Unicode character property: Difference between revisions

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Revision as of 21:26, 2 January 2025

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{{Short description|Unicode code- point property names and their uses}}

{{Use British English}}

The [[Unicode Standard]] assigns various properties to each Unicode character and [[code point]].<ref name="Chapter4">{{cite web|url=https://www.unicode.org/versions/Unicode16.0.0/core-spec/chapter-4/|date=September 2024|title=The Unicode Standard Version 16 |publisher=The Unicode Consortium |access-date=2024-09-13}}</ref><ref name="UAX44" />

The properties can be used to handle characters (code points) in processes, like in line-breaking, script direction right-to-left or applying controls. Some "character properties" are also defined for code points that have no character assigned and code points that are labeledlabelled like "&lt;not a character>&gt;". The character properties are described in Standard Annex #44.<ref name="UAX44">{{cite web |url=https://www.unicode.org/reports/tr44/ |title=Unicode Standard Annex #44: Unicode Character Database |website=Unicode |date=2024-08-27}}</ref>

Properties have levels of forcefulness: normative, informative, contributory, or provisional. For simplicity of specification, a character property can be assigned by specifying a continuous range of code points that have the same property.<ref>{{cite web|url=https://www.unicode.org/reports/tr44/#Code_Point_Ranges|title=Unicode Standard Annex #44: Unicode Character Database, 4.2.3 Code Point Ranges|website=Unicode |date=2024-08-27}}</ref>

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*<code>alias</code> = corrected name. Obsolete. Now tracked with a separate database, but remains for Unicode 1.0 names.

*'<code>bc'</code> = bidi (bidirectional) category [L, R etc]

*'<code>bm'</code> = bidi mirrored [N or Y]

*'<code>cc'</code> = combining class [position of diacritic]

*<code>decomposition</code> type or <mapping> = letter + diacritic, ligature X Y, superscript X, font X, initial X, medial X, final X, isolated X, vertical X, etc.

*'<code>gc'</code> = general category [letter, symbol, digit, punctuation, case behaviorbehaviour, etc.]

*'<code>nv'</code> = numeric type and value [of a digit]. If numeric type is 'decimal', all 3 slots are filled. If 'digit', the first will be null. (This has been discontinued.) If 'numeric', then the first two will be null and only the last will be used.

The property between <code>alias</code> and <code>upper case</code> is obsolete and is now null for all Unicode characters.

=={{anchor|Name}}Name and alias==

A Unicode character is assigned a unique ''Name'' (na).<ref name="Chapter4"/> The name is composed of uppercase letters A–Z, digits 0–9, [[hyphen-minus]] and [[space (character)|space]]. Some sequences are excluded: names beginning with a space or hyphen, names ending with a space or hyphen, repeated spaces or hyphens, and space after hyphen are not allowed. The name is guaranteed to be unique within Unicode, and can be used to identify a code point and its character. Ideographic characters, of which there are tens of thousands, are named in the pattern "{{Smallcaps|{{lc:CJK UNIFIED IDEOGRAPH}}}}-''hhhh''". For example, {{unichar|4E00}}. Formatting characters arealso namedhave toonames: {{unichar|00A0}}.

The following classesUnicode of code pointcategories do not have a Name (na="")value assigned: Controls (General Category: Cc), Private use (Co), Surrogate (Cs), Non-characters (Cn) and Reserved (Cn). They may be referenced, informally, by a generic or specific meta-name, called "Code Point Labels": {{not a typo|<control>, <control-0088>, <reserved>, <noncharacter-''hhhh''>, <private-use-''hhhh''>, or <surrogate>}}. Since these labels contain "<" and ">", they can never appear in a Name, which prevents confusion.

==={{anchor|Version 1.0 names}}Unicode 1.0 names===

In version 2.0 of Unicode, many names were changed. From then on the rule "a name will never change" came into effect, including the strict (normative) use of alias names. Disused versionUnicode 1.0- names were moved to the property Alias, to provide some backward compatibility.

For example, {{Unichar|264}} has the Unicode 1.0 name "LATIN SMALL LETTER BABY GAMMA".

===Character name alias===

{{main|Unicode alias names and abbreviations}}

Starting from Unicode version 2.0, the published name for a code point will never change. Therefore, in the event of a character name being misspelled or if the character name is completely wrong or seriously misleading, a formal ''Character Name Alias'' may be assigned to the character, and this alias may be used by applications instead of the actual defective character name.<ref name="Chapter4"/> For example, {{unichar|FE18|PRESENTATION FORM FOR VERTICAL RIGHT WHITE LENTICULAR BRAKCET}} has the character name alias "{{sc2|PRESENTATION FORM FOR VERTICAL RIGHT WHITE LENTICULAR BRACKET}}" in order to mitigate the misspelling of "bracket" as {{notatypo|"brakcet"}} {{sic}} in the actual character name; {{unichar|A015|YI SYLLABLE WU}} has the character name alias {{sc2|"YI SYLLABLE ITERATION MARK"}} because, contrary to the character name, it does not have a fixed syllabic value.

