View source for Whitespace character

{{Short description|Any character in typography representing a blank space}}
In [[Computer programming|computer programming]], '''whitespace''' is any [[Character (computing)|character]] or series of characters that represent horizontal or vertical space in typography. When rendered, a whitespace character does not correspond to a visible mark, but typically does occupy an area on a page. For example, the common whitespace symbol {{unichar|0020|SPACE}} (also [[ASCII]] 32) represents a blank space punctuation character in text, used as a word divider in Western [[Social:Writing system|script]]s.

== Overview ==
[[File:Punctuation-Spaces.svg|thumb|upright|Relative widths of various spaces in [[Unicode|Unicode]]]]
With many keyboard layouts, a whitespace character may be entered by pressing {{keypress|spacebar}}. Horizontal whitespace may also be entered on many keyboards with the {{keypress|TAB}} key, although the length of the space may vary. Vertical whitespace may be input by typing {{keypress|Return}}, which creates a 'newline' code sequence in most programs. In some systems {{Keypress|Enter}} has a separate meaning but in others the two are conflated. Many early computer games used whitespace characters to draw a screen (e.g. Kingdom of Kroz).

The term "whitespace" is based on the appearance of the characters on ordinary [[Chemistry:Paper|paper]]. However, within an application, whitespace characters can be processed in the same way as any other character code and different programs may define their own semantics for the characters.

== Unicode ==
The table below lists the twenty-five characters defined as whitespace ("WSpace=Y", "WS") characters in the [[Unicode]] Character Database.<ref>{{cite web|url=http://unicode.org/versions/latest/|title=The Unicode Standard|publisher=Unicode Consortium}}</ref> Seventeen use a definition of whitespace consistent with the algorithm for [[Unicode character property#Bidirectional writing|bidirectional writing]] ("Bidirectional Character Type=WS") and are known as "Bidi-WS" characters. The remaining characters may also be used, but are not of this "Bidi" type.
{{clear}}

''Note: Depending on the browser and fonts used to view the following table, not all spaces may be displayed properly.''

