Increment and decrement operators

<h2 id="examples">Examples</h2>
The following C code fragment illustrates the difference between the pre and post increment and decrement operators:

int x;
int y;

// Increment operators
// Pre-increment: x is incremented by 1, then y is assigned the value of x
x = 1;
y = ++x;    // x is now 2, y is also 2

// Post-increment: y is assigned the value of x, then x is incremented by 1
x = 1;
y = x++;    // y is 1, x is now 2

// Decrement operators
// Pre-decrement: x is decremented by 1, then y is assigned the value of x
x = 1;
y = --x;    // x is now 0, y is also 0

// Post-decrement: y is assigned the value of x, then x is decremented by 1
x = 1;
y = x--;    // y is 1, x is now 0

In languages lacking these operators, equivalent results require an extra line of code:

# Pre-increment: y = ++x
x = 1
x = x + 1 # x is now 2 (can be written as "x += 1" in Python)
y = x # y is also 2

# Post-increment: y = x++
x = 1
y = x      # y is 1
x = x + 1  # x is now 2

The post-increment operator is commonly used with <a href="/facts/Array_data_structure/BKGvF8AM">array</a> subscripts. For example:

// Sum the elements of an array
float sum_elements(float arr[], int n)
{
 float sum = 0.0;
 int i = 0;

while (i < n)
 sum += arr[i++]; // Post-increment of i, which steps
 // through n elements of the array
 return sum;
}

The post-increment operator is also commonly used with <a href="/facts/Pointer_(computer_programming)/fPoNzy9b">pointers</a>:

// Copy one array to another
void copy_array(float *src, float *dst, int n)
{
 while (n-- > 0) // Loop that counts down from n to zero
 *dst++ = *src++; // Copies element *(src) to *(dst),
 // then increments both pointers
}

These examples also work in other C-like languages, such as <a href="/facts/C%252B%252B/Et0F2qn9">C++</a>, <a href="/facts/Java_(programming_language)/9ScgFyAL">Java</a>, and <a href="/facts/C_Sharp_(programming_language)/UC2gxeyb">C#</a>.

<ul><li>Increment operator can be demonstrated by an example:#include <stdio.h>
int main()
{
 int c = 2;
 printf("%d\n", c++); // this statement displays 2, then c is incremented by 1 to 3.
 printf("%d", ++c); // this statement increments c by 1, then c is displayed.
 return 0;
}

<ul><li>Output:2
4
</li></ul></li></ul>
<h2 id="supporting-languages">Supporting languages</h2>
The following list, though not complete or all-inclusive, lists some of the major programming languages that support the increment and decrement operators.

