Whitespace character

In computer science, whitespace is any character or series of characters that represents horizontal or vertical space in typography. When rendered, a whitespace character does not correspond to a visual mark, but typically does occupy an area on a page. For example, the common whitespace symbol U+0020   SPACE represents a blank space, used as a word divider in Western scripts.

The term "whitespace" is based on the assumption that the background color used for rendered text is white.

Definition and ambiguity

As is common in technical literature, the two words "white space" have found widespread usage as the single term "whitespace", especially when used as an adjective, as in "whitespace character". Some specifications refer to "white space" while others refer to "whitespace"; there is no difference between the terms, although exactly which characters are being referred to does vary from context to context.

The most common whitespace characters may be typed via the space bar or the tab key. Depending on context, a line-break generated by the return or enter key may be considered whitespace as well.

Unicode

See also: Space (punctuation) § Spaces_in_Unicode

In Unicode (Unicode Character Database) the following 26 characters are defined as whitespace character:

Unicode characters with property White_Space=yes
Name	Code point		Width box	May break?	In IDN?	Script	Block	General category	Notes
character tabulation	U+0009	9		Yes	No	Common	Basic Latin	Other, control	HT, Horizontal Tab. HTML/XML named entity: 	, LaTeX: \tab, C escape: \t
line feed	U+000A	10	Is a line-break			Common	Basic Latin	Other, control	LF, Line feed. HTML/XML named entity: 
, C escape: \n
line tabulation	U+000B	11	Is a line-break			Common	Basic Latin	Other, control	VT, Vertical Tab. C escape: \v
form feed	U+000C	12	Is a line-break			Common	Basic Latin	Other, control	FF, Form feed. C escape: \f
carriage return	U+000D	13	Is a line-break			Common	Basic Latin	Other, control	CR, Carriage return. C escape: \r
space	U+0020	32		Yes	No	Common	Basic Latin	Separator, space	Most common (normal ASCII space). LaTeX: \
next line	U+0085	133	Is a line-break			Common	Latin-1 Supplement	Other, control	NEL, Next line. LaTeX: \\
no-break space	U+00A0	160		No	No	Common	Latin-1 Supplement	Separator, space	Non-breaking space: identical to U+0020, but not a point at which a line may be broken. HTML/XML named entity:  ,  , LaTeX: ~
ogham space mark	U+1680	5760		Yes	No	Ogham	Ogham	Separator, space	Used for interword separation in Ogham text. Normally a vertical line in vertical text or a horizontal line in horizontal text, but may also be a blank space in "stemless" fonts. Requires an Ogham font.
en quad	U+2000	8192		Yes	No	Common	General Punctuation	Separator, space	Width of one en. U+2002 is canonically equivalent to this character; U+2002 is preferred.
em quad	U+2001	8193		Yes	No	Common	General Punctuation	Separator, space	Also known as "mutton quad". Width of one em. U+2003 is canonically equivalent to this character; U+2003 is preferred.
en space	U+2002	8194		Yes	No	Common	General Punctuation	Separator, space	Also known as "nut". Width of one en. U+2000 En Quad is canonically equivalent to this character; U+2002 is preferred. HTML/XML named entity:  , LaTeX: \enspace (the LaTeX en space is a no-break space)
em space	U+2003	8195		Yes	No	Common	General Punctuation	Separator, space	Also known as "mutton". Width of one em. U+2001 Em Quad is canonically equivalent to this character; U+2003 is preferred. HTML/XML named entity:  , LaTeX: \quad
three-per-em space	U+2004	8196		Yes	No	Common	General Punctuation	Separator, space	Also known as "thick space". One third of an em wide. HTML/XML named entity:  , LaTeX: \; (the LaTeX thick space is a no-break space)
four-per-em space	U+2005	8197		Yes	No	Common	General Punctuation	Separator, space	Also known as "mid space". One fourth of an em wide. HTML/XML named entity:  
six-per-em space	U+2006	8198		Yes	No	Common	General Punctuation	Separator, space	One sixth of an em wide. In computer typography, sometimes equated to U+2009.
figure space	U+2007	8199		No	No	Common	General Punctuation	Separator, space	Figure space. In fonts with monospaced digits, equal to the width of one digit. HTML/XML named entity:  
punctuation space	U+2008	8200		Yes	No	Common	General Punctuation	Separator, space	As wide as the narrow punctuation in a font, i.e. the advance width of the period or comma. HTML/XML named entity:  
thin space	U+2009	8201		Yes	No	Common	General Punctuation	Separator, space	Thin space; one-fifth (sometimes one-sixth) of an em wide. Recommended for use as a thousands separator for measures made with SI units. Unlike U+2002 to U+2008, its width may get adjusted in typesetting. HTML/XML named entity:  ,  , LaTeX: \, (the LaTeX thin space is a no-break space)
hair space	U+200A	8202		Yes	No	Common	General Punctuation	Separator, space	Thinner than a thin space. HTML/XML named entity:  ,  
line separator	U+2028	8232	Is a line-break			Common	General Punctuation	Separator, line
paragraph separator	U+2029	8233	Is a line-break			Common	General Punctuation	Separator, paragraph
narrow no-break space	U+202F	8239		No	No	Common	General Punctuation	Separator, space	Narrow no-break space. Similar in function to U+00A0 No-Break Space. When used with Mongolian, its width is usually one third of the normal space; in other context, its width sometimes resembles that of the Thin Space (U+2009). LaTeX: \,
medium mathematical space	U+205F	8287		Yes	No	Common	General Punctuation	Separator, space	MMSP. Used in mathematical formulae. Four-eighteenths of an em. In mathematical typography, the widths of spaces are usually given in integral multiples of an eighteenth of an em, and 4/18 em may be used in several situations, for example between the a and the + and between the + and the b in the expression a + b. HTML/XML named entity:  , LaTeX: \: (the LaTeX medium space is a no-break space)
ideographic space	U+3000	12288		Yes	No	Common	CJK Symbols and Punctuation	Separator, space	As wide as a CJK character cell (fullwidth). Used, for example, in tai tou.

