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{{Short description|Instructions a computer can execute}}
{{for|the TV program|The Computer Programme{{!}}''The Computer Programme''}}
[[File:JavaScript_code.png|thumb|[[Source code]] for a computer program written in the [[JavaScript]] language. It demonstrates the ''appendChild'' method. The method adds a new child node to an existing parent node. It is commonly used to dynamically modify the structure of an HTML document.]][[A]] '''computer program''' is a [[sequence]] or set{{efn|The [[Prolog]] language allows for a database of facts and rules to be entered in any order. However, a question about a database must be at the very end.}} of instructions in a programming language for a [[computer]] to [[Execution (computing)|execute]]. It is one component of [[software]], which also includes [[software documentation|documentation]] and other intangible components.<ref name="ISO 2020">{{cite web▼
[[File:JavaScript_code.png|thumb|[[Source code]] for a computer program written in the [[JavaScript]] language. It demonstrates the ''appendChild'' method. The method adds a new child node to an existing parent node. It is commonly used to dynamically modify the structure of an HTML document.]]
{{Program execution}}
▲
| title=ISO/IEC 2382:2015
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A ''computer program'' in its [[human-readable]] form is called [[source code]]. Source code needs another computer program to execute because computers can only execute their native [[machine instructions]]. Therefore, source code may be [[Translator (computing)|translated]] to machine instructions using a [[compiler]] written for the language. ([[Assembly language]] programs are translated using an [[Assembler (computing)|assembler]].) The resulting file is called an [[executable]]. Alternatively, source code may execute within an [[interpreter (computing)|interpreter]] written for the language.<ref name="cpl_3rd-ch1-7_quoted">{{cite book
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If the executable is requested for execution, then the [[operating system]] [[Loader (computing)|loads]] it into [[Random-access memory|memory]] and starts a [[Process (computing)|process]].<ref name="osc-ch4-p98">{{cite book
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| isbn = 978-0-201-50480-4
}}</ref> The [[central processing unit]] will soon [[Context switch|switch]] to this process so it can [[Instruction cycle|fetch, decode, and then execute]] each machine instruction.<ref name="sco-ch2-p32">{{cite book
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If the source code is requested for execution, then the operating system loads the corresponding interpreter into memory and starts a process. The interpreter then loads the source code into memory to translate and execute each [[Statement (computer science)|statement]]. Running the source code is slower than running an
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==Example computer program==
The [["Hello, World!" program]] is used to illustrate a language's basic
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===ENIAC===
[[File:ENIAC-changing_a_tube.jpg|thumb|right|Glenn A. Beck changing a tube in ENIAC]]
The [[Electronic Numerical Integrator And Computer]] (ENIAC) was built between July 1943 and Fall 1945. It was a
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}}</ref> The MOS transistor is the primary component in ''integrated circuit chips''.<ref name="digital_age"/>
Originally, [[integrated circuit]] chips had their function set during manufacturing. During the 1960s, controlling the electrical flow migrated to programming a [[Diode matrix|matrix]] of [[read-only memory]] (ROM). The matrix resembled a two-dimensional array of fuses. The process to embed instructions onto the matrix was to burn out the unneeded connections. There were so many connections, [[firmware]] programmers wrote a ''computer program'' on another chip to oversee the burning. The technology became known as [[Programmable ROM]]. In 1971, Intel
| url=https://spectrum.ieee.org/chip-hall-of-fame-intel-4004-microprocessor
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===x86 series===
[[File:IBM_PC-IMG_7271_(transparent).png|thumb|right|The original [[IBM Personal Computer]] (1981) used an Intel 8088 microprocessor.]]
In 1978, the modern
| url=https://books.google.com/books?id=VDAEAAAAMBAJ&pg=PA22
| title=Bill Gates, Microsoft and the IBM Personal Computer
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==Programming paradigms and languages==
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}}</ref> ''Machine language'' requires the programmer to enter instructions using ''instruction numbers'' called [[machine code]]. For example, the ADD operation on the [[PDP-11 architecture|PDP-11]] has instruction number 24576.{{efn|Whereas this is a decimal number, PDP-11 code is always expressed as [[octal]].}}<ref name="sco-ch7-p399">{{cite book
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}}</ref> Emerging from a committee of European and American programming language experts, it used standard [[mathematical notation]] and had a readable, structured design. Algol was first to define its
* [[Block (programming)|block structure]], where variables were local to their block.
* arrays with variable bounds.
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The levels of coupling from worst to best are:<ref name="se-ch8-226"/>
* ''Content Coupling'': A module has content coupling if it modifies a [[local variable]] of another function. COBOL used to do this with the ''alter'' verb.
* ''Common Coupling'': A module has common coupling if it modifies a global variable.
* ''Control Coupling'': A module has control coupling if another module can modify its [[control flow]]. For example, <code>perform_arithmetic( perform_addition, a, b )</code>. Instead, control should be on the makeup of the returned object.
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