{{anchor|Visible space}}

=== Substitute images ===
Unicode also provides some visible characters that can be used to represent various whitespace characters, in contexts where a visible symbol must be displayed:
{| class="wikitable nowrap" style="font-size:95%;text-align:center;"
|+ style="font-size:125%;padding-bottom:0.4em;"| Unicode space-illustrating characters (visible)
|- style="vertical-align:bottom;"
! Code !!title="decimal"| Decimal !! Name !! [[Unicode block|Block]]
! Display
! Description
|-  id="U+00B7"
| U+00B7 || 183 || Middle dot || Latin-1 Supplement
|class="Unicode" style="text-align:center;"| <span style="font-size:150%;"> · </span>
|style="text-align:left;white-space:normal;"| Interpunct<br />Named entity: <code>&amp;middot;</code>
|-
| U+21A1 || 8609 || Downwards two headed arrow || Arrows
|class="Unicode" style="text-align:center;"| <span style="font-size:150%;"> ↡ </span>
|-
| U+2261 || 8810 || Identical to || Mathematical <br>Operators
|class="Unicode" style="text-align:center;"| <span style="font-size:150%;"> ≡ </span>
|style="text-align:left;white-space:normal;"| Amongst other uses, is the ECMA-17 / ISO 2047 symbol for line feed<ref name="ECMA-17" />
|-
| U+237D || 9085 || Shouldered open box || Miscellaneous Technical
|class="Unicode" style="text-align:center;"| <span style="font-size:150%;"> ⍽ </span>
|style="text-align:left;white-space:normal;"| Used to indicate a NBSP
|-
| U+23CE || 9166 || Return symbol || Miscellaneous Technical
|class="Unicode" style="text-align:center;"| <span style="font-size:150%;"> ⏎ </span>
|style="text-align:left;white-space:normal;"| Symbol for a return key, which enters a line break
|-
| U+2409 || 9225 || Symbol for horizontal tabulation || Control Pictures
|class="Unicode" style="text-align:center;"| <span style="font-size:150%;"> ␉ </span>
|style="text-align:left;white-space:normal;"| Substitutes for a tab character
|-
| U+240A || 9226 || Symbol for line feed || Control Pictures
|class="Unicode" style="text-align:center;"| <span style="font-size:150%;"> ␊ </span>
|style="text-align:left;white-space:normal;"| Substitutes for a line feed
|-
| U+240B || 9227 || Symbol for vertical tabulation || Control Pictures
|class="Unicode" style="text-align:center;"| <span style="font-size:150%;"> ␋ </span>
|style="text-align:left;white-space:normal;"| Substitutes for a vertical tab (line tab)
|-
| U+240C || 9228 || Symbol for form feed || Control Pictures
|class="Unicode" style="text-align:center;"| <span style="font-size:150%;"> ␌ </span>
|style="text-align:left;white-space:normal;"| Substitutes for a form feed (page break)
|-
| U+240D || 9229 || Symbol for carriage return || Control Pictures
|class="Unicode" style="text-align:center;"| <span style="font-size:150%;"> ␍ </span>
|style="text-align:left;white-space:normal;"| Substitutes for a carriage return
|- id="U+2420"
| U+2420 || 9248 || Symbol for space || Control Pictures
|class="Unicode" style="text-align:center;"| <span style="font-size:150%;"> ␠ </span>
|style="text-align:left;white-space:normal;"| Substitutes for an ASCII space
|- id="U+2422"
| U+2422 || 9250 || Blank symbol || Control Pictures
|class="Unicode" style="text-align:center;"| <span style="font-size:150%;"> ␢ </span>
|style="text-align:left;white-space:normal;"| aka "substitute blank",<ref name="Mackenzie_1980">{{cite book |title=Coded Character Sets, History and Development |series=The Systems Programming Series |author-last=Mackenzie |author-first=Charles E. |year=1980 |edition=1 |publisher=Addison-Wesley Publishing Company, Inc. |isbn=978-0-201-14460-4 |lccn=77-90165 |pages=41, 47, 52, 102–103, 117, 119, 130, 132, 141, 148, 150–151, 212, 424 <!--|ISBN=978-0-201-14460-4 --> |url=https://books.google.com/books?id=6-tQAAAAMAAJ |access-date=2016-05-22}} [https://web.archive.org/web/20160526172151/https://textfiles.meulie.net/bitsaved/Books/Mackenzie_CodedCharSets.pdf]</ref> used in BCDIC,<ref name="Mackenzie_1980"/> [[Software:EBCDIC|EBCDIC]],<ref name="Mackenzie_1980"/> ASCII-1963<ref name="Mackenzie_1980"/><ref name="ASCII-1963">{{cite web |title=American Standard Code for Information Interchange, ASA X3.4-1963 |publisher=American Standards Association (ASA) |date=1963-06-17 |url=https://www.sr-ix.com/Archive/CharCodeHist/X3.4-1963/index.html}}</ref> etc. as a symbol for the word separator
|- id="U+2423"
| U+2423 || 9251 || Open box || Control Pictures
|class="Unicode" style="text-align:center;"| <span style="font-size:150%;"> ␣ </span>
|style="text-align:left;white-space:normal;"| Used in block letter handwriting at least since the 1980s when it is necessary to explicitly indicate the number of space characters (e.g. when programming with pen and paper). Used in a textbook (published 1982, 1984, 1985, 1988 by Springer-Verlag) on [[Modula-2]],<ref>[https://link.springer.com/content/pdf/bfm%3A978-3-642-83565-0%2F1.pdf Niklaus Wirth, ''Programming in Modula-2'' ]</ref> a programming language where space codes require explicit indication. Also used in the keypad<ref group="n">Above the zero "0" or negative "(‒)" key.</ref> of the Texas Instruments' TI-8''x'' series of [[Graphing calculator|graphing calculator]]s.<br />Named entity: <code>&amp;blank;</code>
|-
| U+2424 || 9252 || Symbol for newline || Control Pictures
|class="Unicode" style="text-align:center;"| <span style="font-size:150%;"> ␤ </span>
|style="text-align:left;white-space:normal;"| Substitutes for a line break
|-
| U+25B3 || 9651 || White up-pointing triangle || Geometric Shapes
|class="Unicode" style="text-align:center;"| <span style="font-size:150%;"> △ </span>
|style="text-align:left;white-space:normal;"| Amongst other uses, is the ECMA-17 / ISO 2047 symbol for the ASCII space<ref name="ECMA-17" />
|-
| U+2A5B || 10843 || Logical Or with middle stem || Supplemental <br>Mathematical <br>Operators
|class="Unicode" style="text-align:center;"| <span style="font-size:150%;"> ⩛ </span>
|style="text-align:left;white-space:normal;"| Amongst other uses, is the ECMA-17 / ISO 2047 symbol for vertical tab (line tab)<ref name="ECMA-17" />
|-
| U+2AAA || 10922 || Smaller than || Supplemental <br>Mathematical <br>Operators
|class="Unicode" style="text-align:center;"| <span style="font-size:150%;"> ⪪ </span>
|style="text-align:left;white-space:normal;"| Amongst other uses, is the ECMA-17 / ISO 2047 symbol for carriage return<ref name="ECMA-17" />
|-
| U+2AAB || 10923 || Larger than || Supplemental <br>Mathematical <br>Operators
|class="Unicode" style="text-align:center;"| <span style="font-size:150%;"> ⪫ </span>
|style="text-align:left;white-space:normal;"| Amongst other uses, is the ECMA-17 / ISO 2047 symbol for the tab character<ref name="ECMA-17" />
|-
| U+3037 || 12343 || Ideographic Telegraph Line Feed <br>Separator Symbol || CJK Symbols <br>and Punctuation
|class="Unicode" style="text-align:center;"| <span style="font-size:150%;"> 〷 </span>
|style="text-align:left;white-space:normal;"| Graphic used for code 9999 in [[Chinese telegraph code]], representing a line feed
|}