Related Unicode characters with property White_Space=no
Name	Code point		Width box	May break?	In IDN?	Script	Block	General category	Notes
mongolian vowel separator	U+180E	6158	᠎	Yes	No	Mongolian	Mongolian	Other, Format	MVS. A narrow space character, used in Mongolian to cause the final two characters of a word to take on different shapes. It is no longer classified as space character (i.e. in Zs category) in Unicode 6.3.0, even though it was in previous versions of the standard.
zero width space	U+200B	8203	​	Yes	No	?	General Punctuation	Other, Format	ZWSP, zero-width space. Used to indicate word boundaries to text processing systems when using scripts that do not use explicit spacing. It is similar to the soft hyphen, with the difference that the latter is used to indicate syllable boundaries, and should display a visible hyphen when the line breaks at it. HTML/XML named entity: ​
zero width non-joiner	U+200C	8204	‌	Yes	Context-dependent	?	General Punctuation	Other, Format	ZWNJ, zero-width non-joiner. When placed between two characters that would otherwise be connected, a ZWNJ causes them to be printed in their final and initial forms, respectively. HTML/XML named entity: ‌
zero width joiner	U+200D	8205	‍	Yes	Context-dependent	?	General Punctuation	Other, Format	ZWJ, zero-width joiner. When placed between two characters that would otherwise not be connected, a ZWJ causes them to be printed in their connected forms. Can also be used to display joining forms in isolation. Depending on whether a ligature or conjunct is expected by default, can either induce (as in emoji and in Sinhala) or suppress (as in Devanagari) substitution with a single glyph, whilst still permitting use of individual joining forms (unlike ZWNJ). HTML/XML named entity: ‍
word joiner	U+2060	8288	⁠	No	No	?	General Punctuation	Other, Format	WJ, word joiner. Similar to U+200B, but not a point at which a line may be broken. HTML/XML named entity: ⁠
zero width non-breaking space	U+FEFF	65279		No	No	?	Arabic Presentation Forms-B	Other, Format	Zero-width non-breaking space. Used primarily as a Byte Order Mark. Use as an indication of non-breaking is deprecated as of Unicode 3.2; see U+2060 instead.

Within the algorithm for Bidirectional writing, Unicode uses another definition of "Whitespace" (Bidirectional Character Type=WS). These Bidi-WS characters (18 out of the 26 listed in the table here) are "Neutral", they do not determine a writing direction, they just follow neighboring characters in this. The eight other characters listed here are also "Neutral", but have a different Bidi-type.

Usage

Computer languages

Runs of whitespace (beyond a first whitespace character) occurring within source code written in computer programming languages are generally ignored; such languages are free-form. But, for example, in Haskell and Python, whitespace and indentation are used for syntactical purposes. And in the language called Whitespace, whitespaces are the only valid characters for programming, while any other characters are ignored.

Still, for most programming languages, abundant 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. In interpreted languages, parsing of unnecessary whitespace may affect the speed of execution. In markup languages like HTML, unnecessary whitespace increases the file size, and may so affect the speed of transfer over a network. 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 infringement of license or copyright that was committed by copying and pasting.

The C language defines whitespace to be "... space, horizontal tab, new-line, vertical tab, and form-feed". The HTTP network protocol requires different types of whitespace to be used in different parts of the protocol, such only the space character in the status line, CRLF at the end of a line, and "linear white space" in header values.

Visible symbol

Sometimes the visible symbol ␣ (Unicode U+2423, decimal 9251, open box) is used to indicate a space. It is much like a closing square bracket ], although not as wide, rotated a quarter-turn clockwise and placed below the writing line. Some fonts render it too narrowly.

This symbol is used in a textbook on the Modula-2 computer language published ca. 1985 by Springer-Verlag, where it is necessary to explicitly indicate a space code. The symbol is also used in the keypad silkscreening of TI-8x series graphing calculators from Texas Instruments.

File names

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

Another such symbol was U+2422 ␢ BLANK SYMBOL. This was used in the early years of computer programming when writing on coding forms. Keypunch operators immediately recognized the symbol as an "explicit space".

See also

• Programming style
• Whitespace (programming language)
• Indent style
• Space (punctuation)
• Trimming (computer programming)
• Regular expression#POSIX character classes: the white space character class

External links

• Propertylist of Unicode Character Database