In addition to character name aliases which are corrections to defective character names, some characters are assigned aliases which are alternative names or abbreviations. Five types of character name aliases are defined in the Unicode Standard:

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* Abbreviation: Abbreviations or acronyms for control codes, format characters, spaces, and variation selectors.

All formal character name aliases follow the rules for permissible character names, and are guaranteed to be unique within both the character name alias and the character name namespaces (for this reason, the ISO 6429 name "BELL" is not defined as an alias for {{unichar|0007}} because U+1F514 is named "BELL"; U+0007 instead has the alias of "ALERT").<ref name="Chapter4"/>

As of Unicode version 16.0, thirty-five35 formal character name aliases are defined as corrections for defective character names.<ref>{{Cite web | url=https://www.unicode.org/Public/UCD/latest/ucd/NameAliases.txt | title=UCD: Name Aliases|publisher=Unicode Consortium | work=Unicode Character Database | date=2024-04-24 }}</ref>

Apart from these normative names, ''informal names'' may be shown in the Unicode code charts. These are other commonly used names for a character, and do not have the same character restriction. These informal names are not guaranteed to be unique, and may be changed or removed in later versions of the standard.

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===Whitespace===

{{main|Whitespace character}}

'''Whitespace''' is a commonly used concept for a typographic effect. Basically it covers invisible characters that have a spacing effect in rendered text. It includes [[Space (punctuation)|spaces]], tabs, and new line formatting controls. In Unicode, such a character has the property set "<code>WSpace=yes"</code>. In version {{Unicode version|version=16.0}}, there are 25 whitespace characters.

{{Whitespace (Unicode)|state=collapsed}}

===Casing===

The Case value is Normativenormative in Unicode. It pertains to those scripts with uppercase (aka capital, majuscule) and the lowercase (aka small, minuscule) letters. Case-difference occurs in Adlam, Armenian, Cherokee, Coptic, Cyrillic, Deseret, Garay, Glagolitic, Greek, Khutsuri and Mkhedruli Georgian, Latin, Medefaidrin, Old Hungarian, Osage, Vithkuqi and Warang Citi scripts.

<!--(upper, lower, title, folding—both simple and full)-->

Different languages have different case mapping rules.

In Turkish, {{Unichar|0069}} corresponds to {{Unichar|0130}} instead of {{Unichar|0049}}. Similarly, {{Unichar|0049}} when corresponds to {{Unichar|0131}} instead of {{Unichar|0069}}.

In [[Nawdm]], the letter Ĥ corresponds to ɦ in lowercase instead of the usual case mappings being Ĥĥ and Ɦɦ.

In Greek, the letter sigma has different lowercase forms depending on where it is in a word. {{Unichar|03a3}} converts to {{Unichar|03c3}} if it is at the start or middle of a word, and converts to {{Unichar|03c2}} if it is at the end of a word.

In Lithuanian, the dot in lowercase i and j is preserved when followed by accents. For example: Í in lowercase is i̇́.<ref>[http://ftp.unicode.org/Public/UNIDATA/SpecialCasing.txt]</ref>

Despite the existence of {{Unichar|1E9E}}, {{Unichar|00DF}} corresponds to "SS".

Unicode encodes 31 titlecase characters.

* {{Unichar|01C5}}

* {{Unichar|01C8}}

* {{Unichar|01CB}}

* {{Unichar|01F2}}

* {{Unichar|1F88}}

* {{Unichar|1F89}}

* {{Unichar|1F8A}}

* {{Unichar|1F8B}}

* {{Unichar|1F8C}}

* {{Unichar|1F8D}}

* {{Unichar|1F8E}}

* {{Unichar|1F8F}}

* {{Unichar|1F98}}

* {{Unichar|1F99}}

* {{Unichar|1F9A}}

* {{Unichar|1F9B}}

* {{Unichar|1F9C}}

* {{Unichar|1F9D}}

* {{Unichar|1F9E}}

* {{Unichar|1F9F}}

* {{Unichar|1FA8}}

* {{Unichar|1FA9}}

* {{Unichar|1FAA}}

* {{Unichar|1FAB}}

* {{Unichar|1FAC}}

* {{Unichar|1FAD}}

* {{Unichar|1FAE}}

* {{Unichar|1FAF}}

* {{Unichar|1FBC}}

* {{Unichar|1FCC}}

* {{Unichar|1FFC}}

(upper, lower, title, folding—both simple and full)

{{expand section|date=March 2022}}

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Six character properties pertain to bi-directional writing: ''Bidi_Class'', ''Bidi_Control'', ''Bidi_Mirrored'', ''Bidi_Mirroring_Glyph'', ''Bidi_Paired_Bracket'' and ''Bidi_Paired_Bracket_Type''.

One of Unicode's major features is support of bi-directional (''Bidi'') text display right-to-left (R-to-L) and left-to-right (L-to-R). The Unicode Bidirectional Algorithm UAX9<ref name="UAX9">{{cite web|url=https://www.unicode.org/reports/tr9/ |title=Unicode Standard Annex #9: Unicode Bidirectional Algorithm|work=The Unicode Standard|date=2024-09-02}}</ref> describes the process of presenting text with altering script directions. For example, it enables a Hebrew quote in an English text. The ''Bidi_Character_Type'' marks a character's behaviour in directional writing. To override a direction, Unicode has defined special ''formatting control characters'' (''Bidi-Control''s characters). These characters can enforce a direction, and by definition only affect bi-directional writing.

