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Computer program

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</style><div role="note" class="hatnote navigation-not-searchable">For the TV program, see <a href="The_Computer_Programme" title="The Computer Programme">The Computer Programme</a>.</div>

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</style><table class="sidebar nomobile nowraplinks"><tbody><tr><th class="sidebar-title"><a href="Execution_(computing)" title="Execution (computing)">Program execution</a></th></tr><tr><th class="sidebar-heading">

General concepts</th></tr><tr><td class="sidebar-content hlist">

<ul>

<li><a href="Translator_(computing)" title="Translator (computing)">Translation</a>

<ul><li><a href="Compiler" title="Compiler">Compiler</a></li>

<li><a href="Compile_time" title="Compile time">Compile time</a></li>

<li><a href="Optimizing_compiler" title="Optimizing compiler">Optimizing compiler</a></li></ul></li>

<li><a href="Linker_(computing)" title="Linker (computing)"> Linking</a></li>

<li><a href="Execution_(computing)" title="Execution (computing)">Execution</a>

<ul><li><a href="Runtime_system" title="Runtime system">Runtime system</a></li>

<li><a href="Executable" title="Executable">Executable</a></li>

<li><a href="Interpreter_(computing)" title="Interpreter (computing)">Interpreter</a></li>

<li><a href="Virtual_machine" title="Virtual machine">Virtual machine</a></li></ul></li>

<li><a href="Intermediate_representation" title="Intermediate representation">Intermediate representation</a> (IR)</li></ul></td>

</tr><tr><th class="sidebar-heading">

Types of code</th></tr><tr><td class="sidebar-content hlist">

<ul><li><a href="Source_code" title="Source code">Source code</a></li>

<li><a href="Object_code" title="Object code">Object code</a></li>

<li><a href="Bytecode" title="Bytecode">Bytecode</a></li>

<li><a href="Machine_code" title="Machine code">Machine code</a></li>

<li><a href="Microcode" title="Microcode">Microcode</a></li></ul></td>

</tr><tr><th class="sidebar-heading">

Compilation strategies</th></tr><tr><td class="sidebar-content hlist">

<ul><li><a href="Ahead-of-time_compilation" title="Ahead-of-time compilation">Ahead-of-time</a> (AOT)</li>

<li><a href="Just-in-time_compilation" title="Just-in-time compilation">Just-in-time</a> (JIT)

<ul><li><a href="Tracing_just-in-time_compilation" title="Tracing just-in-time compilation">Tracing just-in-time</a></li>

<li><a href="Compile_and_go_system" title="Compile and go system">Compile and go system</a></li></ul></li>

<li><a href="Precompilation" class="mw-redirect" title="Precompilation">Precompilation</a></li>

<li><a href="Source-to-source_compiler" title="Source-to-source compiler">Transcompilation</a></li>

<li><a href="Dynamic_recompilation" title="Dynamic recompilation">Recompilation</a></li></ul></td>

</tr><tr><th class="sidebar-heading">

Notable runtimes</th></tr><tr><td class="sidebar-content hlist">

<ul><li><a href="Android_Runtime" title="Android Runtime">Android Runtime</a> (ART)</li>

<li><a href="BEAM_(Erlang_virtual_machine)" title="BEAM (Erlang virtual machine)">BEAM</a> (Erlang)</li>

<li><a href="Common_Language_Runtime" title="Common Language Runtime">Common Language Runtime</a> (CLR) and <a href="Mono_(software)#Code_Execution_Engine" title="Mono (software)">Mono</a></li>

<li><a href="CPython" title="CPython">CPython</a> and <a href="PyPy" title="PyPy">PyPy</a></li>

<li><a href="Crt0" title="Crt0">crt0</a> (<a href="C_(programming_language)" title="C (programming language)">C</a> target-specific initializer)</li>

<li><a href="Java_virtual_machine" title="Java virtual machine">Java virtual machine</a> (JVM)</li>

<li><a href="LuaJIT" title="LuaJIT">LuaJIT</a></li>

<li><a href="Objective-C" title="Objective-C">Objective-C</a> and <a href="Swift_(programming_language)" title="Swift (programming language)">Swift</a>'s</li>

<li><a href="Zend_Engine" title="Zend Engine">Zend Engine</a> (PHP)</li></ul></td>

</tr><tr><th class="sidebar-heading">

Notable compilers & toolchains</th></tr><tr><td class="sidebar-content hlist">

<ul><li><a href="GNU_Compiler_Collection" title="GNU Compiler Collection">GNU Compiler Collection</a> (GCC)</li>

<li><a href="LLVM" title="LLVM">LLVM</a> and <a href="Clang" title="Clang">Clang</a></li>

<li><a href="Glasgow_Haskell_Compiler" title="Glasgow Haskell Compiler">Glasgow Haskell Compiler</a> (GHC)</li></ul></td>

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A computer program is a <a href="Sequence" title="Sequence">sequence</a> or set<a href="#cite_note-1">[a]</a> of instructions in a <a href="Programming_language" title="Programming language">programming language</a> for a <a href="Computer" title="Computer">computer</a> to <a href="Execution_(computing)" title="Execution (computing)">execute</a>. It is one component of <a href="Software" title="Software">software</a>, which also includes <a href="Software_documentation" title="Software documentation">documentation</a> and other intangible components.<a href="#cite_note-ISO_2020-2">[1]</a>

A computer program in its <a href="Human-readable" class="mw-redirect" title="Human-readable">human-readable</a> form is called <a href="Source_code" title="Source code">source code</a>. Source code needs another computer program to execute because computers can only execute their native <a href="Machine_instructions" class="mw-redirect" title="Machine instructions">machine instructions</a>. Therefore, source code may be <a href="Translator_(computing)" title="Translator (computing)">translated</a> to machine instructions using a <a href="Compiler" title="Compiler">compiler</a> written for the language. (<a href="Assembly_language" title="Assembly language">Assembly language</a> programs are translated using an <a href="Assembler_(computing)" class="mw-redirect" title="Assembler (computing)">assembler</a>.) The resulting file is called an <a href="Executable" title="Executable">executable</a>. Alternatively, source code may execute within an <a href="Interpreter_(computing)" title="Interpreter (computing)">interpreter</a> written for the language.<a href="#cite_note-cpl_3rd-ch1-7_quoted-3">[2]</a>

If the executable is requested for execution, then the <a href="Operating_system" title="Operating system">operating system</a> <a href="Loader_(computing)" title="Loader (computing)">loads</a> it into <a href="Random-access_memory" title="Random-access memory">memory</a> and starts a <a href="Process_(computing)" title="Process (computing)">process</a>.<a href="#cite_note-osc-ch4-p98-4">[3]</a> The <a href="Central_processing_unit" title="Central processing unit">central processing unit</a> will soon <a href="Context_switch" title="Context switch">switch</a> to this process so it can <a href="Instruction_cycle" title="Instruction cycle">fetch, decode, and then execute</a> each machine instruction.<a href="#cite_note-sco-ch2-p32-5">[4]</a>

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 <a href="Statement_(computer_science)" title="Statement (computer science)">statement</a>. Running the source code is slower than running an executable.<a href="#cite_note-cpl_3rd-ch1-7-6">[5]</a><a href="#cite_note-7">[b]</a> Moreover, the interpreter must be installed on the computer.

<div class="mw-heading mw-heading2"><h2 id="Example_computer_program">Example computer program</h2></div>

The <a href="%22Hello%2C_World!%22_program" title=""Hello, World!" program">"Hello, World!" program</a> is used to illustrate a language's basic syntax. The syntax of the language <a href="Dartmouth_BASIC" title="Dartmouth BASIC">BASIC</a> (1964) was intentionally limited to make the language easy to learn.<a href="#cite_note-cpl_3rd-ch2-30_quote1-8">[6]</a> For example, <a href="Variable_(computer_science)" title="Variable (computer science)">variables</a> are not <a href="Declaration_(computer_programming)" title="Declaration (computer programming)">declared</a> before being used.<a href="#cite_note-cpl_3rd-ch2-31-9">[7]</a> Also, variables are automatically initialized to zero.<a href="#cite_note-cpl_3rd-ch2-31-9">[7]</a> Here is an example computer program, in Basic, to <a href="Average" title="Average">average</a> a list of numbers:<a href="#cite_note-cpl_3rd-ch2-30-10">[8]</a>

<div class="mw-highlight mw-highlight-lang-basic mw-content-ltr" dir="ltr"><pre>10 INPUT "How many numbers to average?", A

20 FOR I = 1 TO A

30 INPUT "Enter number:", B

40 LET C = C + B

50 NEXT I

60 LET D = C/A

70 PRINT "The average is", D

80 END

</pre></div>

Once the mechanics of basic computer programming are learned, more sophisticated and powerful languages are available to build large computer systems.<a href="#cite_note-cpl_3rd-ch2-30_quote2-11">[9]</a>

<div class="mw-heading mw-heading2"><h2 id="History">History</h2></div>

<div role="note" class="hatnote navigation-not-searchable">See also: <a href="Computer_programming#History" title="Computer programming">Computer programming § History</a>, <a href="Programmer#History" title="Programmer">Programmer § History</a>, <a href="History_of_computing" title="History of computing">History of computing</a>, <a href="History_of_programming_languages" title="History of programming languages">History of programming languages</a>, and <a href="History_of_software" title="History of software">History of software</a></div>

Improvements in <a href="Software_development" title="Software development">software development</a> are the result of improvements in <a href="Computer_hardware" title="Computer hardware">computer hardware</a>. At each stage in hardware's history, the task of <a href="Computer_programming" title="Computer programming">computer programming</a> changed dramatically.

<div class="mw-heading mw-heading3"><h3 id="Analytical_Engine">Analytical Engine</h3></div>

In 1837, <a href="Jacquard_machine" title="Jacquard machine">Jacquard's loom</a> inspired <a href="Charles_Babbage" title="Charles Babbage">Charles Babbage</a> to attempt to build the <a href="Analytical_Engine" class="mw-redirect" title="Analytical Engine">Analytical Engine</a>.<a href="#cite_note-eniac-ch1-p16-12">[10]</a>

The names of the components of the calculating device were borrowed from the textile industry. In the textile industry, yarn was brought from the store to be milled. The device had a store which consisted of memory to hold 1,000 numbers of 50 decimal digits each.<a href="#cite_note-sco-ch1-p14-13">[11]</a> Numbers from the store were transferred to the mill for processing. The engine was programmed using two sets of perforated cards. One set directed the operation and the other set inputted the variables.<a href="#cite_note-eniac-ch1-p16-12">[10]</a><a href="#cite_note-14">[12]</a> However, the thousands of cogged wheels and gears never fully worked together.<a href="#cite_note-sco-ch1-p15-15">[13]</a>

<a href="Ada_Lovelace" title="Ada Lovelace">Ada Lovelace</a> worked for Charles Babbage to create a description of the Analytical Engine (1843).<a href="#cite_note-16">[14]</a> The description contained Note G which completely detailed a method for calculating <a href="Bernoulli_number" title="Bernoulli number">Bernoulli numbers</a> using the Analytical Engine. This note is recognized by some historians as the world's first computer program.<a href="#cite_note-sco-ch1-p15-15">[13]</a>

<div class="mw-heading mw-heading3"><h3 id="Universal_Turing_machine">Universal Turing machine</h3></div>

In 1936, <a href="Alan_Turing" title="Alan Turing">Alan Turing</a> introduced the <a href="Universal_Turing_machine" title="Universal Turing machine">Universal Turing machine</a>, a theoretical device that can model every computation.<a href="#cite_note-discrete-ch10-p654-17">[15]</a>

It is a <a href="Finite-state_machine" title="Finite-state machine">finite-state machine</a> that has an infinitely long read/write tape. The machine can move the tape back and forth, changing its contents as it performs an <a href="Algorithm" title="Algorithm">algorithm</a>. The machine starts in the initial state, goes through a sequence of steps, and halts when it encounters the halt state.<a href="#cite_note-formal_languages-ch9-p234-18">[16]</a> All present-day computers are <a href="Turing_complete" class="mw-redirect" title="Turing complete">Turing complete</a>.<a href="#cite_note-formal_languages-ch9-p243-19">[17]</a>

<div class="mw-heading mw-heading3"><h3 id="ENIAC">ENIAC</h3></div>

The <a href="Electronic_Numerical_Integrator_And_Computer" class="mw-redirect" title="Electronic Numerical Integrator And Computer">Electronic Numerical Integrator And Computer</a> (ENIAC) was built between July 1943 and Fall 1945. It was a Turing complete, general-purpose computer that used 17,468 <a href="Vacuum_tube" title="Vacuum tube">vacuum tubes</a> to create the <a href="Electronic_circuit" title="Electronic circuit">circuits</a>. At its core, it was a series of <a href="Pascaline" title="Pascaline">Pascalines</a> wired together.<a href="#cite_note-eniac-ch5-p102-20">[18]</a> Its 40 units weighed 30 tons, occupied 1,800 square feet (167 m2), and consumed $650 per hour (<a href="Inflation" title="Inflation">in 1940s currency</a>) in electricity when idle.<a href="#cite_note-eniac-ch5-p102-20">[18]</a> It had 20 <a href="Base-10" class="mw-redirect" title="Base-10">base-10</a> <a href="Accumulator_(computing)" title="Accumulator (computing)">accumulators</a>. Programming the ENIAC took up to two months.<a href="#cite_note-eniac-ch5-p102-20">[18]</a> Three function tables were on wheels and needed to be rolled to fixed function panels. Function tables were connected to function panels by plugging heavy black cables into <a href="Plugboard" title="Plugboard">plugboards</a>. Each function table had 728 rotating knobs. Programming the ENIAC also involved setting some of the 3,000 switches. Debugging a program took a week.<a href="#cite_note-eniac-ch5-p94-21">[19]</a> It ran from 1947 until 1955 at <a href="Aberdeen_Proving_Ground" title="Aberdeen Proving Ground">Aberdeen Proving Ground</a>, calculating hydrogen bomb parameters, predicting weather patterns, and producing firing tables to aim artillery guns.<a href="#cite_note-eniac-ch5-p107-22">[20]</a>

<div class="mw-heading mw-heading3"><h3 id="Stored-program_computers">Stored-program computers</h3></div>

Instead of plugging in cords and turning switches, a <a href="Stored-program_computer" title="Stored-program computer">stored-program computer</a> loads its instructions into <a href="Random-access_memory" title="Random-access memory">memory</a> just like it loads its data into memory.<a href="#cite_note-eniac-ch6-p120-23">[21]</a> As a result, the computer could be programmed quickly and perform calculations at very fast speeds.<a href="#cite_note-eniac-ch6-p118-24">[22]</a> <a href="Presper_Eckert" class="mw-redirect" title="Presper Eckert">Presper Eckert</a> and <a href="John_Mauchly" title="John Mauchly">John Mauchly</a> built the ENIAC. The two engineers introduced the stored-program concept in a three-page memo dated February 1944.<a href="#cite_note-eniac-ch6-p119-25">[23]</a> Later, in September 1944, <a href="John_von_Neumann" title="John von Neumann">John von Neumann</a> began working on the ENIAC project. On June 30, 1945, von Neumann published the <a href="First_Draft_of_a_Report_on_the_EDVAC" title="First Draft of a Report on the EDVAC">First Draft of a Report on the EDVAC</a>, which equated the structures of the computer with the structures of the human brain.<a href="#cite_note-eniac-ch6-p118-24">[22]</a> The design became known as the <a href="Von_Neumann_architecture" title="Von Neumann architecture">von Neumann architecture</a>. The architecture was simultaneously deployed in the constructions of the <a href="EDVAC" title="EDVAC">EDVAC</a> and <a href="EDSAC" title="EDSAC">EDSAC</a> computers in 1949.<a href="#cite_note-eniac-ch6-p123-26">[24]</a><a href="#cite_note-27">[25]</a>

The <a href="IBM_System/360" title="IBM System/360">IBM System/360</a> (1964) was a family of computers, each having the same <a href="Instruction_set_architecture" title="Instruction set architecture">instruction set architecture</a>. The <a href="IBM_System/360_Model_20" title="IBM System/360 Model 20">Model 20</a> was the smallest and least expensive. Customers could upgrade and retain the same <a href="Application_software" title="Application software">application software</a>.<a href="#cite_note-sco-ch1-p21-28">[26]</a> The <a href="IBM_System/360_Model_195" title="IBM System/360 Model 195">Model 195</a> was the most premium. Each System/360 model featured <a href="Multiprogramming" class="mw-redirect" title="Multiprogramming">multiprogramming</a><a href="#cite_note-sco-ch1-p21-28">[26]</a>—having multiple <a href="Process_(computing)" title="Process (computing)">processes</a> in <a href="Random-access_memory" title="Random-access memory">memory</a> at once. When one process was waiting for <a href="Input/output" title="Input/output">input/output</a>, another could compute.

IBM planned for each model to be programmed using <a href="PL/1" class="mw-redirect" title="PL/1">PL/1</a>.<a href="#cite_note-cpl_3rd-ch2-27-29">[27]</a> A committee was formed that included <a href="COBOL" title="COBOL">COBOL</a>, <a href="Fortran" title="Fortran">Fortran</a> and <a href="ALGOL" title="ALGOL">ALGOL</a> programmers. The purpose was to develop a language that was comprehensive, easy to use, extendible, and would replace Cobol and Fortran.<a href="#cite_note-cpl_3rd-ch2-27-29">[27]</a> The result was a large and complex language that took a long time to <a href="Compile" class="mw-redirect" title="Compile">compile</a>.<a href="#cite_note-cpl_3rd-ch2-29-30">[28]</a>

Computers manufactured until the 1970s had front-panel switches for manual programming.<a href="#cite_note-osc-ch1-p6-31">[29]</a> The computer program was written on paper for reference. An instruction was represented by a configuration of on/off settings. After setting the configuration, an execute button was pressed. This process was then repeated. Computer programs also were automatically inputted via <a href="Paper_tape" class="mw-redirect" title="Paper tape">paper tape</a>, <a href="Punched_cards" class="mw-redirect" title="Punched cards">punched cards</a> or <a href="9-track_tape" title="9-track tape">magnetic-tape</a>. After the medium was loaded, the starting address was set via switches, and the execute button was pressed.<a href="#cite_note-osc-ch1-p6-31">[29]</a>

<div class="mw-heading mw-heading3"><h3 id="Very_Large_Scale_Integration">Very Large Scale Integration</h3></div>

A major milestone in software development was the invention of the <a href="Very_Large_Scale_Integration" class="mw-redirect" title="Very Large Scale Integration">Very Large Scale Integration</a> (VLSI) circuit (1964).

<a href="Robert_Noyce" title="Robert Noyce">Robert Noyce</a>, co-founder of <a href="Fairchild_Semiconductor" title="Fairchild Semiconductor">Fairchild Semiconductor</a> (1957) and <a href="Intel" title="Intel">Intel</a> (1968), achieved a technological improvement to refine the <a href="Semiconductor_device_fabrication" title="Semiconductor device fabrication">production</a> of <a href="Field-effect_transistor" title="Field-effect transistor">field-effect transistors</a> (1963).<a href="#cite_note-digital_age-32">[30]</a> The goal is to alter the <a href="Electrical_resistivity_and_conductivity" title="Electrical resistivity and conductivity">electrical resistivity and conductivity</a> of a <a href="Semiconductor_junction" class="mw-redirect" title="Semiconductor junction">semiconductor junction</a>. First, naturally occurring <a href="Silicate_minerals" class="mw-redirect" title="Silicate minerals">silicate minerals</a> are converted into <a href="Polysilicon" class="mw-redirect" title="Polysilicon">polysilicon</a> rods using the <a href="Siemens_process" class="mw-redirect" title="Siemens process">Siemens process</a>.<a href="#cite_note-osti-33">[31]</a> The <a href="Czochralski_process" class="mw-redirect" title="Czochralski process">Czochralski process</a> then converts the rods into a <a href="Monocrystalline_silicon" title="Monocrystalline silicon">monocrystalline silicon</a>, <a href="Boule_(crystal)" title="Boule (crystal)">boule crystal</a>.<a href="#cite_note-britannica_wafer-34">[32]</a> The <a href="Crystal" title="Crystal">crystal</a> is then thinly sliced to form a <a href="Wafer_(electronics)" title="Wafer (electronics)">wafer</a> <a href="Substrate_(materials_science)" title="Substrate (materials science)">substrate</a>. The <a href="Planar_process" title="Planar process">planar process</a> of <a href="Photolithography" title="Photolithography">photolithography</a> then integrates unipolar transistors, <a href="Capacitor" title="Capacitor">capacitors</a>, <a href="Diode" title="Diode">diodes</a>, and <a href="Resistor" title="Resistor">resistors</a> onto the wafer to build a matrix of <a href="Metal%E2%80%93oxide%E2%80%93semiconductor" class="mw-redirect" title="Metal–oxide–semiconductor">metal–oxide–semiconductor</a> (MOS) transistors.<a href="#cite_note-anysilicon-35">[33]</a><a href="#cite_note-britannica_micropressor-36">[34]</a> The MOS transistor is the primary component in integrated circuit chips.<a href="#cite_note-digital_age-32">[30]</a>

Originally, <a href="Integrated_circuit" title="Integrated circuit">integrated circuit</a> chips had their function set during manufacturing. During the 1960s, controlling the electrical flow migrated to programming a <a href="Diode_matrix" title="Diode matrix">matrix</a> of <a href="Read-only_memory" title="Read-only memory">read-only memory</a> (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, <a href="Firmware" title="Firmware">firmware</a> programmers wrote a computer program on another chip to oversee the burning. The technology became known as <a href="Programmable_ROM" title="Programmable ROM">Programmable ROM</a>. In 1971, Intel installed the computer program onto the chip and named it the <a href="Intel_4004" title="Intel 4004">Intel 4004</a> <a href="Microprocessor" title="Microprocessor">microprocessor</a>.<a href="#cite_note-intel_4004-37">[35]</a>

The terms microprocessor and <a href="Central_processing_unit" title="Central processing unit">central processing unit</a> (CPU) are now used interchangeably. However, CPUs predate microprocessors. For example, the <a href="IBM_System/360" title="IBM System/360">IBM System/360</a> (1964) had a CPU made from <a href="IBM_Solid_Logic_Technology" class="mw-redirect" title="IBM Solid Logic Technology">circuit boards containing discrete components on ceramic substrates</a>.<a href="#cite_note-ibm_360-38">[36]</a>

<div class="mw-heading mw-heading3"><h3 id="x86_series">x86 series</h3></div>

In 1978, the modern software development environment began when Intel upgraded the <a href="Intel_8080" title="Intel 8080">Intel 8080</a> to the <a href="Intel_8086" title="Intel 8086">Intel 8086</a>. Intel simplified the Intel 8086 to manufacture the cheaper <a href="Intel_8088" title="Intel 8088">Intel 8088</a>.<a href="#cite_note-infoworld_8-23-82-39">[37]</a> <a href="IBM" title="IBM">IBM</a> embraced the Intel 8088 when they entered the <a href="Personal_computer" title="Personal computer">personal computer</a> market (1981). As <a href="Consumer" title="Consumer">consumer</a> <a href="Demand" title="Demand">demand</a> for personal computers increased, so did Intel's microprocessor development. The succession of development is known as the <a href="X86" title="X86">x86 series</a>. The <a href="X86_assembly_language" title="X86 assembly language">x86 assembly language</a> is a family of <a href="Backward-compatible" class="mw-redirect" title="Backward-compatible">backward-compatible</a> <a href="Machine_instruction" class="mw-redirect" title="Machine instruction">machine instructions</a>. Machine instructions created in earlier microprocessors were retained throughout microprocessor upgrades. This enabled consumers to purchase new computers without having to purchase new <a href="Application_software" title="Application software">application software</a>. The major categories of instructions are:<a href="#cite_note-40">[c]</a>

<ul><li>Memory instructions to set and access numbers and <a href="String_(computer_science)" title="String (computer science)">strings</a> in <a href="Random-access_memory" title="Random-access memory">random-access memory</a>.</li>

<li>Integer <a href="Arithmetic_logic_unit" title="Arithmetic logic unit">arithmetic logic unit</a> (ALU) instructions to perform the primary arithmetic operations on <a href="Integers" class="mw-redirect" title="Integers">integers</a>.</li>

<li>Floating point ALU instructions to perform the primary arithmetic operations on <a href="Real_number" title="Real number">real numbers</a>.</li>

<li><a href="Call_stack" title="Call stack">Call stack</a> instructions to push and pop <a href="Word_(computer_architecture)" title="Word (computer architecture)">words</a> needed to allocate memory and interface with <a href="Function_(computer_programming)" title="Function (computer programming)">functions</a>.</li>

<li><a href="Single_instruction%2C_multiple_data" title="Single instruction, multiple data">Single instruction, multiple data</a> (SIMD) instructions<a href="#cite_note-41">[d]</a> to increase speed when multiple processors are available to perform the same <a href="Algorithm" title="Algorithm">algorithm</a> on an <a href="Array_data_structure" class="mw-redirect" title="Array data structure">array of data</a>.</li></ul>

<div class="mw-heading mw-heading3"><h3 id="Changing_programming_environment">Changing programming environment</h3></div>

VLSI circuits enabled the <a href="Programming_environment" class="mw-redirect" title="Programming environment">programming environment</a> to advance from a <a href="Computer_terminal" title="Computer terminal">computer terminal</a> (until the 1990s) to a <a href="Graphical_user_interface" title="Graphical user interface">graphical user interface</a> (GUI) computer. Computer terminals limited programmers to a single <a href="Shell_(computing)" title="Shell (computing)">shell</a> running in a <a href="Command-line_interface" title="Command-line interface">command-line environment</a>. During the 1970s, full-screen source code editing became possible through a <a href="Text-based_user_interface" title="Text-based user interface">text-based user interface</a>. Regardless of the technology available, the goal is to program in a <a href="Programming_language" title="Programming language">programming language</a>.