<references group=n />

; {{anchor|Exact space|Dot space}}Exact space
* The [[Engineering:Cambridge Z88|Cambridge Z88]] provided a special "exact space" (code point 160 aka 0xA0) (invokable by key shortcut {{key press|⌑|SPACE}}<ref name="Cambridge_UG_Keyboard">{{cite web |title=Cambridge Z88 User Guide |at=Basic concepts - The keyboard |version=4.7 |publisher=Cambridge Computer Limited |date=2016 |orig-year=1987 |edition=4th |url=https://cambridgez88.jira.com/wiki/display/UG/The+keyboard |access-date=2016-12-12 |url-status=live |archive-url=https://web.archive.org/web/20161212173159/https://cambridgez88.jira.com/wiki/display/UG/The+keyboard |archive-date=2016-12-12}}</ref>), displayed as "…" by the operating system's display driver.<ref name="Cambridge_UG40_AppendixD">{{cite web |title=Cambridge Z88 User Guide |at=Appendix D |version=4.0 |publisher=Cambridge Computer Limited |date=1987 |edition=4th |url=https://cambridgez88.jira.com/wiki/display/UG40/Appendix+D+-+Character+set |access-date=2016-12-12 |url-status=live |archive-url=https://web.archive.org/web/20161212173345/https://cambridgez88.jira.com/wiki/display/UG40/Appendix+D+-+Character+set |archive-date=2016-12-12}}</ref><ref name="Cambridge_UG_AppendixD">{{cite web |title=Cambridge Z88 User Guide |at=Appendix D |version=4.7 |publisher=Cambridge Computer Limited |date=2015 |orig-year=1987 |edition=4th |url=https://cambridgez88.jira.com/wiki/display/UG/Appendix+D+-+Character+set |access-date=2016-12-12 |url-status=live |archive-url=https://web.archive.org/web/20161212173256/https://cambridgez88.jira.com/wiki/display/UG/Appendix+D+-+Character+set |archive-date=2016-12-12}}</ref> It was therefore also known as "dot space" in conjunction with [[BBC BASIC]].<ref name="Cambridge_UG40_AppendixD"/><ref name="Cambridge_UG_AppendixD"/>
*Under code point 224 (0xE0) the computer also provided a special three-character-cells-wide SPACE symbol <code>"SPC"</code> (analogous to Unicode's single-cell-wide U+2420).<ref name="Cambridge_UG40_AppendixD"/><ref name="Cambridge_UG_AppendixD"/>

