Unicode

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Unicode
Logo of the Unicode Consortium
Alias(es)
Language(s)See list of scripts
StandardUnicode Standard
Encoding formats
(uncommon)
(obsolete)
Preceded by
This article contains uncommon Unicode characters. Without proper rendering support, you may see question marks, boxes, or other symbols.

Unicode, formally The Unicode Standard,

text encoding standard maintained by the Unicode Consortium designed to support the use of text written in all of the world's major writing systems. Version 15.1 of the standard[A] defines 149813 characters[3] and 161 scripts
used in various ordinary, literary, academic, and technical contexts.

Many common characters, including numerals, punctuation, and other symbols, are unified within the standard and are not treated as specific to any given writing system. Unicode encodes thousands of emoji, with the continued development thereof conducted by the Consortium as a part of the standard.[4] Moreover, the widespread adoption of Unicode was in large part responsible for the initial popularization of emoji outside of Japan. Unicode is ultimately capable of encoding more than 1.1 million characters.

Unicode has largely supplanted the previous environment of myriad incompatible

web pages
, and relevant Unicode support has become a common consideration in contemporary software development.

The Unicode

character repertoire is synchronized with ISO/IEC 10646, each being code-for-code identical with one another. However, The Unicode Standard is more than just a repertoire within which characters are assigned. To aid developers and designers, the standard also provides charts and reference data, as well as annexes explaining concepts germane to various scripts, providing guidance for their implementation. Topics covered by these annexes include character normalization, character composition and decomposition, collation, and directionality.[5]

Unicode text is processed and stored as binary data using one of several encodings, which define how to translate the standard's abstracted codes for characters into sequences of bytes. The Unicode Standard itself defines three encodings: UTF-8, UTF-16, and UTF-32, though several others exist. Of these, UTF-8 is the most widely used by a large margin, in part due to its backwards-compatibility with ASCII.

Origin and development

Unicode was originally designed with the intent of transcending limitations present in all text encodings designed up to that point: each encoding was relied upon for use in its own context, but with no particular expectation of compatibility with any other. Indeed, any two encodings chosen were often totally unworkable when used together, with text encoded in one

Latin characters
—not between a large number of scripts, and not with all of the scripts supported being treated in a consistent manner.

The philosophy that underpins Unicode seeks to encode the underlying characters—

markup, or by some other means. In particularly complex cases, such as the treatment of orthographical variants in Han characters
, there is considerable disagreement regarding which differences justify their own encodings, and which are only graphical variants of other characters.

At the most abstract level, Unicode assigns a unique number called a code point to each character. Many issues of visual representation—including size, shape, and style—are intended to be up to the discretion of the software actually rendering the text, such as a web browser or word processor. However, partially with the intent of encouraging rapid adoption, the simplicity of this original model has become somewhat more elaborate over time, and various pragmatic concessions have been made over the course of the standard's development.

The first 256 code points mirror the ISO/IEC 8859-1 standard, with the intent of trivializing the conversion of text already written in Western European scripts. To preserve the distinctions made by different legacy encodings, therefore allowing for conversion between them and Unicode without any loss of information, many characters nearly identical to others, in both appearance and intended function, were given distinct code points. For example, the Halfwidth and Fullwidth Forms block encompasses a full semantic duplicate of the Latin alphabet, because legacy CJK encodings contained both "fullwidth" (matching the width of CJK characters) and "halfwidth" (matching ordinary Latin script) characters.

The Unicode Bulldog Award is given to people deemed to be influential in Unicode's development, with recipients including Tatsuo Kobayashi, Thomas Milo, Roozbeh Pournader, Ken Lunde, and Michael Everson.[6]

History

The origins of Unicode can be traced back to the 1980s, to a group of individuals with connections to Xerox's Character Code Standard (XCCS).[7] In 1987, Xerox employee Joe Becker, along with Apple employees Lee Collins and Mark Davis, started investigating the practicalities of creating a universal character set.[8] With additional input from Peter Fenwick and Dave Opstad,[7] Becker published a draft proposal for an "international/multilingual text character encoding system in August 1988, tentatively called Unicode". He explained that "the name 'Unicode' is intended to suggest a unique, unified, universal encoding".[7]

In this document, entitled Unicode 88, Becker outlined a scheme using 16-bit characters:[7]

Unicode is intended to address the need for a workable, reliable world text encoding. Unicode could be roughly described as "wide-body ASCII" that has been stretched to 16 bits to encompass the characters of all the world's living languages. In a properly engineered design, 16 bits per character are more than sufficient for this purpose.

This design decision was made based on the assumption that only scripts and characters in "modern" use would require encoding:[7]

Unicode gives higher priority to ensuring utility for the future than to preserving past antiquities. Unicode aims in the first instance at the characters published in the modern text (e.g. in the union of all newspapers and magazines printed in the world in 1988), whose number is undoubtedly far below 214 = 16,384. Beyond those modern-use characters, all others may be defined to be obsolete or rare; these are better candidates for private-use registration than for congesting the public list of generally useful Unicode.

In early 1989, the Unicode working group expanded to include Ken Whistler and Mike Kernaghan of Metaphor, Karen Smith-Yoshimura and Joan Aliprand of Research Libraries Group, and Glenn Wright of Sun Microsystems. In 1990, Michel Suignard and Asmus Freytag of Microsoft and NeXT's Rick McGowan had also joined the group. By the end of 1990, most of the work of remapping existing standards had been completed, and a final review draft of Unicode was ready.

The Unicode Consortium was incorporated in California on 3 January 1991,[9] and the first volume of The Unicode Standard was published that October. The second volume, now adding Han ideographs, was published in June 1992.

In 1996, a surrogate character mechanism was implemented in Unicode 2.0, so that Unicode was no longer restricted to 16 bits. This increased the Unicode codespace to over a million code points, which allowed for the encoding of many historic scripts, such as Egyptian hieroglyphs, and thousands of rarely used or obsolete characters that had not been anticipated for inclusion in the standard. Among these characters are various rarely used CJK characters—many mainly being used in proper names, making them far more necessary for a universal encoding than the original Unicode architecture envisioned.[10]

Version 1.0 of Microsoft's TrueType specification, published in 1992, used the name "Apple Unicode" instead of "Unicode" for the Platform ID in the naming table.

Unicode Consortium

Main article: Unicode Consortium

The Unicode Consortium is a nonprofit organization that coordinates Unicode's development. Full members include most of the main computer software and hardware companies (and few others) with any interest in text-processing standards, including Adobe, Apple, Google, IBM, Meta (previously as Facebook), Microsoft, Netflix, and SAP.[11]

Over the years several countries or government agencies have been members of the Unicode Consortium. Presently only the Ministry of Endowments and Religious Affairs (Oman) is a full member with voting rights.[11]

The Consortium has the ambitious goal of eventually replacing existing character encoding schemes with Unicode and its standard Unicode Transformation Format (UTF) schemes, as many of the existing schemes are limited in size and scope and are incompatible with multilingual environments.

Scripts covered

Main article: Script (Unicode)
scripts in Unicode, as demonstrated by this screenshot from the OpenOffice.org
application.

Unicode currently covers most major

better source needed
]

As of 2024[update], a total of 161 scripts[13] are included in the latest version of Unicode (covering alphabets, abugidas and syllabaries), although there are still scripts that are not yet encoded, particularly those mainly used in historical, liturgical, and academic contexts. Further additions of characters to the already encoded scripts, as well as symbols, in particular for mathematics and music (in the form of notes and rhythmic symbols), also occur.

The Unicode Roadmap Committee (Michael Everson, Rick McGowan, Ken Whistler, V.S. Umamaheswaran)[14] maintain the list of scripts that are candidates or potential candidates for encoding and their tentative code block assignments on the Unicode Roadmap[15] page of the Unicode Consortium website. For some scripts on the Roadmap, such as Jurchen and Khitan large script, encoding proposals have been made and they are working their way through the approval process. For other scripts, such as Numidian and Rongorongo, no proposal has yet been made, and they await agreement on character repertoire and other details from the user communities involved.