<div class="mw-heading mw-heading2"><h2 id="Programming_paradigms_and_languages">Programming paradigms and languages</h2></div>

Programming language features exist to provide building blocks to be combined to express programming ideals.<a href="#cite_note-stroustrup-ch1-10-42">[38]</a> Ideally, a programming language should:<a href="#cite_note-stroustrup-ch1-10-42">[38]</a>

<ul><li>express ideas directly in the code.</li>

<li>express independent ideas independently.</li>

<li>express relationships among ideas directly in the code.</li>

<li>combine ideas freely.</li>

<li>combine ideas only where combinations make sense.</li>

<li>express simple ideas simply.</li></ul>

The <a href="Programming_style" title="Programming style">programming style</a> of a programming language to provide these building blocks may be categorized into <a href="Programming_paradigm" title="Programming paradigm">programming paradigms</a>.<a href="#cite_note-stroustrup-ch1-11-43">[39]</a> For example, different paradigms may differentiate:<a href="#cite_note-stroustrup-ch1-11-43">[39]</a>

<ul><li><a href="Procedural_programming" title="Procedural programming">procedural languages</a>, <a href="Functional_language" class="mw-redirect" title="Functional language">functional languages</a>, and <a href="Logic_programming" title="Logic programming">logical languages</a>.</li>

<li>different levels of <a href="Data_abstraction" class="mw-redirect" title="Data abstraction">data abstraction</a>.</li>

<li>different levels of <a href="Class_hierarchy" title="Class hierarchy">class hierarchy</a>.</li>

<li>different levels of input <a href="Datatypes" class="mw-redirect" title="Datatypes">datatypes</a>, as in <a href="Container_(abstract_data_type)" title="Container (abstract data type)">container types</a> and <a href="Generic_programming" title="Generic programming">generic programming</a>.</li></ul>

Each of these programming styles has contributed to the synthesis of different programming languages.<a href="#cite_note-stroustrup-ch1-11-43">[39]</a>

A programming language is a set of <a href="Reserved_word" title="Reserved word">keywords</a>, <a href="Character_(computing)" title="Character (computing)">symbols</a>, <a href="Identifier_(computer_languages)" title="Identifier (computer languages)">identifiers</a>, and rules by which programmers can communicate instructions to the computer.<a href="#cite_note-pis-ch4-p159-44">[40]</a> They follow a set of rules called a <a href="Syntax_(programming_languages)" title="Syntax (programming languages)">syntax</a>.<a href="#cite_note-pis-ch4-p159-44">[40]</a>

<ul><li>Keywords are reserved words to form <a href="Declaration_(computer_programming)" title="Declaration (computer programming)">declarations</a> and <a href="Statement_(computer_science)" title="Statement (computer science)">statements</a>.</li>

<li>Symbols are characters to form <a href="Operation_(mathematics)" title="Operation (mathematics)">operations</a>, <a href="Assignment_(computer_science)" title="Assignment (computer science)">assignments</a>, <a href="Control_flow" title="Control flow">control flow</a>, and <a href="Delimiter" title="Delimiter">delimiters</a>.</li>

<li>Identifiers are words created by programmers to form <a href="Constant_(computer_programming)" title="Constant (computer programming)">constants</a>, <a href="Variable_(computer_science)" title="Variable (computer science)">variable names</a>, <a href="Record_(computer_science)" title="Record (computer science)">structure names</a>, and <a href="Function_(computer_programming)" title="Function (computer programming)">function names</a>.</li>

<li>Syntax Rules are defined in the <a href="Backus%E2%80%93Naur_form" title="Backus–Naur form">Backus–Naur form</a>.</li></ul>

Programming languages get their basis from <a href="Formal_language" title="Formal language">formal languages</a>.<a href="#cite_note-fla-ch1-p2-45">[41]</a> The purpose of defining a solution in terms of its formal language is to generate an <a href="Algorithm" title="Algorithm">algorithm</a> to solve the underlining problem.<a href="#cite_note-fla-ch1-p2-45">[41]</a> An algorithm is a sequence of simple instructions that solve a problem.<a href="#cite_note-dsa-ch2-p29-46">[42]</a>

<div class="mw-heading mw-heading3"><h3 id="Generations_of_programming_language">Generations of programming language</h3></div>

<div role="note" class="hatnote navigation-not-searchable">Main article: <a href="Programming_language_generations" title="Programming language generations">Programming language generations</a></div>

The evolution of programming languages began when the <a href="EDSAC" title="EDSAC">EDSAC</a> (1949) used the first <a href="Stored-program_computer" title="Stored-program computer">stored computer program</a> in its <a href="Von_Neumann_architecture" title="Von Neumann architecture">von Neumann architecture</a>.<a href="#cite_note-sco-ch1-p17-47">[43]</a> Programming the EDSAC was in the first <a href="Programming_language_generations" title="Programming language generations">generation of programming language</a>.<a href="#cite_note-48">[44]</a>

<ul><li>The <a href="First-generation_programming_language" title="First-generation programming language">first generation of programming language</a> is <a href="Machine_language" class="mw-redirect" title="Machine language">machine language</a>.<a href="#cite_note-pis-ch4-p160-49">[45]</a> Machine language requires the programmer to enter instructions using instruction numbers called <a href="Machine_code" title="Machine code">machine code</a>. For example, the ADD operation on the <a href="PDP-11_architecture" title="PDP-11 architecture">PDP-11</a> has instruction number 24576.<a href="#cite_note-50">[e]</a><a href="#cite_note-sco-ch7-p399-51">[46]</a></li></ul>

<ul><li>The <a href="Second-generation_programming_language" title="Second-generation programming language">second generation of programming language</a> is <a href="Assembly_language" title="Assembly language">assembly language</a>.<a href="#cite_note-pis-ch4-p160-49">[45]</a> Assembly language allows the programmer to use <a href="Assembly_language#Mnemonics" title="Assembly language">mnemonic</a> <a href="Instruction_set_architecture#Instructions" title="Instruction set architecture">instructions</a> instead of remembering instruction numbers. An <a href="Assembler_(computing)" class="mw-redirect" title="Assembler (computing)">assembler</a> translates each assembly language mnemonic into its machine language number. For example, on the PDP-11, the operation 24576 can be referenced as ADD R0,R0 in the source code.<a href="#cite_note-sco-ch7-p399-51">[46]</a> The four basic arithmetic operations have assembly instructions like ADD, SUB, MUL, and DIV.<a href="#cite_note-sco-ch7-p399-51">[46]</a> Computers also have instructions like DW (Define <a href="Word_(computer_architecture)" title="Word (computer architecture)">Word</a>) to reserve <a href="Random-access_memory" title="Random-access memory">memory</a> cells. Then the MOV instruction can copy <a href="Integer" title="Integer">integers</a> between <a href="Processor_register" title="Processor register">registers</a> and memory.</li></ul>

<dl><dd><ul><li>The basic structure of an assembly language statement is a label, <a href="Operation_(mathematics)" title="Operation (mathematics)">operation</a>, <a href="Operand" title="Operand">operand</a>, and comment.<a href="#cite_note-sco-ch7-p400-52">[47]</a></li></ul>

<dl><dd><ul><li>Labels allow the programmer to work with <a href="Variable_(computer_science)" title="Variable (computer science)">variable names</a>. The assembler will later translate labels into physical <a href="Memory_address" title="Memory address">memory addresses</a>.</li>

<li>Operations allow the programmer to work with mnemonics. The assembler will later translate mnemonics into instruction numbers.</li>

<li>Operands tell the assembler which data the operation will process.</li>

<li>Comments allow the programmer to articulate a narrative because the instructions alone are vague.</li></ul></dd>

<dd>The key characteristic of an assembly language program is it forms a one-to-one mapping to its corresponding machine language target.<a href="#cite_note-sco-ch7-p398-53">[48]</a></dd></dl></dd></dl>

<ul><li>The <a href="Third-generation_programming_language" title="Third-generation programming language">third generation of programming language</a> uses <a href="Compiler" title="Compiler">compilers</a> and <a href="Interpreter_(computing)" title="Interpreter (computing)">interpreters</a> to execute computer programs. The distinguishing feature of a third generation language is its independence from particular hardware.<a href="#cite_note-cpl_3rd-ch2-26-54">[49]</a> Early languages include <a href="Fortran" title="Fortran">Fortran</a> (1958), <a href="COBOL" title="COBOL">COBOL</a> (1959), <a href="ALGOL" title="ALGOL">ALGOL</a> (1960), and <a href="BASIC" title="BASIC">BASIC</a> (1964).<a href="#cite_note-pis-ch4-p160-49">[45]</a> In 1973, the <a href="C_programming_language" class="mw-redirect" title="C programming language">C programming language</a> emerged as a <a href="High-level_language" class="mw-redirect" title="High-level language">high-level language</a> that produced efficient machine language instructions.<a href="#cite_note-cpl_3rd-ch2-37-55">[50]</a> Whereas third-generation languages historically generated many machine instructions for each statement,<a href="#cite_note-pis-ch4-p160_quote1-56">[51]</a> C has statements that may generate a single machine instruction.<a href="#cite_note-57">[f]</a> Moreover, an <a href="Optimizing_compiler" title="Optimizing compiler">optimizing compiler</a> might overrule the programmer and produce fewer machine instructions than statements. Today, an entire <a href="Programming_paradigm" title="Programming paradigm">paradigm</a> of languages fill the <a href="Imperative_programming" title="Imperative programming">imperative</a>, third generation spectrum.</li></ul>

<ul><li>The <a href="Fourth-generation_programming_language" title="Fourth-generation programming language">fourth generation of programming language</a> emphasizes what output results are desired, rather than how programming statements should be constructed.<a href="#cite_note-pis-ch4-p160-49">[45]</a> <a href="Declarative_language" class="mw-redirect" title="Declarative language">Declarative languages</a> attempt to limit <a href="Side_effect_(computer_science)" title="Side effect (computer science)">side effects</a> and allow programmers to write code with relatively few errors.<a href="#cite_note-pis-ch4-p160-49">[45]</a> One popular fourth generation language is called <a href="Structured_Query_Language" class="mw-redirect" title="Structured Query Language">Structured Query Language</a> (SQL).<a href="#cite_note-pis-ch4-p160-49">[45]</a> <a href="Database" title="Database">Database</a> developers no longer need to process each database record one at a time. Also, a simple <a href="Select_(SQL)" title="Select (SQL)">select statement</a> can generate output records without having to understand how they are retrieved.</li></ul>

<div class="mw-heading mw-heading3"><h3 id="Imperative_languages">Imperative languages</h3></div>

<div role="note" class="hatnote navigation-not-searchable">Main article: <a href="Imperative_programming" title="Imperative programming">Imperative programming</a></div>

Imperative languages specify a sequential <a href="Algorithm#Computer_algorithm" title="Algorithm">algorithm</a> using <a href="Declaration_(computer_programming)" title="Declaration (computer programming)">declarations</a>, <a href="Expression_(computer_science)" title="Expression (computer science)">expressions</a>, and <a href="Statement_(computer_science)" title="Statement (computer science)">statements</a>:<a href="#cite_note-cpl-ch4-75-58">[52]</a>

<ul><li>A declaration introduces a <a href="Variable_(programming)" class="mw-redirect" title="Variable (programming)">variable</a> name to the computer program and assigns it to a <a href="Datatype" class="mw-redirect" title="Datatype">datatype</a><a href="#cite_note-stroustrup-ch2-40-59">[53]</a> – for example: <code>var x: integer;</code></li>

<li>An expression yields a value – for example: <code>2 + 2</code> yields 4</li>

<li>A statement might <a href="Assignment_(computer_science)" title="Assignment (computer science)">assign</a> an expression to a variable or use the value of a variable to alter the program's <a href="Control_flow" title="Control flow">control flow</a> – for example: <code>x := 2 + 2; <a href="Conditional_(computer_programming)#If–then(–else)" title="Conditional (computer programming)">if</a> x = 4 then do_something();</code></li></ul>

<div class="mw-heading mw-heading4"><h4 id="Fortran">Fortran</h4></div>

<a href="FORTRAN" class="mw-redirect" title="FORTRAN">FORTRAN</a> (1958) was unveiled as "The IBM Mathematical FORmula TRANslating system". It was designed for scientific calculations, without <a href="String_(computer_science)" title="String (computer science)">string</a> handling facilities. Along with <a href="Declaration_(computer_programming)" title="Declaration (computer programming)">declarations</a>, <a href="Expression_(computer_science)" title="Expression (computer science)">expressions</a>, and <a href="Statement_(computer_science)" title="Statement (computer science)">statements</a>, it supported:

<ul><li><a href="Array_data_structure" class="mw-redirect" title="Array data structure">arrays</a>.</li>

<li><a href="Function_(computer_programming)#Jump_to_subroutine" title="Function (computer programming)">subroutines</a>.</li>

<li><a href="For_loop#1957:_FORTRAN" title="For loop">"do" loops</a>.</li></ul>

It succeeded because:

<ul><li>programming and debugging costs were below computer running costs.</li>

<li>it was supported by IBM.</li>

<li>applications at the time were scientific.<a href="#cite_note-cpl_3rd-ch2-16-60">[54]</a></li></ul>

However, non-IBM vendors also wrote Fortran compilers, but with a syntax that would likely fail IBM's compiler.<a href="#cite_note-cpl_3rd-ch2-16-60">[54]</a> The <a href="American_National_Standards_Institute" title="American National Standards Institute">American National Standards Institute</a> (ANSI) developed the first Fortran standard in 1966. In 1978, Fortran 77 became the standard until 1991. Fortran 90 supports:

<ul><li><a href="Record_(computer_science)" title="Record (computer science)">records</a>.</li>

<li><a href="Pointer_(computer_programming)" title="Pointer (computer programming)">pointers</a> to arrays.</li></ul>

<div class="mw-heading mw-heading4"><h4 id="COBOL">COBOL</h4></div>

<a href="COBOL" title="COBOL">COBOL</a> (1959) stands for "COmmon Business Oriented Language". Fortran manipulated symbols. It was soon realized that symbols did not need to be numbers, so <a href="String_(computer_science)" title="String (computer science)">strings</a> were introduced.<a href="#cite_note-cpl_3rd-ch2-24-61">[55]</a> The <a href="US_Department_of_Defense" class="mw-redirect" title="US Department of Defense">US Department of Defense</a> influenced COBOL's development, with <a href="Grace_Hopper" title="Grace Hopper">Grace Hopper</a> being a major contributor. The statements were English-like and verbose. The goal was to design a language so managers could read the programs. However, the lack of structured statements hindered this goal.<a href="#cite_note-cpl_3rd-ch2-25-62">[56]</a>

COBOL's development was tightly controlled, so dialects did not emerge to require ANSI standards. As a consequence, it was not changed for 15 years until 1974. The 1990s version did make consequential changes, like <a href="Object-oriented_programming" title="Object-oriented programming">object-oriented programming</a>.<a href="#cite_note-cpl_3rd-ch2-25-62">[56]</a>

<div class="mw-heading mw-heading4"><h4 id="Algol">Algol</h4></div>

<a href="ALGOL" title="ALGOL">ALGOL</a> (1960) stands for "ALGOrithmic Language". It had a profound influence on programming language design.<a href="#cite_note-cpl_3rd-ch2-19-63">[57]</a> Emerging from a committee of European and American programming language experts, it used standard <a href="Mathematical_notation" title="Mathematical notation">mathematical notation</a> and had a readable, structured design. Algol was first to define its syntax using the <a href="Backus%E2%80%93Naur_form" title="Backus–Naur form">Backus–Naur form</a>.<a href="#cite_note-cpl_3rd-ch2-19-63">[57]</a> This led to <a href="Syntax-directed_translation" title="Syntax-directed translation">syntax-directed</a> compilers. It added features like:

<ul><li><a href="Block_(programming)" title="Block (programming)">block structure</a>, where variables were local to their block.</li>

<li>arrays with variable bounds.</li>

<li><a href="For_loop" title="For loop">"for" loops</a>.</li>

<li><a href="Function_(computer_programming)" title="Function (computer programming)">functions</a>.</li>

<li><a href="Recursion_(computer_science)" title="Recursion (computer science)">recursion</a>.<a href="#cite_note-cpl_3rd-ch2-19-63">[57]</a></li></ul>

Algol's direct descendants include <a href="Pascal_(programming_language)" title="Pascal (programming language)">Pascal</a>, <a href="Modula-2" title="Modula-2">Modula-2</a>, <a href="Ada_(programming_language)" title="Ada (programming language)">Ada</a>, <a href="Delphi_(software)" title="Delphi (software)">Delphi</a> and <a href="Oberon_(programming_language)" title="Oberon (programming language)">Oberon</a> on one branch. On another branch the descendants include <a href="C_(programming_language)" title="C (programming language)">C</a>, <a href="C%2B%2B" title="C++">C++</a> and <a href="Java_(programming_language)" title="Java (programming language)">Java</a>.<a href="#cite_note-cpl_3rd-ch2-19-63">[57]</a>

<div class="mw-heading mw-heading4"><h4 id="Basic">Basic</h4></div>

<a href="BASIC" title="BASIC">BASIC</a> (1964) stands for "Beginner's All-Purpose Symbolic Instruction Code". It was developed at <a href="Dartmouth_College" title="Dartmouth College">Dartmouth College</a> for all of their students to learn.<a href="#cite_note-cpl_3rd-ch2-30-10">[8]</a> If a student did not go on to a more powerful language, the student would still remember Basic.<a href="#cite_note-cpl_3rd-ch2-30-10">[8]</a> A Basic interpreter was installed in the <a href="Microcomputers" class="mw-redirect" title="Microcomputers">microcomputers</a> manufactured in the late 1970s. As the microcomputer industry grew, so did the language.<a href="#cite_note-cpl_3rd-ch2-30-10">[8]</a>

Basic pioneered the <a href="Read%E2%80%93eval%E2%80%93print_loop" title="Read–eval–print loop">interactive session</a>.<a href="#cite_note-cpl_3rd-ch2-30-10">[8]</a> It offered <a href="Operating_system" title="Operating system">operating system</a> commands within its environment:

<ul><li>The 'new' command created an empty slate.</li>

<li>Statements evaluated immediately.</li>

<li>Statements could be programmed by preceding them with line numbers.<a href="#cite_note-64">[g]</a></li>

<li>The 'list' command displayed the program.</li>

<li>The 'run' command executed the program.</li></ul>

However, the Basic syntax was too simple for large programs.<a href="#cite_note-cpl_3rd-ch2-30-10">[8]</a> Recent dialects added structure and object-oriented extensions. <a href="Microsoft" title="Microsoft">Microsoft</a>'s <a href="Visual_Basic" title="Visual Basic">Visual Basic</a> is still widely used and produces a <a href="Graphical_user_interface" title="Graphical user interface">graphical user interface</a>.<a href="#cite_note-cpl_3rd-ch2-31-9">[7]</a>

<a href="C_programming_language" class="mw-redirect" title="C programming language">C programming language</a> (1973) got its name because the language <a href="BCPL" title="BCPL">BCPL</a> was replaced with <a href="B_(programming_language)" title="B (programming language)">B</a>, and <a href="AT%26T_Bell_Labs" class="mw-redirect" title="AT&T Bell Labs">AT&T Bell Labs</a> called the next version "C". Its purpose was to write the <a href="UNIX" class="mw-redirect" title="UNIX">UNIX</a> <a href="Operating_system" title="Operating system">operating system</a>.<a href="#cite_note-cpl_3rd-ch2-37-55">[50]</a> C is a relatively small language, making it easy to write compilers. Its growth mirrored the hardware growth in the 1980s.<a href="#cite_note-cpl_3rd-ch2-37-55">[50]</a> Its growth also was because it has the facilities of <a href="Assembly_language" title="Assembly language">assembly language</a>, but it uses a <a href="High-level_programming_language" title="High-level programming language">high-level syntax</a>. It added advanced features like:

<ul><li><a href="Inline_assembler" title="Inline assembler">inline assembler</a>.</li>

<li>arithmetic on pointers.</li>

<li>pointers to functions.</li>

<li>bit operations.</li>

<li>freely combining complex <a href="Operators_in_C_and_C%2B%2B" title="Operators in C and C++">operators</a>.<a href="#cite_note-cpl_3rd-ch2-37-55">[50]</a></li></ul>

C allows the programmer to control which region of memory data is to be stored. <a href="Global_variable" title="Global variable">Global variables</a> and <a href="Static_variable" title="Static variable">static variables</a> require the fewest <a href="Clock_cycle" class="mw-redirect" title="Clock cycle">clock cycles</a> to store. The <a href="Call_stack" title="Call stack">stack</a> is automatically used for the standard variable <a href="Declaration_(computer_programming)" title="Declaration (computer programming)">declarations</a>. <a href="Manual_memory_management" title="Manual memory management">Heap</a> memory is returned to a <a href="Pointer_variable" class="mw-redirect" title="Pointer variable">pointer variable</a> from the <a href="C_dynamic_memory_allocation" title="C dynamic memory allocation"><code>malloc()</code></a> function.

