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Wikipedia

Unicode

January 10, 2023

Unicode, formally The Unicode Standard,[note 1][note 2] is an information technology standard for the consistent encoding, representation, and handling of text expressed in most of the world's writing systems. The standard, which is maintained by the Unicode Consortium, defines as of the current version (15.0) 149,186 characters[3][4] covering 161 modern and historic scripts, as well as symbols, emoji (including in colors), and non-visual control and formatting codes.

Unicode
Logo of the Unicode Consortium
Alias(es)Universal Coded Character Set (UCS, ISO/IEC 10646)
Language(s)International
StandardUnicode Standard
Encoding formats
Preceded byISO/IEC 8859, various others
  • Official website
  • Official, technical website
This article contains uncommon Unicode characters. Without proper rendering support, you may see question marks, boxes, or other symbols.

Unicode's success at unifying character sets has led to its widespread and predominant use in the internationalization and localization of computer software. The standard has been implemented in many recent technologies, including modern operating systems, XML, and most modern programming languages.

The Unicode character repertoire is synchronized with ISO/IEC 10646, each being code-for-code identical with the other. The Unicode Standard, however, includes more than just the base code. Alongside the character encodings, the Consortium's official publication includes a wide variety of details about the scripts and how to display them: normalization rules, decomposition, collation, rendering, and bidirectional text display order for multilingual texts, and so on.[5] The Standard also includes reference data files and visual charts to help developers and designers correctly implement the repertoire.

Unicode can be stored using several different encodings, which translate the character codes into sequences of bytes. The Unicode standard defines three and several other encodings exist, all in practice variable-length encodings. The most common encodings are the ASCII-compatible UTF-8, the ASCII-incompatible UTF-16 (compatible with the obsolete UCS-2), and the Chinese Unicode encoding standard GB18030 which is not an official Unicode standard but is used in China and implements Unicode fully.

Origin and development

Unicode has the explicit aim of transcending the limitations of traditional character encodings, such as those defined by the ISO/IEC 8859 standard, which find wide usage in various countries of the world but remain largely incompatible with each other. Many traditional character encodings share a common problem in that they allow bilingual computer processing (usually using Latin characters and the local script), but not multilingual computer processing (computer processing of arbitrary scripts mixed with each other).

Unicode, in intent, encodes the underlying characters—graphemes and grapheme-like units—rather than the variant glyphs (renderings) for such characters. In the case of Chinese characters, this sometimes leads to controversies over distinguishing the underlying character from its variant glyphs (see Han unification).

In text processing, Unicode takes the role of providing a unique code point—a number, not a glyph—for each character. In other words, Unicode represents a character in an abstract way and leaves the visual rendering (size, shape, font, or style) to other software, such as a web browser or word processor. This simple aim becomes complicated, however, because of concessions made by Unicode's designers in the hope of encouraging a more rapid adoption of Unicode.

The first 256 code points were made identical to the content of ISO/IEC 8859-1 so as to make it trivial to convert existing western text. Many essentially identical characters were encoded multiple times at different code points to preserve distinctions used by legacy encodings and therefore, allow conversion from those encodings to Unicode (and back) without losing any information. For example, the "fullwidth forms" section of code points encompasses a full duplicate of the Latin alphabet because Chinese, Japanese, and Korean (CJK) fonts contain two versions of these letters, "fullwidth" matching the width of the CJK characters, and normal width. For other examples, see duplicate characters in Unicode.

Unicode Bulldog Award recipients include many names influential in the development of Unicode and include Tatsuo Kobayashi, Thomas Milo, Roozbeh Pournader, Ken Lunde, and Michael Everson.[6]

History

Based on experiences with the Xerox Character Code Standard (XCCS) since 1980,[7] the origins of Unicode can be traced back to 1987, when Joe Becker from Xerox with Lee Collins and Mark Davis from Apple started investigating the practicalities of creating a universal character set.[8] With additional input from Peter Fenwick and Dave Opstad,[7] Joe 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 16-bit character model:[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.

His original 16-bit design was based on the assumption that only those scripts and characters in modern use would need to be encoded:[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 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 Unicodes.

In early 1989, the Unicode working group expanded to include Ken Whistler and Mike Kernaghan of Metaphor, Karen Smith-Yoshimura and Joan Aliprand of RLG, and Glenn Wright of Sun Microsystems, and in 1990, Michel Suignard and Asmus Freytag from Microsoft and Rick McGowan of NeXT joined the group. By the end of 1990, most of the work on mapping existing character encoding 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 in October 1991, the first volume of the Unicode standard was published. The second volume, covering 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 (e.g., Egyptian hieroglyphs) and thousands of rarely used or obsolete characters that had not been anticipated as needing encoding. Among the characters not originally intended for Unicode are rarely used Kanji or Chinese characters, many of which are part of personal and place names, making them much more essential than envisioned in the original architecture of Unicode.[10]

The Microsoft TrueType specification version 1.0 from 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 with any interest in text-processing standards, including Adobe, Apple, Facebook, Google, IBM, Microsoft, Netflix, and SAP SE.[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)
 
Many modern applications can render a substantial subset of the many scripts in Unicode, as demonstrated by this screenshot from the OpenOffice.org application.

Unicode currently covers most major writing systems in use today.[12][better source needed]

As of 2022, 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 small script, encoding proposals have been made and they are working their way through the approval process. For other scripts, such as Mayan (besides numbers) 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 have been already included into 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 and the International Organization for Standardization (ISO) have together developed a shared repertoire following the initial publication of The Unicode Standard in 1991; 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, and code charts. However, Unicode 5.0, published in 2006, was the last version printed this way. Starting with version 5.2, only the core specification, published as 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, only 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 from March 2021 to September 2021 due to the COVID-19 pandemic.

The latest version of Unicode, 15.0.0, was released on 13 September 2022. Several annexes were updated including Unicode Security Mechanisms (UTS #39), and a total of 4489 new characters were encoded, including 20 new emoji characters, such as "wireless" (network) symbol and hearts in different colors such as pink, two new scripts, CJK Unified Ideographs extension, and multiple additions to existing blocks.[19][20]

Thus far, the following major and minor 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 Corresponding ISO/IEC 10646 edition Scripts Characters
Total[tablenote 1] Notable additions
1.0.0[22] October 1991 ISBN 0-201-56788-1 (Vol. 1) 24 7,129[tablenote 2] Initial repertoire covers these scripts: Arabic, Armenian, Bengali, Bopomofo, Cyrillic, Devanagari, Georgian, Greek and Coptic, Gujarati, Gurmukhi, Hangul, Hebrew, Hiragana, Kannada, Katakana, Lao, Latin, Malayalam, Oriya, Tamil, Telugu, Thai, and Tibetan.[22]
1.0.1[23] June 1992 ISBN 0-201-60845-6 (Vol. 2) 25 28,327
(21,204 added;
6 removed) 		The initial set of 20,902 CJK Unified Ideographs is defined.[23]
1.1[24] June 1993 ISO/IEC 10646-1:1993 24 34,168
(5,963 added;
89 removed;
33 reclassified
as control
characters) 		4,306 more Hangul syllables added to original set of 2,350 characters. Tibetan removed.[24]
2.0[25] July 1996 ISBN 0-201-48345-9 ISO/IEC 10646-1:1993 plus Amendments 5, 6 and 7 25 38,885
(11,373 added;
6,656 removed) 		Original set of Hangul syllables removed, and a new set of 11,172 Hangul syllables added at a new location. Tibetan added back in a new location and with a different character repertoire. Surrogate character mechanism defined, and Plane 15 and Plane 16 Private Use Areas allocated.[25]
2.1[26] May 1998 ISO/IEC 10646-1:1993 plus Amendments 5, 6 and 7, as well as two characters from Amendment 18 25 38,887
(2 added) 		Euro sign and Object Replacement Character added.[26]
3.0 September 1999 ISBN 0-201-61633-5 ISO/IEC 10646-1:2000 38 49,194
(10,307 added) 		Cherokee, Ethiopic, Khmer, Mongolian, Burmese, Ogham, Runic, Sinhala, Syriac, Thaana, Unified Canadian Aboriginal Syllabics, and Yi Syllables added, as well as a set of Braille patterns.[27]
3.1 March 2001 ISO/IEC 10646-1:2000