Some modern invented scripts which have not yet been included in Unicode (e.g., Tengwar) or which do not qualify for inclusion in Unicode due to lack of real-world use (e.g., Klingon) are listed in the ConScript Unicode Registry, along with unofficial but widely used Private Use Areas code assignments.

There is also a Medieval Unicode Font Initiative focused on special Latin medieval characters. Part of these proposals has been already included in Unicode.

Script Encoding Initiative

The Script Encoding Initiative,[16] a project run by Deborah Anderson at the University of California, Berkeley was founded in 2002 with the goal of funding proposals for scripts not yet encoded in the standard. The project has become a major source of proposed additions to the standard in recent years.[17]

Versions

The Unicode Consortium together with the ISO have developed a shared repertoire following the initial publication of The Unicode Standard: Unicode and the ISO's Universal Coded Character Set (UCS) use identical character names and code points. However, the Unicode versions do differ from their ISO equivalents in two significant ways.

While the UCS is a simple character map, Unicode specifies the rules, algorithms, and properties necessary to achieve interoperability between different platforms and languages. Thus, The Unicode Standard includes more information, covering in-depth topics such as bitwise encoding, collation, and rendering. It also provides a comprehensive catalog of character properties, including those needed for supporting bidirectional text, as well as visual charts and reference data sets to aid implementers. Previously, The Unicode Standard was sold as a print volume containing the complete core specification, standard annexes,[note 2] and code charts. However, version 5.0, published in 2006, was the last version printed this way. Starting with version 5.2, only the core specification, published as a print-on-demand paperback, may be purchased.[18] The full text, on the other hand, is published as a free PDF on the Unicode website.

A practical reason for this publication method highlights the second significant difference between the UCS and Unicode—the frequency with which updated versions are released and new characters added. The Unicode Standard has regularly released annual expanded versions, occasionally with more than one version released in a calendar year and with rare cases where the scheduled release had to be postponed. For instance, in April 2020, a month after version 13.0 was published, the Unicode Consortium announced they had changed the intended release date for version 14.0, pushing it back six months to September 2021 due to the COVID-19 pandemic.

Unicode 15.1, the latest version, was released on 12 September 2023. It is a minor version update to version 15.0—released on 13 September 2022—which added a total of 4,489 new characters, including two new scripts, an extension to the CJK Unified Ideographs block, and multiple additions to existing blocks. 33 new emoji were added, such as the "wireless" (network) symbol and additional colored hearts.[19][20]

Thus far, the following versions of The Unicode Standard have been published. Update versions, which do not include any changes to character repertoire, are signified by the third number (e.g., "version 4.0.1") and are omitted in the table below.[21]

Unicode version history and notable changes to characters and scripts
Version Date Book UCS edition Total Details
Scripts Characters[a]
1.0.0[22] October 1991
ISBN 0-201-56788-1
 — 24 7129 Initial scripts covered:
Gurmukhi, Hangul, Hebrew, Hiragana, Kannada, Katakana, Lao, Latin, Malayalam, Odia, Tamil, Telugu, Thai, and Tibetan
1.0.1[23] June 1992 ISBN 0-201-60845-6
(vol. 2)
 25 28327+21204
−6 		The initial 20,902 CJK Unified Ideographs
1.1[24] June 1993 — ISO/IEC 10646-1:1993

[b]

24 34168+5963
−9 		33 reclassified as control characters. 4,306 Hangul syllables, Tibetan removed
2.0[25] July 1996 ISBN 0-201-48345-9 25 38885+11373
−6656 		Original set of Hangul syllables removed, new set of 11,172 Hangul syllables added at new location, Tibetan added back in a new location and with a different character repertoire, Surrogate character mechanism defined, Plane 15 and Plane 16 Private Use Areas allocated
2.1[26] May 1998 — 38887+2
 		U+20AC € EURO SIGN, U+FFFC  OBJECT REPLACEMENT CHARACTER[26]
3.0[27] September 1999 ISBN 0-201-61633-5 ISO/IEC 10646-1:2000 38 49194+10307
 		Cherokee, Geʽez, Khmer, Mongolian, Burmese, Ogham, runes, Sinhala, Syriac, Thaana, Canadian Aboriginal syllabics, and Yi Syllables, Braille patterns
3.1[28] March 2001 — ISO/IEC 10646-1:2000[c]
ISO/IEC 10646-2:2001 		41 94140+44946
Old Italic, sets of symbols for Western and Byzantine music
, 42,711 additional CJK Unified Ideographs
3.2[29] March 2002 45 95156+1016
 		Philippine scripts (Buhid, Hanunoo, Tagalog, and Tagbanwa)
4.0[30] April 2003 ISBN 0-321-18578-1 ISO/IEC 10646:2003

[d]

52 96382+1226
Tai Le, and Ugaritic, Hexagram symbols
4.1[31] March 2005 — 59 97655+1273
Greek numbers and musical symbols First named character sequences were introduced.[32]
5.0 July 2006 ISBN 0-321-48091-0 64 99024+1369
 		Balinese, cuneiform, N'Ko, ʼPhags-pa, Phoenician[33]
5.1[34] April 2008 — 75 100648+1624
U+1E9E ẞ LATIN CAPITAL LETTER SHARP S
5.2[35] October 2009 ISBN 978-1-936213-00-9 90 107296+6648
 		Avestan, Bamum, Gardiner's sign list of Egyptian hieroglyphs, Imperial Aramaic, Inscriptional Pahlavi, Inscriptional Parthian, Javanese, Kaithi, Lisu, Meetei Mayek, Old South Arabian, Old Turkic, Samaritan, Tai Tham and Tai Viet, additional CJK Unified Ideographs, Jamo for Old Hangul, Vedic Sanskrit
6.0[36] October 2010 ISBN 978-1-936213-01-6 ISO/IEC 10646:2010

[e]

93 109384+2088
emoticons and emoji,[37]
additional CJK Unified Ideographs
6.1[38] January 2012 ISBN 978-1-936213-02-3 ISO/IEC 10646:2012

[f]

100 110116+732
 		Chakma, Meroitic cursive, Meroitic hieroglyphs, Miao, Sharada, Sora Sompeng, and Takri
6.2[39] September 2012 ISBN 978-1-936213-07-8 110117+1
 		U+20BA ₺ TURKISH LIRA SIGN
6.3[40] September 2013 ISBN 978-1-936213-08-5 110122+5
 		5 bidirectional formatting characters
7.0[41] June 2014 ISBN 978-1-936213-09-2 123 112956+2834
Mro, Nabataean, Old North Arabian, Old Permic, Pahawh Hmong, Palmyrene, Pau Cin Hau, Psalter Pahlavi, Siddham, Tirhuta, Warang Citi, and dingbats
8.0[42] June 2015 ISBN 978-1-936213-10-8 ISO/IEC 10646:2014

[g]

129 120672+7716
Old Hungarian, SignWriting, additional CJK Unified Ideographs, lowercase letters for Cherokee, 5 emoji skin tone modifiers
9.0[45] June 2016 ISBN 978-1-936213-13-9 135 128172+7500
 		Adlam, Bhaiksuki, Marchen, Newa, Osage, Tangut, 72 emoji[46]
10.0[47] June 2017 ISBN 978-1-936213-16-0 ISO/IEC 10646:2017

[h]

139 136690+8518
Masaram Gondi, Nüshu, hentaigana, 7,494 CJK Unified Ideographs, 56 emoji, bitcoin
symbol
11.0[48] June 2018 ISBN 978-1-936213-19-1 146 137374+684
 		Dogra, Georgian Mtavruli capital letters, Gunjala Gondi, Hanifi Rohingya, Indic Siyaq Numbers, Makasar, Medefaidrin, Old Sogdian and Sogdian, Maya numerals, 5 CJK Unified Ideographs, symbols for xiangqi and star ratings, 145 emoji
12.0[49] March 2019 ISBN 978-1-936213-22-1 150 137928+554
 		Elymaic, Nandinagari, Nyiakeng Puachue Hmong, Wancho, Miao script, hiragana and katakana small letters, Tamil historic fractions and symbols, Lao letters for Pali, Latin letters for Egyptological and Ugaritic transliteration, hieroglyph format controls, 61 emoji
12.1[50] May 2019 ISBN 978-1-936213-25-2 137929+1
 		U+32FF ㋿ SQUARE ERA NAME REIWA
13.0[51] March 2020 ISBN 978-1-936213-26-9 ISO/IEC 10646:2020