<ul><li>The global and static data region is located just above the program region. (The program region is technically called the text region. It is where machine instructions are stored.)</li></ul>

<dl><dd><ul><li>The global and static data region is technically two regions.<a href="#cite_note-geeksforgeeks-65">[58]</a> One region is called the initialized <a href="Data_segment" title="Data segment">data segment</a>, where variables declared with default values are stored. The other region is called the <a href=".bss" title=".bss">block started by segment</a>, where variables declared without default values are stored.</li>

<li>Variables stored in the global and static data region have their <a href="Memory_address" title="Memory address">addresses</a> set at compile time. They retain their values throughout the life of the process.</li></ul></dd></dl>

<dl><dd><ul><li>The global and static region stores the global variables that are declared on top of (outside) the <code>main()</code> function.<a href="#cite_note-cpl-ch1-p31-66">[59]</a> Global variables are visible to <code>main()</code> and every other function in the source code.</li></ul></dd></dl>

<dl><dd>On the other hand, variable declarations inside of <code>main()</code>, other functions, or within <code>{</code> <code>}</code> <a href="Block_(programming)" title="Block (programming)">block delimiters</a> are local variables. Local variables also include <a href="Formal_parameter" class="mw-redirect" title="Formal parameter">formal parameter</a> variables. Parameter variables are enclosed within the parenthesis of a function definition.<a href="#cite_note-cpl_3rd-ch6-128-67">[60]</a> Parameters provide an <a href="Interface_(computing)" title="Interface (computing)">interface</a> to the function.</dd></dl>

<dl><dd><ul><li>Local variables declared using the <code>static</code> prefix are also stored in the global and static data region.<a href="#cite_note-geeksforgeeks-65">[58]</a> Unlike global variables, static variables are only visible within the function or block. Static variables always retain their value. An example usage would be the function <code>int increment_counter(){static int counter = 0; counter++; return counter;}</code><a href="#cite_note-68">[h]</a></li></ul></dd></dl>

<ul><li>The <a href="Call_stack" title="Call stack">stack</a> region is a contiguous block of memory located near the top memory address.<a href="#cite_note-lpi-ch6-p121-69">[61]</a> Variables placed in the stack are populated from top to bottom.<a href="#cite_note-70">[i]</a><a href="#cite_note-lpi-ch6-p121-69">[61]</a> A <a href="Call_stack#STACK-POINTER" title="Call stack">stack pointer</a> is a special-purpose <a href="Processor_register" title="Processor register">register</a> that keeps track of the last memory address populated.<a href="#cite_note-lpi-ch6-p121-69">[61]</a> Variables are placed into the stack via the assembly language PUSH instruction. Therefore, the addresses of these variables are set during <a href="Runtime_(program_lifecycle_phase)" class="mw-redirect" title="Runtime (program lifecycle phase)">runtime</a>. The method for stack variables to lose their <a href="Scope_(computer_science)" title="Scope (computer science)">scope</a> is via the POP instruction.</li></ul>

<dl><dd><ul><li>Local variables declared without the <code>static</code> prefix, including formal parameter variables,<a href="#cite_note-lpi-ch6-p122-71">[62]</a> are called automatic variables<a href="#cite_note-cpl-ch1-p31-66">[59]</a> and are stored in the stack.<a href="#cite_note-geeksforgeeks-65">[58]</a> They are visible inside the function or block and lose their scope upon exiting the function or block.</li></ul></dd></dl>

<ul><li>The <a href="Manual_memory_management" title="Manual memory management">heap</a> region is located below the stack.<a href="#cite_note-geeksforgeeks-65">[58]</a> It is populated from the bottom to the top. The <a href="Operating_system" title="Operating system">operating system</a> manages the heap using a heap pointer and a list of allocated memory blocks.<a href="#cite_note-cpl-ch1-p185-72">[63]</a> Like the stack, the addresses of heap variables are set during runtime. An <a href="Out_of_memory" title="Out of memory">out of memory</a> error occurs when the heap pointer and the stack pointer meet.</li></ul>

<dl><dd><ul><li>C provides the <code>malloc()</code> library function to <a href="C_dynamic_memory_allocation" title="C dynamic memory allocation">allocate</a> heap memory.<a href="#cite_note-73">[j]</a><a href="#cite_note-cpl-ch8-p187-74">[64]</a> Populating the heap with data is an additional copy function.<a href="#cite_note-75">[k]</a> Variables stored in the heap are economically passed to functions using pointers. Without pointers, the entire block of data would have to be passed to the function via the stack.</li></ul></dd></dl>

In the 1970s, <a href="Software_engineers" class="mw-redirect" title="Software engineers">software engineers</a> needed language support to break large projects down into <a href="Modular_programming" title="Modular programming">modules</a>.<a href="#cite_note-cpl_3rd-ch2-38-76">[65]</a> One obvious feature was to decompose large projects physically into separate <a href="Computer_file" title="Computer file">files</a>. A less obvious feature was to decompose large projects logically into <a href="Abstract_data_type" title="Abstract data type">abstract data types</a>.<a href="#cite_note-cpl_3rd-ch2-38-76">[65]</a> At the time, languages supported <a href="Type_system" title="Type system">concrete (scalar)</a> datatypes like <a href="Integer" title="Integer">integer</a> numbers, <a href="Floating-point" class="mw-redirect" title="Floating-point">floating-point</a> numbers, and <a href="String_(computer_science)" title="String (computer science)">strings</a> of <a href="Character_(computing)" title="Character (computing)">characters</a>. Abstract datatypes are <a href="Record_(computer_science)" title="Record (computer science)">structures</a> of concrete datatypes, with a new name assigned. For example, a <a href="List_(abstract_data_type)" title="List (abstract data type)">list</a> of integers could be called <code>integer_list</code>.

In object-oriented jargon, abstract datatypes are called <a href="Class_(computer_programming)" title="Class (computer programming)">classes</a>. However, a class is only a definition; no memory is allocated. When memory is allocated to a class and <a href="Name_binding" title="Name binding">bound</a> to an <a href="Identifier" title="Identifier">identifier</a>, it is called an <a href="Object_(computer_science)" title="Object (computer science)">object</a>.<a href="#cite_note-cpl_3rd-ch8-193-77">[66]</a>

<a href="Object-oriented_programming" title="Object-oriented programming">Object-oriented imperative languages</a> developed by combining the need for classes and the need for safe <a href="Functional_programming" title="Functional programming">functional programming</a>.<a href="#cite_note-cpl_3rd-ch2-39-78">[67]</a> A function, in an object-oriented language, is assigned to a class. An assigned function is then referred to as a <a href="Method_(computer_programming)" title="Method (computer programming)">method</a>, <a href="Member_function" class="mw-redirect" title="Member function">member function</a>, or <a href="Operation_(mathematics)" title="Operation (mathematics)">operation</a>. Object-oriented programming is executing operations on objects.<a href="#cite_note-cpl_3rd-ch2-35-79">[68]</a>

Object-oriented languages support a syntax to model <a href="Subset" title="Subset">subset/superset</a> relationships. In <a href="Set_theory" title="Set theory">set theory</a>, an <a href="Element_(mathematics)" title="Element (mathematics)">element</a> of a subset inherits all the attributes contained in the superset. For example, a student is a person. Therefore, the set of students is a subset of the set of persons. As a result, students inherit all the attributes common to all persons. Additionally, students have unique attributes that other people do not have. Object-oriented languages model subset/superset relationships using <a href="Inheritance_(object-oriented_programming)" title="Inheritance (object-oriented programming)">inheritance</a>.<a href="#cite_note-cpl_3rd-ch8-192-80">[69]</a> Object-oriented programming became the dominant language paradigm by the late 1990s.<a href="#cite_note-cpl_3rd-ch2-38-76">[65]</a>

<a href="C%2B%2B" title="C++">C++</a> (1985) was originally called "C with Classes".<a href="#cite_note-stroustrup-notes-22-81">[70]</a> It was designed to expand <a href="C_(programming_language)" title="C (programming language)">C's</a> capabilities by adding the object-oriented facilities of the language <a href="Simula" title="Simula">Simula</a>.<a href="#cite_note-stroustrup-notes-21-82">[71]</a>

An object-oriented module is composed of two files. The definitions file is called the <a href="Header_file" class="mw-redirect" title="Header file">header file</a>. Here is a C++ header file for the GRADE class in a simple school application:

<div class="mw-highlight mw-highlight-lang-cpp mw-content-ltr" dir="ltr"><pre>// grade.h

// -------

// Used to allow multiple source files to include

// this header file without duplication errors.

// ----------------------------------------------

#ifndef GRADE_H

#define GRADE_H

class GRADE {

public:

// This is the constructor operation.

// ----------------------------------

GRADE ( const char letter );

// This is a class variable.

// -------------------------

char letter;

// This is a member operation.

// ---------------------------

int grade_numeric( const char letter );

// This is a class variable.

// -------------------------

int numeric;

};

#endif

</pre></div>

A <a href="Constructor_(object-oriented_programming)" title="Constructor (object-oriented programming)">constructor</a> operation is a function with the same name as the class name.<a href="#cite_note-stroustrup-ch2-49-83">[72]</a> It is executed when the calling operation executes the <code><a href="New_and_delete_(C%2B%2B)" title="New and delete (C++)">new</a></code> statement.

A module's other file is the <a href="Source_file" class="mw-redirect" title="Source file">source file</a>. Here is a C++ source file for the GRADE class in a simple school application:

<div class="mw-highlight mw-highlight-lang-cpp mw-content-ltr" dir="ltr"><pre>// grade.cpp

// ---------

#include "grade.h"

GRADE::GRADE( const char letter )

{

// Reference the object using the keyword 'this'.

// ----------------------------------------------

this->letter = letter;

// This is Temporal Cohesion

// -------------------------

this->numeric = grade_numeric( letter );

}

int GRADE::grade_numeric( const char letter )

{

if ( ( letter == 'A' || letter == 'a' ) )

return 4;

else

if ( ( letter == 'B' || letter == 'b' ) )

return 3;

else

if ( ( letter == 'C' || letter == 'c' ) )

return 2;

else

if ( ( letter == 'D' || letter == 'd' ) )

return 1;

else

if ( ( letter == 'F' || letter == 'f' ) )

return 0;

else

return -1;

}

</pre></div>

Here is a C++ header file for the PERSON class in a simple school application:

<div class="mw-highlight mw-highlight-lang-cpp mw-content-ltr" dir="ltr"><pre>// person.h

// --------

#ifndef PERSON_H

#define PERSON_H

class PERSON {

public:

PERSON ( const char *name );

const char *name;

};

#endif

</pre></div>

Here is a C++ source file for the PERSON class in a simple school application:

<div class="mw-highlight mw-highlight-lang-cpp mw-content-ltr" dir="ltr"><pre>// person.cpp

// ----------

#include "person.h"

PERSON::PERSON ( const char *name )

{

this->name = name;

}

</pre></div>

Here is a C++ header file for the STUDENT class in a simple school application:

<div class="mw-highlight mw-highlight-lang-cpp mw-content-ltr" dir="ltr"><pre>// student.h

// ---------

#ifndef STUDENT_H

#define STUDENT_H

#include "person.h"

#include "grade.h"

// A STUDENT is a subset of PERSON.

// --------------------------------

class STUDENT : public PERSON{

public:

STUDENT ( const char *name );

GRADE *grade;

};

#endif

</pre></div>

Here is a C++ source file for the STUDENT class in a simple school application:

<div class="mw-highlight mw-highlight-lang-cpp mw-content-ltr" dir="ltr"><pre>// student.cpp

// -----------

#include "student.h"

#include "person.h"

STUDENT::STUDENT ( const char *name ):

// Execute the constructor of the PERSON superclass.

// -------------------------------------------------

PERSON( name )

{

// Nothing else to do.

// -------------------

}

</pre></div>

Here is a driver program for demonstration:

<div class="mw-highlight mw-highlight-lang-cpp mw-content-ltr" dir="ltr"><pre>// student_dvr.cpp

// ---------------

#include <iostream>

#include "student.h"

int main( void )

{

STUDENT *student = new STUDENT( "The Student" );

student->grade = new GRADE( 'a' );

std::cout

// Notice student inherits PERSON's name

<< student->name

<< ": Numeric grade = "

<< student->grade->numeric

<< "\n";

return 0;

}

</pre></div>

Here is a <a href="Makefile" class="mw-redirect" title="Makefile">makefile</a> to compile everything:

<div class="mw-highlight mw-highlight-lang-make mw-content-ltr" dir="ltr"><pre># makefile

# --------

all: student_dvr

clean:

rm student_dvr *.o

student_dvr: student_dvr.cpp grade.o student.o person.o

c++ student_dvr.cpp grade.o student.o person.o -o student_dvr

grade.o: grade.cpp grade.h

c++ -c grade.cpp

student.o: student.cpp student.h

c++ -c student.cpp

person.o: person.cpp person.h

c++ -c person.cpp

</pre></div>

<div class="mw-heading mw-heading3"><h3 id="Declarative_languages">Declarative languages</h3></div>

<div role="note" class="hatnote navigation-not-searchable">Main article: <a href="Declarative_programming" title="Declarative programming">Declarative programming</a></div>

Imperative languages have one major criticism: assigning an expression to a non-local variable may produce an unintended <a href="Side_effect_(computer_science)" title="Side effect (computer science)">side effect</a>.<a href="#cite_note-cpl_3rd-ch9-218-84">[73]</a> <a href="Declarative_language" class="mw-redirect" title="Declarative language">Declarative languages</a> generally omit the assignment statement and the control flow. They describe what computation should be performed and not how to compute it. Two broad categories of declarative languages are <a href="Functional_language" class="mw-redirect" title="Functional language">functional languages</a> and <a href="Logic_programming" title="Logic programming">logical languages</a>.

The principle behind a functional language is to use <a href="Lambda_calculus" title="Lambda calculus">lambda calculus</a> as a guide for a well defined <a href="Semantics_(computer_science)" title="Semantics (computer science)">semantic</a>.<a href="#cite_note-cpl_3rd-ch9-217-85">[74]</a> In mathematics, a function is a rule that maps elements from an expression to a range of values. Consider the function:

<code>times_10(x) = 10 * x</code>

The expression <code>10 * x</code> is mapped by the function <code>times_10()</code> to a range of values. One value happens to be 20. This occurs when x is 2. So, the application of the function is mathematically written as:

<code>times_10(2) = 20</code>

A functional language compiler will not store this value in a variable. Instead, it will push the value onto the computer's <a href="Call_stack" title="Call stack">stack</a> before setting the <a href="Program_counter" title="Program counter">program counter</a> back to the calling function. The calling function will then pop the value from the stack.<a href="#cite_note-dsa-ch3-p103-86">[75]</a>

Imperative languages do support functions. Therefore, functional programming can be achieved in an imperative language, if the programmer uses discipline. However, a functional language will force this discipline onto the programmer through its syntax. Functional languages have a syntax tailored to emphasize the what.<a href="#cite_note-cpl_3rd-ch9-230-87">[76]</a>

A functional program is developed with a set of primitive functions followed by a single driver function.<a href="#cite_note-cpl_3rd-ch9-218-84">[73]</a> Consider the <a href="Snippet_(programming)" title="Snippet (programming)">snippet</a>:

<code>function max( a, b ){/* code omitted */}</code>

<code>function min( a, b ){/* code omitted */}</code>

<code>function range( a, b, c ) {</code>

<dl><dd><code>return max( a, max( b, c ) ) - min( a, min( b, c ) );</code></dd></dl>

The primitives are <code>max()</code> and <code>min()</code>. The driver function is <code>range()</code>. Executing:

<code>put( range( 10, 4, 7) );</code> will output 6.

Functional languages are used in <a href="Computer_science" title="Computer science">computer science</a> research to explore new language features.<a href="#cite_note-cpl_3rd-ch9-240-88">[77]</a> Moreover, their lack of side-effects have made them popular in <a href="Parallel_programming" class="mw-redirect" title="Parallel programming">parallel programming</a> and <a href="Concurrent_programming" class="mw-redirect" title="Concurrent programming">concurrent programming</a>.<a href="#cite_note-cpl_3rd-ch9-241-89">[78]</a> However, application developers prefer the <a href="Object-oriented_programming" title="Object-oriented programming">object-oriented features</a> of imperative languages.<a href="#cite_note-cpl_3rd-ch9-241-89">[78]</a>

<a href="Lisp_(programming_language)" title="Lisp (programming language)">Lisp</a> (1958) stands for "LISt Processor".<a href="#cite_note-ArtOfLisp-90">[79]</a> It is tailored to process <a href="List_(abstract_data_type)" title="List (abstract data type)">lists</a>. A full structure of the data is formed by building lists of lists. In memory, a <a href="Tree_data_structure" class="mw-redirect" title="Tree data structure">tree data structure</a> is built. Internally, the tree structure lends nicely for <a href="Recursion_(computer_science)" title="Recursion (computer science)">recursive</a> functions.<a href="#cite_note-cpl_3rd-ch9-220-91">[80]</a> The syntax to build a tree is to enclose the space-separated <a href="Element_(mathematics)" title="Element (mathematics)">elements</a> within parenthesis. The following is a <a href="List" title="List">list</a> of three elements. The first two elements are themselves lists of two elements:

<code>((A B) (HELLO WORLD) 94)</code>

Lisp has functions to extract and reconstruct elements.<a href="#cite_note-cpl_3rd-ch9-221-92">[81]</a> The function <code>head()</code> returns a list containing the first element in the list. The function <code>tail()</code> returns a list containing everything but the first element. The function <code>cons()</code> returns a list that is the concatenation of other lists. Therefore, the following expression will return the list <code>x</code>:

One drawback of Lisp is when many functions are nested, the parentheses may look confusing.<a href="#cite_note-cpl_3rd-ch9-230-87">[76]</a> Modern Lisp <a href="Integrated_development_environment" title="Integrated development environment">environments</a> help ensure parenthesis match. As an aside, Lisp does support the imperative language operations of the assignment statement and goto loops.<a href="#cite_note-cpl_3rd-ch9-229-93">[82]</a> Also, Lisp is not concerned with the <a href="Datatype" class="mw-redirect" title="Datatype">datatype</a> of the elements at compile time.<a href="#cite_note-cpl_3rd-ch9-227-94">[83]</a> Instead, it assigns (and may reassign) the datatypes at <a href="Runtime_(program_lifecycle_phase)" class="mw-redirect" title="Runtime (program lifecycle phase)">runtime</a>. Assigning the datatype at runtime is called <a href="Name_binding#Binding_time" title="Name binding">dynamic binding</a>.<a href="#cite_note-cpl_3rd-ch9-222-95">[84]</a> Whereas dynamic binding increases the language's flexibility, programming errors may linger until late in the <a href="Software_development_process" title="Software development process">software development process</a>.<a href="#cite_note-cpl_3rd-ch9-222-95">[84]</a>

Writing large, reliable, and readable Lisp programs requires forethought. If properly planned, the program may be much shorter than an equivalent imperative language program.<a href="#cite_note-cpl_3rd-ch9-230-87">[76]</a> Lisp is widely used in <a href="Artificial_intelligence" title="Artificial intelligence">artificial intelligence</a>. However, its usage has been accepted only because it has imperative language operations, making unintended side-effects possible.<a href="#cite_note-cpl_3rd-ch9-241-89">[78]</a>

<a href="ML_(programming_language)" title="ML (programming language)">ML</a> (1973)<a href="#cite_note-Gordon1996-96">[85]</a> stands for "Meta Language". ML checks to make sure only data of the same type are compared with one another.<a href="#cite_note-cpl_3rd-ch9-233-97">[86]</a> For example, this function has one input parameter (an integer) and returns an integer:

<div class="mw-highlight mw-highlight-lang-sml mw-content-ltr" dir="ltr"><pre>fun times_10(n : int) : int = 10 * n;

</pre></div>

ML is not parenthesis-eccentric like Lisp. The following is an application of <code>times_10()</code>:

<pre>times_10 2

</pre>

It returns "20 : int". (Both the results and the datatype are returned.)

Like Lisp, ML is tailored to process lists. Unlike Lisp, each element is the same datatype.<a href="#cite_note-cpl_3rd-ch9-235-98">[87]</a> Moreover, ML assigns the datatype of an element at <a href="Compile_time" title="Compile time">compile time</a>. Assigning the datatype at compile time is called <a href="Name_binding#Binding_time" title="Name binding">static binding</a>. Static binding increases reliability because the compiler checks the context of variables before they are used.<a href="#cite_note-cpl_3rd-ch3-55-99">[88]</a>

<div class="mw-heading mw-heading4"><h4 id="Prolog">Prolog</h4></div>

<a href="Prolog" title="Prolog">Prolog</a> (1972) stands for "PROgramming in LOGic". It is a <a href="Logic_programming" title="Logic programming">logic programming</a> language, based on formal <a href="Logic" title="Logic">logic</a>. The language was developed by <a href="Alain_Colmerauer" title="Alain Colmerauer">Alain Colmerauer</a> and Philippe Roussel in Marseille, France. It is an implementation of <a href="SLD_resolution" title="SLD resolution">Selective Linear Definite clause resolution</a>, pioneered by <a href="Robert_Kowalski" title="Robert Kowalski">Robert Kowalski</a> and others at the <a href="University_of_Edinburgh" title="University of Edinburgh">University of Edinburgh</a>.<a href="#cite_note-100">[89]</a>

The building blocks of a Prolog program are facts and rules. Here is a simple example:

<div class="mw-highlight mw-highlight-lang-prolog mw-content-ltr" dir="ltr"><pre>cat(tom). % tom is a cat

mouse(jerry). % jerry is a mouse

animal(X) :- cat(X). % each cat is an animal

animal(X) :- mouse(X). % each mouse is an animal

big(X) :- cat(X). % each cat is big

small(X) :- mouse(X). % each mouse is small

eat(X,Y) :- mouse(X), cheese(Y). % each mouse eats each cheese

eat(X,Y) :- big(X), small(Y). % each big animal eats each small animal

</pre></div>

After all the facts and rules are entered, then a question can be asked:

<dl><dd>Will Tom eat Jerry?</dd></dl>

<div class="mw-highlight mw-highlight-lang-prolog mw-content-ltr" dir="ltr"><pre>?- eat(tom,jerry).

true

</pre></div>

The following example shows how Prolog will convert a letter grade to its numeric value:

<div class="mw-highlight mw-highlight-lang-prolog mw-content-ltr" dir="ltr"><pre>numeric_grade('A', 4).

numeric_grade('B', 3).

numeric_grade('C', 2).

numeric_grade('D', 1).

numeric_grade('F', 0).

numeric_grade(X, -1) :- not X = 'A', not X = 'B', not X = 'C', not X = 'D', not X = 'F'.

grade('The Student', 'A').

</pre></div>

<div class="mw-highlight mw-highlight-lang-prolog mw-content-ltr" dir="ltr"><pre>?- grade('The Student', X), numeric_grade(X, Y).