ISO/IEC 10646-2:2001

41 94,140
(44,946 added) 		Deseret, Gothic and Old Italic added, as well as sets of symbols for Western music and Byzantine music, and 42,711 additional CJK Unified Ideographs.[28]
3.2 March 2002 ISO/IEC 10646-1:2000 plus Amendment 1

ISO/IEC 10646-2:2001

45 95,156
(1,016 added) 		Philippine scripts Buhid, Hanunó'o, Tagalog, and Tagbanwa added.[29]
4.0 April 2003 ISBN 0-321-18578-1 ISO/IEC 10646:2003 52 96,382
(1,226 added) 		Cypriot syllabary, Limbu, Linear B, Osmanya, Shavian, Tai Le, and Ugaritic added, as well as Hexagram symbols.[30]
4.1 March 2005 ISO/IEC 10646:2003 plus Amendment 1 59 97,655
(1,273 added) 		Buginese, Glagolitic, Kharoshthi, New Tai Lue, Old Persian, Syloti Nagri, and Tifinagh added, and Coptic was disunified from Greek. Ancient Greek numbers and musical symbols were also added.[31]
5.0 July 2006 ISBN 0-321-48091-0 ISO/IEC 10646:2003 plus Amendments 1 and 2, as well as four characters from Amendment 3 64 99,024
(1,369 added) 		Balinese, Cuneiform, N'Ko, Phags-pa, and Phoenician added.[32]
5.1 April 2008 ISO/IEC 10646:2003 plus Amendments 1, 2, 3 and 4 75 100,648
(1,624 added) 		Carian, Cham, Kayah Li, Lepcha, Lycian, Lydian, Ol Chiki, Rejang, Saurashtra, Sundanese, and Vai added, as well as sets of symbols for the Phaistos Disc, Mahjong tiles, and Domino tiles. There were also important additions for Burmese, additions of letters and Scribal abbreviations used in medieval manuscripts, and the addition of Capital ẞ.[33]
5.2 October 2009 ISBN 978-1-936213-00-9 ISO/IEC 10646:2003 plus Amendments 1, 2, 3, 4, 5 and 6 90 107,296
(6,648 added) 		Avestan, Bamum, Egyptian hieroglyphs (the Gardiner Set, comprising 1,071 characters), Imperial Aramaic, Inscriptional Pahlavi, Inscriptional Parthian, Javanese, Kaithi, Lisu, Meetei Mayek, Old South Arabian, Old Turkic, Samaritan, Tai Tham and Tai Viet added. 4,149 additional CJK Unified Ideographs (CJK-C), as well as extended Jamo for Old Hangul, and characters for Vedic Sanskrit.[34]
6.0 October 2010 ISBN 978-1-936213-01-6 ISO/IEC 10646:2010 plus the Indian rupee sign 93 109,384
(2,088 added) 		Batak, Brahmi, Mandaic, playing card symbols, transport and map symbols, alchemical symbols, emoticons and emojis.[35] 222 additional CJK Unified Ideographs (CJK-D) added.[36]
6.1 January 2012 ISBN 978-1-936213-02-3 ISO/IEC 10646:2012 100 110,116
(732 added) 		Chakma, Meroitic cursive, Meroitic hieroglyphs, Miao, Sharada, Sora Sompeng, and Takri.[37]
6.2 September 2012 ISBN 978-1-936213-07-8 ISO/IEC 10646:2012 plus the Turkish lira sign 100 110,117
(1 added) 		Turkish lira sign.[38]
6.3 September 2013 ISBN 978-1-936213-08-5 ISO/IEC 10646:2012 plus six characters 100 110,122
(5 added) 		5 bidirectional formatting characters.[39]
7.0 June 2014 ISBN 978-1-936213-09-2 ISO/IEC 10646:2012 plus Amendments 1 and 2, as well as the Ruble sign 123 112,956
(2,834 added) 		Bassa Vah, Caucasian Albanian, Duployan, Elbasan, Grantha, Khojki, Khudawadi, Linear A, Mahajani, Manichaean, Mende Kikakui, Modi, Mro, Nabataean, Old North Arabian, Old Permic, Pahawh Hmong, Palmyrene, Pau Cin Hau, Psalter Pahlavi, Siddham, Tirhuta, Warang Citi, and Dingbats.[40]
8.0 June 2015 ISBN 978-1-936213-10-8 ISO/IEC 10646:2014 plus Amendment 1, as well as the Lari sign, nine CJK unified ideographs, and 41 emoji characters[41] 129 120,672
(7,716 added) 		Ahom, Anatolian hieroglyphs, Hatran, Multani, Old Hungarian, SignWriting, 5,771 CJK Unified Ideographs, a set of lowercase letters for Cherokee, and five emoji skin tone modifiers.[42]
9.0 June 2016 ISBN 978-1-936213-13-9 ISO/IEC 10646:2014 plus Amendments 1 and 2, as well as Adlam, Newa, Japanese TV symbols, and 74 emoji and symbols[43] 135 128,172
(7,500 added) 		Adlam, Bhaiksuki, Marchen, Newa, Osage, Tangut, and 72 emoji.[44][45]
10.0 June 2017 ISBN 978-1-936213-16-0 ISO/IEC 10646:2017 plus 56 emoji characters, 285 hentaigana characters, and 3 Zanabazar Square characters[46] 139 136,690
(8,518 added) 		Zanabazar Square, Soyombo, Masaram Gondi, Nüshu, hentaigana (non-standard hiragana), 7,494 CJK Unified Ideographs, 56 emoji, and bitcoin symbol.[47]
11.0 June 2018 ISBN 978-1-936213-19-1 ISO/IEC 10646:2017 plus Amendment 1, as well as 46 Mtavruli Georgian capital letters, 5 CJK unified ideographs, and 66 emoji characters.[48] 146 137,374
(684 added) 		Dogra, Georgian Mtavruli capital letters, Gunjala Gondi, Hanifi Rohingya, Indic Siyaq Numbers, Makasar, Medefaidrin, Old Sogdian and Sogdian, Mayan numerals, 5 urgently needed CJK Unified Ideographs, symbols for xiangqi (Chinese chess) and star ratings, and 145 emoji.[49]
12.0 March 2019 ISBN 978-1-936213-22-1 ISO/IEC 10646:2017 plus Amendments 1 and 2, as well as 62 additional characters.[50] 150 137,928
(554 added) 		Elymaic, Nandinagari, Nyiakeng Puachue Hmong, Wancho, Miao script additions for several Miao and Yi languages of China, hiragana and katakana small letters for writing archaic Japanese, Tamil historic fractions and symbols, Lao letters for Pali, Latin letters for Egyptological and Ugaritic transliteration, hieroglyph format controls, and 61 emoji.[51]
12.1 May 2019 ISBN 978-1-936213-25-2 150 137,929
(1 added) 		Adds a single character at U+32FF for the square ligature form of the name of the Reiwa era.[52]
13.0[53] March 2020 ISBN 978-1-936213-26-9 ISO/IEC 10646:2020[54] 154 143,859
(5,930 added) 		Chorasmian, Dives Akuru, Khitan small script, Yezidi, 4,969 CJK unified ideographs added (including 4,939 in Ext. G), Arabic script additions used to write Hausa, Wolof, and other languages in Africa and other 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 from the 1970s and 1980s, and 55 emoji.[53]
14.0[55] September 2021 ISBN 978-1-936213-29-0 159 144,697
(838 added) 		Toto, Cypro-Minoan, Vithkuqi, Old Uyghur, Tangsa, Latin script additions at SMP blocks (Ext-F, Ext-G) for use in extended IPA, Arabic script additions for use in languages across Africa and in Iran, Pakistan, Malaysia, Indonesia, Java, and Bosnia, and to write honorifics, additions for Quranic use, other additions to support languages in North America, the Philippines, India, and Mongolia, addition of the Kyrgyzstani som currency symbol, support for Znamenny musical notation, and 37 emoji.[55]
15.0[56] September 2022 ISBN 978-1-936213-32-0 161 149,186
(4,489 added) 		Kawi and Mundari, several new characters, including 20 emoji, 4,192 CJK ideographs, and control characters for Egyptian hieroglyphs.[56]
  1. ^ The number of characters listed for each version of Unicode is the total number of graphic and format characters (i.e., excluding private-use characters, control characters, noncharacters and surrogate code points).
  2. ^ Not counting 'space' or 33 non-printing characters (7,163 total)[22]