<table><tbody><tr><td><ul><li><a href="/facts/AWK/lAQ0leyj">AWK</a><a class="footnote-ref" id="fnref:3" href="#fn:3">3</a></li><li><a href="/facts/Bash_(Unix_shell)/RrYLtEJT">Bash</a><a class="footnote-ref" id="fnref:4" href="#fn:4">4</a></li><li><a href="/facts/C_(programming_language)/Ky2No763">C</a><a class="footnote-ref" id="fnref:5" href="#fn:5">5</a></li><li><a href="/facts/C%252B%252B/Et0F2qn9">C++</a><a class="footnote-ref" id="fnref:6" href="#fn:6">6</a></li><li><a href="/facts/C_Sharp_(programming_language)/UC2gxeyb">C#</a><a class="footnote-ref" id="fnref:7" href="#fn:7">7</a></li><li><a href="/facts/ColdFusion_Markup_Language/AbjNUunm">CFML</a></li><li><a href="/facts/D_(programming_language)/4qIzRjkF">D</a><a class="footnote-ref" id="fnref:8" href="#fn:8">8</a></li></ul></td><td><ul><li><a href="/facts/Go_(programming_language)/oWlsmAFJ">Go</a></li><li><a href="/facts/Java_(programming_language)/9ScgFyAL">Java</a></li><li><a href="/facts/JavaScript/XhhIIEsl">JavaScript</a></li><li><a href="/facts/Objective-C/5mM557BW">Objective-C</a></li><li><a href="/facts/GNU_Octave/vVVq5evM">GNU Octave</a></li><li><a href="/facts/PARI%2fGP/JhTL8ysP">PARI/GP</a><a class="footnote-ref" id="fnref:9" href="#fn:9">9</a></li></ul></td><td><ul><li><a href="/facts/Perl/fx31kjlT">Perl</a></li><li><a href="/facts/PHP/vU6YRJX0">PHP</a></li><li><a href="/facts/PowerShell/G1d10lwn">PowerShell</a><a class="footnote-ref" id="fnref:10" href="#fn:10">10</a></li><li><a href="/facts/Vala_(programming_language)/VnSxeM1b">Vala</a></li><li>Vex, a scripting language in <a href="/facts/Houdini_(software)/h7PwskFC">Houdini</a></li><li><a href="/facts/Wolfram_Language/MDxl50Yq">Wolfram Language</a><a class="footnote-ref" id="fnref:11" href="#fn:11">11</a><a class="footnote-ref" id="fnref:12" href="#fn:12">12</a> </li></ul></td></tr></tbody></table>
Apple's <a href="/facts/Swift_(programming_language)/A7qHQC32">Swift</a> once supported these operators, but they have been depreciated since version 2.2<a class="footnote-ref" id="fnref:13" href="#fn:13">13</a> and removed as of version 3.0.<a class="footnote-ref" id="fnref:14" href="#fn:14">14</a><a class="footnote-ref" id="fnref:15" href="#fn:15">15</a>
<a href="/facts/Pascal_(programming_language)/b3yvp8bF">Pascal</a>, <a href="/facts/Delphi_(programming_language)/sUFUXQ8r">Delphi</a>, <a href="/facts/Modula-2/DFyUTdAq">Modula-2</a>, and <a href="/facts/Oberon_(programming_language)/YHFyy3UU">Oberon</a> uses functions (inc(x) and dec(x)) instead of operators. <a href="/facts/Tcl/s7fbKYtR">Tcl</a> uses the incr command.
Notably <a href="/facts/Python_(programming_language)/YbuGqofa">Python</a> and <a href="/facts/Rust_(programming_language)/8JNMV19F">Rust</a> do not support these operators.

<h2 id="history">History</h2>
The concept was introduced in the <a href="/facts/B_(programming_language)/b9n2WoNN">B programming language</a> circa 1969 by <a href="/facts/Ken_Thompson/KQtrw9YM">Ken Thompson</a>.<a class="footnote-ref" id="fnref:16" href="#fn:16">16</a>

<blockquote>Thompson went a step further by inventing the ++ and -- operators, which increment or decrement; their prefix or postfix position determines whether the alteration occurs before or after noting the value of the operand. They were not in the earliest versions of B, but appeared along the way. People often guess that they were created to use the auto-increment and auto-decrement address modes provided by the DEC PDP-11 on which C and Unix first became popular. This is historically impossible, since there was no PDP-11 when B was developed. The PDP-7, however, did have a few 'auto-increment' memory cells, with the property that an indirect memory reference through them incremented the cell. This feature probably suggested such operators to Thompson; the generalization to make them both prefix and postfix was his own. Indeed, the auto-increment cells were not used directly in implementation of the operators, and a stronger motivation for the innovation was probably his observation that the translation of ++x was smaller than that of x=x+1.</blockquote>
<h2 id="see-also">See also</h2>
<ul><li><a href="/facts/Augmented_assignment/Iu1lCYFP">Augmented assignment</a> – for += and -= operators</li>
<li><a href="/facts/PDP-7/DzyogXEE">PDP-7</a></li>
<li><a href="/facts/PDP-11/9HkGUzFn">PDP-11</a></li>
<li><a href="/facts/Successor_function/R1hhkSEG">Successor function</a></li></ul>

