View source for Indentation (typesetting)

{{Short description|Empty space at the beginning of a line to signal the start of a new paragraph}}
__FORCETOC__
In the written form of many [[Social:Language|language]]s, an '''indentation''' or '''indent''' is an empty space at the beginning of a line to signal the start of a new paragraph. Many computer languages have adopted this technique to designate "paragraphs" or other logical blocks in the program.

For example, the following lines are indented, using between one and six spaces:

&nbsp;This paragraph is indented by 1 space.

&nbsp;&nbsp;&nbsp;This paragraph is indented by 3 spaces.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;This paragraph is indented by 6 spaces.

In computer programming, the neologisms '''outdent''', '''unindent''' and '''dedent''' are used to describe the reversal of the indentation process, realigning text with the page margin (or with previous, lesser, levels of indentation).

In [[Right-to-left|right-to-left]] languages (e.g. Hebrew and [[Social:Arabic|Arabic]]), indentation is used just the same, but from the right margin of the paper, where the line begins.

==Indentation in typesetting==
There are three main types of indentation, illustrated below in relation to borders representing the page dimensions.

{{glossary begin}}
{{term|1=first-line indentation|style=font-weight: normal;|content={{anchors|first-line indent|first line indent|first line indentation|1st-line indent|1st-line indentation|1st line indent|1st line indentation|first-line|first line|1st-line|first line|firstline|firstline indent|firstline indentation}}
A '''first-line indentation''' indents only the first line of each paragraph.
}}
{{defn|content=
A first-line indentation of 2&nbsp;[[Em (typography)|em]]:
<div style="background: #ECCFFF; width: 50%;"><div style="text-indent: 2em; border-left: thin solid #999999; border-right: thin solid #999999; padding-left: 1em; padding-right: 1em; margin-top: 0.5em; margin-bottom: 1em;">{{lorem ipsum|link=yes}}&nbsp;</div></div>
}}
{{term|1=hanging indentation|style=font-weight: normal;|content={{anchor|hanging indent}}
A '''hanging indentation''' indents the remaining lines of each paragraph while leaving the first line of each paragraph in place.
}}
{{defn|content=
A hanging indentation of 2&nbsp;em:
<div style="background: #FFFCFA; width: 50%;"><div style="padding-left: 3em; text-indent: -2em; border-left: thin solid #999999; border-right: thin solid #999999; padding-right:1em; margin-top: 0.5em; margin-bottom: 1em;">{{lorem ipsum}}</div></div>
}}
{{term|1=block indentation|style=font-weight: normal;|content={{anchor|block indent|block quote|block quotation|blockquote}}
A '''block indentation''' indents the entire block of text.
}}
{{defn|content=
A block indentation of 2&nbsp;em on the left:
<div style="background: #FFFCFA; width: 50%;"><div style="padding-left: 3em; border-left: thin solid #999999; border-right: thin solid #999999; padding-right:1em; margin-top: 0.5em; margin-bottom: 1em;">{{lorem ipsum}}</div></div>
}}
{{defn|1=Indentation from both sides is commonly used for block quotations, here shown with 2&nbsp;em on the left and right (which may amount to more on the right for certain lines, depending on word wrapping, if the text does not have justified alignment):
<div style="background: #FFFCFA; width: 50%;"><div style="padding-left: 3em; padding-right:3em; border-left: thin solid #999999; border-right: thin solid #999999; margin-top: 0.5em; margin-bottom: 1em;">{{lorem ipsum}}</div></div>
}}
{{defn|1=A justified-text example of a block quotation that has been block-indented from both sides by 3&nbsp;em:
<div style="background: #FFFCFA; width: 50%;"><div style="padding-left: 3em; padding-right:3em; text-align: justify; border-left: thin solid #999999; border-right: thin solid #999999; margin-top: 0.5em; margin-bottom: 1em;">{{lorem ipsum}}</div></div>
}}
{{glossary end}}

==Indentation in programming==
{{main|Indentation style}}
In computer [[Programming language|programming language]]s, indentation is used to format program [[Source code|source code]] to improve readability. Indentation is generally only of use to programmers; [[Compiler|compiler]]s and [[Interpreter (computing)|interpreters]] rarely care how much [[Whitespace character|whitespace]] is present in between programming statements. However, certain programming languages rely on the use of indentation to demarcate programming structure, often using a variation of the [[Off-side rule|off-side rule]]. The [[Haskell (programming language)|Haskell]], [[Occam (programming language)|Occam]], [[Python (programming language)|Python]], MoonScript, and Ya programming languages rely on indentation in this way.