Architecture and terminology

See also: Universal Character Set characters

Codespace and Code Points

The Unicode Standard defines a codespace,[57] a set of numerical values ranging from 0 through 10FFFF16,[58] called code points[59] and denoted as U+0000 through U+10FFFF ("U+"[60] followed by the code point value in hexadecimal, which is prepended with leading zeros to a minimum of four digits; e. g., U+00F7 for the division sign ÷ but U+13254 (not U+013254) for the Egyptian hieroglyph  .[61]). Of these 216 + 220 defined code points, the code points from U+D800 through U+DFFF, which are used to encode surrogate pairs in UTF-16, are reserved by the Unicode Standard and may not be used to encode valid characters, resulting in a net total of 216 − 211 + 220 = 1,112,064 assignable code points.

Code planes and blocks

Main article: Plane (Unicode)

The Unicode codespace is divided into seventeen planes, numbered 0 to 16. Plane 0 is the Basic Multilingual Plane (BMP), which contains 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 (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. Although blocks are an arbitrary size, they are always a multiple of 16 code points and often a multiple of 128 code points. Characters required for a given script may be spread out over several different blocks.

General Category property

Each code point has a single General Category property. The major categories are denoted: Letter, Mark, Number, Punctuation, Symbol, Separator and Other. Within these categories, there are subdivisions. In most cases other properties must be used to sufficiently specify the characteristics of a code point. The possible General Categories are:

General Category (Unicode Character Property)[a]
Value Category Major, minor Basic type[b] Character assigned[b] Count[c]
(as of 15.0)		 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 Ligatures containing uppercase followed by lowercase letters (e.g., Dž, Lj, Nj, and Dz)
Lm Letter, modifier Graphic Character 397 A modifier letter
Lo Letter, other Graphic Character 131,612 An ideograph or a letter in a 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., vulgar fractions, superscript and 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 Mathematical symbols (e.g., +, −, =, ×, ÷, √, ∊, ≠). 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 6,634
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)[e] (6,400 in BMP, 131,068 in Planes 15–16) No name,[g] <private-use>
Cn Other, not assigned Noncharacter Not 66 (will never change)[e] No name,[g] <noncharacter>
Reserved Not 825,279 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>.

Code points in the range U+D800–U+DBFF (1,024 code points) are known as high-surrogate code points, and code points in the range U+DC00–U+DFFF (1,024 code points) are known as low-surrogate code points. A high-surrogate code point followed by a low-surrogate code point form a surrogate pair in UTF-16 to represent code points greater than U+FFFF. These code points otherwise cannot be used (this rule is ignored often in practice especially when not using UTF-16).

A small set of code points are guaranteed never to be used for encoding characters, although applications may make use of these code points internally if they wish. There are sixty-six of these noncharacters: U+FDD0–U+FDEF and any code point ending in the value FFFE or FFFF (i.e., 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.[62] Like surrogates, the rule that these cannot be used is often ignored, although the operation of the byte order mark (BOM) assumes that U+FFFE will never be the first code point in a text.

Excluding surrogates and noncharacters leaves 1,111,998 code points available for use.

Private-use code points are considered to be assigned characters, but they have no interpretation specified by the Unicode standard[63] so any interchange of such characters requires an agreement between sender and receiver on their interpretation. There are three private-use areas in the Unicode codespace:

  • Private Use Area: U+E000–U+F8FF (6,400 characters),
  • Supplementary Private Use Area-A: U+F0000–U+FFFFD (65,534 characters),
  • Supplementary Private Use Area-B: U+100000–U+10FFFD (65,534 characters).

Graphic characters are characters defined by Unicode to have particular semantics, and either have a visible glyph shape or represent a visible space. As of Unicode 15.0 there are 149,014 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 NON-JOINER and U+200D 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 15.0.

Sixty-five code points (U+0000–U+001F and U+007F–U+009F) are reserved as control codes, and correspond to the C0 and C1 control codes defined in ISO/IEC 6429. U+0009 (Tab), U+000A (Line Feed), and U+000D (Carriage Return) are widely used in Unicode-encoded texts. In practice the C1 code points are often improperly-translated (mojibake) as the legacy Windows-1252 characters used by some English and Western European texts.

Graphic characters, format characters, control code characters, and private use characters are known collectively as assigned characters. Reserved code points are those code points which are available for use, but are not yet assigned. As of Unicode 15.0 there are 825,279 reserved code points.

Abstract characters

The set of graphic and format characters defined by Unicode does not correspond directly to the repertoire of abstract characters that is representable under Unicode. Unicode encodes characters by associating an abstract character with a particular code point.[64] However, not all abstract characters are encoded as a single Unicode character, and some abstract characters may be represented in Unicode by a sequence of two or more characters. For example, a Latin small letter "i" with an ogonek, a 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.[65]

All graphic, format, and private use characters have a unique and immutable name by which they may be identified. This immutability has been guaranteed since Unicode version 2.0 by the Name Stability policy.[62] In cases where the name is seriously defective and misleading, or has a serious typographical error, a formal alias may be defined, and applications are encouraged to use the formal alias 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.[66]

Ready-made versus composite characters

Unicode includes a mechanism for modifying characters that greatly extends the supported glyph repertoire. This covers the use of combining diacritical marks that may be added after the base character by the user. Multiple combining diacritics may be simultaneously applied to the same character. Unicode also contains precomposed versions of most letter/diacritic combinations in normal use. These make conversion to and from legacy encodings simpler, and allow applications to use Unicode as an internal text format without having to implement combining characters. For example, é can be represented in Unicode as U+0065 (LATIN SMALL LETTER E) followed by U+0301 (COMBINING ACUTE ACCENT), but it can also be represented as the precomposed character U+00E9 (LATIN SMALL LETTER E WITH ACUTE). Thus, in many cases, users have multiple ways of encoding the same character. To deal with this, Unicode provides the mechanism of canonical equivalence.

