very easy to understand [[programming language]].  For example, a line of this code is, <code>MULTIPLY HOURLY-RATE BY TOTAL-HOURS GIVING TOTAL-PAY</code>.<ref>https://answers.yahoo.com/question/index?qid=20110121224151AAaIkmF</ref>  Although not used exclusively by mainframes, this is one of the main ways it is used.  In 2009, 70-75% of the world's business transactions and 90% of global financial transactions were processed by COBOL programs.<ref>https://cis.hfcc.edu/faq/cobol</ref>  In 2016, it was estimated that at least 60% of business systems still used it, much of which was running on mainframes.<ref name="interview with DavidB4"/> Although now an outdated technology, mainframes are still a vital part of many systems.<ref>https://www.theguardian.com/technology/2009/apr/09/cobol-internet-programming</ref><ref>http://www.mainframes.com/COBOL.html</ref><ref>http://www.eweek.com/servers/ibm-mainframe-keeps-major-chinese-bank-up-and-running</ref>

Most mainframes, including the IBM System Z, use the [[Cobol|COBOL]] language (short for COmmon Business-Oriented Language).  This is a very easy-to-understand [[programming language]].  For example, a line of this code is, <code>MULTIPLY HOURLY-RATE BY TOTAL-HOURS GIVING TOTAL-PAY</code>.<ref>https://answers.yahoo.com/question/index?qid=20110121224151AAaIkmF</ref>  Although not used exclusively by mainframes, this is one of the main ways it is used.  In 2009, 70-75% of the world's business transactions and 90% of global financial transactions were processed by COBOL programs.<ref>https://cis.hfcc.edu/faq/cobol</ref>  In 2016, it was estimated that at least 60% of business systems still used it, much of which was running on mainframes.<ref name="interview with DavidB4"/> Although now an outdated technology, mainframes are still a vital part of many systems.<ref>https://www.theguardian.com/technology/2009/apr/09/cobol-internet-programming</ref><ref>http://www.mainframes.com/COBOL.html</ref><ref>http://www.eweek.com/servers/ibm-mainframe-keeps-major-chinese-bank-up-and-running</ref>

===Supercomputer===

===Supercomputer===

{{main|Supercomputer}}

{{main|Supercomputer}}

Supercomputers are the most powerful computers available, which have replaced mainframe computers.  These computers, which generally fill large rooms like mainframes, are generally used by government agencies and large corporations.  Since these computers are so expensive, they are reserved for important and complicated computations such as nuclear simulations and weather modeling.<ref name="Britannica">"Computer." Encyclopaedia Britannica. Britannica Academic. Encyclopædia Britannica Inc., 2016. Web. 30 Apr. 2016. <http://0-academic.eb.com.www.consuls.org/EBchecked/topic/130429/computer>.</ref>  [[Quantum computer]]s are also often considered supercomputers, due to their extensive capabilities (and size).

Supercomputers are the most powerful computers available and have replaced mainframe computers.  These computers, which generally fill large rooms like mainframes, are generally used by government agencies and large corporations.  Since these computers are so expensive, they are reserved for important and complicated computations such as nuclear simulations and weather modeling.<ref name="Britannica">"Computer." Encyclopaedia Britannica. Britannica Academic. Encyclopædia Britannica Inc., 2016. Web. 30 Apr. 2016. <http://0-academic.eb.com.www.consuls.org/EBchecked/topic/130429/computer>.</ref>  [[Quantum computer]]s are also often considered supercomputers, due to their extensive capabilities (and size).

===Minicomputer===

===Minicomputer===

Minicomputers were smaller, cheaper cousins of the mainframe computer.  They were also slower than mainframes.  Over time, minicomputers became available in many configurations and sizes, up to the threshold of mainframes.  In the 1970s, a typical minicomputer cost between $100,000 and $200,000 and could support up to 63 timeshared users.  Larger minicomputers had large power requirements and often required special rooms with adequate air conditioning to remove the large amounts of heat that they generated.  The first commercially successful minicomputer was the pdp/8, released by Digital Equipment Corporation in 1958.  Unlike mainframes, the entire computer could fit on top of a desk.  Minicomputers fell out of favor when powerful microcomputers became wildly available.

Minicomputers were smaller, cheaper cousins of the mainframe computer.  They were also slower than mainframes.  Over time, minicomputers became available in many configurations and sizes, up to the threshold of mainframes.  In the 1970s, a typical minicomputer cost between $100,000 and $200,000 and could support up to 63 timeshared users.  Larger minicomputers had large power requirements and often required special rooms with adequate air conditioning to remove the large amounts of heat that they generated.  The first commercially successful minicomputer was the pdp/8, released by Digital Equipment Corporation in 1958.  Unlike mainframes, the entire computer could fit on top of a desk.  Minicomputers fell out of favor when powerful microcomputers became widely available.

===Microcomputers===

===Microcomputers===