X = 'A',

Y = 4

</pre></div>

Here is a comprehensive example:<a href="#cite_note-Logical_English-101">[90]</a>

1) All dragons billow fire, or equivalently, a thing billows fire if the thing is a dragon:

<div class="mw-highlight mw-highlight-lang-prolog mw-content-ltr" dir="ltr"><pre>billows_fire(X) :-

is_a_dragon(X).

</pre></div>

2) A creature billows fire if one of its parents billows fire:

is_a_creature(X),

is_a_parent_of(Y,X),

billows_fire(Y).

</pre></div>

3) A thing X is a parent of a thing Y if X is the mother of Y or X is the father of Y:

<div class="mw-highlight mw-highlight-lang-prolog mw-content-ltr" dir="ltr"><pre>is_a_parent_of(X, Y):- is_the_mother_of(X, Y).

is_a_parent_of(X, Y):- is_the_father_of(X, Y).

</pre></div>

4) A thing is a creature if the thing is a dragon:

<div class="mw-highlight mw-highlight-lang-prolog mw-content-ltr" dir="ltr"><pre>is_a_creature(X) :-

is_a_dragon(X).

</pre></div>

5) Norberta is a dragon, and Puff is a creature. Norberta is the mother of Puff.

<div class="mw-highlight mw-highlight-lang-prolog mw-content-ltr" dir="ltr"><pre>is_a_dragon(norberta).

is_a_creature(puff).

is_the_mother_of(norberta, puff).

</pre></div>

Rule (2) is a <a href="Recursion_(computer_science)" title="Recursion (computer science)">recursive</a> (inductive) definition. It can be understood declaratively, without the need to understand how it is executed.

Rule (3) shows how <a href="Function_(computer_programming)" title="Function (computer programming)">functions</a> are represented by using relations. Here, the mother and father functions ensure that every individual has only one mother and only one father.

Prolog is an untyped language. Nonetheless, <a href="Inheritance_(object-oriented_programming)" title="Inheritance (object-oriented programming)">inheritance</a> can be represented by using predicates. Rule (4) asserts that a creature is a superclass of a dragon.

Questions are answered using <a href="Backward_reasoning" class="mw-redirect" title="Backward reasoning">backward reasoning</a>. Given the question:

<div class="mw-highlight mw-highlight-lang-prolog mw-content-ltr" dir="ltr"><pre> ?- billows_fire(X).

</pre></div>

Prolog generates two answers :

<div class="mw-highlight mw-highlight-lang-prolog mw-content-ltr" dir="ltr"><pre>X = norberta

X = puff

</pre></div>

Practical applications for Prolog are <a href="Knowledge_representation" class="mw-redirect" title="Knowledge representation">knowledge representation</a> and <a href="Problem_solving" title="Problem solving">problem solving</a> in <a href="Artificial_intelligence" title="Artificial intelligence">artificial intelligence</a>.

<div class="mw-heading mw-heading3"><h3 id="Object-oriented_programming">Object-oriented programming</h3></div>

<a href="Object-oriented_programming" title="Object-oriented programming">Object-oriented programming</a> is a programming method to execute <a href="Method_(computer_programming)" title="Method (computer programming)">operations</a> (<a href="Function_(computer_programming)" title="Function (computer programming)">functions</a>) on <a href="Object_(computer_science)" title="Object (computer science)">objects</a>.<a href="#cite_note-cpl_3rd-ch2-35_quote1-102">[91]</a> The basic idea is to group the characteristics of a <a href="Phenomenon" title="Phenomenon">phenomenon</a> into an object <a href="Record_(computer_science)" title="Record (computer science)">container</a> and give the container a name. The operations on the phenomenon are also grouped into the container.<a href="#cite_note-cpl_3rd-ch2-35_quote1-102">[91]</a> Object-oriented programming developed by combining the need for containers and the need for safe <a href="Functional_programming" title="Functional programming">functional programming</a>.<a href="#cite_note-cpl_3rd-ch2-39_quote1-103">[92]</a> This programming method need not be confined to an object-oriented language.<a href="#cite_note-se-ch9-284_quote1-104">[93]</a> In an object-oriented language, an object container is called a <a href="Class_(computer_programming)" title="Class (computer programming)">class</a>. In a non-object-oriented language, a <a href="Data_structure" title="Data structure">data structure</a> (which is also known as a <a href="Record_(computer_science)" title="Record (computer science)">record</a>) may become an object container. To turn a data structure into an object container, operations need to be written specifically for the structure. The resulting structure is called an <a href="Abstract_datatype" class="mw-redirect" title="Abstract datatype">abstract datatype</a>.<a href="#cite_note-dsa-ch3-p57-105">[94]</a> However, <a href="Inheritance_(object-oriented_programming)" title="Inheritance (object-oriented programming)">inheritance</a> will be missing. Nonetheless, this shortcoming can be overcome.

Here is a <a href="C_programming_language" class="mw-redirect" title="C programming language">C programming language</a> header file for the GRADE abstract datatype in a simple school application:

<div class="mw-highlight mw-highlight-lang-c mw-content-ltr" dir="ltr"><pre>/* grade.h */

/* ------- */

/* Used to allow multiple source files to include */

/* this header file without duplication errors. */

/* ---------------------------------------------- */

#ifndef GRADE_H

#define GRADE_H

typedef struct

{

char letter;

} GRADE;

/* Constructor */

/* ----------- */

GRADE *grade_new( char letter );

int grade_numeric( char letter );

#endif

</pre></div>

The <code>grade_new()</code> function performs the same algorithm as the C++ <a href="Constructor_(object-oriented_programming)" title="Constructor (object-oriented programming)">constructor</a> operation.

Here is a C programming language <a href="Source_file" class="mw-redirect" title="Source file">source file</a> for the GRADE abstract datatype in a simple school application:

<div class="mw-highlight mw-highlight-lang-c mw-content-ltr" dir="ltr"><pre>/* grade.c */

/* ------- */

#include "grade.h"

{

GRADE *grade;

/* Allocate heap memory */

/* -------------------- */

if ( ! ( grade = calloc( 1, sizeof ( GRADE ) ) ) )

{

fprintf(stderr,

"ERROR in %s/%s/%d: calloc() returned empty.\n",

__FILE__,

__FUNCTION__,

__LINE__ );

exit( 1 );

}

grade->letter = letter;

return grade;

}

{

return 4;

else

if ( ( letter == 'B' || letter == 'b' ) )

return 3;

else

if ( ( letter == 'C' || letter == 'c' ) )

return 2;

else

if ( ( letter == 'D' || letter == 'd' ) )

return 1;

else

if ( ( letter == 'F' || letter == 'f' ) )

return 0;

else

return -1;

}

</pre></div>

In the constructor, the function <code>calloc()</code> is used instead of <code>malloc()</code> because each memory cell will be set to zero.

Here is a C programming language header file for the PERSON abstract datatype in a simple school application:

<div class="mw-highlight mw-highlight-lang-cpp mw-content-ltr" dir="ltr"><pre>/* person.h */

/* -------- */

#ifndef PERSON_H

#define PERSON_H

typedef struct

{

char *name;

} PERSON;

/* Constructor */

/* ----------- */

PERSON *person_new( char *name );

#endif

</pre></div>

Here is a C programming language source file for the PERSON abstract datatype in a simple school application:

<div class="mw-highlight mw-highlight-lang-cpp mw-content-ltr" dir="ltr"><pre>/* person.c */

/* -------- */

#include "person.h"

{

PERSON *person;

if ( ! ( person = calloc( 1, sizeof ( PERSON ) ) ) )

{

fprintf(stderr,

"ERROR in %s/%s/%d: calloc() returned empty.\n",

__FILE__,

__FUNCTION__,

__LINE__ );

exit( 1 );

}

person->name = name;

return person;

}

</pre></div>

Here is a C programming language header file for the STUDENT abstract datatype in a simple school application:

<div class="mw-highlight mw-highlight-lang-c mw-content-ltr" dir="ltr"><pre>/* student.h */

/* --------- */

#ifndef STUDENT_H

#define STUDENT_H

#include "person.h"

#include "grade.h"

typedef struct

{

/* A STUDENT is a subset of PERSON. */

/* -------------------------------- */

PERSON *person;

GRADE *grade;

} STUDENT;

/* Constructor */

/* ----------- */

STUDENT *student_new( char *name );

#endif

</pre></div>

Here is a C programming language source file for the STUDENT abstract datatype in a simple school application:

<div class="mw-highlight mw-highlight-lang-cpp mw-content-ltr" dir="ltr"><pre>/* student.c */

/* --------- */

#include "student.h"

#include "person.h"

{

STUDENT *student;

if ( ! ( student = calloc( 1, sizeof ( STUDENT ) ) ) )

{

fprintf(stderr,

"ERROR in %s/%s/%d: calloc() returned empty.\n",

__FILE__,

__FUNCTION__,

__LINE__ );

exit( 1 );

}

/* Execute the constructor of the PERSON superclass. */

/* ------------------------------------------------- */

student->person = person_new( name );

return student;

}

</pre></div>

Here is a driver program for demonstration:

<div class="mw-highlight mw-highlight-lang-c mw-content-ltr" dir="ltr"><pre>/* student_dvr.c */

/* ------------- */

#include <stdio.h>

#include "student.h"

{

STUDENT *student = student_new( "The Student" );

student->grade = grade_new( 'a' );

printf( "%s: Numeric grade = %d\n",

/* Whereas a subset exists, inheritance does not. */

student->person->name,

/* Functional programming is executing functions just-in-time (JIT) */

grade_numeric( student->grade->letter ) );

return 0;

}

</pre></div>

Here is a <a href="Makefile" class="mw-redirect" title="Makefile">makefile</a> to compile everything:

<div class="mw-highlight mw-highlight-lang-make mw-content-ltr" dir="ltr"><pre># makefile

# --------

all: student_dvr

clean:

rm student_dvr *.o

student_dvr: student_dvr.c grade.o student.o person.o

gcc student_dvr.c grade.o student.o person.o -o student_dvr

grade.o: grade.c grade.h

gcc -c grade.c

student.o: student.c student.h

gcc -c student.c

person.o: person.c person.h

gcc -c person.c

</pre></div>

The formal strategy to build object-oriented objects is to:<a href="#cite_note-se-ch9-285-106">[95]</a>

<ul><li>Identify the objects. Most likely these will be nouns.</li>

<li>Identify each object's attributes. What helps to describe the object?</li>

<li>Identify each object's actions. Most likely these will be verbs.</li>

<li>Identify the relationships from object to object. Most likely these will be verbs.</li></ul>

For example:

<ul><li>A person is a human identified by a name.</li>

<li>A grade is an achievement identified by a letter.</li>

<li>A student is a person who earns a grade.</li></ul>

<div class="mw-heading mw-heading3"><h3 id="Syntax_and_semantics">Syntax and semantics</h3></div>

The <a href="Syntax_(programming_languages)" title="Syntax (programming languages)">syntax</a> of a computer program is a <a href="List" title="List">list</a> of <a href="Production_(computer_science)" title="Production (computer science)">production rules</a> which form its <a href="Formal_grammar" title="Formal grammar">grammar</a>.<a href="#cite_note-cpl_3rd-ch12-290_quote-107">[96]</a> A programming language's grammar correctly places its <a href="Declaration_(computer_programming)" title="Declaration (computer programming)">declarations</a>, <a href="Expression_(computer_science)" title="Expression (computer science)">expressions</a>, and <a href="Statement_(computer_science)" title="Statement (computer science)">statements</a>.<a href="#cite_note-cpl_3rd-ch4-78_quote1-108">[97]</a> Complementing the syntax of a language are its <a href="Semantics_(computer_science)" title="Semantics (computer science)">semantics</a>. The semantics describe the meanings attached to various syntactic constructs.<a href="#cite_note-cpl_3rd-ch12-290-109">[98]</a> A syntactic construct may need a semantic description because a production rule may have an invalid interpretation.<a href="#cite_note-cpl_3rd-ch12-294-110">[99]</a> Also, different languages might have the same syntax; however, their behaviors may be different.

The syntax of a language is formally described by listing the production rules. Whereas the syntax of a <a href="Natural_language" title="Natural language">natural language</a> is extremely complicated, a subset of the English language can have this production rule listing:<a href="#cite_note-discrete-ch10-p615-111">[100]</a>

<ol><li>a sentence is made up of a noun-phrase followed by a verb-phrase;</li>

<li>a noun-phrase is made up of an article followed by an adjective followed by a noun;</li>

<li>a verb-phrase is made up of a verb followed by a noun-phrase;</li>

<li>an article is 'the';</li>

<li>an adjective is 'big' or</li>

<li>an adjective is 'small';</li>

<li>a noun is 'mouse';</li>

The words in bold-face are known as non-terminals. The words in 'single quotes' are known as terminals.<a href="#cite_note-cpl_3rd-ch12-291-112">[101]</a>

From this production rule listing, complete sentences may be formed using a series of replacements.<a href="#cite_note-discrete-ch10-p616-113">[102]</a> The process is to replace non-terminals with either a valid non-terminal or a valid terminal. The replacement process repeats until only terminals remain. One valid sentence is:

<ul><li>sentence</li>

<li>noun-phrase verb-phrase</li>

<li>article adjective noun verb-phrase</li>

<li>the adjective noun verb-phrase</li>

<li>the big noun verb-phrase</li>

<li>the big cat verb-phrase</li>

<li>the big cat verb noun-phrase</li>

<li>the big cat eats noun-phrase</li>

<li>the big cat eats article adjective noun</li>

<li>the big cat eats the adjective noun</li>

<li>the big cat eats the small noun</li>

<li>the big cat eats the small mouse</li></ul>

However, another combination results in an invalid sentence:

<ul><li>the small mouse eats the big cat</li></ul>

Therefore, a semantic is necessary to correctly describe the meaning of an eat activity.

One production rule listing method is called the <a href="Backus%E2%80%93Naur_form" title="Backus–Naur form">Backus–Naur form</a> (BNF).<a href="#cite_note-discrete-ch10-p623-114">[103]</a> BNF describes the syntax of a language and itself has a syntax. This recursive definition is an example of a <a href="Metalanguage" title="Metalanguage">metalanguage</a>.<a href="#cite_note-cpl_3rd-ch12-290-109">[98]</a> The syntax of BNF includes:

<ul><li><code>::=</code> which translates to is made up of a[n] when a non-terminal is to its right. It translates to is when a terminal is to its right.</li>

<li><code>|</code> which translates to or.</li>

<li><code><</code> and <code>></code> which surround non-terminals.</li></ul>

Using BNF, a subset of the English language can have this production rule listing:

<noun-phrase> ::= <article><adjective><noun>

<verb-phrase> ::= <verb><noun-phrase>

<article> ::= the

<adjective> ::= big | small

<noun> ::= cat | mouse

<verb> ::= eats

</pre></div>

Using BNF, a signed-<a href="Integer_(computer_science)" title="Integer (computer science)">integer</a> has the production rule listing:<a href="#cite_note-discrete-ch10-p624-115">[104]</a>

<sign> ::= + | -

<digit> ::= 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9

</pre></div>

Notice the recursive production rule:

</pre></div>

This allows for an infinite number of possibilities. Therefore, a semantic is necessary to describe a limitation of the number of digits.

Notice the leading zero possibility in the production rules:

<digit> ::= 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9

</pre></div>

Therefore, a semantic is necessary to describe that leading zeros need to be ignored.

Two formal methods are available to describe semantics. They are <a href="Denotational_semantics" title="Denotational semantics">denotational semantics</a> and <a href="Axiomatic_semantics" title="Axiomatic semantics">axiomatic semantics</a>.<a href="#cite_note-cpl_3rd-ch12-297-116">[105]</a>

<div class="mw-heading mw-heading2"><h2 id="Software_engineering_and_computer_programming">Software engineering and computer programming</h2></div>

<a href="Software_engineering" title="Software engineering">Software engineering</a> is a variety of techniques to produce <a href="Software_quality" title="Software quality">quality</a> computer programs.<a href="#cite_note-se-preface1-117">[106]</a> <a href="Computer_programming" title="Computer programming">Computer programming</a> is the process of writing or editing <a href="Source_code" title="Source code">source code</a>. In a formal environment, a <a href="Systems_analyst" title="Systems analyst">systems analyst</a> will gather information from managers about all the organization's processes to automate. This professional then prepares a <a href="Functional_requirement" title="Functional requirement">detailed plan</a> for the new or modified system.<a href="#cite_note-pis-ch12-p507-118">[107]</a> The plan is analogous to an architect's blueprint.<a href="#cite_note-pis-ch12-p507-118">[107]</a>

<div class="mw-heading mw-heading3"><h3 id="Performance_objectives">Performance objectives</h3></div>

The systems analyst has the objective to deliver the right information to the right person at the right time.<a href="#cite_note-pis-ch12-p513-119">[108]</a> The critical factors to achieve this objective are:<a href="#cite_note-pis-ch12-p513-119">[108]</a>

<ol><li>The quality of the output. Is the output useful for decision-making?</li>

<li>The accuracy of the output. Does it reflect the true situation?</li>

<li>The format of the output. Is the output easily understood?</li>

<li>The speed of the output. Time-sensitive information is important when communicating with the customer in real time.</li></ol>

<div class="mw-heading mw-heading3"><h3 id="Cost_objectives">Cost objectives</h3></div>

Achieving performance objectives should be balanced with all of the costs, including:<a href="#cite_note-pis-ch12-p514-120">[109]</a>

<ol><li>Development costs.</li>

<li>Uniqueness costs. A reusable system may be expensive. However, it might be preferred over a limited-use system.</li>

<li>Hardware costs.</li>

<li>Operating costs.</li></ol>

Applying a <a href="Systems_development_life_cycle" title="Systems development life cycle">systems development process</a> will mitigate the axiom: the later in the process an error is detected, the more expensive it is to correct.<a href="#cite_note-pis-ch12-p516-121">[110]</a>

<div class="mw-heading mw-heading3"><h3 id="Waterfall_model">Waterfall model</h3></div>

The <a href="Waterfall_model" title="Waterfall model">waterfall model</a> is an implementation of a systems development process.<a href="#cite_note-se-ch1-8-122">[111]</a> As the waterfall label implies, the basic phases overlap each other:<a href="#cite_note-pis-ch12-p517-123">[112]</a>

<ol><li>The investigation phase is to understand the underlying problem.</li>

<li>The analysis phase is to understand the possible solutions.</li>

<li>The design phase is to <a href="Software_design" title="Software design">plan</a> the best solution.</li>

<li>The implementation phase is to program the best solution.</li>

<li>The maintenance phase lasts throughout the life of the system. Changes to the system after it is deployed may be necessary.<a href="#cite_note-se-ch11-345-124">[113]</a> Faults may exist, including specification faults, design faults, or coding faults. Improvements may be necessary. Adaption may be necessary to react to a changing environment.</li></ol>

<div class="mw-heading mw-heading3"><h3 id="Computer_programmer">Computer programmer</h3></div>

A <a href="Computer_programmer" class="mw-redirect" title="Computer programmer">computer programmer</a> is a specialist responsible for writing or modifying the source code to implement the detailed plan.<a href="#cite_note-pis-ch12-p507-118">[107]</a> A programming team is likely to be needed because most systems are too large to be completed by a single programmer.<a href="#cite_note-se-ch10-319-125">[114]</a> However, adding programmers to a project may not shorten the completion time. Instead, it may lower the quality of the system.<a href="#cite_note-se-ch10-319-125">[114]</a> To be effective, program modules need to be defined and distributed to team members.<a href="#cite_note-se-ch10-319-125">[114]</a> Also, team members must interact with one another in a meaningful and effective way.<a href="#cite_note-se-ch10-319-125">[114]</a>

Computer programmers may be <a href="Programming_in_the_large_and_programming_in_the_small#Programming_in_the_small" title="Programming in the large and programming in the small">programming in the small</a>: programming within a single module.<a href="#cite_note-se-ch10-331-126">[115]</a> Chances are a module will execute modules located in other source code files. Therefore, computer programmers may be <a href="Programming_in_the_large" class="mw-redirect" title="Programming in the large">programming in the large</a>: programming modules so they will effectively couple with each other.<a href="#cite_note-se-ch10-331-126">[115]</a> Programming-in-the-large includes contributing to the <a href="Application_programming_interface" class="mw-redirect" title="Application programming interface">application programming interface</a> (API).

<div class="mw-heading mw-heading3"><h3 id="Program_modules">Program modules</h3></div>

<a href="Modular_programming" title="Modular programming">Modular programming</a> is a technique to refine imperative language programs. Refined programs may reduce the software size, separate responsibilities, and thereby mitigate <a href="Software_aging" title="Software aging">software aging</a>. A program module is a sequence of statements that are bounded within a <a href="Block_(programming)" title="Block (programming)">block</a> and together identified by a name.<a href="#cite_note-se-ch8-216-127">[116]</a> Modules have a function, context, and logic:<a href="#cite_note-se-ch8-219-128">[117]</a>

<ul><li>The function of a module is what it does.</li>

<li>The context of a module are the elements being performed upon.</li>

<li>The logic of a module is how it performs the function.</li></ul>

The module's name should be derived first by its function, then by its context. Its logic should not be part of the name.<a href="#cite_note-se-ch8-219-128">[117]</a> For example, <code>function compute_square_root( x )</code> or <code>function compute_square_root_integer( i : integer )</code> are appropriate module names. However, <code>function compute_square_root_by_division( x )</code> is not.

The degree of interaction within a module is its level of <a href="Cohesion_(computer_science)" title="Cohesion (computer science)">cohesion</a>.<a href="#cite_note-se-ch8-219-128">[117]</a> Cohesion is a judgment of the relationship between a module's name and its function. The degree of interaction between modules is the level of <a href="Coupling_(computer_science)" class="mw-redirect" title="Coupling (computer science)">coupling</a>.<a href="#cite_note-se-ch8-226-129">[118]</a> Coupling is a judgement of the relationship between a module's context and the elements being performed upon.