An example of this arises with Hangul, the Korean alphabet. Unicode provides a mechanism for composing Hangul syllables with their individual subcomponents, known as Hangul Jamo. However, it also provides 11,172 combinations of precomposed syllables made from the most common jamo.

The CJK characters currently have codes only for their precomposed form. Still, most of those characters comprise simpler elements (called radicals), so in principle Unicode could have decomposed them as it did with Hangul. This would have greatly reduced the number of required code points, while allowing the display of virtually every conceivable character (which might do away with some of the problems caused by Han unification). A similar idea is used by some input methods, such as Cangjie and Wubi. However, attempts to do this for character encoding have stumbled over the fact that Chinese characters do not decompose as simply or as regularly as Hangul does.

A set of radicals was provided in Unicode 3.0 (CJK radicals between U+2E80 and U+2EFF, KangXi radicals in U+2F00 to U+2FDF, and ideographic description characters from U+2FF0 to U+2FFB), but the Unicode standard (ch. 12.2 of Unicode 5.2) warns against using ideographic description sequences as an alternate representation for previously encoded characters:

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

 
The Devanāgarī ddhrya-ligature (द् + ध् + र् + य = द्ध्र्य) of JanaSanskritSans[67]
 
The Arabic lām-alif ligature (ل ‎+‎ ا ‎=‎ لا)

Many scripts, including Arabic and Devanāgarī, have special orthographic rules that require certain combinations of letterforms to be combined into special ligature forms. The rules governing ligature formation can be quite complex, requiring special script-shaping technologies such as ACE (Arabic Calligraphic Engine by DecoType in the 1980s and used to generate all the Arabic examples in the printed editions of the Unicode Standard), which became the proof of concept for OpenType (by Adobe and Microsoft), 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 Windows NT 4.0 supports 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:[68] MES-1 (Latin scripts only, 335 characters), MES-2 (Latin, Greek and Cyrillic 1062 characters)[69] and MES-3A & MES-3B (two larger subsets, not shown here). Note that MES-2 includes every character in MES-1 and WGL-4.

The standard DIN 91379[70] 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 specification supports all official languages of European Union countries as well as the official languages of Iceland, Liechtenstein, Norway, and Switzerland, and also the German minority languages. 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 which cannot process a Unicode character appropriately often displays it as an open rectangle, or the Unicode "replacement character" (U+FFFD, �), to indicate the position of the unrecognized character. Some systems have made attempts to provide more information about such characters. Apple's Last Resort font will display a substitute glyph indicating the Unicode range of the character, and the SIL International'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.[71] 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, uses one to four bytes for each code point, maximizes compatibility with ASCII
  • UTF-EBCDIC, similar to UTF-8 but designed for compatibility with EBCDIC (not part of The Unicode Standard)
  • UTF-16, uses one or two 16-bit code units per code point, cannot encode surrogates
  • UTF-32, uses one 32-bit code unit per code point

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 interchange of Unicode text. It is used by FreeBSD and most recent Linux distributions as a direct replacement for legacy encodings in general text handling.

The UCS-2 and UTF-16 encodings specify the Unicode byte order mark (BOM) for use at the beginnings of text files, which may be used for byte-order detection (or byte endianness detection). The BOM, code point U+FEFF, has the important property of unambiguity on byte reorder, regardless of the Unicode encoding used; U+FFFE (the result of byte-swapping U+FEFF) does not equate to a legal character, and U+FEFF in places other than the beginning of text conveys the zero-width non-break space (a character with no appearance and no effect other than preventing the formation of ligatures).

The same character converted to UTF-8 becomes the byte sequence EF BB BF. The Unicode Standard allows that the BOM "can serve as signature for UTF-8 encoded text where the character set is unmarked".[72] Some software developers have adopted it for other encodings, including UTF-8, in an attempt to distinguish UTF-8 from local 8-bit code pages. However 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 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.

Punycode, another encoding form, enables the encoding of Unicode strings into the limited character set supported by the ASCII-based Domain Name System (DNS). The encoding is used as part of IDNA, which is a system enabling the use of Internationalized Domain Names in all scripts that are supported by Unicode. Earlier and now historical proposals include UTF-5 and UTF-6.

GB18030 is another encoding form for Unicode, from the Standardization Administration of China. It is the official character set of the People's Republic of China (PRC). BOCU-1 and SCSU are Unicode compression schemes. The April Fools' Day RFC of 2005 specified two parody UTF encodings, UTF-9 and 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.[73] 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 2022, UTF-8 accounts for on average 97.8% of all web pages (and 988 of the top 1,000 highest ranked web pages).[74] 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.[75] Over a third of the languages tracked have 100% UTF-8 use.

All internet protocols maintained by Internet Engineering Task Force, e.g. FTP,[76] have required support for UTF-8 since the publication of RFC 2277 in 1998, which specified that all IETF protocols "MUST be able to use the UTF-8 charset".[77]

Operating systems

Unicode has become the dominant scheme for 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)[78] 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 Uniscribe and DirectWrite for Microsoft Windows, ATSUI and Core Text for macOS, and Pango for 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,[79] 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 in a screen, such as with a character map program.

Online tools for finding the code point for a known character include Unicode Lookup[80] by Jonathan Hedley and Shapecatcher[81] 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[82][83] a framework for internationalized email using UTF-8, and has updated[84][85][86][87] several protocols in accordance with that framework.

The adoption of Unicode in email has been very slow.[citation needed] Some East Asian text is still encoded in encodings such as 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.[88]

Although syntax rules may affect the order in which characters are allowed to appear, XML (including XHTML) documents, by definition,[89] comprise characters from most of the Unicode code points, with the exception of:

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

HTML characters manifest either directly as bytes according to 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 URIs, for example as URLs in HTTP requests, non-ASCII characters must be percent-encoded.

Fonts

Main article: Unicode font

Unicode is not in principle concerned with fonts per se, seeing them as implementation choices.[90] 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.[91] 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 fonts based on Unicode are widely available, since TrueType and OpenType support Unicode (and Web Open Font Format (WOFF and 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".

Thousands of fonts exist on the market, but fewer than a dozen fonts—sometimes described as "pan-Unicode" fonts—attempt to support the majority of Unicode's character repertoire. Instead, Unicode-based 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

Han unification

Han unification (the identification of forms in the East Asian languages which one can treat as stylistic variations of the same historical character) has become one of the most controversial aspects of Unicode, despite the presence of a majority of experts from all three regions in the Ideographic Research Group (IRG), which advises the Consortium and ISO on additions to the repertoire and on Han unification.[92]

Unicode has been criticized for failing to separately encode older and alternative forms of kanji which, critics argue, complicates the processing of ancient Japanese and uncommon Japanese names. This is often due to the fact that Unicode encodes characters rather than glyphs (the visual representations of the basic character that often vary from one language to another). Unification of glyphs leads to the perception that the languages themselves, not just the basic character representation, are being merged.[93][clarification needed] There have been several attempts to create alternative encodings that preserve the stylistic differences between Chinese, Japanese, and Korean characters in opposition to Unicode's policy of Han unification. An example of one is TRON (although it is not widely adopted in Japan, there are some users who need to handle historical Japanese text and favor it).

Although the repertoire of fewer than 21,000 Han characters in the earliest version of Unicode was largely limited to characters in common modern usage, Unicode now includes more than 97,000 Han characters, and work is continuing to add thousands more historic and dialectal characters used in China, Japan, Korea, Taiwan, and Vietnam.