=== Non-space blanks ===
* The [[Braille Patterns]] Unicode block contains {{unichar|2800|Braille pattern blank|html=}}, a [[Braille]] pattern with no dots raised. Some fonts display the character as a fixed-width blank, however the Unicode standard explicitly states that it does not act as a space.<ref name="Unicode chart U2800">[https://www.unicode.org/charts/PDF/U2800.pdf Unicode chart U+2800], braille patterns</ref>
* Unicode's coverage of the Korean alphabet includes several code points which represent the absence of a written letter, and thus do not display a glyph:
** Unicode includes a [[KS X 1001#Hangul Filler|Hangul Filler]] character in the [[Hangul Compatibility Jamo]] block ({{unichar|3164|Hangul filler|html=}}). This is classified as a letter, but displayed as an empty space, like a Hangul block containing no jamo. It is used in [[KS X 1001]] Hangul combining sequences to introduce them or denote the absence of a letter in a position, but not in Unicode's combining jamo system.<ref>{{citation|mode=cs1 |url=https://unicode.org/L2/L2017/17081-hangul-filler.pdf |title=Proposal to add an informative note to U+3164 HANGUL FILLER |date=2017-03-30 |first=Jaemin |last=Chung |id=UTC L2/17-081 |publisher=[[Organization:Unicode Consortium|Unicode Consortium]]}}</ref>
** Unicode's combining jamo system uses similar Hangul Choseong Filler and Hangul Jungseong Filler characters to denote the absence of a letter in initial or medial position within a syllable block, which are included in the [[Hangul Jamo (Unicode block)|Hangul Jamo block]] ({{unichar|115F|Hangul Choseong Filler|html=}}, {{unichar|1160|Hangul Jungseong Filler|html=}}).<ref>{{citation|mode=cs1 |url=http://www.unicode.org/charts/PDF/U1100.pdf |title=Hangul Jamo |date=2020-10-25 |publisher=[[Organization:Unicode Consortium|Unicode Consortium]]}}</ref>
** Additionally, a [[KS X 1001#Hangul Filler|Halfwidth Hangul Filler]] is included in the [[Halfwidth and Fullwidth Forms (Unicode block)|Halfwidth and Fullwidth Forms]] ({{unichar|FFA0|Halfwidth Hangul filler|html=}}), which is used when mapping from encodings which include characters from both Johab (or [[KS X 1001#Wansung code charts|Wansung]]) and [[KS X 1001#1974|N-byte Hangul]] (or its [[Software:EBCDIC|EBCDIC]] counterpart), such as IBM-933, which includes both Johab and EBCDIC fillers.<ref>{{cite web|url=http://icu-project.org/icu-bin/convexp?conv=ibm-933|title=ibm-933_P110-1995|work=ICU Demonstration - Converter Explorer|publisher=[[Software:International Components for Unicode|International Components for Unicode]]}}</ref><ref>{{cite web|url=http://icu-project.org/icu-bin/convexp?conv=ibm-933&b=0E84&s=ALL|title=ibm-933_P110-1995 (lead bytes 0E84)|work=ICU Demonstration - Converter Explorer|publisher=[[Software:International Components for Unicode|International Components for Unicode]]}}</ref>

== Whitespace and digital typography ==
[[File:Traditional spacing examples from the 1911 Chicago Manual of Style.png|thumb|upright|The Chicago Manual of Style has rules for using the different sized whitespaces.]]

=== On-screen display ===
[[Software:Text editor|Text editor]]s, [[Software:Word processor|word processor]]s, and desktop publishing software differ in how they represent whitespace on the screen, and how they represent spaces at the ends of lines longer than the screen or column width. In some cases, spaces are shown simply as blank space; in other cases they may be represented by an interpunct or other symbols. Many different characters (described below) could be used to produce spaces, and non-character functions (such as margins and tab settings) can also affect whitespace.