<div class="mw-heading mw-heading3"><h3 id="Cohesion">Cohesion</h3></div>

The levels of cohesion from worst to best are:<a href="#cite_note-se-ch8-220-130">[119]</a>

<ul><li>Coincidental Cohesion: A module has coincidental cohesion if it performs multiple functions, and the functions are completely unrelated. For example, <code>function read_sales_record_print_next_line_convert_to_float()</code>. Coincidental cohesion occurs in practice if management enforces silly rules. For example, "Every module will have between 35 and 50 executable statements."<a href="#cite_note-se-ch8-220-130">[119]</a></li>

<li>Logical Cohesion: A module has logical cohesion if it has available a series of functions, but only one of them is executed. For example, <code>function perform_arithmetic( perform_addition, a, b )</code>.</li>

<li>Temporal Cohesion: A module has temporal cohesion if it performs functions related to time. One example, <code>function initialize_variables_and_open_files()</code>. Another example, <code>stage_one()</code>, <code>stage_two()</code>, ...</li>

<li>Procedural Cohesion: A module has procedural cohesion if it performs multiple loosely related functions. For example, <code>function read_part_number_update_employee_record()</code>.</li>

<li>Communicational Cohesion: A module has communicational cohesion if it performs multiple closely related functions. For example, <code>function read_part_number_update_sales_record()</code>.</li>

<li>Informational Cohesion: A module has informational cohesion if it performs multiple functions, but each function has its own entry and exit points. Moreover, the functions share the same data structure. Object-oriented classes work at this level.</li>

<li>Functional Cohesion: a module has functional cohesion if it achieves a single goal working only on local variables. Moreover, it may be reusable in other contexts.</li></ul>

<div class="mw-heading mw-heading3"><h3 id="Coupling">Coupling</h3></div>

The levels of coupling from worst to best are:<a href="#cite_note-se-ch8-226-129">[118]</a>

<ul><li>Content Coupling: A module has content coupling if it modifies a <a href="Local_variable" title="Local variable">local variable</a> of another function. COBOL used to do this with the alter verb.</li>

<li>Common Coupling: A module has common coupling if it modifies a global variable.</li>

<li>Control Coupling: A module has control coupling if another module can modify its <a href="Control_flow" title="Control flow">control flow</a>. For example, <code>perform_arithmetic( perform_addition, a, b )</code>. Instead, control should be on the makeup of the returned object.</li>

<li>Stamp Coupling: A module has stamp coupling if an element of a data structure passed as a parameter is modified. Object-oriented classes work at this level.</li>

<li> Data Coupling: A module has data coupling if all of its input parameters are needed and none of them are modified. Moreover, the result of the function is returned as a single object.</li></ul>

<div class="mw-heading mw-heading3"><h3 id="Data_flow_analysis">Data flow analysis</h3></div>

Data flow analysis is a design method used to achieve modules of functional cohesion and data coupling.<a href="#cite_note-se-ch9-258-131">[120]</a> The input to the method is a <a href="Data-flow_diagram" title="Data-flow diagram">data-flow diagram</a>. A data-flow diagram is a set of ovals representing modules. Each module's name is displayed inside its oval. Modules may be at the executable level or the function level.

The diagram also has arrows connecting modules to each other. Arrows pointing into modules represent a set of inputs. Each module should have only one arrow pointing out from it to represent its single output object. (Optionally, an additional exception arrow points out.) A <a href="Daisy_chain_(electrical_engineering)" title="Daisy chain (electrical engineering)">daisy chain</a> of ovals will convey an entire <a href="Algorithm" title="Algorithm">algorithm</a>. The input modules should start the diagram. The input modules should connect to the transform modules. The transform modules should connect to the output modules.<a href="#cite_note-se-ch9-259-132">[121]</a>

<div class="mw-heading mw-heading2"><h2 id="Functional_categories">Functional categories</h2></div>

Computer programs may be categorized along functional lines. The main functional categories are <a href="Application_software" title="Application software">application software</a> and <a href="System_software" title="System software">system software</a>. System software includes the <a href="Operating_system" title="Operating system">operating system</a>, which couples <a href="Computer_hardware" title="Computer hardware">computer hardware</a> with application software.<a href="#cite_note-osc-overview-133">[122]</a> The purpose of the operating system is to provide an environment where application software executes in a convenient and efficient manner.<a href="#cite_note-osc-overview-133">[122]</a> Both application software and system software execute <a href="Utility_software" title="Utility software">utility programs</a>. At the hardware level, a <a href="Microcode" title="Microcode">microcode program</a> controls the circuits throughout the <a href="Central_processing_unit" title="Central processing unit">central processing unit</a>.

<div class="mw-heading mw-heading3"><h3 id="Application_software">Application software</h3></div>

<div role="note" class="hatnote navigation-not-searchable">Main article: <a href="Application_software" title="Application software">Application software</a></div>

Application software is the key to unlocking the potential of the computer system.<a href="#cite_note-pis-ch4-p147_quote1-134">[123]</a> <a href="Enterprise_application_software" class="mw-redirect" title="Enterprise application software">Enterprise application software</a> bundles accounting, personnel, customer, and vendor applications. Examples include <a href="Enterprise_resource_planning" title="Enterprise resource planning">enterprise resource planning</a>, <a href="Customer_relationship_management" title="Customer relationship management">customer relationship management</a>, and <a href="Supply_chain_management_software" class="mw-redirect" title="Supply chain management software">supply chain management software</a>.

Enterprise applications may be developed in-house as a one-of-a-kind <a href="Proprietary_software" title="Proprietary software">proprietary software</a>.<a href="#cite_note-pis-ch4-p148-135">[124]</a> Alternatively, they may be purchased as <a href="Off-the-shelf_software" class="mw-redirect" title="Off-the-shelf software">off-the-shelf software</a>. Purchased software may be modified to provide <a href="Custom_software" title="Custom software">custom software</a>. If the application is customized, then either the company's resources are used or the resources are outsourced. Outsourced software development may be from the original software vendor or a third-party developer.<a href="#cite_note-pis-ch4-p147_quote2-136">[125]</a>

The potential advantages of in-house software are features and reports may be developed exactly to specification.<a href="#cite_note-pis-ch4-p148_quote1-137">[126]</a> Management may also be involved in the development process and offer a level of control.<a href="#cite_note-pis-ch4-p148_quote2-138">[127]</a> Management may decide to counteract a competitor's new initiative or implement a customer or vendor requirement.<a href="#cite_note-pis-ch4-p148_quote3-139">[128]</a> A merger or acquisition may necessitate enterprise software changes. The potential disadvantages of in-house software are time and resource costs may be extensive.<a href="#cite_note-pis-ch4-p148-135">[124]</a> Furthermore, risks concerning features and performance may be looming.

The potential advantages of off-the-shelf software are upfront costs are identifiable, the basic needs should be fulfilled, and its performance and reliability have a track record.<a href="#cite_note-pis-ch4-p148-135">[124]</a> The potential disadvantages of off-the-shelf software are it may have unnecessary features that confuse end users, it may lack features the enterprise needs, and the data flow may not match the enterprise's work processes.<a href="#cite_note-pis-ch4-p148-135">[124]</a>

<div class="mw-heading mw-heading4"><h4 id="Application_service_provider">Application service provider</h4></div>

One approach to economically obtaining a customized enterprise application is through an <a href="Application_service_provider" title="Application service provider">application service provider</a>.<a href="#cite_note-pis-ch4-p149-140">[129]</a> Specialty companies provide hardware, custom software, and end-user support. They may speed the development of new applications because they possess skilled information system staff. The biggest advantage is it frees in-house resources from staffing and managing complex computer projects.<a href="#cite_note-pis-ch4-p149-140">[129]</a> Many application service providers target small, fast-growing companies with limited information system resources.<a href="#cite_note-pis-ch4-p149-140">[129]</a> On the other hand, larger companies with major systems will likely have their technical infrastructure in place. One risk is having to trust an external organization with sensitive information. Another risk is having to trust the provider's infrastructure reliability.<a href="#cite_note-pis-ch4-p149-140">[129]</a>

<div class="mw-heading mw-heading3"><h3 id="Operating_system">Operating system</h3></div>

<div role="note" class="hatnote navigation-not-searchable">See also: <a href="Operating_system" title="Operating system">Operating system</a></div>

An <a href="Operating_system" title="Operating system">operating system</a> is the low-level software that supports a computer's basic functions, such as <a href="Scheduling_(computing)" title="Scheduling (computing)">scheduling</a> <a href="Process_(computing)" title="Process (computing)">processes</a> and controlling <a href="Peripheral" title="Peripheral">peripherals</a>.<a href="#cite_note-osc-overview-133">[122]</a>

In the 1950s, the programmer, who was also the operator, would write a program and run it. After the program finished executing, the output may have been printed, or it may have been punched onto paper tape or cards for later processing.<a href="#cite_note-osc-ch1-p6-31">[29]</a> More often than not the program did not work. The programmer then looked at the console lights and fiddled with the console switches. If less fortunate, a memory printout was made for further study. In the 1960s, programmers reduced the amount of wasted time by automating the operator's job. A program called an operating system was kept in the computer at all times.<a href="#cite_note-sco-ch1-p11-141">[130]</a>

The term operating system may refer to two levels of software.<a href="#cite_note-lpi-ch2-p21-142">[131]</a> The operating system may refer to the <a href="Kernel_(operating_system)" title="Kernel (operating system)">kernel program</a> that manages the <a href="Process_(computing)" title="Process (computing)">processes</a>, <a href="Computer_memory" title="Computer memory">memory</a>, and <a href="Peripheral" title="Peripheral">devices</a>. More broadly, the operating system may refer to the entire package of the central software. The package includes a kernel program, <a href="Command-line_interface" title="Command-line interface">command-line interpreter</a>, <a href="Graphical_user_interface" title="Graphical user interface">graphical user interface</a>, <a href="Utility_software" title="Utility software">utility programs</a>, and <a href="Source-code_editor" title="Source-code editor">editor</a>.<a href="#cite_note-lpi-ch2-p21-142">[131]</a>

<div class="mw-heading mw-heading4"><h4 id="Kernel_Program">Kernel Program</h4></div>

The kernel's main purpose is to manage the limited resources of a computer:

<ul><li>The kernel program should perform <a href="Process_scheduling" class="mw-redirect" title="Process scheduling">process scheduling</a>,<a href="#cite_note-lpi-ch2-p22-143">[132]</a> which is also known as a <a href="Context_switch" title="Context switch">context switch</a>. The kernel creates a <a href="Process_control_block" title="Process control block">process control block</a> when a computer program is <a href="Loader_(computing)" title="Loader (computing)">selected for execution</a>. However, an executing program gets exclusive access to the <a href="Central_processing_unit" title="Central processing unit">central processing unit</a> only for a <a href="Preemption_(computing)#Time_slice" title="Preemption (computing)">time slice</a>. To provide each user with the <a href="Time-sharing" title="Time-sharing">appearance of continuous access</a>, the kernel quickly <a href="Preemption_(computing)" title="Preemption (computing)">preempts</a> each process control block to execute another one. The goal for <a href="Systems_programming" title="Systems programming">system developers</a> is to minimize <a href="Dispatch_latency" class="mw-redirect" title="Dispatch latency">dispatch latency</a>.</li></ul>

<ul><li>The kernel program should perform <a href="Memory_management" title="Memory management">memory management</a>.</li></ul>

<dl><dd><ul><li>When the kernel initially <a href="Loader_(computing)" title="Loader (computing)">loads</a> an executable into memory, it divides the address space logically into <a href="Region-based_memory_management" title="Region-based memory management">regions</a>.<a href="#cite_note-duos-ch6-p152-144">[133]</a> The kernel maintains a master-region table and many per-process-region (pregion) tables—one for each running <a href="Process_(computing)" title="Process (computing)">process</a>.<a href="#cite_note-duos-ch6-p152-144">[133]</a> These tables constitute the <a href="Virtual_address_space" title="Virtual address space">virtual address space</a>. The master-region table is used to determine where its contents are located in <a href="Physical_memory" class="mw-redirect" title="Physical memory">physical memory</a>. The pregion tables allow each process to have its own program (text) pregion, data pregion, and stack pregion.</li>

<li>The program pregion stores machine instructions. Since machine instructions do not change, the program pregion may be shared by many processes of the same executable.<a href="#cite_note-duos-ch6-p152-144">[133]</a></li>

<li>To save time and memory, the kernel may load only blocks of execution instructions from the disk drive, not the entire execution file completely.<a href="#cite_note-lpi-ch2-p22-143">[132]</a></li>

<li>The kernel is responsible for translating virtual addresses into <a href="Physical_address" title="Physical address">physical addresses</a>. The kernel may request data from the <a href="Memory_controller" title="Memory controller">memory controller</a> and, instead, receive a <a href="Page_fault" title="Page fault">page fault</a>.<a href="#cite_note-sco6th-ch6-p443-145">[134]</a> If so, the kernel accesses the <a href="Memory_management_unit" title="Memory management unit">memory management unit</a> to populate the physical data region and translate the address.<a href="#cite_note-esa-ch1-p8-146">[135]</a></li>

<li>The kernel allocates memory from the heap upon request by a process.<a href="#cite_note-cpl-ch8-p187-74">[64]</a> When the process is finished with the memory, the process may request for it to be <a href="Manual_memory_management" title="Manual memory management">freed</a>. If the process exits without requesting all allocated memory to be freed, then the kernel performs <a href="Garbage_collection_(computer_science)" title="Garbage collection (computer science)">garbage collection</a> to free the memory.</li>

<li>The kernel also ensures that a process only accesses its own memory, and not that of the kernel or other processes.<a href="#cite_note-lpi-ch2-p22-143">[132]</a></li></ul></dd></dl>

<ul><li>The kernel program should perform <a href="File_system" title="File system">file system management</a>.<a href="#cite_note-lpi-ch2-p22-143">[132]</a> The kernel has instructions to create, retrieve, update, and delete files.</li>

<li>The kernel program should perform <a href="Peripheral" title="Peripheral">device management</a>.<a href="#cite_note-lpi-ch2-p22-143">[132]</a> The kernel provides programs to standardize and simplify the interface to the mouse, keyboard, disk drives, printers, and other devices. Moreover, the kernel should arbitrate access to a device if two processes request it at the same time.</li>

<li>The kernel program should perform <a href="Network_management" title="Network management">network management</a>.<a href="#cite_note-lpi-ch2-p23-147">[136]</a> The kernel transmits and receives <a href="Network_packet" title="Network packet">packets</a> on behalf of processes. One key service is to find an efficient <a href="Routing_table" title="Routing table">route</a> to the target system.</li>

<li>The kernel program should provide <a href="System_calls" class="mw-redirect" title="System calls">system level functions</a> for programmers to use.<a href="#cite_note-upe-ch7-p201-148">[137]</a>

<ul><li>Programmers access files through a relatively simple interface that in turn executes a relatively complicated low-level I/O interface. The low-level interface includes file creation, <a href="File_descriptor" title="File descriptor">file descriptors</a>, file seeking, physical reading, and physical writing.</li>

<li>Programmers create processes through a relatively simple interface that in turn executes a relatively complicated low-level interface.</li>

<li>Programmers perform date/time arithmetic through a relatively simple interface that in turn executes a relatively complicated low-level time interface.<a href="#cite_note-lpi-ch10-p187-149">[138]</a></li></ul></li>

<li>The kernel program should provide a <a href="Inter-process_communication" title="Inter-process communication">communication channel</a> between executing processes.<a href="#cite_note-usp-ch6-p121-150">[139]</a> For a large software system, it may be desirable to <a href="Software_engineering" title="Software engineering">engineer</a> the system into smaller processes. Processes may communicate with one another by sending and receiving <a href="Signal_(IPC)" title="Signal (IPC)">signals</a>.</li></ul>

Originally, operating systems were programmed in <a href="Assembly_language" title="Assembly language">assembly</a>; however, modern operating systems are typically written in higher-level languages like <a href="C_(programming_language)" title="C (programming language)">C</a>, <a href="Objective-C" title="Objective-C">Objective-C</a>, and <a href="Swift_(programming_language)" title="Swift (programming language)">Swift</a>.<a href="#cite_note-151">[l]</a>

<div class="mw-heading mw-heading3"><h3 id="Utility_program">Utility program</h3></div>

A <a href="Utility_program" class="mw-redirect" title="Utility program">utility program</a> is designed to aid system administration and software execution. Operating systems execute hardware utility programs to check the status of disk drives, memory, speakers, and printers.<a href="#cite_note-pis-ch4-p145-152">[140]</a> A utility program may optimize the placement of a file on a crowded disk. System utility programs monitor hardware and network performance. When a metric is outside an acceptable range, a trigger alert is generated.<a href="#cite_note-pis-ch4-p146-153">[141]</a>

Utility programs include compression programs so data files are stored on less disk space.<a href="#cite_note-pis-ch4-p145-152">[140]</a> Compressed programs also save time when data files are transmitted over the network.<a href="#cite_note-pis-ch4-p145-152">[140]</a> Utility programs can sort and merge data sets.<a href="#cite_note-pis-ch4-p146-153">[141]</a> Utility programs detect <a href="Computer_virus" title="Computer virus">computer viruses</a>.<a href="#cite_note-pis-ch4-p146-153">[141]</a>

<div class="mw-heading mw-heading3"><h3 id="Microcode_program">Microcode program</h3></div>

<div role="note" class="hatnote navigation-not-searchable">Main article: <a href="Microcode" title="Microcode">Microcode</a></div>

A <a href="Microcode" title="Microcode">microcode program</a> is the bottom-level interpreter that controls the <a href="Data_path" class="mw-redirect" title="Data path">data path</a> of software-driven computers.<a href="#cite_note-sco6th-ch1-p6-154">[142]</a>

(Advances in <a href="Random_logic" title="Random logic">hardware</a> have migrated these operations to <a href="Control_unit#Hardwired_control_unit" title="Control unit">hardware execution circuits</a>.)<a href="#cite_note-sco6th-ch1-p6-154">[142]</a> Microcode instructions allow the programmer to more easily implement the <a href="Logic_level" title="Logic level">digital logic level</a><a href="#cite_note-sco6th-ch4-p243-155">[143]</a>—the computer's real hardware. The digital logic level is the boundary between <a href="Computer_science" title="Computer science">computer science</a> and <a href="Computer_engineering" title="Computer engineering">computer engineering</a>.<a href="#cite_note-sco6th-ch3-p147-156">[144]</a>

A <a href="Logic_gate" title="Logic gate">logic gate</a> is a tiny <a href="Field-effect_transistor" title="Field-effect transistor">transistor</a> that can return one of two signals: on or off.<a href="#cite_note-sco6th-ch3-p148-157">[145]</a>

<ul><li>Having one transistor forms the <a href="NOT_gate" class="mw-redirect" title="NOT gate">NOT gate</a>.</li>

<li>Connecting two transistors in series forms the <a href="NAND_gate" title="NAND gate">NAND gate</a>.</li>

<li>Connecting two transistors in parallel forms the <a href="NOR_gate" title="NOR gate">NOR gate</a>.</li>

<li>Connecting a NOT gate to a NAND gate forms the <a href="AND_gate" title="AND gate">AND gate</a>.</li>

<li>Connecting a NOT gate to a NOR gate forms the <a href="OR_gate" title="OR gate">OR gate</a>.</li></ul>

These five gates form the building blocks of <a href="Boolean_algebra" title="Boolean algebra">binary algebra</a>—the digital logic functions of the computer.

Microcode instructions are <a href="Assembly_language#Mnemonics" title="Assembly language">mnemonics</a> programmers may use to execute digital logic functions instead of forming them in binary algebra. They are stored in a <a href="Central_processing_unit" title="Central processing unit">central processing unit's</a> (CPU) <a href="Control_store" title="Control store">control store</a>.<a href="#cite_note-sco6th-ch4-p253-158">[146]</a>

These hardware-level instructions move data throughout the <a href="Data_path" class="mw-redirect" title="Data path">data path</a>.

The micro-instruction cycle begins when the <a href="Microsequencer" title="Microsequencer">microsequencer</a> uses its microprogram counter to fetch the next <a href="Machine_instruction" class="mw-redirect" title="Machine instruction">machine instruction</a> from <a href="Random-access_memory" title="Random-access memory">random-access memory</a>.<a href="#cite_note-sco6th-ch4-p255-159">[147]</a> The next step is to decode the machine instruction by selecting the proper output line to the hardware module.<a href="#cite_note-sco6th-ch3-p161-160">[148]</a>

The final step is to execute the instruction using the hardware module's set of gates.

Instructions to perform arithmetic are passed through an <a href="Arithmetic_logic_unit" title="Arithmetic logic unit">arithmetic logic unit</a> (ALU).<a href="#cite_note-sco6th-ch3-p166-161">[149]</a> The ALU has circuits to perform elementary operations to add, shift, and compare integers. By combining and looping the elementary operations through the ALU, the CPU performs its complex arithmetic.

Microcode instructions move data between the CPU and the <a href="Memory_controller" title="Memory controller">memory controller</a>. Memory controller microcode instructions manipulate two <a href="Processor_register" title="Processor register">registers</a>. The <a href="Memory_address_register" title="Memory address register">memory address register</a> is used to access each memory cell's address. The <a href="Memory_data_register" class="mw-redirect" title="Memory data register">memory data register</a> is used to set and read each cell's contents.<a href="#cite_note-sco6th-ch4-p249-162">[150]</a>

<div class="mw-heading mw-heading2"><h2 id="Notes">Notes</h2></div>

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<li id="cite_note-1"><a href="#cite_ref-1">^</a> The <a href="Prolog" title="Prolog">Prolog</a> 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.

</li>

<li id="cite_note-7"><a href="#cite_ref-7">^</a> An executable has each <a href="Machine_instruction" class="mw-redirect" title="Machine instruction">machine instruction</a> ready for the <a href="CPU" class="mw-redirect" title="CPU">CPU</a>.

</li>

<li id="cite_note-40"><a href="#cite_ref-40">^</a> For more information, visit <a href="X86_assembly_language#Instruction_types" title="X86 assembly language">X86 assembly language#Instruction types</a>.

</li>

<li id="cite_note-41"><a href="#cite_ref-41">^</a> introduced in 1999

</li>

<li id="cite_note-50"><a href="#cite_ref-50">^</a> Whereas this is a decimal number, PDP-11 code is always expressed as <a href="Octal" title="Octal">octal</a>.

</li>

<li id="cite_note-57"><a href="#cite_ref-57">^</a> <a href="Operators_in_C_and_C%2B%2B" title="Operators in C and C++">Operators</a> like <code>x++</code> will usually compile to a single instruction.

</li>

<li id="cite_note-64"><a href="#cite_ref-64">^</a> The line numbers were typically incremented by 10 to leave room if additional statements were added later.

</li>

<li id="cite_note-68"><a href="#cite_ref-68">^</a> This function could be written more concisely as <code>int increment_counter(){ static int counter; return ++counter;}</code>. 1) Static variables are automatically initialized to zero. 2) <code>++counter</code> is a prefix <a href="Increment_operator" class="mw-redirect" title="Increment operator">increment operator</a>.

</li>

<li id="cite_note-70"><a href="#cite_ref-70">^</a> This is despite the metaphor of a stack, which normally grows from bottom to top.

</li>

<li id="cite_note-73"><a href="#cite_ref-73">^</a> C also provides the <code>calloc()</code> function to allocate heap memory. It provides two additional services: 1) It allows the programmer to create an <a href="Array_(data_structure)" title="Array (data structure)">array</a> of arbitrary size. 2) It sets each <a href="Memory_cell_(computing)" title="Memory cell (computing)">memory cell</a> to zero.

</li>

<li id="cite_note-75"><a href="#cite_ref-75">^</a> For <a href="String_(computer_science)" title="String (computer science)">string</a> variables, C provides the <code>strdup()</code> function. It executes both the allocation function and the copy function.

</li>

<li id="cite_note-151"><a href="#cite_ref-151">^</a> The <a href="UNIX" class="mw-redirect" title="UNIX">UNIX</a> operating system was written in C, <a href="MacOS" title="MacOS">macOS</a> was written in Objective-C, and Swift replaced Objective-C.