[52]

154 143859+5930
 		Chorasmian, Dhives Akuru, Khitan small script, Yezidi, 4,969 CJK ideographs, Arabic script additions used to write Hausa, Wolof, and other African languages, additions used to write Hindko and Punjabi in Pakistan, Bopomofo additions used for Cantonese, Creative Commons license symbols, graphic characters for compatibility with teletext and home computer systems, 55 emoji
14.0[53] September 2021 ISBN 978-1-936213-29-0 159 144697+838
U+20C0 ⃀ SOM SIGN, Znamenny
musical notation, 37 emoji
15.0[54] September 2022 ISBN 978-1-936213-32-0 161 149186+4489
 		Kawi and Mundari, 20 emoji, 4,192 CJK ideographs, control characters for Egyptian hieroglyphs
15.1[55] September 2023 ISBN 978-1-936213-33-7 149813+627
 		Additional CJK ideographs
  1. surrogate code points
    ).
  2. ^
    • 2.0 added Amendments 5, 6, and 7
    • 2.1 added two characters from Amendment 18.
  3. ^ 3.2 added Amendment 1.
  4. ^
    • 4.1 added Amendment 1
    • 5.0 added Amendment 2 as well as four characters from Amendment 3
    • 5.1 added Amendment 4
    • 5.2 added Amendments 5 and 6
  5. ^ Plus the Indian rupee sign
  6. ^
  7. ^ Plus Amendment 1, as well as the Lari sign, nine CJK unified ideographs, and 41 emoji;[43]
    9.0 added Amendment 2, as well as Adlam, Newa, Japanese TV symbols, and 74 emoji and symbols.[44]
  8. ^
    • Plus 56 emoji, 285 hentaigana characters, and 3 Zanabazar Square characters
    • 11.0 added 46 Mtavruli Georgian capital letters, 5 CJK unified ideographs, and 66 emoji
    • 12.0 added 62 additional characters.

Projected versions

The Unicode Consortium normally releases a new version of The Unicode Standard once a year, or occasionally twice a year. Version 16.0, the next major version, is scheduled to be published in 2024, and is projected to include six new scripts (Todhri, Sunuwar, Gurung Khema, Kirat Rai, Garay, and Ol Onal), additional Burmese numerals for Shan and Mon alphabets, additional symbols for legacy computing, and at least six new emoji.[56][57]

Architecture and terminology

See also: Universal Character Set characters

Codespace and code points

The Unicode Standard defines a codespace:[58] a sequence of integers called code points[59] covering the interval , notated according to the standard as U+0000–U+10FFFF.[60] The codespace is a systematic, architecture-independent representation of The Unicode Standard; actual text is processed as binary data via one of several Unicode encodings, such as UTF-8.

In this normative notation, the two-character prefix U+ always precedes a written code point,[61] and the code points themselves are written as hexadecimal numbers. At least four hexadecimal digits are always written, with leading zeros prepended as needed. For example, the code point U+00F7 ÷ DIVISION SIGN is padded with two leading zeros, but U+13254 𓉔 EGYPTIAN HIEROGLYPH O004 () is not padded.[62]

There are a total of 220 + (216 − 211) = 1112064 valid code points within the codespace. (This number arises from the limitations of the UTF-16 character encoding, which can encode the 216 code points in the range U+0000 through U+FFFF except for the 211 code points in the range U+D800 through U+DFFF, which are used as surrogate pairs to encode the 220 code points in the range U+10000 through U+10FFFF.)

Code planes and blocks

Main article: Plane (Unicode)

The Unicode codespace is divided into 17 planes, numbered 0 to 16. Plane 0 is the

Basic Multilingual Plane (BMP), and contains the most commonly used characters. All code points in the BMP are accessed as a single code unit in UTF-16 encoding and can be encoded in one, two or three bytes in UTF-8. Code points in planes 1 through 16 (the supplementary planes) are accessed as surrogate pairs in UTF-16 and encoded in four bytes in UTF-8
.

Within each plane, characters are allocated within named

blocks
of related characters. The size of a block is always a multiple of 16, and is often a multiple of 128, but is otherwise arbitrary. Characters required for a given script may be spread out over several different, potentially disjunct blocks within the codespace.

General Category property

Each code point is assigned a classification, listed as the code point's

General Category
property. Here, at the uppermost level code points are categorized as one of Letter, Mark, Number, Punctuation, Symbol, Separator, or Other. Under each category, each code point is then further subcategorized. In most cases, other properties must be used to adequately describe all the characteristics of any given code point.

General Category (Unicode Character Property)[a]
Value Category Major, minor Basic type[b] Character assigned[b] Count[c]
(as of 15.1)		 Remarks
 
L, Letter; LC, Cased Letter (Lu, Ll, and Lt only)[d]
Lu Letter, uppercase Graphic Character 1,831
Ll Letter, lowercase Graphic Character 2,233
Lt Letter, titlecase Graphic Character 31
Dz
)
Lm Letter, modifier Graphic Character 397 A modifier letter
Lo Letter, other Graphic Character 132,234 An
unicase alphabet
M, Mark
Mn Mark, nonspacing Graphic Character 1,985
Mc Mark, spacing combining Graphic Character 452
Me Mark, enclosing Graphic Character 13
N, Number
Nd Number, decimal digit Graphic Character 680 All these, and only these, have Numeric Type = De[e]
Nl Number, letter Graphic Character 236 Numerals composed of letters or letterlike symbols (e.g., Roman numerals)
No Number, other Graphic Character 915 E.g.,
subscript
digits
P, Punctuation
Pc Punctuation, connector Graphic Character 10 Includes spacing underscore characters such as "_", and other spacing tie characters. Unlike other punctuation characters, these may be classified as "word" characters by regular expression libraries.[f]
Pd Punctuation, dash Graphic Character 26 Includes several hyphen characters
Ps Punctuation, open Graphic Character 79 Opening bracket characters
Pe Punctuation, close Graphic Character 77 Closing bracket characters
Pi Punctuation, initial quote Graphic Character 12 Opening quotation mark. Does not include the ASCII "neutral" quotation mark. May behave like Ps or Pe depending on usage
Pf Punctuation, final quote Graphic Character 10 Closing quotation mark. May behave like Ps or Pe depending on usage
Po Punctuation, other Graphic Character 628
S, Symbol
Sm Symbol, math Graphic Character 948
≠). Does not include parentheses and brackets, which are in categories Ps and Pe. Also does not include !, *, -, or /
, which despite frequent use as mathematical operators, are primarily considered to be "punctuation".
Sc Symbol, currency Graphic Character 63 Currency symbols
Sk Symbol, modifier Graphic Character 125
So Symbol, other Graphic Character 6,639
Z, Separator
Zs Separator, space Graphic Character 17 Includes the space, but not TAB, CR, or LF, which are Cc
Zl Separator, line Format Character 1 Only U+2028 LINE SEPARATOR (LSEP)
Zp Separator, paragraph Format Character 1 Only U+2029 PARAGRAPH SEPARATOR (PSEP)
C, Other
Cc Other, control Control Character 65 (will never change)[e] No name,[g] <control>
Cf Other, format Format Character 170 Includes the soft hyphen, joining control characters (ZWNJ and ZWJ), control characters to support bidirectional text, and language tag characters
Cs Other, surrogate Surrogate Not (only used in UTF-16) 2,048 (will never change)[e] No name,[g] <surrogate>
Co Other, private use Private-use Character (but no interpretation specified) 137,468 total (will never change)
BMP, 131,068 in Planes 15–16
)		 No name,[g] <private-use>
Cn Other, not assigned Noncharacter Not 66 (will not change unless the range of Unicode code points is expanded)[e] No name,[g] <noncharacter>
Reserved Not 824,652 No name,[g] <reserved>
  1. ^ "Table 4-4: General Category" (PDF). The Unicode Standard. Unicode Consortium. September 2022.
  2. ^ a b "Table 2-3: Types of code points" (PDF). The Unicode Standard. Unicode Consortium. September 2022.
  3. ^ "DerivedGeneralCategory.txt". The Unicode Consortium. 2022-04-26.
  4. ^ "5.7.1 General Category Values". UTR #44: Unicode Character Database. Unicode Consortium. 2020-03-04.
  5. ^ a b c d e Unicode Character Encoding Stability Policies: Property Value Stability Stability policy: Some gc groups will never change. gc=Nd corresponds with Numeric Type=De (decimal).
  6. ^ "Annex C: Compatibility Properties (§ word)". Unicode Regular Expressions. Version 23. Unicode Consortium. 2022-02-08. Unicode Technical Standard #18.
  7. ^ a b c d e "Table 4-9: Construction of Code Point Labels" (PDF). The Unicode Standard. Unicode Consortium. September 2022. A Code Point Label may be used to identify a nameless code point. E.g. <control-hhhh>, <control-0088>. The Name remains blank, which can prevent inadvertently replacing, in documentation, a Control Name with a true Control code. Unicode also uses <not a character> for <noncharacter>.