Opinions about where to indent, whether to use spaces or tabs, and how many spaces to use are often hotly debated among programmers, leading some to describe indentation disputes as akin to a [[Social:Religious war|religious war]].<ref>{{cite web|url=http://www.jwz.org/doc/tabs-vs-spaces.html |title=Tabs versus Spaces: An Eternal Holy War |website=Jwz.org |date=2007-01-05 |access-date=2014-01-18}}</ref> In 2006 a third method of indentation was proposed, called elastic tabstops.

In addition to general indentation of statements, different bracket indentation styles are commonly used.

{{undue weight|table|to=a single company's coding practices|reason=Do we actually care what Google does?  Google is a company writing code, not an organization, publisher, or author setting coding standards.|date=March 2016}}
{| class="wikitable"
|-
!Language !! Indentation !! Note
|-
| [[Software:Bash (Unix shell)|Bash]] || varies || Fritz Mehner's Style Guide<ref>{{cite web|url=https://lug.fh-swf.de/vim/vim-bash/StyleGuideShell.en.pdf|title=Bash Style Guide and Coding Standard|website=Lug.fh-swf.de}}</ref> suggests 2, 4, or 8 spaces and uses 2 in all examples. [[Company:Google|Google]] uses 2 spaces.<ref>{{cite web |url=https://google-styleguide.googlecode.com/svn/trunk/shell.xml |title=Archived copy |access-date=2014-06-23 |url-status=dead |archive-url=https://web.archive.org/web/20140626134128/http://google-styleguide.googlecode.com/svn/trunk/shell.xml |archive-date=2014-06-26 }} </ref>
|-
| [[C (programming language)|C]] || varies || The [[Software:Linux kernel|Linux kernel]] uses 1 tab.<ref>{{cite web |url=https://www.kernel.org/doc/Documentation/CodingStyle |title=Archived copy |access-date=2015-02-15 |url-status=dead |archive-url=https://web.archive.org/web/20150214004842/https://www.kernel.org/doc/Documentation/CodingStyle |archive-date=2015-02-14 }} </ref><ref>
{{cite web
|url=https://www.kernel.org/doc/html/latest/process/coding-style.html
|title=Linux kernel coding style
|access-date=2022-07-21
|url-status=live
|archive-url=https://web.archive.org/web/20220611181038/https://www.kernel.org/doc/html/latest/process/coding-style.html
|archive-date=2022-06-11
}}
</ref> [[Organization:NASA|NASA]] uses 4 spaces.<ref>{{cite web|url=https://ntrs.nasa.gov/citations/19950022400|title=C STYLE GUIDE|date=August 1994|website=NASA Technical Reports Server}}</ref> Clinton Staley advocates 3 spaces.<ref>{{Cite web|last=Staley|first=Clinton|date=2006|title=C Program Style Rules|url=https://users.csc.calpoly.edu/~cstaley/General/CStyle.htm|website=Cal Poly Department of Computer Science & Software Engineering}}</ref>
|-
| [[C++]] || varies || WebKit recommends 4 spaces.<ref>{{Cite web|date=2015-11-07|title=Code Style Guidelines|url=https://webkit.org/code-style-guidelines/|access-date=2021-12-31|website=WebKit}}</ref> Google uses 2 spaces.<ref>[http://google-styleguide.googlecode.com/svn/trunk/cppguide.html#Spaces_vs._Tabs]  {{webarchive|url=https://web.archive.org/web/20141006093744/http://google-styleguide.googlecode.com/svn/trunk/cppguide.html|date=2014-10-06}}</ref>
|-
| [[C Sharp (programming language)|C#]] || 4&nbsp;spaces || Per [[Company:Microsoft|Microsoft]]'s C# Coding Conventions.<ref>{{cite web|url=http://msdn.microsoft.com/en-us/library/vstudio/ff926074.aspx|title=C# Coding Conventions (C# Programming Guide)|author=Bill Wagner|website=Msdn.microsoft.com|access-date=3 September 2017}}</ref>
|-