</li>

</ol></div></div>

<div class="mw-heading mw-heading2"><h2 id="References">References</h2></div>

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</style><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.iso.org/obp/ui/#iso:std:iso-iec:2382:ed-1:v1:en">"ISO/IEC 2382:2015"</a>. ISO. 2020-09-03. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20160617031837/https://www.iso.org/obp/ui/#iso:std:iso-iec:2382:ed-1:v1:en">Archived</a> from the original on 2016-06-17. Retrieved 2022-05-26. <q>[Software includes] all or part of the programs, procedures, rules, and associated documentation of an information processing system.</q></cite>

</li>

<li id="cite_note-cpl_3rd-ch1-7_quoted-3"><a href="#cite_ref-cpl_3rd-ch1-7_quoted_3-0">^</a> <cite id="CITEREFWilson2001" class="citation book cs1">Wilson, Leslie B. (2001). Comparative Programming Languages, Third Edition. Addison-Wesley. p. 7. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-201-71012-9</bdi>. <q>An alternative to compiling a source program is to use an interpreter. An interpreter can directly execute a source program[.]</q></cite>

</li>

<li id="cite_note-osc-ch4-p98-4"><a href="#cite_ref-osc-ch4-p98_4-0">^</a> <cite id="CITEREFSilberschatz1994" class="citation book cs1">Silberschatz, Abraham (1994). Operating System Concepts, Fourth Edition. Addison-Wesley. p. 98. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-201-50480-4</bdi>.</cite>

</li>

<li id="cite_note-sco-ch2-p32-5"><a href="#cite_ref-sco-ch2-p32_5-0">^</a> <cite id="CITEREFTanenbaum1990" class="citation book cs1">Tanenbaum, Andrew S. (1990). <a rel="nofollow" class="external text" href="https://archive.org/details/structuredcomput00tane/page/32">Structured Computer Organization, Third Edition</a>. Prentice Hall. p. <a rel="nofollow" class="external text" href="https://archive.org/details/structuredcomput00tane/page/32">32</a>. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-13-854662-5</bdi>.</cite>

</li>

<li id="cite_note-cpl_3rd-ch1-7-6"><a href="#cite_ref-cpl_3rd-ch1-7_6-0">^</a> <cite id="CITEREFWilson2001" class="citation book cs1">Wilson, Leslie B. (2001). Comparative Programming Languages, Third Edition. Addison-Wesley. p. 7. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-201-71012-9</bdi>.</cite>

</li>

<li id="cite_note-cpl_3rd-ch2-30_quote1-8"><a href="#cite_ref-cpl_3rd-ch2-30_quote1_8-0">^</a> <cite id="CITEREFWilson2001" class="citation book cs1">Wilson, Leslie B. (2001). Comparative Programming Languages, Third Edition. Addison-Wesley. p. 30. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-201-71012-9</bdi>. <q>Their intention was to produce a language that was very simple for students to learn[.]</q></cite>

</li>

<li id="cite_note-cpl_3rd-ch2-31-9">^ <a href="#cite_ref-cpl_3rd-ch2-31_9-0">a</a> <a href="#cite_ref-cpl_3rd-ch2-31_9-1">b</a> <a href="#cite_ref-cpl_3rd-ch2-31_9-2">c</a> <cite id="CITEREFWilson2001" class="citation book cs1">Wilson, Leslie B. (2001). Comparative Programming Languages, Third Edition. Addison-Wesley. p. 31. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-201-71012-9</bdi>.</cite>

</li>

<li id="cite_note-cpl_3rd-ch2-30-10">^ <a href="#cite_ref-cpl_3rd-ch2-30_10-0">a</a> <a href="#cite_ref-cpl_3rd-ch2-30_10-1">b</a> <a href="#cite_ref-cpl_3rd-ch2-30_10-2">c</a> <a href="#cite_ref-cpl_3rd-ch2-30_10-3">d</a> <a href="#cite_ref-cpl_3rd-ch2-30_10-4">e</a> <a href="#cite_ref-cpl_3rd-ch2-30_10-5">f</a> <cite id="CITEREFWilson2001" class="citation book cs1">Wilson, Leslie B. (2001). Comparative Programming Languages, Third Edition. Addison-Wesley. p. 30. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-201-71012-9</bdi>.</cite>

</li>

<li id="cite_note-cpl_3rd-ch2-30_quote2-11"><a href="#cite_ref-cpl_3rd-ch2-30_quote2_11-0">^</a> <cite id="CITEREFWilson2001" class="citation book cs1">Wilson, Leslie B. (2001). Comparative Programming Languages, Third Edition. Addison-Wesley. p. 30. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-201-71012-9</bdi>. <q>The idea was that students could be merely casual users or go on from Basic to more sophisticated and powerful languages[.]</q></cite>

</li>

<li id="cite_note-eniac-ch1-p16-12">^ <a href="#cite_ref-eniac-ch1-p16_12-0">a</a> <a href="#cite_ref-eniac-ch1-p16_12-1">b</a> <cite id="CITEREFMcCartney1999" class="citation book cs1">McCartney, Scott (1999). <a rel="nofollow" class="external text" href="https://archive.org/details/eniac00scot/page/16">ENIAC – The Triumphs and Tragedies of the World's First Computer</a>. Walker and Company. p. <a rel="nofollow" class="external text" href="https://archive.org/details/eniac00scot/page/16">16</a>. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-8027-1348-3</bdi>.</cite>

</li>

<li id="cite_note-sco-ch1-p14-13"><a href="#cite_ref-sco-ch1-p14_13-0">^</a> <cite id="CITEREFTanenbaum1990" class="citation book cs1">Tanenbaum, Andrew S. (1990). <a rel="nofollow" class="external text" href="https://archive.org/details/structuredcomput00tane/page/14">Structured Computer Organization, Third Edition</a>. Prentice Hall. p. <a rel="nofollow" class="external text" href="https://archive.org/details/structuredcomput00tane/page/14">14</a>. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-13-854662-5</bdi>.</cite>

</li>

<li id="cite_note-14"><a href="#cite_ref-14">^</a> <cite id="CITEREFBromley1998" class="citation journal cs1"><a href="Allan_G._Bromley" title="Allan G. Bromley">Bromley, Allan G.</a> (1998). <a rel="nofollow" class="external text" href="http://profs.scienze.univr.it/~manca/storia-informatica/babbage.pdf">"Charles Babbage's Analytical Engine, 1838"</a> (PDF). <a href="IEEE_Annals_of_the_History_of_Computing" title="IEEE Annals of the History of Computing">IEEE Annals of the History of Computing</a>. 20 (4): 29–45. <a href="Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1109%2F85.728228">10.1109/85.728228</a>. <a href="S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:2285332">2285332</a>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20160304081812/http://profs.scienze.univr.it/~manca/storia-informatica/babbage.pdf">Archived</a> (PDF) from the original on 2016-03-04. Retrieved 2015-10-30.</cite>

</li>

<li id="cite_note-sco-ch1-p15-15">^ <a href="#cite_ref-sco-ch1-p15_15-0">a</a> <a href="#cite_ref-sco-ch1-p15_15-1">b</a> <cite id="CITEREFTanenbaum1990" class="citation book cs1">Tanenbaum, Andrew S. (1990). <a rel="nofollow" class="external text" href="https://archive.org/details/structuredcomput00tane/page/15">Structured Computer Organization, Third Edition</a>. Prentice Hall. p. <a rel="nofollow" class="external text" href="https://archive.org/details/structuredcomput00tane/page/15">15</a>. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-13-854662-5</bdi>.</cite>

</li>

<li id="cite_note-16"><a href="#cite_ref-16">^</a> <cite id="CITEREFJ._FuegiJ._Francis2003" class="citation cs2">J. Fuegi; J. Francis (October–December 2003), "Lovelace & Babbage and the creation of the 1843 'notes'", Annals of the History of Computing, 25 (4): 16, 19, 25, <a href="Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1109%2FMAHC.2003.1253887">10.1109/MAHC.2003.1253887</a></cite>

</li>

<li id="cite_note-discrete-ch10-p654-17"><a href="#cite_ref-discrete-ch10-p654_17-0">^</a> <cite id="CITEREFRosen1991" class="citation book cs1">Rosen, Kenneth H. (1991). <a rel="nofollow" class="external text" href="https://archive.org/details/discretemathemat00rose/page/654">Discrete Mathematics and Its Applications</a>. McGraw-Hill, Inc. p. <a rel="nofollow" class="external text" href="https://archive.org/details/discretemathemat00rose/page/654">654</a>. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-07-053744-6</bdi>. <q>Turing machines can model all the computations that can be performed on a computing machine.</q></cite>

</li>

<li id="cite_note-formal_languages-ch9-p234-18"><a href="#cite_ref-formal_languages-ch9-p234_18-0">^</a> <cite id="CITEREFLinz1990" class="citation book cs1">Linz, Peter (1990). An Introduction to Formal Languages and Automata. D. C. Heath and Company. p. 234. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-669-17342-0</bdi>.</cite>

</li>

<li id="cite_note-formal_languages-ch9-p243-19"><a href="#cite_ref-formal_languages-ch9-p243_19-0">^</a> <cite id="CITEREFLinz1990" class="citation book cs1">Linz, Peter (1990). An Introduction to Formal Languages and Automata. D. C. Heath and Company. p. 243. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-669-17342-0</bdi>. <q>[A]ll the common mathematical functions, no matter how complicated, are Turing-computable.</q></cite>

</li>

<li id="cite_note-eniac-ch5-p102-20">^ <a href="#cite_ref-eniac-ch5-p102_20-0">a</a> <a href="#cite_ref-eniac-ch5-p102_20-1">b</a> <a href="#cite_ref-eniac-ch5-p102_20-2">c</a> <cite id="CITEREFMcCartney1999" class="citation book cs1">McCartney, Scott (1999). <a rel="nofollow" class="external text" href="https://archive.org/details/eniac00scot/page/102">ENIAC – The Triumphs and Tragedies of the World's First Computer</a>. Walker and Company. p. <a rel="nofollow" class="external text" href="https://archive.org/details/eniac00scot/page/102">102</a>. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-8027-1348-3</bdi>.</cite>

</li>

<li id="cite_note-eniac-ch5-p94-21"><a href="#cite_ref-eniac-ch5-p94_21-0">^</a> <cite id="CITEREFMcCartney1999" class="citation book cs1">McCartney, Scott (1999). <a rel="nofollow" class="external text" href="https://archive.org/details/eniac00scot/page/94">ENIAC – The Triumphs and Tragedies of the World's First Computer</a>. Walker and Company. p. <a rel="nofollow" class="external text" href="https://archive.org/details/eniac00scot/page/94">94</a>. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-8027-1348-3</bdi>.</cite>

</li>

<li id="cite_note-eniac-ch5-p107-22"><a href="#cite_ref-eniac-ch5-p107_22-0">^</a> <cite id="CITEREFMcCartney1999" class="citation book cs1">McCartney, Scott (1999). <a rel="nofollow" class="external text" href="https://archive.org/details/eniac00scot/page/107">ENIAC – The Triumphs and Tragedies of the World's First Computer</a>. Walker and Company. p. <a rel="nofollow" class="external text" href="https://archive.org/details/eniac00scot/page/107">107</a>. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-8027-1348-3</bdi>.</cite>

</li>

<li id="cite_note-eniac-ch6-p120-23"><a href="#cite_ref-eniac-ch6-p120_23-0">^</a> <cite id="CITEREFMcCartney1999" class="citation book cs1">McCartney, Scott (1999). <a rel="nofollow" class="external text" href="https://archive.org/details/eniac00scot/page/120">ENIAC – The Triumphs and Tragedies of the World's First Computer</a>. Walker and Company. p. <a rel="nofollow" class="external text" href="https://archive.org/details/eniac00scot/page/120">120</a>. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-8027-1348-3</bdi>.</cite>

</li>

<li id="cite_note-eniac-ch6-p118-24">^ <a href="#cite_ref-eniac-ch6-p118_24-0">a</a> <a href="#cite_ref-eniac-ch6-p118_24-1">b</a> <cite id="CITEREFMcCartney1999" class="citation book cs1">McCartney, Scott (1999). <a rel="nofollow" class="external text" href="https://archive.org/details/eniac00scot/page/118">ENIAC – The Triumphs and Tragedies of the World's First Computer</a>. Walker and Company. p. <a rel="nofollow" class="external text" href="https://archive.org/details/eniac00scot/page/118">118</a>. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-8027-1348-3</bdi>.</cite>

</li>

<li id="cite_note-eniac-ch6-p119-25"><a href="#cite_ref-eniac-ch6-p119_25-0">^</a> <cite id="CITEREFMcCartney1999" class="citation book cs1">McCartney, Scott (1999). <a rel="nofollow" class="external text" href="https://archive.org/details/eniac00scot/page/119">ENIAC – The Triumphs and Tragedies of the World's First Computer</a>. Walker and Company. p. <a rel="nofollow" class="external text" href="https://archive.org/details/eniac00scot/page/119">119</a>. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-8027-1348-3</bdi>.</cite>

</li>

<li id="cite_note-eniac-ch6-p123-26"><a href="#cite_ref-eniac-ch6-p123_26-0">^</a> <cite id="CITEREFMcCartney1999" class="citation book cs1">McCartney, Scott (1999). <a rel="nofollow" class="external text" href="https://archive.org/details/eniac00scot/page/123">ENIAC – The Triumphs and Tragedies of the World's First Computer</a>. Walker and Company. p. <a rel="nofollow" class="external text" href="https://archive.org/details/eniac00scot/page/123">123</a>. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-8027-1348-3</bdi>.</cite>

</li>

<li id="cite_note-27"><a href="#cite_ref-27">^</a> <cite id="CITEREFHuskey2003" class="citation cs2">Huskey, Harry D. (2003-01-01), <a rel="nofollow" class="external text" href="https://dl.acm.org/doi/10.5555/1074100.1074362">"EDVAC"</a>, Encyclopedia of Computer Science, GBR: John Wiley and Sons Ltd., pp. 626–628, <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-470-86412-8</bdi>, retrieved 2025-04-25</cite>

</li>

<li id="cite_note-sco-ch1-p21-28">^ <a href="#cite_ref-sco-ch1-p21_28-0">a</a> <a href="#cite_ref-sco-ch1-p21_28-1">b</a> <cite id="CITEREFTanenbaum1990" class="citation book cs1">Tanenbaum, Andrew S. (1990). <a rel="nofollow" class="external text" href="https://archive.org/details/structuredcomput00tane">Structured Computer Organization, Third Edition</a>. Prentice Hall. p. <a rel="nofollow" class="external text" href="https://archive.org/details/structuredcomput00tane/page/n42">21</a>. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-13-854662-5</bdi>.</cite>

</li>

<li id="cite_note-cpl_3rd-ch2-27-29">^ <a href="#cite_ref-cpl_3rd-ch2-27_29-0">a</a> <a href="#cite_ref-cpl_3rd-ch2-27_29-1">b</a> <cite id="CITEREFWilson2001" class="citation book cs1">Wilson, Leslie B. (2001). Comparative Programming Languages, Third Edition. Addison-Wesley. p. 27. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-201-71012-9</bdi>.</cite>

</li>

<li id="cite_note-cpl_3rd-ch2-29-30"><a href="#cite_ref-cpl_3rd-ch2-29_30-0">^</a> <cite id="CITEREFWilson2001" class="citation book cs1">Wilson, Leslie B. (2001). Comparative Programming Languages, Third Edition. Addison-Wesley. p. 29. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-201-71012-9</bdi>.</cite>

</li>

<li id="cite_note-osc-ch1-p6-31">^ <a href="#cite_ref-osc-ch1-p6_31-0">a</a> <a href="#cite_ref-osc-ch1-p6_31-1">b</a> <a href="#cite_ref-osc-ch1-p6_31-2">c</a> <cite id="CITEREFSilberschatz1994" class="citation book cs1">Silberschatz, Abraham (1994). Operating System Concepts, Fourth Edition. Addison-Wesley. p. 6. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-201-50480-4</bdi>.</cite>

</li>

<li id="cite_note-digital_age-32">^ <a href="#cite_ref-digital_age_32-0">a</a> <a href="#cite_ref-digital_age_32-1">b</a> <cite class="citation book cs1"><a rel="nofollow" class="external text" href="https://books.google.com/books?id=UUbB3d2UnaAC&pg=PA46">To the Digital Age: Research Labs, Start-up Companies, and the Rise of MOS</a>. Johns Hopkins University Press. 2002. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>9780801886393</bdi>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20230202181649/https://books.google.com/books?id=UUbB3d2UnaAC&pg=PA46">Archived</a> from the original on February 2, 2023. Retrieved February 3, 2022.</cite>

</li>

<li id="cite_note-osti-33"><a href="#cite_ref-osti_33-0">^</a> <cite id="CITEREFChalamala2017" class="citation web cs1">Chalamala, Babu (2017). <a rel="nofollow" class="external text" href="https://www.osti.gov/servlets/purl/1497235">"Manufacturing of Silicon Materials for Microelectronics and Solar PV"</a>. Sandia National Laboratories. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20230323163602/https://www.osti.gov/biblio/1497235">Archived</a> from the original on March 23, 2023. Retrieved February 8, 2022.</cite>

</li>

<li id="cite_note-britannica_wafer-34"><a href="#cite_ref-britannica_wafer_34-0">^</a> <cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.britannica.com/technology/integrated-circuit/Fabricating-ICs#ref837156">"Fabricating ICs Making a base wafer"</a>. Britannica. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20220208103132/https://www.britannica.com/technology/integrated-circuit/Fabricating-ICs#ref837156">Archived</a> from the original on February 8, 2022. Retrieved February 8, 2022.</cite>

</li>

<li id="cite_note-anysilicon-35"><a href="#cite_ref-anysilicon_35-0">^</a> <cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://anysilicon.com/introduction-to-nmos-and-pmos-transistors/">"Introduction to NMOS and PMOS Transistors"</a>. Anysilicon. 4 November 2021. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20220206051146/https://anysilicon.com/introduction-to-nmos-and-pmos-transistors/">Archived</a> from the original on 6 February 2022. Retrieved February 5, 2022.</cite>

</li>

<li id="cite_note-britannica_micropressor-36"><a href="#cite_ref-britannica_micropressor_36-0">^</a> <cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.britannica.com/technology/microprocessor#ref36149">"microprocessor definition"</a>. Britannica. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20220401085141/https://www.britannica.com/technology/microprocessor#ref36149">Archived</a> from the original on April 1, 2022. Retrieved April 1, 2022.</cite>

</li>

<li id="cite_note-intel_4004-37"><a href="#cite_ref-intel_4004_37-0">^</a> <cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://spectrum.ieee.org/chip-hall-of-fame-intel-4004-microprocessor">"Chip Hall of Fame: Intel 4004 Microprocessor"</a>. Institute of Electrical and Electronics Engineers. July 2, 2018. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20220207101915/https://spectrum.ieee.org/chip-hall-of-fame-intel-4004-microprocessor">Archived</a> from the original on February 7, 2022. Retrieved January 31, 2022.</cite>

</li>

<li id="cite_note-ibm_360-38"><a href="#cite_ref-ibm_360_38-0">^</a> <cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.computer-museum.ru/books/archiv/ibm36040.pdf">"360 Revolution"</a> (PDF). Father, Son & Co. 1990. <a rel="nofollow" class="external text" href="https://ghostarchive.org/archive/20221010/https://www.computer-museum.ru/books/archiv/ibm36040.pdf">Archived</a> (PDF) from the original on 2022-10-10. Retrieved February 5, 2022.</cite>

</li>

<li id="cite_note-infoworld_8-23-82-39"><a href="#cite_ref-infoworld_8-23-82_39-0">^</a> <cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://books.google.com/books?id=VDAEAAAAMBAJ&pg=PA22">"Bill Gates, Microsoft and the IBM Personal Computer"</a>. InfoWorld. August 23, 1982. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20230218183644/https://books.google.com/books?id=VDAEAAAAMBAJ&pg=PA22">Archived</a> from the original on 18 February 2023. Retrieved 1 February 2022.</cite>

</li>

<li id="cite_note-stroustrup-ch1-10-42">^ <a href="#cite_ref-stroustrup-ch1-10_42-0">a</a> <a href="#cite_ref-stroustrup-ch1-10_42-1">b</a> <cite id="CITEREFStroustrup2013" class="citation book cs1">Stroustrup, Bjarne (2013). The C++ Programming Language, Fourth Edition. Addison-Wesley. p. 10. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-321-56384-2</bdi>.</cite>

</li>

<li id="cite_note-stroustrup-ch1-11-43">^ <a href="#cite_ref-stroustrup-ch1-11_43-0">a</a> <a href="#cite_ref-stroustrup-ch1-11_43-1">b</a> <a href="#cite_ref-stroustrup-ch1-11_43-2">c</a> <cite id="CITEREFStroustrup2013" class="citation book cs1">Stroustrup, Bjarne (2013). The C++ Programming Language, Fourth Edition. Addison-Wesley. p. 11. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-321-56384-2</bdi>.</cite>

</li>

<li id="cite_note-pis-ch4-p159-44">^ <a href="#cite_ref-pis-ch4-p159_44-0">a</a> <a href="#cite_ref-pis-ch4-p159_44-1">b</a> <cite id="CITEREFStair2003" class="citation book cs1">Stair, Ralph M. (2003). Principles of Information Systems, Sixth Edition. Thomson. p. 159. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-619-06489-7</bdi>.</cite>

</li>

<li id="cite_note-fla-ch1-p2-45">^ <a href="#cite_ref-fla-ch1-p2_45-0">a</a> <a href="#cite_ref-fla-ch1-p2_45-1">b</a> <cite id="CITEREFLinz1990" class="citation book cs1">Linz, Peter (1990). An Introduction to Formal Languages and Automata. D. C. Heath and Company. p. 2. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-669-17342-0</bdi>.</cite>

</li>

<li id="cite_note-dsa-ch2-p29-46"><a href="#cite_ref-dsa-ch2-p29_46-0">^</a> <cite id="CITEREFWeiss1994" class="citation book cs1">Weiss, Mark Allen (1994). Data Structures and Algorithm Analysis in C++. Benjamin/Cummings Publishing Company, Inc. p. 29. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-8053-5443-3</bdi>.</cite>

</li>

<li id="cite_note-sco-ch1-p17-47"><a href="#cite_ref-sco-ch1-p17_47-0">^</a> <cite id="CITEREFTanenbaum1990" class="citation book cs1">Tanenbaum, Andrew S. (1990). <a rel="nofollow" class="external text" href="https://archive.org/details/structuredcomput00tane/page/17">Structured Computer Organization, Third Edition</a>. Prentice Hall. p. <a rel="nofollow" class="external text" href="https://archive.org/details/structuredcomput00tane/page/17">17</a>. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-13-854662-5</bdi>.</cite>

</li>

<li id="cite_note-48"><a href="#cite_ref-48">^</a> <cite id="CITEREFWilkesRenwick1982" class="citation cs2">Wilkes, M. V.; Renwick, W. (1982), Randell, Brian (ed.), <a rel="nofollow" class="external text" href="https://link.springer.com/chapter/10.1007/978-3-642-61812-3_34">"The EDSAC"</a>, The Origins of Digital Computers: Selected Papers, Berlin, Heidelberg: Springer, pp. 417–421, <a href="Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1007%2F978-3-642-61812-3_34">10.1007/978-3-642-61812-3_34</a>, <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-3-642-61812-3</bdi>, retrieved 2025-04-25</cite>