The 1024 points in the range U+D800–U+DBFF are known as high-surrogate code points, and code points in the range U+DC00–U+DFFF (1024 code points) are known as low-surrogate code points. A high-surrogate code point followed by a low-surrogate code point forms a surrogate pair in UTF-16 in order to represent code points greater than U+FFFF. In principle, these code points cannot otherwise be used, though in practice this rule is often ignored, especially when not using UTF-16.

A small set of code points are guaranteed never to be assigned to characters, although third-parties may make independent use of them at their discretion. There are 66 of these noncharacters: U+FDD0–U+FDEF and the last two code points in each of the 17 planes (e.g. U+FFFE, U+FFFF, U+1FFFE, U+1FFFF, ..., U+10FFFE, U+10FFFF). The set of noncharacters is stable, and no new noncharacters will ever be defined.[63] Like surrogates, the rule that these cannot be used is often ignored, although the operation of the byte order mark assumes that U+FFFE will never be the first code point in a text. The exclusion of surrogates and noncharacters leaves 1111998 code points available for use.

Private-use code points are considered to be assigned, but they intentionally have no interpretation specified by The Unicode Standard[64] such that any interchange of such code points requires an independent agreement between the sender and receiver as to their interpretation. There are three private-use areas in the Unicode codespace:

  • Private Use Area: U+E000–U+F8FF (6400 characters),
  • Supplementary Private Use Area-A: U+F0000–U+FFFFD (65534 characters),
  • Supplementary Private Use Area-B: U+100000–U+10FFFD (65534 characters).

Graphic characters are those defined by The Unicode Standard to have particular semantics, either having a visible glyph shape or representing a visible space. As of Unicode 15.1, there are 149641 graphic characters.

Format characters are characters that do not have a visible appearance but may have an effect on the appearance or behavior of neighboring characters. For example, U+200C

ZERO WIDTH JOINER
may be used to change the default shaping behavior of adjacent characters (e.g. to inhibit ligatures or request ligature formation). There are 172 format characters in Unicode 15.1.

65 code points, the ranges U+0000–U+001F and U+007F–U+009F, are reserved as control codes, corresponding to the

ISO/IEC 6429. U+0089 LINE TABULATION, U+008A LINE FEED, and U+000D CARRIAGE RETURN are widely used in texts using Unicode. In a phenomenon known as mojibake, the C1 code points are improperly decoded according to the Windows-1252
codepage, previously widely used in Western European contexts.

Together, graphic, format, control code, and private use characters are collectively referred to as assigned characters. Reserved code points are those code points that are valid and available for use, but have not yet been assigned. As of Unicode 15.1, there are 824652 reserved code points.

Abstract characters

Further information: Universal Character Set characters § Characters, grapheme clusters and glyphs

The set of graphic and format characters defined by Unicode does not correspond directly to the repertoire of abstract characters representable under Unicode. Unicode encodes characters by associating an abstract character with a particular code point.

dot above, and an acute accent, which is required in Lithuanian, is represented by the character sequence U+012F; U+0307; U+0301. Unicode maintains a list of uniquely named character sequences for abstract characters that are not directly encoded in Unicode.[66]

All assigned characters have a unique and immutable name by which they are identified. This immutability has been guaranteed since version 2.0 of The Unicode Standard by its Name Stability policy.[63] In cases where a name is seriously defective and misleading, or has a serious typographical error, a formal alias may be defined that applications are encouraged to use in place of the official character name. For example, U+A015 ꀕ YI SYLLABLE WU has the formal alias YI SYLLABLE ITERATION MARK, and U+FE18 ︘ PRESENTATION FORM FOR VERTICAL RIGHT WHITE LENTICULAR BRAKCET (sic) has the formal alias PRESENTATION FORM FOR VERTICAL RIGHT WHITE LENTICULAR BRACKET.[67]

Ready-made versus composite characters

Unicode includes a mechanism for modifying characters that greatly extends the supported repertoire of glyphs. This covers the use of

canonical equivalence
within The Unicode Standard ensures the practical interchangeability of these equivalent encodings.

An example of this arises with the Korean alphabet

Hangul Jamo
subcomponents. However, it also provides 11172 combinations of precomposed syllables made from the most common jamo.

radicals
, so in principle Unicode could have enabled their composition as it did with Hangul. While this could have greatly reduced the number of required code points, as well as allowing the algorithmic synthesis of many arbitrary new characters, the complexities of character etymologies and the post-hoc nature of radical systems add immense complexity to the proposal. Indeed, attempts to design CJK encodings on the basis of composing radicals have been met with difficulties resulting from the reality that Chinese characters do not decompose as simply or as regularly as Hangul does.

The

Ideographic Description Sequences
block covers the range U+2FF0–U+2FFB, but The Unicode Standard warns against using its characters as an alternate representation for characters encoded elsewhere:

This process is different from a formal encoding of an ideograph. There is no canonical description of unencoded ideographs; there is no semantic assigned to described ideographs; there is no equivalence defined for described ideographs. Conceptually, ideographic descriptions are more akin to the English phrase "an 'e' with an acute accent on it" than to the character sequence <U+0065, U+0301>.

Ligatures

lām-alif
 ligature (ل ‎+‎ ا ‎=‎ لا)

Many scripts, including

Graphite (by SIL International), or AAT
(by Apple).

Instructions are also embedded in fonts to tell the operating system how to properly output different character sequences. A simple solution to the placement of combining marks or diacritics is assigning the marks a width of zero and placing the glyph itself to the left or right of the left sidebearing (depending on the direction of the script they are intended to be used with). A mark handled this way will appear over whatever character precedes it, but will not adjust its position relative to the width or height of the base glyph; it may be visually awkward and it may overlap some glyphs. Real stacking is impossible but can be approximated in limited cases (for example, Thai top-combining vowels and tone marks can just be at different heights to start with). Generally, this approach is only effective in monospaced fonts but may be used as a fallback rendering method when more complex methods fail.

Standardized subsets

Several subsets of Unicode are standardized: Microsoft Windows since

WGL-4 with 657 characters, which is considered to support all contemporary European languages using the Latin, Greek, or Cyrillic script. Other standardized subsets of Unicode include the Multilingual European Subsets:[69] MES-1 (Latin scripts only, 335 characters), MES-2 (Latin, Greek, and Cyrillic 1062 characters)[70]
and MES-3A & MES-3B (two larger subsets, not shown here). MES-2 includes every character in MES-1 and WGL-4.

The standard DIN 91379[71] specifies a subset of Unicode letters, special characters, and sequences of letters and diacritic signs to allow the correct representation of names and to simplify data exchange in Europe. This standard supports all of the official languages of all European Union countries, as well as the German minority languages and the official languages of Iceland, Liechtenstein, Norway, and Switzerland. To allow the transliteration of names in other writing systems to the Latin script according to the relevant ISO standards, all necessary combinations of base letters and diacritic signs are provided.