Modern font technology provides a means to address the practical issue of needing to depict a unified Han character in terms of a collection of alternative glyph representations, in the form of Unicode variation sequences. For example, the Advanced Typographic tables of OpenType permit one of a number of alternative glyph representations to be selected when performing the character to glyph mapping process. In this case, information can be provided within plain text to designate which alternate character form to select.

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

Italic or cursive characters in Cyrillic

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.

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 combining sequence of already existing characters can no longer be added to the standard in order to preserve interoperability between software using different versions of Unicode.

Injective mappings must be provided between characters in existing legacy character sets and characters in Unicode to facilitate conversion to Unicode and allow interoperability with legacy software. Lack of consistency in various mappings between earlier Japanese encodings such as Shift-JIS or 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).[94]

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.[95] (This encoding also replaces tilde '~' 0x7E with macron '¯', now 0xAF.) The separation of these characters exists in ISO 8859-1, from long before Unicode.

Indic scripts

Indic scripts such as Tamil and Devanagari are each allocated only 128 code points, matching the ISCII standard. The correct rendering of Unicode Indic text requires transforming the stored logical order characters into visual order and the forming of ligatures (aka 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.[96][97][98] 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,[99] but these were rejected for encoding by the relevant ISO committee (ISO/IEC JTC 1/SC 2).[100]

Thai alphabet support has been criticized for its ordering of Thai characters. The vowels เ, แ, โ, ใ, ไ that are written to the left of the preceding consonant are in visual order instead of phonetic order, unlike the Unicode representations of other Indic scripts. This complication is due to Unicode inheriting the 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.[93] 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 e with a macron and acute accent, but in practice, their appearance may vary depending upon what rendering engine and fonts are being used to display the characters. Similarly, underdots, as needed in the romanization of Indic, will often be placed incorrectly.[citation needed]. Unicode characters that map to precomposed glyphs can be used in many cases, thus avoiding the problem, but where no precomposed character has been encoded the problem can often be solved by using a specialist Unicode font such as Charis SIL that uses Graphite, OpenType, 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.[101] 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 from then on, an assigned name to a code point would never change anymore. 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,[102] 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.[105][106]

Security issues

Unicode has a large number of homoglyphs, many of which look very similar or identical to ASCII letters. Substitution of these can make an identifier or URL that looks correct, but directs to a different location than expected,[107] and could also be used for manipulating the output of natural language processing (NLP) systems.[108]

Mitigation requires disallowing these characters, displaying them differently, or requiring that they resolve to the same identifier; all of this is complicated due to the huge and constantly changing set of characters.[109][110]

A security advisory was released in 2021 from two researchers, one from the University of Cambridge and the other from the same and from the University of Edinburgh, in which they assert that the BIDI codes can be used to make large sections of code do something different from what they appear to do.[111]

See also

Notes

  1. ^ The formal version reference is The Unicode Consortium: The Unicode Standard, Version 15.0.0. Mountain View, CA: The Unicode Consortium. 2022. ISBN 978-1-936213-32-0.
  2. ^ Sometimes abbr. TUS is used.[1][2]