Each code point has a property called ''Bidi_Class''. It defines its behaviour in a bidirectional text as interpreted by the algorithm:

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{{Bidi Class (Unicode)}}

In normal situations, the algorithm can determine the direction of a text by this character property. To control more complex Bidi situations, e.g. when an English text has a Hebrew quote, extra options are added to Unicode. Twelve12 characters have the property {{code|1=Bidi_Control=Yes}}: ALM, FSI, LRE, LRI, LRM, LRO, PDF, PDI, RLE, RLI, RLM and RLO as named in the table. These are invisible formatting control characters, only used by the algorithm and with no effect outside of bidirectional formatting.<ref name="UAX9"/> Despite the name, they are formatting characters, not control characters, and have General category ''Other, format (Cf)'' in the Unicode definition.

Basically, the algorithm determines a sequence of characters with the same strong direction type (R-to-L ''or'' L-to-R), taking in account an overruling by the special Bidi-controls. Number strings (Weak types) are assigned a direction according to their strong environment, as are Neutral characters. Finally, the characters are displayed per a string's direction.

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===Hexadecimal digits===

[[Hexadecimal]] characters are those in the series with hexadecimal values 0...9ABCDEF0123456789ABCDEF (sixteen characters, decimal value 0–15). The character property ''Hex_Digit'' is set to Yes when a character is in such a series:

{{Hexadecimal digit (Unicode)}}

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==Block==

{{main|Unicode block}}

A ''block'' is a uniquely named, contiguous range of code points. It is identified by its first and last code point. Blocks do not [[intersection (set theory)|overlap]], nor do they extend across planes. The number of code points in each block must be a multiple of 16. A block may contain code points that are reserved, not-assigned, etc. Each character that ''is'' assigned, has a single "block name" value from the 338 names assigned as of Unicode version {{Unicode version|version=16.0}}. Unassigned code points outside of an existing block have the default value "No_block".

{{Unicode blocks|state=mw-collapsed}}

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==Age==

''Age'' is the version of the Standardstandard in which the code point was first designated. The version number is shortened to the numbering ''major.minor''', although there more detailed version numbers are used: versions 4.0.0 and 4.0.1 both are named 4.0 as Age. Given the releases, Age can be from the range: 1.1, 2.0, 2.1, 3.0, 3.1, 3.2, 4.0, 4.1, 5.0, 5.1, 5.2, 6.0, 6.1, 6.2, 6.3, 7.0, 8.0, 9.0, 10.0, 11.0, 12.0, 12.1, 13.0, 14.0, 15.0, 15.1, and 16.0.<ref name=DerivedAge>{{Cite web|url=https://www.unicode.org/Public/UCD/latest/ucd/DerivedAge.txt|title=UCD: Derived Age|publisher=Unicode Consortium|work=Unicode Character Database|date=2024-04-30}}</ref> The long values for Age begin in a V and use an underscore instead of a dot: V1_1, for example.<ref name=UAX44 /> Codepoints without a specifically assigned age value have the value "NA", with the long form "Unassigned".

==Deprecated==

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|U+0627 U+065F

|اٟ

|

|-

|U+0F77

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* Line

* Sentence

{{expand section|date=January 2025}}

==Alias name==

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;2. Control

:[[ISO 6429]] names for C0 and C1 control functions and similar commonly occurring names, are added as an alias to the character.

:For example, {{unichar|0008}} has the alias {{smallcaps2|BACKSPACE}}.

;3. Correction

:This is a correction for a "serious problem" in the primary character name, usually an error.

:For example, {{unichar|2118|SCRIPT CAPITAL P}} is actually a ''lowercase'' p, and so is given alias name {{smallcaps2|1=WEIERSTRASS ELLIPTIC FUNCTION}}: "actually this has the form of a lowercase calligraphic p, despite its name, and through the alias the correct spelling is added." In descriptions, with preceding symbol [[reference mark|※]].

;4. Alternate

:A widely used alternate name for a character.

:Example: {{unichar|FEFF|ZERO WIDTH NO-BREAK SPACE}} has the alternate alias {{smallcaps2|1=BYTE ORDER MARK}}.

;5. Figment

:Several documented labels for C1 control code points which were never actually approved in any standard (''[[:wikt:figment|figment]]'' =meaning "feigned, in fiction").

:For example, {{unichar|0099}} has the figment alias {{smallcaps2|1=SINGLE GRAPHIC CHARACTER INTRODUCER}}. This name is an architectural concept from early drafts of ISO/IEC 10646-1, but it was never approved andor standardized.

==External links==

*[https://www.unicode.org/reports/tr44/ Unicode Character Database], annex #44, explaining the different properties

*[https://www.unicode.org/Public/UCD/latest/ucd/UnicodeData.txt UnicodeData.txt] &ndash; a list of all Unicode characters, with their properties