WGL-4, MES-1 and MES-2
Row Cells Range(s)
00 20–7E Basic Latin (00–7F)
A0–FF
Latin-1 Supplement
(80–FF)
01 00–13, 14–15, 16–2B, 2C–2D, 2E–4D, 4E–4F, 50–7E, 7F Latin Extended-A (00–7F)
8F, 92, B7, DE-EF, FA–FF Latin Extended-B (80–FF ...)
02 18–1B, 1E–1F Latin Extended-B (... 00–4F)
59, 7C, 92 IPA Extensions (50–AF)
BB–BD, C6, C7, C9, D6, D8–DB, DC, DD, DF, EE Spacing Modifier Letters (B0–FF)
03 74–75, 7A, 7E, 84–8A, 8C, 8E–A1, A3–CE, D7, DA–E1 Greek (70–FF)
04 00–5F, 90–91, 92–C4, C7–C8, CB–CC, D0–EB, EE–F5, F8–F9 Cyrillic (00–FF)
1E 02–03, 0A–0B, 1E–1F, 40–41, 56–57, 60–61, 6A–6B, 80–85, 9B, F2–F3 Latin Extended Additional (00–FF)
1F 00–15, 18–1D, 20–45, 48–4D, 50–57, 59, 5B, 5D, 5F–7D, 80–B4, B6–C4, C6–D3, D6–DB, DD–EF, F2–F4, F6–FE Greek Extended (00–FF)
20 13–14, 15, 17, 18–19, 1A–1B, 1C–1D, 1E, 20–22, 26, 30, 32–33, 39–3A, 3C, 3E, 44, 4A General Punctuation (00–6F)
7F, 82
Superscripts and Subscripts
(70–9F)
A3–A4, A7, AC, AF Currency Symbols (A0–CF)
21 05, 13, 16, 22, 26, 2E Letterlike Symbols (00–4F)
5B–5E Number Forms (50–8F)
90–93, 94–95, A8 Arrows (90–FF)
22 00, 02, 03, 06, 08–09, 0F, 11–12, 15, 19–1A, 1E–1F, 27–28, 29, 2A, 2B, 48, 59, 60–61, 64–65, 82–83, 95, 97
Mathematical Operators
(00–FF)
23 02, 0A, 20–21, 29–2A Miscellaneous Technical (00–FF)
25 00, 02, 0C, 10, 14, 18, 1C, 24, 2C, 34, 3C, 50–6C Box Drawing (00–7F)
80, 84, 88, 8C, 90–93 Block Elements (80–9F)
A0–A1, AA–AC, B2, BA, BC, C4, CA–CB, CF, D8–D9, E6
Geometric Shapes
(A0–FF)
26 3A–3C, 40, 42, 60, 63, 65–66, 6A, 6B Miscellaneous Symbols (00–FF)
F0 (01–02)
Private Use Area
(00–FF ...)
FB 01–02 Alphabetic Presentation Forms (00–4F)
FF FD Specials

Rendering software that cannot process a Unicode character appropriately often displays it as an open rectangle, or as U+FFFD to indicate the position of the unrecognized character. Some systems have made attempts to provide more information about such characters. Apple's

Unicode fallback font
will display a box showing the hexadecimal scalar value of the character.

Mapping and encodings

Several mechanisms have been specified for storing a series of code points as a series of bytes.

Unicode defines two mapping methods: the Unicode Transformation Format (UTF) encodings, and the Universal Coded Character Set (UCS) encodings. An encoding maps (possibly a subset of) the range of Unicode code points to sequences of values in some fixed-size range, termed code units. All UTF encodings map code points to a unique sequence of bytes.[72] The numbers in the names of the encodings indicate the number of bits per code unit (for UTF encodings) or the number of bytes per code unit (for UCS encodings and UTF-1). UTF-8 and UTF-16 are the most commonly used encodings. UCS-2 is an obsolete subset of UTF-16; UCS-4 and UTF-32 are functionally equivalent.

UTF encodings include:

  • UTF-8, which uses one to four bytes per code point, and has maximal compatibility with ASCII
  • UTF-16, which uses either one or two 16-bit units per code point, but cannot encode surrogates
  • UTF-32, which uses one 32-bit unit per code point
  • UTF-EBCDIC, not specified as part of The Unicode Standard, which uses one to five bytes per code point, intended to maximize compatibility with EBCDIC

UTF-8 uses one to four bytes per code point and, being compact for Latin scripts and ASCII-compatible, provides the de facto standard encoding for the interchange of Unicode text. It is used by

Linux distributions
as a direct replacement for legacy encodings in general text handling.

The UCS-2 and UTF-16 encodings specify the Unicode

ligatures
).

The same character converted to UTF-8 becomes the byte sequence EF BB BF. The Unicode Standard allows the BOM "can serve as a signature for UTF-8 encoded text where the character set is unmarked".

RFC 3629
, the UTF-8 standard, recommends that byte order marks be forbidden in protocols using UTF-8, but discusses the cases where this may not be possible. In addition, the large restriction on possible patterns in UTF-8 (for instance there cannot be any lone bytes with the high bit set) means that it should be possible to distinguish UTF-8 from other character encodings without relying on the BOM.

In UTF-32 and UCS-4, one 32-bit code unit serves as a fairly direct representation of any character's code point (although the endianness, which varies across different platforms, affects how the code unit manifests as a byte sequence). In the other encodings, each code point may be represented by a variable number of code units. UTF-32 is widely used as an internal representation of text in programs (as opposed to stored or transmitted text), since every Unix operating system that uses the gcc compilers to generate software uses it as the standard "wide character" encoding. Some programming languages, such as Seed7, use UTF-32 as an internal representation for strings and characters. Recent versions of the Python programming language (beginning with 2.2) may also be configured to use UTF-32 as the representation for Unicode strings, effectively disseminating such encoding in high-level coded software.

UTF-6
.

UTF-18
.

Adoption

See also: UTF-8 § Adoption

Unicode, in the form of UTF-8, has been the most common encoding for the World Wide Web since 2008.[74] It has near-universal adoption, and much of the non-UTF-8 content is found in other Unicode encodings, e.g. UTF-16. As of 2024, UTF-8 accounts for on average 97.8% of all web pages (and 987 of the top 1,000 highest-ranked web pages).[75] Although many pages only use ASCII characters to display content, UTF-8 was designed with 8-bit ASCII as a subset and almost no websites now declare their encoding to only be ASCII instead of UTF-8.[76] Over a third of the languages tracked have 100% UTF-8 use.

All internet protocols maintained by

RFC 2277 in 1998, which specified that all IETF protocols "MUST be able to use the UTF-8 charset".[78]

Operating systems

Unicode has become the dominant scheme for the internal processing and storage of text. Although a great deal of text is still stored in legacy encodings, Unicode is used almost exclusively for building new information processing systems. Early adopters tended to use UCS-2 (the fixed-length two-byte obsolete precursor to UTF-16) and later moved to UTF-16 (the variable-length current standard), as this was the least disruptive way to add support for non-BMP characters. The best known such system is Windows NT (and its descendants, 2000, XP, Vista, 7, 8, 10, and 11), which uses UTF-16 as the sole internal character encoding. The Java and .NET bytecode environments, macOS, and KDE also use it for internal representation. Partial support for Unicode can be installed on Windows 9x through the Microsoft Layer for Unicode.

UTF-8 (originally developed for Plan 9)[79] has become the main storage encoding on most Unix-like operating systems (though others are also used by some libraries) because it is a relatively easy replacement for traditional extended ASCII character sets. UTF-8 is also the most common Unicode encoding used in HTML documents on the World Wide Web.

Multilingual text-rendering engines which use Unicode include

GTK+ and the GNOME
desktop.

Input methods

Main article: Unicode input

Because keyboard layouts cannot have simple key combinations for all characters, several operating systems provide alternative input methods that allow access to the entire repertoire.

ISO/IEC 14755,[80] which standardises methods for entering Unicode characters from their code points, specifies several methods. There is the Basic method, where a beginning sequence is followed by the hexadecimal representation of the code point and the ending sequence. There is also a screen-selection entry method specified, where the characters are listed in a table on a screen, such as with a character map program.