</li>

<li id="cite_note-pis-ch4-p160-49">^ <a href="#cite_ref-pis-ch4-p160_49-0">a</a> <a href="#cite_ref-pis-ch4-p160_49-1">b</a> <a href="#cite_ref-pis-ch4-p160_49-2">c</a> <a href="#cite_ref-pis-ch4-p160_49-3">d</a> <a href="#cite_ref-pis-ch4-p160_49-4">e</a> <a href="#cite_ref-pis-ch4-p160_49-5">f</a> <cite id="CITEREFStair2003" class="citation book cs1">Stair, Ralph M. (2003). Principles of Information Systems, Sixth Edition. Thomson. p. 160. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-619-06489-7</bdi>.</cite>

</li>

<li id="cite_note-sco-ch7-p399-51">^ <a href="#cite_ref-sco-ch7-p399_51-0">a</a> <a href="#cite_ref-sco-ch7-p399_51-1">b</a> <a href="#cite_ref-sco-ch7-p399_51-2">c</a> <cite id="CITEREFTanenbaum1990" class="citation book cs1">Tanenbaum, Andrew S. (1990). <a rel="nofollow" class="external text" href="https://archive.org/details/structuredcomput00tane/page/399">Structured Computer Organization, Third Edition</a>. Prentice Hall. p. <a rel="nofollow" class="external text" href="https://archive.org/details/structuredcomput00tane/page/399">399</a>. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-13-854662-5</bdi>.</cite>

</li>

<li id="cite_note-sco-ch7-p400-52"><a href="#cite_ref-sco-ch7-p400_52-0">^</a> <cite id="CITEREFTanenbaum1990" class="citation book cs1">Tanenbaum, Andrew S. (1990). <a rel="nofollow" class="external text" href="https://archive.org/details/structuredcomput00tane/page/400">Structured Computer Organization, Third Edition</a>. Prentice Hall. p. <a rel="nofollow" class="external text" href="https://archive.org/details/structuredcomput00tane/page/400">400</a>. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-13-854662-5</bdi>.</cite>

</li>

<li id="cite_note-sco-ch7-p398-53"><a href="#cite_ref-sco-ch7-p398_53-0">^</a> <cite id="CITEREFTanenbaum1990" class="citation book cs1">Tanenbaum, Andrew S. (1990). <a rel="nofollow" class="external text" href="https://archive.org/details/structuredcomput00tane/page/398">Structured Computer Organization, Third Edition</a>. Prentice Hall. p. <a rel="nofollow" class="external text" href="https://archive.org/details/structuredcomput00tane/page/398">398</a>. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-13-854662-5</bdi>.</cite>

</li>

<li id="cite_note-cpl_3rd-ch2-26-54"><a href="#cite_ref-cpl_3rd-ch2-26_54-0">^</a> <cite id="CITEREFWilson2001" class="citation book cs1">Wilson, Leslie B. (2001). Comparative Programming Languages, Third Edition. Addison-Wesley. p. 26. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-201-71012-9</bdi>.</cite>

</li>

<li id="cite_note-cpl_3rd-ch2-37-55">^ <a href="#cite_ref-cpl_3rd-ch2-37_55-0">a</a> <a href="#cite_ref-cpl_3rd-ch2-37_55-1">b</a> <a href="#cite_ref-cpl_3rd-ch2-37_55-2">c</a> <a href="#cite_ref-cpl_3rd-ch2-37_55-3">d</a> <cite id="CITEREFWilson2001" class="citation book cs1">Wilson, Leslie B. (2001). Comparative Programming Languages, Third Edition. Addison-Wesley. p. 37. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-201-71012-9</bdi>.</cite>

</li>

<li id="cite_note-pis-ch4-p160_quote1-56"><a href="#cite_ref-pis-ch4-p160_quote1_56-0">^</a> <cite id="CITEREFStair2003" class="citation book cs1">Stair, Ralph M. (2003). Principles of Information Systems, Sixth Edition. Thomson. p. 160. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-619-06489-7</bdi>. <q>With third-generation and higher-level programming languages, each statement in the language translates into several instructions in machine language.</q></cite>

</li>

<li id="cite_note-cpl-ch4-75-58"><a href="#cite_ref-cpl-ch4-75_58-0">^</a> <cite id="CITEREFWilson1993" class="citation book cs1">Wilson, Leslie B. (1993). Comparative Programming Languages, Second Edition. Addison-Wesley. p. 75. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-201-56885-1</bdi>.</cite>

</li>

<li id="cite_note-stroustrup-ch2-40-59"><a href="#cite_ref-stroustrup-ch2-40_59-0">^</a> <cite id="CITEREFStroustrup2013" class="citation book cs1">Stroustrup, Bjarne (2013). The C++ Programming Language, Fourth Edition. Addison-Wesley. p. 40. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-321-56384-2</bdi>.</cite>

</li>

<li id="cite_note-cpl_3rd-ch2-16-60">^ <a href="#cite_ref-cpl_3rd-ch2-16_60-0">a</a> <a href="#cite_ref-cpl_3rd-ch2-16_60-1">b</a> <cite id="CITEREFWilson2001" class="citation book cs1">Wilson, Leslie B. (2001). Comparative Programming Languages, Third Edition. Addison-Wesley. p. 16. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-201-71012-9</bdi>.</cite>

</li>

<li id="cite_note-cpl_3rd-ch2-24-61"><a href="#cite_ref-cpl_3rd-ch2-24_61-0">^</a> <cite id="CITEREFWilson2001" class="citation book cs1">Wilson, Leslie B. (2001). Comparative Programming Languages, Third Edition. Addison-Wesley. p. 24. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-201-71012-9</bdi>.</cite>

</li>

<li id="cite_note-cpl_3rd-ch2-25-62">^ <a href="#cite_ref-cpl_3rd-ch2-25_62-0">a</a> <a href="#cite_ref-cpl_3rd-ch2-25_62-1">b</a> <cite id="CITEREFWilson2001" class="citation book cs1">Wilson, Leslie B. (2001). Comparative Programming Languages, Third Edition. Addison-Wesley. p. 25. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-201-71012-9</bdi>.</cite>

</li>

<li id="cite_note-cpl_3rd-ch2-19-63">^ <a href="#cite_ref-cpl_3rd-ch2-19_63-0">a</a> <a href="#cite_ref-cpl_3rd-ch2-19_63-1">b</a> <a href="#cite_ref-cpl_3rd-ch2-19_63-2">c</a> <a href="#cite_ref-cpl_3rd-ch2-19_63-3">d</a> <cite id="CITEREFWilson2001" class="citation book cs1">Wilson, Leslie B. (2001). Comparative Programming Languages, Third Edition. Addison-Wesley. p. 19. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-201-71012-9</bdi>.</cite>

</li>

<li id="cite_note-geeksforgeeks-65">^ <a href="#cite_ref-geeksforgeeks_65-0">a</a> <a href="#cite_ref-geeksforgeeks_65-1">b</a> <a href="#cite_ref-geeksforgeeks_65-2">c</a> <a href="#cite_ref-geeksforgeeks_65-3">d</a> <cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.geeksforgeeks.org/memory-layout-of-c-program/">"Memory Layout of C Programs"</a>. 12 September 2011. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20211106175644/https://www.geeksforgeeks.org/memory-layout-of-c-program/">Archived</a> from the original on 6 November 2021. Retrieved 6 November 2021.</cite>

</li>

<li id="cite_note-cpl-ch1-p31-66">^ <a href="#cite_ref-cpl-ch1-p31_66-0">a</a> <a href="#cite_ref-cpl-ch1-p31_66-1">b</a> <cite id="CITEREFKernighanRitchie1988" class="citation book cs1">Kernighan, Brian W.; Ritchie, Dennis M. (1988). The C Programming Language Second Edition. Prentice Hall. p. 31. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-13-110362-8</bdi>.</cite>

</li>

<li id="cite_note-cpl_3rd-ch6-128-67"><a href="#cite_ref-cpl_3rd-ch6-128_67-0">^</a> <cite id="CITEREFWilson2001" class="citation book cs1">Wilson, Leslie B. (2001). Comparative Programming Languages, Third Edition. Addison-Wesley. p. 128. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-201-71012-9</bdi>.</cite>

</li>

<li id="cite_note-lpi-ch6-p121-69">^ <a href="#cite_ref-lpi-ch6-p121_69-0">a</a> <a href="#cite_ref-lpi-ch6-p121_69-1">b</a> <a href="#cite_ref-lpi-ch6-p121_69-2">c</a> <cite id="CITEREFKerrisk2010" class="citation book cs1">Kerrisk, Michael (2010). The Linux Programming Interface. No Starch Press. p. 121. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-1-59327-220-3</bdi>.</cite>

</li>

<li id="cite_note-lpi-ch6-p122-71"><a href="#cite_ref-lpi-ch6-p122_71-0">^</a> <cite id="CITEREFKerrisk2010" class="citation book cs1">Kerrisk, Michael (2010). The Linux Programming Interface. No Starch Press. p. 122. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-1-59327-220-3</bdi>.</cite>

</li>

<li id="cite_note-cpl-ch1-p185-72"><a href="#cite_ref-cpl-ch1-p185_72-0">^</a> <cite id="CITEREFKernighanRitchie1988" class="citation book cs1">Kernighan, Brian W.; Ritchie, Dennis M. (1988). The C Programming Language Second Edition. Prentice Hall. p. 185. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-13-110362-8</bdi>.</cite>

</li>

<li id="cite_note-cpl-ch8-p187-74">^ <a href="#cite_ref-cpl-ch8-p187_74-0">a</a> <a href="#cite_ref-cpl-ch8-p187_74-1">b</a> <cite id="CITEREFKernighanRitchie1988" class="citation book cs1">Kernighan, Brian W.; Ritchie, Dennis M. (1988). The C Programming Language Second Edition. Prentice Hall. p. 187. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-13-110362-8</bdi>.</cite>

</li>

<li id="cite_note-cpl_3rd-ch2-38-76">^ <a href="#cite_ref-cpl_3rd-ch2-38_76-0">a</a> <a href="#cite_ref-cpl_3rd-ch2-38_76-1">b</a> <a href="#cite_ref-cpl_3rd-ch2-38_76-2">c</a> <cite id="CITEREFWilson2001" class="citation book cs1">Wilson, Leslie B. (2001). Comparative Programming Languages, Third Edition. Addison-Wesley. p. 38. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-201-71012-9</bdi>.</cite>

</li>

<li id="cite_note-cpl_3rd-ch8-193-77"><a href="#cite_ref-cpl_3rd-ch8-193_77-0">^</a> <cite id="CITEREFWilson2001" class="citation book cs1">Wilson, Leslie B. (2001). Comparative Programming Languages, Third Edition. Addison-Wesley. p. 193. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-201-71012-9</bdi>.</cite>

</li>

<li id="cite_note-cpl_3rd-ch2-39-78"><a href="#cite_ref-cpl_3rd-ch2-39_78-0">^</a> <cite id="CITEREFWilson2001" class="citation book cs1">Wilson, Leslie B. (2001). Comparative Programming Languages, Third Edition. Addison-Wesley. p. 39. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-201-71012-9</bdi>.</cite>

</li>

<li id="cite_note-cpl_3rd-ch2-35-79"><a href="#cite_ref-cpl_3rd-ch2-35_79-0">^</a> <cite id="CITEREFWilson2001" class="citation book cs1">Wilson, Leslie B. (2001). Comparative Programming Languages, Third Edition. Addison-Wesley. p. 35. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-201-71012-9</bdi>.</cite>

</li>

<li id="cite_note-cpl_3rd-ch8-192-80"><a href="#cite_ref-cpl_3rd-ch8-192_80-0">^</a> <cite id="CITEREFWilson2001" class="citation book cs1">Wilson, Leslie B. (2001). Comparative Programming Languages, Third Edition. Addison-Wesley. p. 192. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-201-71012-9</bdi>.</cite>

</li>

<li id="cite_note-stroustrup-notes-22-81"><a href="#cite_ref-stroustrup-notes-22_81-0">^</a> <cite id="CITEREFStroustrup2013" class="citation book cs1">Stroustrup, Bjarne (2013). The C++ Programming Language, Fourth Edition. Addison-Wesley. p. 22. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-321-56384-2</bdi>.</cite>

</li>

<li id="cite_note-stroustrup-notes-21-82"><a href="#cite_ref-stroustrup-notes-21_82-0">^</a> <cite id="CITEREFStroustrup2013" class="citation book cs1">Stroustrup, Bjarne (2013). The C++ Programming Language, Fourth Edition. Addison-Wesley. p. 21. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-321-56384-2</bdi>.</cite>

</li>

<li id="cite_note-stroustrup-ch2-49-83"><a href="#cite_ref-stroustrup-ch2-49_83-0">^</a> <cite id="CITEREFStroustrup2013" class="citation book cs1">Stroustrup, Bjarne (2013). The C++ Programming Language, Fourth Edition. Addison-Wesley. p. 49. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-321-56384-2</bdi>.</cite>

</li>

<li id="cite_note-cpl_3rd-ch9-218-84">^ <a href="#cite_ref-cpl_3rd-ch9-218_84-0">a</a> <a href="#cite_ref-cpl_3rd-ch9-218_84-1">b</a> <cite id="CITEREFWilson2001" class="citation book cs1">Wilson, Leslie B. (2001). Comparative Programming Languages, Third Edition. Addison-Wesley. p. 218. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-201-71012-9</bdi>.</cite>

</li>

<li id="cite_note-cpl_3rd-ch9-217-85"><a href="#cite_ref-cpl_3rd-ch9-217_85-0">^</a> <cite id="CITEREFWilson2001" class="citation book cs1">Wilson, Leslie B. (2001). Comparative Programming Languages, Third Edition. Addison-Wesley. p. 217. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-201-71012-9</bdi>.</cite>

</li>

<li id="cite_note-dsa-ch3-p103-86"><a href="#cite_ref-dsa-ch3-p103_86-0">^</a> <cite id="CITEREFWeiss1994" class="citation book cs1">Weiss, Mark Allen (1994). Data Structures and Algorithm Analysis in C++. Benjamin/Cummings Publishing Company, Inc. p. 103. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-8053-5443-3</bdi>. <q>When there is a function call, all the important information needs to be saved, such as register values (corresponding to variable names) and the return address (which can be obtained from the program counter)[.] ... When the function wants to return, it ... restores all the registers. It then makes the return jump. Clearly, all of this work can be done using a stack, and that is exactly what happens in virtually every programming language that implements recursion.</q></cite>

</li>

<li id="cite_note-cpl_3rd-ch9-230-87">^ <a href="#cite_ref-cpl_3rd-ch9-230_87-0">a</a> <a href="#cite_ref-cpl_3rd-ch9-230_87-1">b</a> <a href="#cite_ref-cpl_3rd-ch9-230_87-2">c</a> <cite id="CITEREFWilson2001" class="citation book cs1">Wilson, Leslie B. (2001). Comparative Programming Languages, Third Edition. Addison-Wesley. p. 230. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-201-71012-9</bdi>.</cite>

</li>

<li id="cite_note-cpl_3rd-ch9-240-88"><a href="#cite_ref-cpl_3rd-ch9-240_88-0">^</a> <cite id="CITEREFWilson2001" class="citation book cs1">Wilson, Leslie B. (2001). Comparative Programming Languages, Third Edition. Addison-Wesley. p. 240. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-201-71012-9</bdi>.</cite>

</li>

<li id="cite_note-cpl_3rd-ch9-241-89">^ <a href="#cite_ref-cpl_3rd-ch9-241_89-0">a</a> <a href="#cite_ref-cpl_3rd-ch9-241_89-1">b</a> <a href="#cite_ref-cpl_3rd-ch9-241_89-2">c</a> <cite id="CITEREFWilson2001" class="citation book cs1">Wilson, Leslie B. (2001). Comparative Programming Languages, Third Edition. Addison-Wesley. p. 241. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-201-71012-9</bdi>.</cite>

</li>

<li id="cite_note-ArtOfLisp-90"><a href="#cite_ref-ArtOfLisp_90-0">^</a> <cite id="CITEREFJonesMaynardStewart2012" class="citation book cs1">Jones, Robin; Maynard, Clive; Stewart, Ian (December 6, 2012). The Art of Lisp Programming. Springer Science & Business Media. p. 2. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>9781447117193</bdi>.</cite>

</li>

<li id="cite_note-cpl_3rd-ch9-220-91"><a href="#cite_ref-cpl_3rd-ch9-220_91-0">^</a> <cite id="CITEREFWilson2001" class="citation book cs1">Wilson, Leslie B. (2001). Comparative Programming Languages, Third Edition. Addison-Wesley. p. 220. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-201-71012-9</bdi>.</cite>

</li>

<li id="cite_note-cpl_3rd-ch9-221-92"><a href="#cite_ref-cpl_3rd-ch9-221_92-0">^</a> <cite id="CITEREFWilson2001" class="citation book cs1">Wilson, Leslie B. (2001). Comparative Programming Languages, Third Edition. Addison-Wesley. p. 221. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-201-71012-9</bdi>.</cite>

</li>

<li id="cite_note-cpl_3rd-ch9-229-93"><a href="#cite_ref-cpl_3rd-ch9-229_93-0">^</a> <cite id="CITEREFWilson2001" class="citation book cs1">Wilson, Leslie B. (2001). Comparative Programming Languages, Third Edition. Addison-Wesley. p. 229. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-201-71012-9</bdi>.</cite>

</li>

<li id="cite_note-cpl_3rd-ch9-227-94"><a href="#cite_ref-cpl_3rd-ch9-227_94-0">^</a> <cite id="CITEREFWilson2001" class="citation book cs1">Wilson, Leslie B. (2001). Comparative Programming Languages, Third Edition. Addison-Wesley. p. 227. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-201-71012-9</bdi>.</cite>

</li>

<li id="cite_note-cpl_3rd-ch9-222-95">^ <a href="#cite_ref-cpl_3rd-ch9-222_95-0">a</a> <a href="#cite_ref-cpl_3rd-ch9-222_95-1">b</a> <cite id="CITEREFWilson2001" class="citation book cs1">Wilson, Leslie B. (2001). Comparative Programming Languages, Third Edition. Addison-Wesley. p. 222. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-201-71012-9</bdi>.</cite>

</li>

<li id="cite_note-Gordon1996-96"><a href="#cite_ref-Gordon1996_96-0">^</a> <cite id="CITEREFGordon1996" class="citation web cs1"><a href="Michael_J._C._Gordon" title="Michael J. C. Gordon">Gordon, Michael J. C.</a> (1996). <a rel="nofollow" class="external text" href="http://www.cl.cam.ac.uk/~mjcg/papers/HolHistory.html">"From LCF to HOL: a short history"</a>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20160905201847/http://www.cl.cam.ac.uk/~mjcg/papers/HolHistory.html">Archived</a> from the original on 2016-09-05. Retrieved 2021-10-30.</cite>

</li>

<li id="cite_note-cpl_3rd-ch9-233-97"><a href="#cite_ref-cpl_3rd-ch9-233_97-0">^</a> <cite id="CITEREFWilson2001" class="citation book cs1">Wilson, Leslie B. (2001). Comparative Programming Languages, Third Edition. Addison-Wesley. p. 233. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-201-71012-9</bdi>.</cite>

</li>

<li id="cite_note-cpl_3rd-ch9-235-98"><a href="#cite_ref-cpl_3rd-ch9-235_98-0">^</a> <cite id="CITEREFWilson2001" class="citation book cs1">Wilson, Leslie B. (2001). Comparative Programming Languages, Third Edition. Addison-Wesley. p. 235. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-201-71012-9</bdi>.</cite>

</li>

<li id="cite_note-cpl_3rd-ch3-55-99"><a href="#cite_ref-cpl_3rd-ch3-55_99-0">^</a> <cite id="CITEREFWilson2001" class="citation book cs1">Wilson, Leslie B. (2001). Comparative Programming Languages, Third Edition. Addison-Wesley. p. 55. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-201-71012-9</bdi>.</cite>

</li>

<li id="cite_note-100"><a href="#cite_ref-100">^</a> <cite id="CITEREFColmerauerRoussel1992" class="citation journal cs1">Colmerauer, A.; Roussel, P. (1992). <a rel="nofollow" class="external text" href="http://alain.colmerauer.free.fr/alcol/ArchivesPublications/PrologHistory/19november92.pdf">"The birth of Prolog"</a> (PDF). ACM SIGPLAN Notices. 28 (3). Association for Computing Machinery: 5. <a href="Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1145%2F155360.155362">10.1145/155360.155362</a>.</cite>

</li>

<li id="cite_note-Logical_English-101"><a href="#cite_ref-Logical_English_101-0">^</a> Kowalski, R., Dávila, J., Sartor, G. and Calejo, M., 2023. Logical English for law and education. In Prolog: The Next 50 Years (pp. 287–299). Cham: Springer Nature Switzerland.