Many of the Unicode space characters were created for compatibility with classic print typography.<ref>{{cite book |title=The Unicode Standard 15.0, electronic edition |chapter=Chapter 6 — Writing Systems and Punctuation |chapter-url=https://www.unicode.org/versions/Unicode15.0.0/ch06.pdf |pages=12–13 (267–268) |quote=The fixed-width space characters (U+2000..U+200A) are derived from conventional (hot lead) typography. Algorithmic kerning and justification in computerized typography do not use these characters. However, where they are used (for example, in typesetting mathematical formulae), their width is generally font-specified, and they typically do not expand during justification. The exception is U+2009 thin space, which sometimes gets adjusted. |url=https://www.unicode.org/versions/Unicode15.0.0/ |publisher=[[Organization:Unicode Consortium|Unicode Consortium]] |date=2022-09-13 |access-date=2022-12-23}}</ref>

Even if digital typography has algorithmic kerning and justification, those space characters can be used to supplement the electronic formatting when needed.

=== Variable-width general-purpose space ===
In computer [[Character encoding|character encoding]]s, there is a normal '''general-purpose space''' (Unicode character U+0020) whose width will vary according to the design of the typeface. Typical values range from 1/5 em to 1/3 em (in digital typography an [[Em (typography)|em]] is equal to the nominal size of the font, so for a 10-point font the space will probably be between 2 and 3.3 points). Sophisticated fonts may have differently sized spaces for bold, italic, and small-caps faces, and often compositors will manually adjust the width of the space depending on the size and prominence of the text.

In addition to this general-purpose space, it is possible to encode a space of a specific width. See the table below for a complete list.

=== Hair spaces around dashes ===
Em dashes used as parenthetical dividers, and en dashes when used as word joiners, are usually set continuous with the text.<ref>Usage of the different dash types is illustrated, e.g., in ''The Chicago Manual of Style'', §§ 6.80, 6.83–6.86</ref> However, such a dash can optionally be surrounded with a '''hair space''', U+200A, or '''thin space''', U+2009. The hair space can be written in HTML by using the [[Numeric character reference|numeric character reference]]s <code>&amp;#x200A;</code> or <code>&amp;#8202;</code>, or the named entity <code>&amp;hairsp;</code>, but is not universally supported in browsers yet, {{as of|lc=y|2016|post=.}}{{needs update inline|date=November 2023}} The thin space is named entity <code>&amp;thinsp;</code> and numeric references <code>&amp;#x2009;</code> or <code>&amp;#8201;</code>. These spaces are much thinner than a normal space (except in a [[Monospaced font|monospaced (non-proportional) font]]), with the hair space in particular being the thinnest of horizontal whitespace characters.

{| class="wikitable"
|+ Normal space versus hair and thin spaces (as rendered by your browser)
|-
! <!--Note: spaced em dashes are excluded in the MOS from normal WPian usage-->Normal space with em dash
| left&nbsp;&mdash;&nbsp;right
|-
! Thin space with em dash
| left{{thin space}}&mdash;{{thin space}}right
|-
! Hair space with em dash
| left &mdash; right
|-
! No space with em dash
| left&mdash;right
|}

== Computing applications ==
=== Programming languages ===
In [[Programming language|programming language]] syntax, spaces are frequently used to explicitly separate tokens. In most languages multiple whitespace characters are treated the same as a single whitespace character (outside of quoted strings); such languages are called ''[[Free-form language|free-form]]''. In a few languages, including [[Haskell (programming language)|Haskell]], [[Occam (programming language)|occam]], [[ABC (programming language)|ABC]], and [[Python (programming language)|Python]], whitespace and indentation are used for syntactical purposes. In the satirical language called [[Whitespace (programming language)|Whitespace]], whitespace characters are the only valid characters for programming, while any other characters are ignored.

Excessive use of whitespace, especially ''trailing whitespace'' at the end of lines, is considered a nuisance. However correct use of whitespace can make the code easier to read and help group related logic.

Most languages only recognize ASCII characters as whitespace, or in some cases Unicode newlines as well, but not most of the characters listed above. The C language defines whitespace characters to be "space, horizontal tab, new-line, vertical tab, and form-feed".<ref>http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1548.pdf Section 6.4, paragraph 3</ref> The [[Hypertext Transfer Protocol|HTTP]] network protocol requires different types of whitespace to be used in different parts of the protocol, such as: only the space character in the status line, CRLF at the end of a line, and "linear whitespace" in header values.<ref>{{citation
| title=Hypertext Transfer Protocol—HTTP/1.1| rfc=2616| chapter=2.2 Basic Rules| first1=R. | last1=Fielding| date=June 1999| doi=10.17487/RFC2616| display-authors=0}}</ref>

=== Command-line user interfaces ===
In commands processed by command processors, e.g., in scripts and typed in, the space character can cause problems as it has two possible functions: as part of a command or parameter, or as a parameter or name [[Delimiter|separator]]. Ambiguity can be prevented either by prohibiting embedded spaces, or by enclosing a name with embedded spaces between quote characters.