| [[CSS]] || varies || [[Software:Drupal|Drupal]], [[GitHub]], and Google use 2 spaces.<ref>{{cite web|url=https://drupal.org/node/1887862 |title=CSS formatting guidelines |website=Drupal.org |date=14 January 2013 |access-date=2014-01-18}}</ref><ref>{{cite web|url=https://github.com/styleguide/css |title=CSS · Styleguide · GitHub |website=Github.com |access-date=2014-01-18}}</ref><ref name="google">{{cite web |url=http://google-styleguide.googlecode.com/svn/trunk/htmlcssguide.xml#Indentation |title=Google HTML/CSS Style Guide |at=Indentation |quote=Indent by 2 spaces at a time. |work=Google GitHub |access-date=2016-03-13 |archive-url=https://web.archive.org/web/20160313125550/https://google-styleguide.googlecode.com/svn/trunk/htmlcssguide.xml#Indentation |archive-date=2016-03-13 |url-status=dead }} This is an HTML-rendered copy of the official version, which is maintained in XML format</ref><ref>{{cite web|url=https://github.com/google/styleguide|title=styleguide: Style guides for Google-originated open-source projects|date=3 September 2017|website=Github.com|access-date=3 September 2017}}</ref> [[Software:WordPress|WordPress]] uses tabs.<ref>{{cite web|url=https://make.wordpress.org/core/handbook/best-practices/coding-standards/css/#structure |title=WordPress › CSS Coding Standards « Make WordPress Core |website=Make.wordpress.org |date=17 July 2012 |access-date=2018-07-20}}</ref>
|-
| [[Dart (programming language)|Dart]] || || <code>dart format</code> uses 2 spaces.
|-
| [[Delphi (programming language)|Delphi]] || 2 spaces || Per Delphi Style Guide.<ref>{{cite web|url=https://docwiki.embarcadero.com/RADStudio/Alexandria/en/White_Space_Usage#Indentation|title=Delphi's Object Pascal Style Guide - White Space Usage|access-date=13 December 2022 |language=en-us}}</ref>
|-
| [[F Sharp (programming language)|F#]] || 4 spaces || As per the F# style guide.<ref>{{cite web |title=F# code formatting guidelines |url=https://docs.microsoft.com/en-us/dotnet/fsharp/style-guide/formatting |website=docs.microsoft.com |access-date=14 October 2020 |language=en-us}}</ref>
|-
| [[Go (programming language)|Go]] || 1&nbsp;tab || Per "Effective Go".<ref>{{cite web|url=http://golang.org/doc/effective_go.html|title=Effective Go – The Go Programming Language|website=golang.org|access-date=3 September 2017}}</ref>
|-
| [[Haskell (programming language)|Haskell]] || varies || Google uses 2 spaces.<ref>{{cite web|url=https://code.google.com/p/ganeti/wiki/HaskellStyleGuide#Indentation |title=HaskellStyleGuide – ganeti – Style Guide for the Haskell code – Cluster-based virtualization management software – Google Project Hosting |website=Code.google.com |date=2014-01-08 |access-date=2014-01-18 |url-status=dead |archive-url=https://web.archive.org/web/20130627194135/http://code.google.com/p/ganeti/wiki/HaskellStyleGuide |archive-date=June 27, 2013 }}</ref>
|-
| [[HTML]] || varies || Google uses 2 spaces.<ref name="google" /> [[Software:HTML Tidy|HTML Tidy]] defaults to 2 spaces.<ref>{{cite web|url=http://tidy.sourceforge.net/docs/quickref.html#indent-spaces |title=HTML Tidy Configuration Options Quick Reference |website=Tidy.sourceforge.net |date=2008-06-18 |access-date=2014-01-18}}</ref>
|-
| [[Java (programming language)|Java]] || varies || [[Company:Oracle Corporation|Oracle]] uses 4 spaces.<ref>{{cite web|url=http://www.oracle.com/technetwork/java/javase/documentation/codeconventions-136091.html#262 |title=Code Conventions for the Java Programming Language: 4. Indentation |website=Oracle.com |access-date=2014-01-18}}</ref> [[Software:Android (operating system)|Android]] uses 4 spaces.<ref>{{cite web|url=http://source.android.com/source/code-style.html#use-spaces-for-indentation |title=Code Style Guidelines for Contributors &#124; Android Developers |website=Source.android.com |access-date=2014-01-18}}</ref> Most [[Software:Eclipse|Eclipse IDE]] components use tabs.