</li>

<li id="cite_note-cpl_3rd-ch2-35_quote1-102">^ <a href="#cite_ref-cpl_3rd-ch2-35_quote1_102-0">a</a> <a href="#cite_ref-cpl_3rd-ch2-35_quote1_102-1">b</a> <cite id="CITEREFWilson2001" class="citation book cs1">Wilson, Leslie B. (2001). Comparative Programming Languages, Third Edition. Addison-Wesley. p. 35. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-201-71012-9</bdi>. <q>Simula was based on Algol 60 with one very important addition — the class concept. ... The basic idea was that the data (or data structure) and the operations performed on it belong together[.]</q></cite>

</li>

<li id="cite_note-cpl_3rd-ch2-39_quote1-103"><a href="#cite_ref-cpl_3rd-ch2-39_quote1_103-0">^</a> <cite id="CITEREFWilson2001" class="citation book cs1">Wilson, Leslie B. (2001). Comparative Programming Languages, Third Edition. Addison-Wesley. p. 39. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-201-71012-9</bdi>. <q>Originally, a large number of experimental languages were designed, many of which combined object-oriented and functional programming.</q></cite>

</li>

<li id="cite_note-se-ch9-284_quote1-104"><a href="#cite_ref-se-ch9-284_quote1_104-0">^</a> <cite id="CITEREFSchach1990" class="citation book cs1">Schach, Stephen R. (1990). Software Engineering. Aksen Associates Incorporated Publishers. p. 284. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-256-08515-3</bdi>. <q>While it is true that OOD [(object oriented design)] as such is not supported by the majority of popular languages, a large subset of OOD can be used.</q></cite>

</li>

<li id="cite_note-dsa-ch3-p57-105"><a href="#cite_ref-dsa-ch3-p57_105-0">^</a> <cite id="CITEREFWeiss1994" class="citation book cs1">Weiss, Mark Allen (1994). Data Structures and Algorithm Analysis in C++. Benjamin/Cummings Publishing Company, Inc. p. 57. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-8053-5443-3</bdi>.</cite>

</li>

<li id="cite_note-se-ch9-285-106"><a href="#cite_ref-se-ch9-285_106-0">^</a> <cite id="CITEREFSchach1990" class="citation book cs1">Schach, Stephen R. (1990). Software Engineering. Aksen Associates Incorporated Publishers. p. 285. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-256-08515-3</bdi>.</cite>

</li>

<li id="cite_note-cpl_3rd-ch12-290_quote-107"><a href="#cite_ref-cpl_3rd-ch12-290_quote_107-0">^</a> <cite id="CITEREFWilson2001" class="citation book cs1">Wilson, Leslie B. (2001). Comparative Programming Languages, Third Edition. Addison-Wesley. p. 290. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-201-71012-9</bdi>. <q>The syntax (or grammar) of a programming language describes the correct form in which programs may be written[.]</q></cite>

</li>

<li id="cite_note-cpl_3rd-ch4-78_quote1-108"><a href="#cite_ref-cpl_3rd-ch4-78_quote1_108-0">^</a> <cite id="CITEREFWilson2001" class="citation book cs1">Wilson, Leslie B. (2001). Comparative Programming Languages, Third Edition. Addison-Wesley. p. 78. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-201-71012-9</bdi>. <q>The main components of an imperative language are declarations, expressions, and statements.</q></cite>

</li>

<li id="cite_note-cpl_3rd-ch12-290-109">^ <a href="#cite_ref-cpl_3rd-ch12-290_109-0">a</a> <a href="#cite_ref-cpl_3rd-ch12-290_109-1">b</a> <cite id="CITEREFWilson2001" class="citation book cs1">Wilson, Leslie B. (2001). Comparative Programming Languages, Third Edition. Addison-Wesley. p. 290. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-201-71012-9</bdi>.</cite>

</li>

<li id="cite_note-cpl_3rd-ch12-294-110"><a href="#cite_ref-cpl_3rd-ch12-294_110-0">^</a> <cite id="CITEREFWilson2001" class="citation book cs1">Wilson, Leslie B. (2001). Comparative Programming Languages, Third Edition. Addison-Wesley. p. 294. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-201-71012-9</bdi>.</cite>

</li>

<li id="cite_note-discrete-ch10-p615-111"><a href="#cite_ref-discrete-ch10-p615_111-0">^</a> <cite id="CITEREFRosen1991" class="citation book cs1">Rosen, Kenneth H. (1991). <a rel="nofollow" class="external text" href="https://archive.org/details/discretemathemat00rose/page/615">Discrete Mathematics and Its Applications</a>. McGraw-Hill, Inc. p. <a rel="nofollow" class="external text" href="https://archive.org/details/discretemathemat00rose/page/615">615</a>. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-07-053744-6</bdi>.</cite>

</li>

<li id="cite_note-cpl_3rd-ch12-291-112"><a href="#cite_ref-cpl_3rd-ch12-291_112-0">^</a> <cite id="CITEREFWilson2001" class="citation book cs1">Wilson, Leslie B. (2001). Comparative Programming Languages, Third Edition. Addison-Wesley. p. 291. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-201-71012-9</bdi>.</cite>

</li>

<li id="cite_note-discrete-ch10-p616-113"><a href="#cite_ref-discrete-ch10-p616_113-0">^</a> <cite id="CITEREFRosen1991" class="citation book cs1">Rosen, Kenneth H. (1991). <a rel="nofollow" class="external text" href="https://archive.org/details/discretemathemat00rose/page/616">Discrete Mathematics and Its Applications</a>. McGraw-Hill, Inc. p. <a rel="nofollow" class="external text" href="https://archive.org/details/discretemathemat00rose/page/616">616</a>. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-07-053744-6</bdi>.</cite>

</li>

<li id="cite_note-discrete-ch10-p623-114"><a href="#cite_ref-discrete-ch10-p623_114-0">^</a> <cite id="CITEREFRosen1991" class="citation book cs1">Rosen, Kenneth H. (1991). <a rel="nofollow" class="external text" href="https://archive.org/details/discretemathemat00rose/page/623">Discrete Mathematics and Its Applications</a>. McGraw-Hill, Inc. p. <a rel="nofollow" class="external text" href="https://archive.org/details/discretemathemat00rose/page/623">623</a>. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-07-053744-6</bdi>.</cite>

</li>

<li id="cite_note-discrete-ch10-p624-115"><a href="#cite_ref-discrete-ch10-p624_115-0">^</a> <cite id="CITEREFRosen1991" class="citation book cs1">Rosen, Kenneth H. (1991). <a rel="nofollow" class="external text" href="https://archive.org/details/discretemathemat00rose/page/624">Discrete Mathematics and Its Applications</a>. McGraw-Hill, Inc. p. <a rel="nofollow" class="external text" href="https://archive.org/details/discretemathemat00rose/page/624">624</a>. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-07-053744-6</bdi>.</cite>

</li>

<li id="cite_note-cpl_3rd-ch12-297-116"><a href="#cite_ref-cpl_3rd-ch12-297_116-0">^</a> <cite id="CITEREFWilson2001" class="citation book cs1">Wilson, Leslie B. (2001). Comparative Programming Languages, Third Edition. Addison-Wesley. p. 297. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-201-71012-9</bdi>.</cite>

</li>

<li id="cite_note-se-preface1-117"><a href="#cite_ref-se-preface1_117-0">^</a> <cite id="CITEREFSchach1990" class="citation book cs1">Schach, Stephen R. (1990). Software Engineering. Aksen Associates Incorporated Publishers. p. Preface. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-256-08515-3</bdi>.</cite>

</li>

<li id="cite_note-pis-ch12-p507-118">^ <a href="#cite_ref-pis-ch12-p507_118-0">a</a> <a href="#cite_ref-pis-ch12-p507_118-1">b</a> <a href="#cite_ref-pis-ch12-p507_118-2">c</a> <cite id="CITEREFStair2003" class="citation book cs1">Stair, Ralph M. (2003). Principles of Information Systems, Sixth Edition. Thomson. p. 507. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-619-06489-7</bdi>.</cite>

</li>

<li id="cite_note-pis-ch12-p513-119">^ <a href="#cite_ref-pis-ch12-p513_119-0">a</a> <a href="#cite_ref-pis-ch12-p513_119-1">b</a> <cite id="CITEREFStair2003" class="citation book cs1">Stair, Ralph M. (2003). Principles of Information Systems, Sixth Edition. Thomson. p. 513. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-619-06489-7</bdi>.</cite>

</li>

<li id="cite_note-pis-ch12-p514-120"><a href="#cite_ref-pis-ch12-p514_120-0">^</a> <cite id="CITEREFStair2003" class="citation book cs1">Stair, Ralph M. (2003). Principles of Information Systems, Sixth Edition. Thomson. p. 514. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-619-06489-7</bdi>.</cite>

</li>

<li id="cite_note-pis-ch12-p516-121"><a href="#cite_ref-pis-ch12-p516_121-0">^</a> <cite id="CITEREFStair2003" class="citation book cs1">Stair, Ralph M. (2003). Principles of Information Systems, Sixth Edition. Thomson. p. 516. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-619-06489-7</bdi>.</cite>

</li>

<li id="cite_note-se-ch1-8-122"><a href="#cite_ref-se-ch1-8_122-0">^</a> <cite id="CITEREFSchach1990" class="citation book cs1">Schach, Stephen R. (1990). Software Engineering. Aksen Associates Incorporated Publishers. p. 8. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-256-08515-3</bdi>.</cite>

</li>

<li id="cite_note-pis-ch12-p517-123"><a href="#cite_ref-pis-ch12-p517_123-0">^</a> <cite id="CITEREFStair2003" class="citation book cs1">Stair, Ralph M. (2003). Principles of Information Systems, Sixth Edition. Thomson. p. 517. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-619-06489-7</bdi>.</cite>

</li>

<li id="cite_note-se-ch11-345-124"><a href="#cite_ref-se-ch11-345_124-0">^</a> <cite id="CITEREFSchach1990" class="citation book cs1">Schach, Stephen R. (1990). Software Engineering. Aksen Associates Incorporated Publishers. p. 345. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-256-08515-3</bdi>.</cite>

</li>

<li id="cite_note-se-ch10-319-125">^ <a href="#cite_ref-se-ch10-319_125-0">a</a> <a href="#cite_ref-se-ch10-319_125-1">b</a> <a href="#cite_ref-se-ch10-319_125-2">c</a> <a href="#cite_ref-se-ch10-319_125-3">d</a> <cite id="CITEREFSchach1990" class="citation book cs1">Schach, Stephen R. (1990). Software Engineering. Aksen Associates Incorporated Publishers. p. 319. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-256-08515-3</bdi>.</cite>

</li>

<li id="cite_note-se-ch10-331-126">^ <a href="#cite_ref-se-ch10-331_126-0">a</a> <a href="#cite_ref-se-ch10-331_126-1">b</a> <cite id="CITEREFSchach1990" class="citation book cs1">Schach, Stephen R. (1990). Software Engineering. Aksen Associates Incorporated Publishers. p. 331. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-256-08515-3</bdi>.</cite>

</li>

<li id="cite_note-se-ch8-216-127"><a href="#cite_ref-se-ch8-216_127-0">^</a> <cite id="CITEREFSchach1990" class="citation book cs1">Schach, Stephen R. (1990). Software Engineering. Aksen Associates Incorporated Publishers. p. 216. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-256-08515-3</bdi>.</cite>

</li>

<li id="cite_note-se-ch8-219-128">^ <a href="#cite_ref-se-ch8-219_128-0">a</a> <a href="#cite_ref-se-ch8-219_128-1">b</a> <a href="#cite_ref-se-ch8-219_128-2">c</a> <cite id="CITEREFSchach1990" class="citation book cs1">Schach, Stephen R. (1990). Software Engineering. Aksen Associates Incorporated Publishers. p. 219. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-256-08515-3</bdi>.</cite>

</li>

<li id="cite_note-se-ch8-226-129">^ <a href="#cite_ref-se-ch8-226_129-0">a</a> <a href="#cite_ref-se-ch8-226_129-1">b</a> <cite id="CITEREFSchach1990" class="citation book cs1">Schach, Stephen R. (1990). Software Engineering. Aksen Associates Incorporated Publishers. p. 226. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-256-08515-3</bdi>.</cite>

</li>

<li id="cite_note-se-ch8-220-130">^ <a href="#cite_ref-se-ch8-220_130-0">a</a> <a href="#cite_ref-se-ch8-220_130-1">b</a> <cite id="CITEREFSchach1990" class="citation book cs1">Schach, Stephen R. (1990). Software Engineering. Aksen Associates Incorporated Publishers. p. 220. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-256-08515-3</bdi>.</cite>

</li>

<li id="cite_note-se-ch9-258-131"><a href="#cite_ref-se-ch9-258_131-0">^</a> <cite id="CITEREFSchach1990" class="citation book cs1">Schach, Stephen R. (1990). Software Engineering. Aksen Associates Incorporated Publishers. p. 258. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-256-08515-3</bdi>.</cite>

</li>

<li id="cite_note-se-ch9-259-132"><a href="#cite_ref-se-ch9-259_132-0">^</a> <cite id="CITEREFSchach1990" class="citation book cs1">Schach, Stephen R. (1990). Software Engineering. Aksen Associates Incorporated Publishers. p. 259. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-256-08515-3</bdi>.</cite>

</li>

<li id="cite_note-osc-overview-133">^ <a href="#cite_ref-osc-overview_133-0">a</a> <a href="#cite_ref-osc-overview_133-1">b</a> <a href="#cite_ref-osc-overview_133-2">c</a> <cite id="CITEREFSilberschatz1994" class="citation book cs1">Silberschatz, Abraham (1994). Operating System Concepts, Fourth Edition. Addison-Wesley. p. 1. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-201-50480-4</bdi>.</cite>

</li>

<li id="cite_note-pis-ch4-p147_quote1-134"><a href="#cite_ref-pis-ch4-p147_quote1_134-0">^</a> <cite id="CITEREFStair2003" class="citation book cs1">Stair, Ralph M. (2003). Principles of Information Systems, Sixth Edition. Thomson. p. 147. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-619-06489-7</bdi>. <q>The key to unlocking the potential of any computer system is application software.</q></cite>

</li>

<li id="cite_note-pis-ch4-p148-135">^ <a href="#cite_ref-pis-ch4-p148_135-0">a</a> <a href="#cite_ref-pis-ch4-p148_135-1">b</a> <a href="#cite_ref-pis-ch4-p148_135-2">c</a> <a href="#cite_ref-pis-ch4-p148_135-3">d</a> <cite id="CITEREFStair2003" class="citation book cs1">Stair, Ralph M. (2003). Principles of Information Systems, Sixth Edition. Thomson. p. 147. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-619-06489-7</bdi>.</cite>

</li>

<li id="cite_note-pis-ch4-p147_quote2-136"><a href="#cite_ref-pis-ch4-p147_quote2_136-0">^</a> <cite id="CITEREFStair2003" class="citation book cs1">Stair, Ralph M. (2003). Principles of Information Systems, Sixth Edition. Thomson. p. 147. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-619-06489-7</bdi>. <q>[A] third-party software firm, often called a value-added software vendor, may develop or modify a software program to meet the needs of a particular industry or company.</q></cite>

</li>

<li id="cite_note-pis-ch4-p148_quote1-137"><a href="#cite_ref-pis-ch4-p148_quote1_137-0">^</a> <cite id="CITEREFStair2003" class="citation book cs1">Stair, Ralph M. (2003). Principles of Information Systems, Sixth Edition. Thomson. p. 148. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-619-06489-7</bdi>. <q>Heading: Proprietary Software; Subheading: Advantages; Quote: You can get exactly what you need in terms of features, reports, and so on.</q></cite>

</li>

<li id="cite_note-pis-ch4-p148_quote2-138"><a href="#cite_ref-pis-ch4-p148_quote2_138-0">^</a> <cite id="CITEREFStair2003" class="citation book cs1">Stair, Ralph M. (2003). Principles of Information Systems, Sixth Edition. Thomson. p. 148. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-619-06489-7</bdi>. <q>Heading: Proprietary Software; Subheading: Advantages; Quote: Being involved in the development offers a further level of control over the results.</q></cite>

</li>

<li id="cite_note-pis-ch4-p148_quote3-139"><a href="#cite_ref-pis-ch4-p148_quote3_139-0">^</a> <cite id="CITEREFStair2003" class="citation book cs1">Stair, Ralph M. (2003). Principles of Information Systems, Sixth Edition. Thomson. p. 147. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-619-06489-7</bdi>. <q>Heading: Proprietary Software; Subheading: Advantages; Quote: There is more flexibility in making modifications that may be required to counteract a new initiative by one of your competitors or to meet new supplier and/or customer requirements.</q></cite>

</li>

<li id="cite_note-pis-ch4-p149-140">^ <a href="#cite_ref-pis-ch4-p149_140-0">a</a> <a href="#cite_ref-pis-ch4-p149_140-1">b</a> <a href="#cite_ref-pis-ch4-p149_140-2">c</a> <a href="#cite_ref-pis-ch4-p149_140-3">d</a> <cite id="CITEREFStair2003" class="citation book cs1">Stair, Ralph M. (2003). Principles of Information Systems, Sixth Edition. Thomson. p. 149. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-619-06489-7</bdi>.</cite>

</li>

<li id="cite_note-sco-ch1-p11-141"><a href="#cite_ref-sco-ch1-p11_141-0">^</a> <cite id="CITEREFTanenbaum1990" class="citation book cs1">Tanenbaum, Andrew S. (1990). <a rel="nofollow" class="external text" href="https://archive.org/details/structuredcomput00tane/page/11">Structured Computer Organization, Third Edition</a>. Prentice Hall. p. <a rel="nofollow" class="external text" href="https://archive.org/details/structuredcomput00tane/page/11">11</a>. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-13-854662-5</bdi>.</cite>

</li>

<li id="cite_note-lpi-ch2-p21-142">^ <a href="#cite_ref-lpi-ch2-p21_142-0">a</a> <a href="#cite_ref-lpi-ch2-p21_142-1">b</a> <cite id="CITEREFKerrisk2010" class="citation book cs1">Kerrisk, Michael (2010). The Linux Programming Interface. No Starch Press. p. 21. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-1-59327-220-3</bdi>.</cite>

</li>

<li id="cite_note-lpi-ch2-p22-143">^ <a href="#cite_ref-lpi-ch2-p22_143-0">a</a> <a href="#cite_ref-lpi-ch2-p22_143-1">b</a> <a href="#cite_ref-lpi-ch2-p22_143-2">c</a> <a href="#cite_ref-lpi-ch2-p22_143-3">d</a> <a href="#cite_ref-lpi-ch2-p22_143-4">e</a> <cite id="CITEREFKerrisk2010" class="citation book cs1">Kerrisk, Michael (2010). The Linux Programming Interface. No Starch Press. p. 22. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-1-59327-220-3</bdi>.</cite>

</li>

<li id="cite_note-duos-ch6-p152-144">^ <a href="#cite_ref-duos-ch6-p152_144-0">a</a> <a href="#cite_ref-duos-ch6-p152_144-1">b</a> <a href="#cite_ref-duos-ch6-p152_144-2">c</a> <cite id="CITEREFBach1986" class="citation book cs1">Bach, Maurice J. (1986). The Design of the UNIX Operating System. Prentice-Hall, Inc. p. 152. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-13-201799-7</bdi>.</cite>

</li>

<li id="cite_note-sco6th-ch6-p443-145"><a href="#cite_ref-sco6th-ch6-p443_145-0">^</a> <cite id="CITEREFTanenbaum2013" class="citation book cs1">Tanenbaum, Andrew S. (2013). Structured Computer Organization, Sixth Edition. Pearson. p. 443. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-13-291652-3</bdi>.</cite>

</li>

<li id="cite_note-esa-ch1-p8-146"><a href="#cite_ref-esa-ch1-p8_146-0">^</a> <cite id="CITEREFLacamera2018" class="citation book cs1">Lacamera, Daniele (2018). Embedded Systems Architecture. Packt. p. 8. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-1-78883-250-2</bdi>.</cite>

</li>

<li id="cite_note-lpi-ch2-p23-147"><a href="#cite_ref-lpi-ch2-p23_147-0">^</a> <cite id="CITEREFKerrisk2010" class="citation book cs1">Kerrisk, Michael (2010). The Linux Programming Interface. No Starch Press. p. 23. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-1-59327-220-3</bdi>.</cite>

</li>

<li id="cite_note-upe-ch7-p201-148"><a href="#cite_ref-upe-ch7-p201_148-0">^</a> <cite id="CITEREFKernighan1984" class="citation book cs1">Kernighan, Brian W. (1984). The Unix Programming Environment. Prentice Hall. p. 201. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-13-937699-2</bdi>.</cite>

</li>

<li id="cite_note-lpi-ch10-p187-149"><a href="#cite_ref-lpi-ch10-p187_149-0">^</a> <cite id="CITEREFKerrisk2010" class="citation book cs1">Kerrisk, Michael (2010). The Linux Programming Interface. No Starch Press. p. 187. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-1-59327-220-3</bdi>.</cite>

</li>

<li id="cite_note-usp-ch6-p121-150"><a href="#cite_ref-usp-ch6-p121_150-0">^</a> <cite id="CITEREFHaviland1987" class="citation book cs1">Haviland, Keith (1987). Unix System Programming. Addison-Wesley Publishing Company. p. 121. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-201-12919-1</bdi>.</cite>

</li>

<li id="cite_note-pis-ch4-p145-152">^ <a href="#cite_ref-pis-ch4-p145_152-0">a</a> <a href="#cite_ref-pis-ch4-p145_152-1">b</a> <a href="#cite_ref-pis-ch4-p145_152-2">c</a> <cite id="CITEREFStair2003" class="citation book cs1">Stair, Ralph M. (2003). Principles of Information Systems, Sixth Edition. Thomson. p. 145. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-619-06489-7</bdi>.</cite>

</li>

<li id="cite_note-pis-ch4-p146-153">^ <a href="#cite_ref-pis-ch4-p146_153-0">a</a> <a href="#cite_ref-pis-ch4-p146_153-1">b</a> <a href="#cite_ref-pis-ch4-p146_153-2">c</a> <cite id="CITEREFStair2003" class="citation book cs1">Stair, Ralph M. (2003). Principles of Information Systems, Sixth Edition. Thomson. p. 146. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-619-06489-7</bdi>.</cite>

</li>

<li id="cite_note-sco6th-ch1-p6-154">^ <a href="#cite_ref-sco6th-ch1-p6_154-0">a</a> <a href="#cite_ref-sco6th-ch1-p6_154-1">b</a> <cite id="CITEREFTanenbaum2013" class="citation book cs1">Tanenbaum, Andrew S. (2013). Structured Computer Organization, Sixth Edition. Pearson. p. 6. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-13-291652-3</bdi>.</cite>

</li>

<li id="cite_note-sco6th-ch4-p243-155"><a href="#cite_ref-sco6th-ch4-p243_155-0">^</a> <cite id="CITEREFTanenbaum2013" class="citation book cs1">Tanenbaum, Andrew S. (2013). Structured Computer Organization, Sixth Edition. Pearson. p. 243. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-13-291652-3</bdi>.</cite>

</li>

<li id="cite_note-sco6th-ch3-p147-156"><a href="#cite_ref-sco6th-ch3-p147_156-0">^</a> <cite id="CITEREFTanenbaum2013" class="citation book cs1">Tanenbaum, Andrew S. (2013). Structured Computer Organization, Sixth Edition. Pearson. p. 147. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-13-291652-3</bdi>.</cite>

</li>

<li id="cite_note-sco6th-ch3-p148-157"><a href="#cite_ref-sco6th-ch3-p148_157-0">^</a> <cite id="CITEREFTanenbaum2013" class="citation book cs1">Tanenbaum, Andrew S. (2013). Structured Computer Organization, Sixth Edition. Pearson. p. 148. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-13-291652-3</bdi>.</cite>

</li>

<li id="cite_note-sco6th-ch4-p253-158"><a href="#cite_ref-sco6th-ch4-p253_158-0">^</a> <cite id="CITEREFTanenbaum2013" class="citation book cs1">Tanenbaum, Andrew S. (2013). Structured Computer Organization, Sixth Edition. Pearson. p. 253. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-13-291652-3</bdi>.</cite>

</li>

<li id="cite_note-sco6th-ch4-p255-159"><a href="#cite_ref-sco6th-ch4-p255_159-0">^</a> <cite id="CITEREFTanenbaum2013" class="citation book cs1">Tanenbaum, Andrew S. (2013). Structured Computer Organization, Sixth Edition. Pearson. p. 255. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-13-291652-3</bdi>.</cite>

</li>

<li id="cite_note-sco6th-ch3-p161-160"><a href="#cite_ref-sco6th-ch3-p161_160-0">^</a> <cite id="CITEREFTanenbaum2013" class="citation book cs1">Tanenbaum, Andrew S. (2013). Structured Computer Organization, Sixth Edition. Pearson. p. 161. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-13-291652-3</bdi>.</cite>

</li>

<li id="cite_note-sco6th-ch3-p166-161"><a href="#cite_ref-sco6th-ch3-p166_161-0">^</a> <cite id="CITEREFTanenbaum2013" class="citation book cs1">Tanenbaum, Andrew S. (2013). Structured Computer Organization, Sixth Edition. Pearson. p. 166. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-13-291652-3</bdi>.</cite>

</li>

<li id="cite_note-sco6th-ch4-p249-162"><a href="#cite_ref-sco6th-ch4-p249_162-0">^</a> <cite id="CITEREFTanenbaum2013" class="citation book cs1">Tanenbaum, Andrew S. (2013). Structured Computer Organization, Sixth Edition. Pearson. p. 249. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-13-291652-3</bdi>.</cite>

</li>

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