References

  1. ^ Members of the Unicode Editorial Committee (2002-03-27). "Unicode Technical Report #28: Unicode 3.2". Unicode Consortium. Retrieved 2022-06-23.{{cite web}}: CS1 maint: uses authors parameter (link)
  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 15.0.0".
  4. ^ "Unicode Version 15.0 Character Counts".
  5. ^ "The Unicode Standard: A Technical Introduction". Retrieved 2010-03-16.
  6. ^ "The Unicode® Bulldog Award".
  7. ^ a b c d e Becker, Joseph D. (1998-09-10) [1988-08-29]. "Unicode 88" (PDF). unicode.org (10th anniversary reprint ed.). Unicode Consortium. (PDF) from the original on 2016-11-25. Retrieved 2016-10-25. In 1978, the initial proposal for a set of "Universal Signs" was made by Bob Belleville at 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 which 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 have been proved over the years in an international line of communication multilingual system products.
  8. ^ "Summary Narrative". Retrieved 2010-03-15.
  9. ^ History of Unicode Release and Publication Dates on unicode.org. Retrieved February 28, 2017.
  10. ^ Searle, Stephen J. "Unicode Revisited". Retrieved 2013-01-18.
  11. ^ a b "The Unicode Consortium Members". Retrieved 2019-01-04.
  12. ^ "Unicode FAQ". Retrieved 2020-04-02.
  13. ^ "Supported Scripts". unicode.org. Retrieved 2022-09-16.
  14. ^ "Roadmap to the BMP". Unicode Consortium. Retrieved 2018-07-30.
  15. ^ "Unicode Roadmap".
  16. ^ "Script Encoding Initiative".
  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. ^ "BETA Unicode 15.0.0". www.unicode.org. Retrieved 2022-07-16.
  20. ^ "Emoji Counts, v15.0β". www.unicode.org. Retrieved 2022-07-16.
  21. ^ "Enumerated Versions of The Unicode Standard". Retrieved 2016-06-21.
  22. ^ a b c
    • "Unicode version 1.0". 1991.
    • "1.0.0/UnicodeData.txt (reconstructed)". 2004. Retrieved 2010-03-16.
  23. ^ a b "Unicode Data 1.0.1". Retrieved 2010-03-16.
  24. ^ a b
    • "Unicode version 1.1".
    • "Unicode Data 1995". Retrieved 2010-03-16.
  25. ^ a b
    • "Unicode version 2.0.0".
    • "Unicode Data-2.0.14". Retrieved 2010-03-16.
  26. ^ a b
    • "Unicode version 2.1.0".
    • "Unicode Data-2.1.2". Retrieved 2010-03-16.
  27. ^ "Unicode Data-3.0.0". Retrieved 2010-03-16.
  28. ^ "Unicode Data-3.1.0". Retrieved 2010-03-16.
  29. ^ "Unicode Data-3.2.0". Retrieved 2010-03-16.
  30. ^ and "ș" and "ț" characters to support Romanian"Unicode Data-4.0.0". Retrieved 2010-03-16.
  31. ^ "Unicode Data-4.1.0". Retrieved 2010-03-16.
  32. ^ "Unicode Data 5.0.0". Retrieved 2010-03-17.
  33. ^ "Unicode Data 5.1.0". Retrieved 2010-03-17.
  34. ^ "Unicode Data 5.2.0". Retrieved 2010-03-17.
  35. ^ "Unicode 6.0 Emoji List". emojipedia.org. Retrieved 2022-09-21.
  36. ^ "Unicode Data 6.0.0". Retrieved 2010-10-11.
  37. ^ "Unicode Data 6.1.0". Retrieved 2012-01-31.
  38. ^ "Unicode Data 6.2.0". Retrieved 2012-09-26.
  39. ^ "Unicode Data 6.3.0". Retrieved 2013-09-30.
  40. ^ "Unicode Data 7.0.0". Retrieved 2014-06-15.
  41. ^ "Unicode 8.0.0". Unicode Consortium. Retrieved 2015-06-17.
  42. ^ "Unicode Data 8.0.0". Retrieved 2015-06-17.
  43. ^ "Unicode 9.0.0". Unicode Consortium. Retrieved 2016-06-21.
  44. ^ "Unicode Data 9.0.0". Retrieved 2016-06-21.
  45. ^ 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.
  46. ^ "Unicode 10.0.0". Unicode Consortium. Retrieved 2017-06-20.
  47. ^ "Bitcoin symbol - Bitcoin Wiki". en.bitcoin.it. Retrieved 2021-09-29.
  48. ^ "The Unicode Standard, Version 11.0.0 Appendix C" (PDF). Unicode Consortium. Retrieved 2018-06-11.
  49. ^ "Announcing The Unicode Standard, Version 11.0". blog.unicode.org. Retrieved 2018-06-06.
  50. ^ "The Unicode Standard, Version 12.0.0 Appendix C" (PDF). Unicode Consortium. Retrieved 2019-03-05.
  51. ^ "Announcing The Unicode Standard, Version 12.0". blog.unicode.org. Retrieved 2019-03-05.
  52. ^ "Unicode Version 12.1 released in support of the Reiwa Era". blog.unicode.org. Retrieved 2019-05-07.
  53. ^ a b
    • "Unicode 13.0.0".
    • "Announcing The Unicode Standard, Version 13.0". blog.unicode.org. Retrieved 2020-03-11.
  54. ^ "The Unicode Standard, Version 13.0– Core Specification Appendix C" (PDF). Unicode Consortium. Retrieved 2020-03-11.
  55. ^ a b
    • "Unicode 14.0.0".
    • "Announcing The Unicode® Standard, Version 14.0".
  56. ^ a b
    • "Unicode 15.0.0".
  57. ^ "Glossary of Unicode Terms". Retrieved 2010-03-16.
  58. ^ "3.4 Characters and Encoding". The Unicode Standard, Version 15.0 (PDF). 2022. p. 88.
  59. ^ "2.4 Code Points and Characters". The Unicode Standard Version 15.0 – Core Specification (PDF). 2022. p. 29.
  60. ^ "Re: Origin of the U+nnnn notation". Unicode Mail List Archive (Mailing list). 2005-11-08.
  61. ^ "Appendix A: Notational Conventions" (PDF). The Unicode Standard. Unicode Consortium. September 2022. In conformity with the bullet point relating to Unicode in MOS:ALLCAPS, the formal Unicode names are not used in this paragraph.
  62. ^ a b "Unicode Character Encoding Stability Policy". Retrieved 2010-03-16.
  63. ^ "Properties" (PDF). Retrieved 2022-09-16.
  64. ^ "Unicode Character Encoding Model". Retrieved 2022-09-16.
  65. ^ "Unicode Named Sequences". Retrieved 2022-09-16.
  66. ^ "Unicode Name Aliases". Retrieved 2010-03-16.
  67. ^ . Archived from the original on 2011-07-16.
  68. ^ CWA 13873:2000 – Multilingual European Subsets in ISO/IEC 10646-1 CEN Workshop Agreement 13873
  69. ^ Multilingual European Character Set 2 (MES-2) Rationale, Markus Kuhn, 1998
  70. ^ "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.
  71. ^ "UTF-8, UTF-16, UTF-32 & BOM". Unicode.org FAQ. Retrieved 2016-12-12.
  72. ^ The Unicode Standard, Version 6.2. The Unicode Consortium. 2013. p. 561. ISBN 978-1-936213-08-5.
  73. ^ Davis, Mark (2008-05-05). "Moving to Unicode 5.1". Retrieved 2021-02-19.
  74. ^ "Usage Survey of Character Encodings broken down by Ranking". w3techs.com. Retrieved 2022-10-03.
  75. ^ "Usage Statistics and Market Share of US-ASCII for Websites, October 2021". w3techs.com. Retrieved 2020-11-01.
  76. ^ B. Curtin (July 1999). Internationalization of the File Transfer Protocol. doi:10.17487/RFC2640. RFC 2640. Retrieved 2022-08-17.
  77. ^ H. Alvestrand (January 1998). IETF Policy on Character Sets and Languages. doi:10.17487/RFC2277. BCP 18. RFC 2277. Retrieved 2022-08-17.
  78. ^ Pike, Rob (2003-04-30). "UTF-8 history".
  79. ^ "ISO/IEC JTC1/SC 18/WG 9 N" (PDF). Retrieved 2012-06-04.
  80. ^ Hedley, Jonathan (2009). "Unicode Lookup".
  81. ^ Milde, Benjamin (2011). "Unicode Character Recognition".
  82. ^ J. Klensin; Y. Ko (July 2007). Overview and Framework for Internationalized Email. doi:10.17487/RFC4952. RFC 4952. Retrieved 2022-08-17.
  83. ^ J. Klensin; Y. Ko (February 2012). Overview and Framework for Internationalized Email. doi:10.17487/RFC6530. RFC 6530. Retrieved 2022-08-17.
  84. ^ J. Yao; W. Mao (February 2012). SMTP Extension for Internationalized Email. doi:10.17487/RFC6531. RFC 6531. Retrieved 2022-08-17.
  85. ^ A. Yang; S. Steele; N. Freed (February 2012). Internationalized Email Headers. doi:10.17487/RFC6532. RFC 6532. Retrieved 2022-08-17.
  86. ^ C. Newman; A. Gulbrandsen; A. Melnikov (June 2008). Internet Message Access Protocol Internationalization. doi:10.17487/RFC5255. RFC 5255. Retrieved 2022-08-17.
  87. ^ R. Gellens; C. Newman (February 2010). POP3 Support for UTF-8. doi:10.17487/RFC5721. RFC 5721. Retrieved 2022-08-17.
  88. ^ Wood, Alan. "Setting up Windows Internet Explorer 5, 5.5 and 6 for Multilingual and Unicode Support". Alan Wood. Retrieved 2012-06-04.
  89. ^ "Extensible Markup Language (XML) 1.1 (Second Edition)". Retrieved 2013-11-01.
  90. ^ Bigelow, Charles; Holmes, Kris (September 1993). "The design of a Unicode font" (PDF). Electronic Publishing. 6 (3): 292.
  91. ^ "Fonts and keyboards". Unicode Consortium. 2017-06-28. Retrieved 2019-10-13.
  92. ^ A Brief History of Character Codes, Steven J. Searle, originally written , last updated 2004
  93. ^ a b , Suzanne Topping, 1 May 2001 (Internet Archive)
  94. ^ AFII contribution about WAVE DASH, . web.archive.org. 2011-04-22. Archived from the original on 2011-04-22.
  95. ^ ISO 646-* Problem, Section 4.4.3.5 of Introduction to I18n, Tomohiro KUBOTA, 2001
  96. ^ "Arabic Presentation Forms-A" (PDF). Retrieved 2010-03-20.
  97. ^ "Arabic Presentation Forms-B" (PDF). Retrieved 2010-03-20.
  98. ^ "Alphabetic Presentation Forms" (PDF). Retrieved 2010-03-20.
  99. ^ China (2002-12-02). "Proposal on Tibetan BrdaRten Characters Encoding for ISO/IEC 10646 in BMP" (PDF).
  100. ^ V. S. Umamaheswaran (2003-11-07). "Resolutions of WG 2 meeting 44" (PDF). Resolution M44.20.
  101. ^ "Unicode stability policy".
  102. ^ a b "Unicode Technical Note #27: Known Anomalies in Unicode Character Names". unicode.org. 2021-06-14.
  103. ^ "Unicode chart: "actually this has the form of a lowercase calligraphic p, despite its name"" (PDF).
  104. ^ ""Misspelling of BRACKET in character name is a known defect"" (PDF).
  105. ^ "Unicode Standard Annex #24: Unicode Script Property". The Unicode Consortium. 2021. 2.2 Relation to ISO 15924 Codes. Retrieved 2022-04-29.
  106. ^ "Scripts-15.0.0.txt". The Unicode Consortium. 2022. Retrieved 2022-09-16.
  107. ^ "UTR #36: Unicode Security Considerations". unicode.org.
  108. ^ Boucher, Nicholas; Shumailov, Ilia; Anderson, Ross; Papernot, Nicolas (2022). "Bad Characters: Imperceptible NLP Attacks". 2022 IEEE Symposium on Security and Privacy (SP). San Francisco, CA, USA: IEEE: 1987–2004. arXiv:2106.09898. doi:10.1109/SP46214.2022.9833641. ISBN 978-1-6654-1316-9.
  109. ^ Wheeler, David A. (2020). "Countermeasures". Initial Analysis of Underhanded Source Code: 4–1.
  110. ^ "UTR #36: Unicode Security Considerations". unicode.org. Retrieved 2022-06-27.
  111. ^ Nicholas Boucher, Ross Anderson. "Trojan Source: Invisible Vulnerabilities" (PDF). Retrieved 2021-11-02.