Online tools for finding the code point for a known character include Unicode Lookup[81] by Jonathan Hedley and Shapecatcher[82] by Benjamin Milde. In Unicode Lookup, one enters a search key (e.g. "fractions"), and a list of corresponding characters with their code points is returned. In Shapecatcher, based on Shape context, one draws the character in a box and a list of characters approximating the drawing, with their code points, is returned.

Email

Main article: Unicode and email

MIME defines two different mechanisms for encoding non-ASCII characters in email, depending on whether the characters are in email headers (such as the "Subject:"), or in the text body of the message; in both cases, the original character set is identified as well as a transfer encoding. For email transmission of Unicode, the UTF-8 character set and the Base64 or the Quoted-printable transfer encoding are recommended, depending on whether much of the message consists of ASCII characters. The details of the two different mechanisms are specified in the MIME standards and generally are hidden from users of email software.

The IETF has defined[83][84] a framework for internationalized email using UTF-8, and has updated[85][86][87][88] several protocols in accordance with that framework.

The adoption of Unicode in email has been very slow.[

ISO-2022, and some devices, such as mobile phones,[citation needed] still cannot correctly handle Unicode data. Support has been improving, however. Many major free mail providers such as Yahoo! Mail, Gmail, and Outlook.com
support it.

Web

Main article: Unicode and HTML

All

W3C recommendations have used Unicode as their document character set since HTML 4.0. Web browsers have supported Unicode, especially UTF-8, for many years. There used to be display problems resulting primarily from font related issues; e.g. v6 and older of Microsoft Internet Explorer did not render many code points unless explicitly told to use a font that contains them.[89]

Although syntax rules may affect the order in which characters are allowed to appear, XML (including XHTML) documents, by definition,[90] comprise characters from most of the Unicode code points, with the exception of:

  • FFFE or FFFF.
  • most of the C0 control codes,
  • the permanently unassigned code points D800–DFFF,

HTML characters manifest either directly as bytes according to the document's encoding, if the encoding supports them, or users may write them as numeric character references based on the character's Unicode code point. For example, the references &#916;, &#1049;, &#1511;, &#1605;, &#3671;, &#12354;, &#21494;, &#33865;, and &#47568; (or the same numeric values expressed in hexadecimal, with &#x as the prefix) should display on all browsers as Δ, Й, ק ,م, ๗, あ, 叶, 葉, and 말.

When specifying

percent-encoded
.

Fonts

Main article: Unicode font

Unicode is not in principle concerned with fonts per se, seeing them as implementation choices.[91] Any given character may have many allographs, from the more common bold, italic and base letterforms to complex decorative styles. A font is "Unicode compliant" if the glyphs in the font can be accessed using code points defined in The Unicode Standard.[92] The standard does not specify a minimum number of characters that must be included in the font; some fonts have quite a small repertoire.

Free and retail

WOFF2
) is based on those). These font formats map Unicode code points to glyphs, but OpenType and TrueType font files are restricted to 65,535 glyphs. Collection files provide a "gap mode" mechanism for overcoming this limit in a single font file. (Each font within the collection still has the 65,535 limit, however.) A TrueType Collection file would typically have a file extension of ".ttc".

fonts typically focus on supporting only basic ASCII and particular scripts or sets of characters or symbols. Several reasons justify this approach: applications and documents rarely need to render characters from more than one or two writing systems; fonts tend to demand resources in computing environments; and operating systems and applications show increasing intelligence in regard to obtaining glyph information from separate font files as needed, i.e., font substitution. Furthermore, designing a consistent set of rendering instructions for tens of thousands of glyphs constitutes a monumental task; such a venture passes the point of diminishing returns
for most typefaces.

Newlines

Unicode partially addresses the newline problem that occurs when trying to read a text file on different platforms. Unicode defines a large number of characters that conforming applications should recognize as line terminators.

In terms of the newline, Unicode introduced U+2028 LINE SEPARATOR and U+2029 PARAGRAPH SEPARATOR. This was an attempt to provide a Unicode solution to encoding paragraphs and lines semantically, potentially replacing all of the various platform solutions. In doing so, Unicode does provide a way around the historical platform-dependent solutions. Nonetheless, few if any Unicode solutions have adopted these Unicode line and paragraph separators as the sole canonical line ending characters. However, a common approach to solving this issue is through newline normalization. This is achieved with the Cocoa text system in Mac OS X and also with W3C XML and HTML recommendations. In this approach, every possible newline character is converted internally to a common newline (which one does not really matter since it is an internal operation just for rendering). In other words, the text system can correctly treat the character as a newline, regardless of the input's actual encoding.

Issues

Character unification

Han unification

Main article: Han unification

The Ideographic Research Group (IRG) is tasked with advising the Consortium and ISO regarding Han unification, or Unihan, especially the further addition of CJK unified and compatibility ideographs to the repertoire. The IRG is composed of experts from each region that has historically used Chinese characters. However, despite the deliberation within the committee, Han unification has consistently been one of the most contested aspects of The Unicode Standard since the genesis of the project.[93]

Existing character set standards such as the Japanese

variant Chinese character is to be considered a handwriting/font difference (and thus unified), versus a spelling difference (to be encoded separately). Unicode's character model for CJK characters was based on the unification criteria used by JIS X 0208, as well as those developed by the Association for a Common Chinese Code in China.[94] Due to the standard's principle of encoding semantic instead of stylistic variants, Unicode has received criticism for not assigning code points to certain rare and archaic kanji variants, possibly complicating processing of ancient and uncommon Japanese names. Since it places particular emphasis on Chinese, Japanese and Korean sharing many characters in common, Han unification is also sometimes perceived as treating the three as the same thing.[95]

Less-frequently-used alternative encodings exist, often predating Unicode, with character models differing from this paradigm, aimed at preserving the various stylistic differences between regional and/or nonstandard character forms. One example is the

Unihan set, Unicode adopted the JIS-style unification model.[94]

The earliest version of Unicode had a repertoire of fewer than 21,000 Han characters, largely limited to those in relatively common modern usage. As of version 15.1, the standard now encodes more than 97,000 Han characters, and work is continuing to add thousands more—largely historical and dialectal variant characters used throughout the Sinosphere.

Modern typefaces provide a means to address some of the practical issues in depicting unified Han characters with various regional graphical representations. The 'locl'

Ideographic Variation Database
.

Italic or cursive characters in Cyrillic

Cyrillic
characters shown with upright, oblique, and italic alternate forms

If the appropriate glyphs for characters in the same script differ only in the italic, Unicode has generally unified them, as can be seen in the comparison among a set of seven characters' italic glyphs as typically appearing in Russian, traditional Bulgarian, Macedonian, and Serbian texts at right, meaning that the differences are displayed through smart font technology or manually changing fonts. The same OpenType 'locl' technique is used.[98]

Mapping to legacy character sets

Unicode was designed to provide code-point-by-code-point round-trip format conversion to and from any preexisting character encodings, so that text files in older character sets can be converted to Unicode and then back and get back the same file, without employing context-dependent interpretation. That has meant that inconsistent legacy architectures, such as combining diacritics and precomposed characters, both exist in Unicode, giving more than one method of representing some text. This is most pronounced in the three different encoding forms for Korean Hangul. Since version 3.0, any precomposed characters that can be represented by a combined sequence of already existing characters can no longer be added to the standard to preserve interoperability between software using different versions of Unicode.

EUC-JP and Unicode led to round-trip format conversion mismatches, particularly the mapping of the character JIS X 0208 '～' (1-33, WAVE DASH), heavily used in legacy database data, to either U+FF5E ～ FULLWIDTH TILDE (in Microsoft Windows) or U+301C 〜 WAVE DASH (other vendors).[99]

Some Japanese computer programmers objected to Unicode because it requires them to separate the use of U+005C \ REVERSE SOLIDUS (backslash) and U+00A5 ¥ YEN SIGN, which was mapped to 0x5C in JIS X 0201, and a lot of legacy code exists with this usage.

ISO 8859-1
, from long before Unicode.