<h2 id="references">References</h2>

<ol>
<li id="fn:1">Richard M Reese.
"Understanding and Using C Pointers".
"Chapter 4. Pointers and Arrays".
O'Reilly Media, Inc.
2013.
ISBN 9781449344184 <a href="https://books.google.com/books?id=-U155tRMLJgC" target="_blank">https://books.google.com/books?id=-U155tRMLJgC</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></li>
<li id="fn:2">Richard Petersen.
"Introductory C with C++".
2019.
Figure 12-12. <a href="https://www.google.com/books/edition/Introductory_C_with_C++/euCvDwAAQBAJ" target="_blank">https://www.google.com/books/edition/Introductory_C_with_C++/euCvDwAAQBAJ</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></li>
<li id="fn:3">"GNU Awk's User Guide". Free Software Foundation. <a href="https://www.gnu.org/software/gawk/manual/html_node/Increment-Ops.html" target="_blank">https://www.gnu.org/software/gawk/manual/html_node/Increment-Ops.html</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></li>
<li id="fn:4">"8.3. The Double-Parentheses Construct". The Linux Documentation Project. <a href="http://tldp.org/LDP/abs/html/dblparens.html" target="_blank">http://tldp.org/LDP/abs/html/dblparens.html</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></li>
<li id="fn:5">Ritchie, Brian W. Kernighan; Dennis M.; Ritchie, Dennis (1988). The C programming language (2. ed., [Nachdr.] ed.). Englewood Cliffs, N.J.: Prentice Hall. p. 18. ISBN 0-13-110362-8.{{cite book}}: CS1 maint: multiple names: authors list (link) <a href="0-13-110362-8" target="_blank">0-13-110362-8</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></li>
<li id="fn:6">"Increment/decrement operators". cppreference.com. <a href="http://en.cppreference.com/w/cpp/language/operator_incdec" target="_blank">http://en.cppreference.com/w/cpp/language/operator_incdec</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></li>
<li id="fn:7">"++ Operator (C# Reference)". Microsoft Developer Network. 8 April 2023. <a href="http://msdn.microsoft.com/en-us/library/36x43w8w.aspx" target="_blank">http://msdn.microsoft.com/en-us/library/36x43w8w.aspx</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></li>
<li id="fn:8">"Operator Overloading". dlang.org. <a href="https://dlang.org/spec/operatoroverloading.html" target="_blank">https://dlang.org/spec/operatoroverloading.html</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></li>
<li id="fn:9">"GP Operators and their Priorities". <a href="https://pari.math.u-bordeaux.fr/dochtml/html-stable/operators.html" target="_blank">https://pari.math.u-bordeaux.fr/dochtml/html-stable/operators.html</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></li>
<li id="fn:10">"About Assignment Operators". 19 January 2024. <a href="https://docs.microsoft.com/en-us/powershell/module/microsoft.powershell.core/about/about_assignment_operators" target="_blank">https://docs.microsoft.com/en-us/powershell/module/microsoft.powershell.core/about/about_assignment_operators</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></li>
<li id="fn:11">"Increment Wolfram Language Symbol". Wolfram Language Documentation Center. <a href="https://reference.wolfram.com/language/ref/Increment.html" target="_blank">https://reference.wolfram.com/language/ref/Increment.html</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></li>
<li id="fn:12">"Decrement Wolfram Language Symbol". Wolfram Language Documentation Center. <a href="https://reference.wolfram.com/language/ref/Decrement.html" target="_blank">https://reference.wolfram.com/language/ref/Decrement.html</a> <a href="#fnref:12" class="footnote-back-ref">↩</a></li>
<li id="fn:13">"New Features in Swift 2.2". Swift Official Website. 30 March 2016. <a href="https://www.swift.org/blog/swift-2.2-new-features/#-and----are-deprecated" target="_blank">https://www.swift.org/blog/swift-2.2-new-features/#-and----are-deprecated</a> <a href="#fnref:13" class="footnote-back-ref">↩</a></li>
<li id="fn:14">"Swift 3.0 Released!". Swift Official Website. 13 September 2016. <a href="https://www.swift.org/blog/swift-3.0-released/" target="_blank">https://www.swift.org/blog/swift-3.0-released/</a> <a href="#fnref:14" class="footnote-back-ref">↩</a></li>
<li id="fn:15">"Remove the ++ and -- operators". Swift evolution. <a href="https://github.com/swiftlang/swift-evolution/blob/main/proposals/0004-remove-pre-post-inc-decrement.md" target="_blank">https://github.com/swiftlang/swift-evolution/blob/main/proposals/0004-remove-pre-post-inc-decrement.md</a> <a href="#fnref:15" class="footnote-back-ref">↩</a></li>
<li id="fn:16">Ritchie, Dennis M. (March 1993). "The Development of the C Language". ACM SIGPLAN Notices. 28 (3): 5. doi:10.1145/155360.155580. <a href="/wiki/Dennis_Ritchie" target="_blank">/wiki/Dennis_Ritchie</a> <a href="#fnref:16" class="footnote-back-ref">↩</a></li>
</ol>

Increment and decrement operators open-in-new

Increment and decrement operators