=== Markup languages ===
Some [[Markup language|markup language]]s, such as SGML, preserve whitespace as written.

Web markup languages such as [[XML]] and [[HTML]] treat whitespace characters specially, including space characters, for programmers' convenience. One or more space characters read by conforming display-time processors of those markup languages are collapsed to 0 or 1 space, depending on their semantic context. For example, double (or more) spaces within text are collapsed to a single space, and spaces which appear on either side of the "<code>=</code>" that separates an attribute name from its value have no effect on the interpretation of the document. Element end tags can contain trailing spaces, and empty-element tags in XML can contain spaces before the "<code>/></code>". In these languages, unnecessary whitespace increases the file size, and so may slow network transfers. On the other hand, unnecessary whitespace can also inconspicuously mark code, similar to, but less obvious than comments in code. This can be desirable to prove an [[Copyright infringement|infringement]] of license or copyright that was committed by copying and pasting.

In XML attribute values, sequences of whitespace characters are treated as a single space when the document is read by a parser.<ref>{{cite web |url=http://www.w3.org/TR/REC-xml/#AVNormalize |title=3.3.3 Attribute-Value Normalization |work=Extensible Markup Language (XML) 1.0 (Fifth Edition) |publisher=World Wide Web Consortium}}</ref> Whitespace in XML element content is not changed in this way by the parser, but an application receiving information from the parser may choose to apply similar rules to element content. An XML document author can use the <code>xml:space="preserve"</code> attribute on an element to instruct the parser to discourage the downstream application from altering whitespace in that element's content.

In most [[HTML element]]s, a sequence of whitespace characters is treated as a single ''inter-word separator'', which may manifest as a single space character when rendering text in a language that normally inserts such space between words.<ref>{{cite web |url=http://www.w3.org/TR/html4/struct/text.html#h-9.1 |title=9.1 Whitespace |work=W3CHTML 4.01 Specification |publisher=World Wide Web Consortium}}</ref> Conforming HTML renderers are required to apply a more literal treatment of whitespace within a few prescribed elements, such as the <code>pre</code> tag and any element for which [[Cascading Style Sheets|CSS]] has been used to apply <code>pre</code>-like whitespace processing. In such elements, space characters will not be "collapsed" into inter-word separators.

In both XML and HTML, the non-breaking space character, along with other non-"standard" spaces, is not treated as collapsible "whitespace", so it is not subject to the rules above.

=== File names ===
Such usage is similar to multiword file names written for operating systems and applications that are confused by embedded space codes&mdash;such file names instead use an underscore (_) as a word separator, as_in_this_phrase.

Another such symbol was {{unichar|2422|Blank symbol}}. This was used in the early years of computer programming when writing on coding forms. [[Engineering:Keypunch|Keypunch]] operators immediately recognized the symbol as an "explicit space".<ref name="Mackenzie_1980"/> It was used in BCDIC,<ref name="Mackenzie_1980"/> [[Software:EBCDIC|EBCDIC]],<ref name="Mackenzie_1980"/> and ASCII-1963.<ref name="Mackenzie_1980"/>

== See also ==
{{div col}}
* Carriage return
* [[Em (typography)]]
* En (typography)
* Form feed
* Indent style
* Line feed
* Newline
* [[Programming style]]
* Prosigns for Morse code
* {{section link|Regular expression|Character classes}} for the white-space character class.
* Space bar
* Space (punctuation)
* Tab key
* [[Trimming (computer programming)]]
* [[Whitespace (programming language)]]
* Zero-width space
{{div col end}}

== References ==
{{reflist|30em}}

== External links ==
* [http://unicode.org/Public/UNIDATA/PropList.txt Property List of Unicode Character Database]

{{DEFAULTSORT:Whitespace (Computer Science)}}
[[Category:Character encoding]]
[[Category:Source code]]

{{Sourceattribution|Whitespace character}}