Further reading

  • The Unicode Standard, Version 3.0, The Unicode Consortium, Addison-Wesley Longman, Inc., April 2000. ISBN 0-201-61633-5
  • The Unicode Standard, Version 4.0, The Unicode Consortium, Addison-Wesley Professional, 27 August 2003. ISBN 0-321-18578-1
  • The Unicode Standard, Version 5.0, Fifth Edition, The Unicode Consortium, Addison-Wesley Professional, 27 October 2006. ISBN 0-321-48091-0
  • Julie D. Allen. The Unicode Standard, Version 6.0, The Unicode Consortium, Mountain View, 2011, ISBN 9781936213016, ([1]).
  • The Complete Manual of Typography, James Felici, Adobe Press; 1st edition, 2002. ISBN 0-321-12730-7
  • Unicode: A Primer, Tony Graham, M&T books, 2000. ISBN 0-7645-4625-2.
  • Unicode Demystified: A Practical Programmer's Guide to the Encoding Standard, Richard Gillam, Addison-Wesley Professional; 1st edition, 2002. ISBN 0-201-70052-2
  • Unicode Explained, Jukka K. Korpela, O'Reilly; 1st edition, 2006. ISBN 0-596-10121-X
  • Yannis Haralambous; Martin Dürst (2019). "Unicode from a Linguistic Point of View". In Haralambous, Yannis (ed.). Proceedings of Graphemics in the 21st Century, Brest 2018. Brest: Fluxus Editions. pp. 167–183. doi:10.36824/2018-graf-hara1. ISBN 978-2-9570549-1-6.

External links

  • Official website    · Official technical site
  • Latest Unicode Standard
  • The Unicode Character Database, a text document listing the names, code points and properties of all Unicode characters
  • Unicode at Curlie
  • Alan Wood's Unicode Resources – contains lists of word processors with Unicode capability; fonts and characters are grouped by type; characters are presented in lists, not grids.
  • The World's Writing Systems, all 294 known writing systems with their Unicode status (131 not yet encoded)
  • Unicode BMP Fallback Font – displays the Unicode 6.1 value of any character in a document, including in the Private Use Area, rather than the glyph itself.