Indic scripts

ISCII standard. The correct rendering of Unicode Indic text requires transforming the stored logical order characters into visual order and the forming of ligatures (also known as conjuncts) out of components. Some local scholars argued in favor of assignments of Unicode code points to these ligatures, going against the practice for other writing systems, though Unicode contains some Arabic and other ligatures for backward compatibility purposes only.[101][102][103] Encoding of any new ligatures in Unicode will not happen, in part, because the set of ligatures is font-dependent, and Unicode is an encoding independent of font variations. The same kind of issue arose for the Tibetan script in 2003 when the Standardization Administration of China proposed encoding 956 precomposed Tibetan syllables,[104] but these were rejected for encoding by the relevant ISO committee (ISO/IEC JTC 1/SC 2).[105]

Thai Industrial Standard 620, which worked in the same way, and was the way in which Thai had always been written on keyboards. This ordering problem complicates the Unicode collation process slightly, requiring table lookups to reorder Thai characters for collation.[95] Even if Unicode had adopted encoding according to spoken order, it would still be problematic to collate words in dictionary order. E.g., the word แสดง [sa dɛːŋ]
"perform" starts with a consonant cluster "สด" (with an inherent vowel for the consonant "ส"), the vowel แ-, in spoken order would come after the ด, but in a dictionary, the word is collated as it is written, with the vowel following the ส.

Combining characters

Main article: Combining character
See also:
Unicode normalization § Normalization

Characters with diacritical marks can generally be represented either as a single precomposed character or as a decomposed sequence of a base letter plus one or more non-spacing marks. For example, ḗ (precomposed e with macron and acute above) and ḗ (e followed by the combining macron above and combining acute above) should be rendered identically, both appearing as an

Graphite, OpenType ('gsub'), or AAT
technologies for advanced rendering features.

Anomalies

Main article: Unicode alias names and abbreviations

The Unicode Standard has imposed rules intended to guarantee stability.[106] Depending on the strictness of a rule, a change can be prohibited or allowed. For example, a "name" given to a code point cannot and will not change. But a "script" property is more flexible, by Unicode's own rules. In version 2.0, Unicode changed many code point "names" from version 1. At the same moment, Unicode stated that, thenceforth, an assigned name to a code point would never change. This implies that when mistakes are published, these mistakes cannot be corrected, even if they are trivial (as happened in one instance with the spelling BRAKCET for BRACKET in a character name). In 2006 a list of anomalies in character names was first published, and, as of June 2021, there were 104 characters with identified issues,[107] for example:

While Unicode defines the script designator (name) to be "Phags_Pa", in that script's character names, a hyphen is added: U+A840 ꡀ PHAGS-PA LETTER KA.[110][111] This, however, is not an anomaly, but the rule: hyphens are replaced by underscores in script designators.[110]

Security

Unicode has a large number of

natural language processing (NLP) systems.[113] Mitigation requires disallowing these characters, displaying them differently, or requiring that they resolve to the same identifier;[114] all of this is complicated due to the huge and constantly changing set of characters.[115][116]

A security advisory was released in 2021 by two researchers, one from the

BiDi marks can be used to make large sections of code do something different from what they appear to do. The problem was named "Trojan Source".[117] In response, code editors started highlighting marks to indicate forced text-direction changes.[118]

See also

Notes

  1. ^ Sometimes abbreviated as TUS.[1][2]
  2. ^ "A Unicode Standard Annex (UAX) forms an integral part of The Unicode Standard, but is published as a separate document."[1]