|-
| [[JavaScript]] || varies || Douglas Crockford advocates 4 spaces.<ref>{{cite web|url=http://javascript.crockford.com/code.html |title=Code Conventions for the JavaScript Programming Language |website=Javascript.crockford.com |date=2006-11-13 |access-date=2014-01-18}}</ref> GitHub and Google uses 2 spaces.<ref>{{cite web |url=https://github.com/styleguide/javascript |title=JavaScript 路 Styleguide |website=Github.com |access-date=2014-01-18 |url-status=dead |archive-url=https://web.archive.org/web/20130815075924/https://github.com/styleguide/javascript |archive-date=2013-08-15 }}</ref><ref>{{cite web |url=http://google-styleguide.googlecode.com/svn/trunk/javascriptguide.xml#Code_formatting |title=JaveScript Style Rules |website=Google-styleguide.googlecode.com |access-date=2014-02-18 |archive-url=https://web.archive.org/web/20140216111413/http://google-styleguide.googlecode.com/svn/trunk/javascriptguide.xml#Code_formatting |archive-date=2014-02-16 |url-status=dead }}</ref> [[Software:JQuery|jQuery]] uses tabs.<ref>{{cite web|author=jQuery Foundation - jquery.org |url=http://contribute.jquery.org/style-guide/js/ |title=JavaScript Style Guide &#124; Contribute to jQuery |website=Contribute.jquery.org |access-date=2014-01-18}}</ref> [[Software:Firefox|Firefox]]'s built-in jsbeautifier defaults to 2 spaces. The built-in [[Prettyprint|prettyprint]]er in [[Software:Google Chrome|Google Chrome]] and [[Software:Internet Explorer|Internet Explorer]] uses 4 spaces.
|-
| [[Julia (programming language)|Julia]]
| 4 spaces
| Per Julia style guide.<ref>{{cite web |title=Style Guide · The Julia Language |url=https://docs.julialang.org/en/v1.6/manual/style-guide/#Indentation |website=docs.julialang.org}}</ref>
|-
| [[Kotlin (programming language)|Kotlin]]
| 4&nbsp;spaces
| Per Kotlin style guide.<ref>{{cite web |title=Coding Conventions – Kotlin Programming Language |url=https://kotlinlang.org/docs/reference/coding-conventions.html |website=Kotlin}}</ref>
|-
| [[Lua (programming language)|Lua]] || 2&nbsp;spaces || Per Lua Style Guide.<ref>{{cite web|url=http://lua-users.org/wiki/LuaStyleGuide|title=lua-users wiki: Lua Style Guide|website=lua-users.org|access-date=3 September 2017}}</ref>
|-
| [[Perl]] || varies || "perlstyle: Perl style guide" says Larry Wall prefers but does not mandate 4&nbsp;spaces.<ref>{{cite web |url= http://perldoc.perl.org/perlstyle.html |title=perlstyle: Perl style guide |work=Perl 5 Version 32.1 Documentation |editor-first=Jon (JJ) |editor-last=Allen |publisher=Perl Foundation |access-date=2021-04-19}}</ref>
|-
| [[Organization:PHP|PHP]] || varies || [[Software:Drupal|Drupal]] use 2 spaces.<ref>{{cite web|url=https://drupal.org/coding-standards#indenting |title=Coding standards |website=Drupal.org |access-date=2014-01-18}}</ref> PEAR and Zend use 4 spaces.<ref>{{cite web|url=http://pear.php.net/manual/en/standards.indenting.php |title=Manual :: Indenting and Line Length |website=Pear.php.net |access-date=2014-01-18}}</ref><ref>{{cite web |url=http://framework.zend.com/wiki/display/ZFDEV/PHP+Coding+Standard+%28draft%29 |title=PHP Coding Standard (draft) – Contributors – Zend Framework Wiki |website=Framework.zend.com |access-date=2014-01-18 |archive-url=https://web.archive.org/web/20080103203245/http://framework.zend.com/wiki/display/ZFDEV/PHP+Coding+Standard+(draft) |archive-date=2008-01-03 |url-status=dead }}</ref> CodeIgniter and WordPress uses tabs.