References

  1. ISBN 978-1-936213-33-7
    .
  1. ^ "Unicode Technical Report #28: Unicode 3.2". Unicode Consortium. 2002-03-27. Retrieved 2022-06-23.
  2. ^ Jenkins, John H. (2021-08-26). "Unicode Standard Annex #45: U-source Ideographs". Unicode Consortium. Retrieved 2022-06-23. 2.2 The Source Field
  3. ^ "Unicode Character Count V15.1". Unicode. Archived from the original on 2023-10-09. Retrieved 2023-09-12.
  4. ^ "Emoji Counts, v15.1". Unicode. Archived from the original on 2023-09-28. Retrieved 2023-09-12.
  5. ^ "The Unicode Standard: A Technical Introduction". Retrieved 2010-03-16.
  6. ^ "Unicode Bulldog Award". Unicode. Archived from the original on 2023-11-11.
  7. ^
    Xerox PARC. Many persons contributed ideas to the development of a new encoding design. Beginning in 1980, these efforts evolved into the Xerox Character Code Standard (XCCS) by the present author, a multilingual encoding that has been maintained by Xerox as an internal corporate standard since 1982, through the efforts of Ed Smura, Ron Pellar, and others.
    Unicode arose as the result of eight years of working experience with XCCS. Its fundamental differences from XCCS were proposed by Peter Fenwick and Dave Opstad (pure 16-bit codes) and by Lee Collins
    (ideographic character unification). Unicode retains the many features of XCCS whose utility has been proved over the years in an international line of communication multilingual system products.
  8. ^ "Summary Narrative". Unicode. 2006-08-31. Retrieved 2010-03-15.
  9. ^ "History of Unicode Release and Publication Dates". Unicode. Retrieved 2023-03-20.
  10. ^ Searle, Stephen J. "Unicode Revisited". Retrieved 2013-01-18.
  11. ^ a b "The Unicode Consortium Members". Retrieved 2024-02-12.
  12. ^ "Unicode FAQ". Retrieved 2020-04-02.
  13. ^ "Supported Scripts". Unicode. Retrieved 2022-09-16.
  14. ^ "Roadmap to the BMP". Unicode Consortium. Retrieved 2018-07-30.
  15. ^ "Roadmaps to Unicode". Unicode. Archived from the original on 2023-12-08.
  16. ^ "script encoding initiative". Berkeley Linguistics. Archived from the original on 2023-03-25.
  17. ^ "About The Script Encoding Initiative". The Unicode Consortium. Retrieved 2012-06-04.
  18. ^ "Unicode 6.1 Paperback Available". announcements_at_unicode.org. Retrieved 2012-05-30.
  19. ^ "Unicode 15.0.0". Unicode. Retrieved 2023-09-12.
  20. ^ "Emoji Counts, v15.0". Unicode. Retrieved 2023-09-12.
  21. ^ "Enumerated Versions of The Unicode Standard". Retrieved 2016-06-21.
  22. ^
  23. ^ "Unicode Data 1.0.1". Retrieved 2010-03-16.
  24. ^
  25. ^
  26. ^ a b
  27. ^
  28. ^
  29. ^
  30. ^
  31. ^ "Unicode Data-4.1.0". Retrieved 2010-03-16.
  32. ^ "Named Sequences-4.1.0". Retrieved 2010-03-16.
  33. ^ "Unicode Data 5.0.0". Retrieved 2010-03-17.
  34. ^ "Unicode Data 5.1.0". Retrieved 2010-03-17.
  35. ^ "Unicode Data 5.2.0". Retrieved 2010-03-17.
  36. ^ "Unicode Data 6.0.0". Retrieved 2010-10-11.
  37. ^ "Unicode 6.0 Emoji List". emojipedia.org. Retrieved 2022-09-21.
  38. ^ "Unicode Data 6.1.0". Retrieved 2012-01-31.
  39. ^ "Unicode Data 6.2.0". Retrieved 2012-09-26.
  40. ^ "Unicode Data 6.3.0". Retrieved 2013-09-30.
  41. ^ "Unicode Data 7.0.0". Retrieved 2014-06-15.
  42. ^ "Unicode Data 8.0.0". Retrieved 2015-06-17.
  43. ^ "Unicode 8.0.0". Unicode Consortium. Retrieved 2015-06-17.
  44. ^ "Unicode 9.0.0". Unicode Consortium. Retrieved 2016-06-21.
  45. ^ "Unicode Data 9.0.0". Retrieved 2016-06-21.
  46. ^ Lobao, Martim (2016-06-07). "These Are The Two Emoji That Weren't Approved For Unicode 9 But Which Google Added To Android Anyway". Android Police. Retrieved 2016-09-04.
  47. ^ "Unicode 10.0.0". Unicode Consortium. Retrieved 2017-06-20.
  48. ^ "The Unicode Standard, Version 11.0.0 Appendix C" (PDF). Unicode Consortium. Retrieved 2018-06-11.
  49. ^ "The Unicode Standard, Version 12.0.0 Appendix C" (PDF). Unicode Consortium. Retrieved 2019-03-05.
  50. ^ "Unicode Version 12.1 released in support of the Reiwa Era". The Unicode Blog. Retrieved 2019-05-07.
  51. ^
  52. ^ "The Unicode Standard, Version 13.0– Core Specification Appendix C" (PDF). Unicode Consortium. Retrieved 2020-03-11.
  53. ^
  54. ^
  55. ^
  56. ^ "Proposed New Characters: The Pipeline". Unicode. 2023-09-12. Retrieved 2023-09-13.
  57. ^ "Unicode Version 16.0". emojipedia.org. Retrieved 2023-09-13.
  58. ^ "Glossary of Unicode Terms". Retrieved 2010-03-16.
  59. ^ "2.4 Code Points and Characters". The Unicode Standard Version 15.1 – Core Specification (PDF). 2023. p. 29.
  60. ^ "3.4 Characters and Encoding". The Unicode Standard, Version 15.1 (PDF). 2023. p. 88.
  61. ^ "Re: Origin of the U+nnnn notation". Unicode Mail List Archive (Mailing list). 2005-11-08.
  62. ^ "Appendix A: Notational Conventions" (PDF). The Unicode Standard. Unicode Consortium. September 2023.
  63. ^ a b "Unicode Character Encoding Stability Policy". Retrieved 2010-03-16.
  64. ^ "Properties" (PDF). Retrieved 2023-09-12.
  65. ^ "Unicode Character Encoding Model". Retrieved 2023-09-12.
  66. ^ "Unicode Named Sequences". Retrieved 2022-09-16.
  67. ^ "Unicode Name Aliases". Retrieved 2010-03-16.
  68. ^ "JanaSanskritSans". Archived from the original on 2011-07-16.
  69. ^ CWA 13873:2000 – Multilingual European Subsets in ISO/IEC 10646-1 CEN Workshop Agreement 13873
  70. ^ Kuhn, Markus (1998). "Multilingual European Character Set 2 (MES-2) Rationale". University of Cambridge. Retrieved 2023-03-20.
  71. ^ "DIN 91379:2022-08: Characters and defined character sequences in Unicode for the electronic processing of names and data exchange in Europe, with CD-ROM". Beuth Verlag. Retrieved 2022-08-21.
  72. ^ "UTF-8, UTF-16, UTF-32 & BOM". Unicode.org FAQ. Retrieved 2016-12-12.
  73. ISBN 978-1-936213-08-5
    .
  74. ^ Davis, Mark (2008-05-05). "Moving to Unicode 5.1". Official Google Blog. Retrieved 2021-02-19.
  75. ^ "Usage Survey of Character Encodings broken down by Ranking". W3Techs. Retrieved 2023-01-16.
  76. ^ "Usage Statistics and Market Share of US-ASCII for Websites, October 2021". W3Techs. Retrieved 2020-11-01.
  77. doi:10.17487/RFC2640. RFC 2640
    . Retrieved 2022-08-17.
  78. doi:10.17487/RFC2277. BCP 18. RFC 2277
    . Retrieved 2022-08-17.
  79. ^ Pike, Rob (2003-04-30). "UTF-8 history".
  80. ^ "ISO/IEC JTC1/SC 18/WG 9 N" (PDF). Retrieved 2012-06-04.
  81. ^ Hedley, Jonathan (2009). "Unicode Lookup".
  82. ^ Milde, Benjamin (2011). "Unicode Character Recognition".
  83. doi:10.17487/RFC4952. RFC 4952
    . Retrieved 2022-08-17.
  84. doi:10.17487/RFC6530. RFC 6530
    . Retrieved 2022-08-17.
  85. doi:10.17487/RFC6531. RFC 6531
    . Retrieved 2022-08-17.
  86. doi:10.17487/RFC6532. RFC 6532
    . Retrieved 2022-08-17.
  87. doi:10.17487/RFC5255. RFC 5255
    . Retrieved 2022-08-17.
  88. doi:10.17487/RFC5721. RFC 5721
    . Retrieved 2022-08-17.
  89. ^ Wood, Alan. "Setting up Windows Internet Explorer 5, 5.5 and 6 for Multilingual and Unicode Support". Alan Wood. Retrieved 2012-06-04.
  90. ^ "Extensible Markup Language (XML) 1.1 (Second Edition)". Retrieved 2013-11-01.
  91. ^ Bigelow, Charles; Holmes, Kris (September 1993). "The design of a Unicode font" (PDF). Electronic Publishing. 6 (3): 292.
  92. ^ "Fonts and keyboards". Unicode Consortium. 2017-06-28. Retrieved 2019-10-13.
  93. ^ A Brief History of Character Codes, Steven J. Searle, originally written 1999, last updated 2004
  94. ^ a b "Appendix E: Han Unification History" (PDF). The Unicode Standard Version 15.0 – Core Specification. Unicode Consortium. 2022.
  95. ^ a b Topping, Suzanne (2013-06-25). "The secret life of Unicode". IBM. Archived from the original on 2013-06-25. Retrieved 2023-03-20.
  96. ^ Wittern, Christian (1995-05-01). "Chinese character codes: an update". International Research Institute for Zen Buddhism / Hanazono University. Archived from the original on 2004-10-12.
  97. ^ "Noto CJK fonts". Noto Fonts. 2023-02-18. Select this deployment format if your system supports variable fonts and you prefer to use only one language, but also want full character coverage or the ability to language-tag text to use glyphs that are appropriate for the other languages (this requires an app that supports language tagging and the OpenType 'locl' GSUB feature).
  98. ^ Preuss, Ingo. "OpenType Feature: locl – Localized Forms". preusstype.com.
  99. ^ AFII contribution about WAVE DASH, "An Unicode vendor-specific character table for japanese". 2011-04-22. Archived from the original on 2011-04-22. Retrieved 2019-05-20.
  100. ^ ISO 646-* Problem, Section 4.4.3.5 of Introduction to I18n, Tomohiro KUBOTA, 2001
  101. ^ "Arabic Presentation Forms-A" (PDF). Retrieved 2010-03-20.
  102. ^ "Arabic Presentation Forms-B" (PDF). Retrieved 2010-03-20.
  103. ^ "Alphabetic Presentation Forms" (PDF). Retrieved 2010-03-20.
  104. ^ "Proposal on Tibetan BrdaRten Characters Encoding for ISO/IEC 10646 in BMP" (PDF). 2002-12-02.
  105. ^ Umamaheswaran, V. S. (2003-11-07). "Resolutions of WG 2 meeting 44" (PDF). Resolution M44.20.
  106. ^ "Character Encoding Stability". Unicode. Archived from the original on 2024-01-01.
  107. ^ a b "Unicode Technical Note #27: Known Anomalies in Unicode Character Names". Unicode. 2021-06-14.
  108. ^ "Unicode chart: "actually this has the form of a lowercase calligraphic p, despite its name"" (PDF).
  109. ^ "Misspelling of BRACKET in character name is a known defect" (PDF).
  110. ^ a b "Unicode Standard Annex #24: Unicode Script Property". The Unicode Consortium. 2021. 2.2 Relation to ISO 15924 Codes. Retrieved 2022-04-29.
  111. ^ "Scripts-15.1.0.txt". The Unicode Consortium. 2023. Retrieved 2023-09-12.
  112. ^ "UTR #36: Unicode Security Considerations". Unicode.
  113. S2CID 235485405
    .
  114. ^ Engineering, Spotify (2013-06-18). "Creative usernames and Spotify account hijacking". Spotify Engineering. Retrieved 2023-04-15.
  115. ^ Wheeler, David A. (2020). "Countermeasures". Initial Analysis of Underhanded Source Code: 4–1.
  116. ^ "UTR #36: Unicode Security Considerations". Unicode. Retrieved 2022-06-27.
  117. ^ Boucher, Nicholas; Anderson, Ross. "Trojan Source: Invisible Vulnerabilities" (PDF). Retrieved 2021-11-02.
  118. ^ "Visual Studio Code October 2021". code.visualstudio.com. Retrieved 2021-11-11.

Further reading

External links
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