<ref>{{cite web|url=http://ellislab.com/codeigniter/user-guide/general/styleguide.html#code_indenting |title=Style Guide : CodeIgniter User Guide |website=Ellislab.com |access-date=2014-01-18}}</ref><ref>{{cite web|url=http://make.wordpress.org/core/handbook/coding-standards/php/#indentation |title=WordPress › PHP Coding Standards « Make WordPress Core |website=Make.wordpress.org |date=23 July 2012 |access-date=2014-01-18}}</ref> PSR-2 specifies 4 spaces.<ref>{{cite web |url=http://www.php-fig.org/psr/2/ |website=Php-fig.org |access-date=2014-02-18 |title=PHP : Coding Style Guide |url-status=dead |archive-url=https://web.archive.org/web/20140315044508/http://www.php-fig.org/psr/2/ |archive-date=2014-03-15 }}</ref>
|-
| [[PowerShell]] || varies || 4 spaces in The Unofficial PowerShell Best Practices and Style Guide.<ref>{{cite web |title=Code Layout and Formatting – PowerShell Practice and Style |url=https://poshcode.gitbook.io/powershell-practice-and-style/style-guide/code-layout-and-formatting |website=PowerShell Practice and Style |access-date=17 October 2021}}</ref>
|-
| [[Python (programming language)|Python]] || 4&nbsp;spaces || Per PEP-8.<ref>{{cite web|url=https://www.python.org/dev/peps/pep-0008/#indentation|title=PEP 8 – Style Guide for Python Code|website=Python.org|access-date=3 September 2017}}</ref> (1 tab is also sometimes used, but 4 spaces is preferred.)
|-
| [[Ruby (programming language)|Ruby]] || 2&nbsp;spaces || Per Ruby Style Guide.<ref>{{cite web|url=https://github.com/bbatsov/ruby-style-guide|title=ruby-style-guide: A community-driven Ruby coding style guide|first=Bozhidar|last=Batsov|date=3 September 2017|access-date=3 September 2017|website=Github.com}}</ref>
|-
| [[Rust (programming language)|Rust]] || 4&nbsp;spaces || Per Rust Style Guide.<ref>{{cite web|url=https://github.com/rust-lang/rust|title=rust: A safe, concurrent, practical language|date=3 September 2017|website=Github.com|access-date=3 September 2017}}</ref>
|-
| [[Scala (programming language)|Scala]] || 2&nbsp;spaces || Per Scala style guide.<ref>{{cite web|url=http://docs.scala-lang.org/style/indentation.html|title=Indentation – Scala Documentation|website=docs.scala-lang.org|access-date=3 September 2017}}</ref>
|-
| [[Swift (programming language)|Swift]] || varies || Google uses 2 spaces.<ref>{{cite web |title=Swift Style Guide |url=https://google.github.io/swift/ |website=google.github.io |access-date=17 October 2021}}</ref>
|-
| [[Tcl]] || 4&nbsp;spaces || Per Tcl style guide.<ref>{{cite web|url=http://www.tcl.tk/doc/styleGuide.pdf|title=Tcl Style Guide|author=Ray Johnson|website=Tcl.tk|access-date=3 September 2017}}</ref>
|-
| [[Visual Basic .NET|Visual&nbsp;Basic]] || 4&nbsp;spaces || Per Microsoft's Visual Basic Coding Conventions.<ref>{{cite web|url=http://msdn.microsoft.com/en-us/library/aa733583(v=vs.60).aspx|title=Structured Coding Conventions|website=msdn.microsoft.com|access-date=3 September 2017}}</ref>
|-
| [[XML]] || varies || Google uses 2 spaces.<ref>{{cite web |title=Google XML Document Format Style Guide |url=https://google.github.io/styleguide/xmlstyle.html |website=google.github.io |publisher=Google |access-date=17 October 2021}}</ref>
|}

==References==
{{Reflist}}


[[Category:Source code]]

{{Sourceattribution|Indentation (typesetting)}}