January 10, 2023
unicode, formally, standard, note, note, information, technology, standard, consistent, encoding, representation, handling, text, expressed, most, world, writing, systems, standard, which, maintained, consortium, defines, current, version, characters, covering. Unicode formally The Unicode Standard note 1 note 2 is an information technology standard for the consistent encoding representation and handling of text expressed in most of the world s writing systems The standard which is maintained by the Unicode Consortium defines as of the current version 15 0 149 186 characters 3 4 covering 161 modern and historic scripts as well as symbols emoji including in colors and non visual control and formatting codes UnicodeLogo of the Unicode ConsortiumAlias es Universal Coded Character Set UCS ISO IEC 10646 Language s InternationalStandardUnicode StandardEncoding formatsUTF 8UTF 16GB18030Less common UTF 32BOCUSCSUObsolete UTF 7Preceded byISO IEC 8859 various othersOfficial websiteOfficial technical websitevteThis article contains uncommon Unicode characters Without proper rendering support you may see question marks boxes or other symbols Unicode s success at unifying character sets has led to its widespread and predominant use in the internationalization and localization of computer software The standard has been implemented in many recent technologies including modern operating systems XML and most modern programming languages The Unicode character repertoire is synchronized with ISO IEC 10646 each being code for code identical with the other The Unicode Standard however includes more than just the base code Alongside the character encodings the Consortium s official publication includes a wide variety of details about the scripts and how to display them normalization rules decomposition collation rendering and bidirectional text display order for multilingual texts and so on 5 The Standard also includes reference data files and visual charts to help developers and designers correctly implement the repertoire Unicode can be stored using several different encodings which translate the character codes into sequences of bytes The Unicode standard defines three and several other encodings exist all in practice variable length encodings The most common encodings are the ASCII compatible UTF 8 the ASCII incompatible UTF 16 compatible with the obsolete UCS 2 and the Chinese Unicode encoding standard GB18030 which is not an official Unicode standard but is used in China and implements Unicode fully Contents 1 Origin and development 1 1 History 1 2 Unicode Consortium 1 3 Scripts covered 1 4 Script Encoding Initiative 1 5 Versions 2 Architecture and terminology 2 1 Codespace and Code Points 2 2 Code planes and blocks 2 3 General Category property 2 4 Abstract characters 2 5 Ready made versus composite characters 2 6 Ligatures 2 7 Standardized subsets 2 8 Mapping and encodings 3 Adoption 3 1 Operating systems 3 2 Input methods 3 3 Email 3 4 Web 3 5 Fonts 3 6 Newlines 4 Issues 4 1 Han unification 4 2 Italic or cursive characters in Cyrillic 4 3 Mapping to legacy character sets 4 4 Indic scripts 4 5 Combining characters 4 6 Anomalies 4 7 Security issues 5 See also 6 Notes 7 References 8 Further reading 9 External linksOrigin and development EditUnicode has the explicit aim of transcending the limitations of traditional character encodings such as those defined by the ISO IEC 8859 standard which find wide usage in various countries of the world but remain largely incompatible with each other Many traditional character encodings share a common problem in that they allow bilingual computer processing usually using Latin characters and the local script but not multilingual computer processing computer processing of arbitrary scripts mixed with each other Unicode in intent encodes the underlying characters graphemes and grapheme like units rather than the variant glyphs renderings for such characters In the case of Chinese characters this sometimes leads to controversies over distinguishing the underlying character from its variant glyphs see Han unification In text processing Unicode takes the role of providing a unique code point a number not a glyph for each character In other words Unicode represents a character in an abstract way and leaves the visual rendering size shape font or style to other software such as a web browser or word processor This simple aim becomes complicated however because of concessions made by Unicode s designers in the hope of encouraging a more rapid adoption of Unicode The first 256 code points were made identical to the content of ISO IEC 8859 1 so as to make it trivial to convert existing western text Many essentially identical characters were encoded multiple times at different code points to preserve distinctions used by legacy encodings and therefore allow conversion from those encodings to Unicode and back without losing any information For example the fullwidth forms section of code points encompasses a full duplicate of the Latin alphabet because Chinese Japanese and Korean CJK fonts contain two versions of these letters fullwidth matching the width of the CJK characters and normal width For other examples see duplicate characters in Unicode Unicode Bulldog Award recipients include many names influential in the development of Unicode and include Tatsuo Kobayashi Thomas Milo Roozbeh Pournader Ken Lunde and Michael Everson 6 History Edit Based on experiences with the Xerox Character Code Standard XCCS since 1980 7 the origins of Unicode can be traced back to 1987 when Joe Becker from Xerox with Lee Collins and Mark Davis from Apple started investigating the practicalities of creating a universal character set 8 With additional input from Peter Fenwick and Dave Opstad 7 Joe 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 16 bit character model 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 His original 16 bit design was based on the assumption that only those scripts and characters in modern use would need to be encoded 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 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 Unicodes In early 1989 the Unicode working group expanded to include Ken Whistler and Mike Kernaghan of Metaphor Karen Smith Yoshimura and Joan Aliprand of RLG and Glenn Wright of Sun Microsystems and in 1990 Michel Suignard and Asmus Freytag from Microsoft and Rick McGowan of NeXT joined the group By the end of 1990 most of the work on mapping existing character encoding 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 in October 1991 the first volume of the Unicode standard was published The second volume covering 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 e g Egyptian hieroglyphs and thousands of rarely used or obsolete characters that had not been anticipated as needing encoding Among the characters not originally intended for Unicode are rarely used Kanji or Chinese characters many of which are part of personal and place names making them much more essential than envisioned in the original architecture of Unicode 10 The Microsoft TrueType specification version 1 0 from 1992 used the name Apple Unicode instead of Unicode for the Platform ID in the naming table Unicode Consortium Edit 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 with any interest in text processing standards including Adobe Apple Facebook Google IBM Microsoft Netflix and SAP SE 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 Edit Main article Script Unicode Many modern applications can render a substantial subset of the many scripts in Unicode as demonstrated by this screenshot from the OpenOffice org application Unicode currently covers most major writing systems in use today 12 better source needed As of 2022 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 small script encoding proposals have been made and they are working their way through the approval process For other scripts such as Mayan besides numbers 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 have been already included into Unicode Script Encoding Initiative Edit 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 Edit The Unicode Consortium and the International Organization for Standardization ISO have together developed a shared repertoire following the initial publication of The Unicode Standard in 1991 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 and code charts However Unicode 5 0 published in 2006 was the last version printed this way Starting with version 5 2 only the core specification published as 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 only 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 from March 2021 to September 2021 due to the COVID 19 pandemic The latest version of Unicode 15 0 0 was released on 13 September 2022 Several annexes were updated including Unicode Security Mechanisms UTS 39 and a total of 4489 new characters were encoded including 20 new emoji characters such as wireless network symbol and hearts in different colors such as pink two new scripts CJK Unified Ideographs extension and multiple additions to existing blocks 19 20 Thus far the following major and minor 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 vteUnicode version history and notable changes to characters and scripts Version Date Book Corresponding ISO IEC 10646 edition Scripts CharactersTotal tablenote 1 Notable additions1 0 0 22 October 1991 ISBN 0 201 56788 1 Vol 1 24 7 129 tablenote 2 Initial repertoire covers these scripts Arabic Armenian Bengali Bopomofo Cyrillic Devanagari Georgian Greek and Coptic Gujarati Gurmukhi Hangul Hebrew Hiragana Kannada Katakana Lao Latin Malayalam Oriya Tamil Telugu Thai and Tibetan 22 1 0 1 23 June 1992 ISBN 0 201 60845 6 Vol 2 25 28 327 21 204 added 6 removed The initial set of 20 902 CJK Unified Ideographs is defined 23 1 1 24 June 1993 ISO IEC 10646 1 1993 24 34 168 5 963 added 89 removed 33 reclassifiedas controlcharacters 4 306 more Hangul syllables added to original set of 2 350 characters Tibetan removed 24 2 0 25 July 1996 ISBN 0 201 48345 9 ISO IEC 10646 1 1993 plus Amendments 5 6 and 7 25 38 885 11 373 added 6 656 removed Original set of Hangul syllables removed and a new set of 11 172 Hangul syllables added at a new location Tibetan added back in a new location and with a different character repertoire Surrogate character mechanism defined and Plane 15 and Plane 16 Private Use Areas allocated 25 2 1 26 May 1998 ISO IEC 10646 1 1993 plus Amendments 5 6 and 7 as well as two characters from Amendment 18 25 38 887 2 added Euro sign and Object Replacement Character added 26 3 0 September 1999 ISBN 0 201 61633 5 ISO IEC 10646 1 2000 38 49 194 10 307 added Cherokee Ethiopic Khmer Mongolian Burmese Ogham Runic Sinhala Syriac Thaana Unified Canadian Aboriginal Syllabics and Yi Syllables added as well as a set of Braille patterns 27 3 1 March 2001 ISO IEC 10646 1 2000 ISO IEC 10646 2 2001 41 94 140 44 946 added Deseret Gothic and Old Italic added as well as sets of symbols for Western music and Byzantine music and 42 711 additional CJK Unified Ideographs 28 3 2 March 2002 ISO IEC 10646 1 2000 plus Amendment 1 ISO IEC 10646 2 2001 45 95 156 1 016 added Philippine scripts Buhid Hanuno o Tagalog and Tagbanwa added 29 4 0 April 2003 ISBN 0 321 18578 1 ISO IEC 10646 2003 52 96 382 1 226 added Cypriot syllabary Limbu Linear B Osmanya Shavian Tai Le and Ugaritic added as well as Hexagram symbols 30 4 1 March 2005 ISO IEC 10646 2003 plus Amendment 1 59 97 655 1 273 added Buginese Glagolitic Kharoshthi New Tai Lue Old Persian Syloti Nagri and Tifinagh added and Coptic was disunified from Greek Ancient Greek numbers and musical symbols were also added 31 5 0 July 2006 ISBN 0 321 48091 0 ISO IEC 10646 2003 plus Amendments 1 and 2 as well as four characters from Amendment 3 64 99 024 1 369 added Balinese Cuneiform N Ko Phags pa and Phoenician added 32 5 1 April 2008 ISO IEC 10646 2003 plus Amendments 1 2 3 and 4 75 100 648 1 624 added Carian Cham Kayah Li Lepcha Lycian Lydian Ol Chiki Rejang Saurashtra Sundanese and Vai added as well as sets of symbols for the Phaistos Disc Mahjong tiles and Domino tiles There were also important additions for Burmese additions of letters and Scribal abbreviations used in medieval manuscripts and the addition of Capital ẞ 33 5 2 October 2009 ISBN 978 1 936213 00 9 ISO IEC 10646 2003 plus Amendments 1 2 3 4 5 and 6 90 107 296 6 648 added Avestan Bamum Egyptian hieroglyphs the Gardiner Set comprising 1 071 characters Imperial Aramaic Inscriptional Pahlavi Inscriptional Parthian Javanese Kaithi Lisu Meetei Mayek Old South Arabian Old Turkic Samaritan Tai Tham and Tai Viet added 4 149 additional CJK Unified Ideographs CJK C as well as extended Jamo for Old Hangul and characters for Vedic Sanskrit 34 6 0 October 2010 ISBN 978 1 936213 01 6 ISO IEC 10646 2010 plus the Indian rupee sign 93 109 384 2 088 added Batak Brahmi Mandaic playing card symbols transport and map symbols alchemical symbols emoticons and emojis 35 222 additional CJK Unified Ideographs CJK D added 36 6 1 January 2012 ISBN 978 1 936213 02 3 ISO IEC 10646 2012 100 110 116 732 added Chakma Meroitic cursive Meroitic hieroglyphs Miao Sharada Sora Sompeng and Takri 37 6 2 September 2012 ISBN 978 1 936213 07 8 ISO IEC 10646 2012 plus the Turkish lira sign 100 110 117 1 added Turkish lira sign 38 6 3 September 2013 ISBN 978 1 936213 08 5 ISO IEC 10646 2012 plus six characters 100 110 122 5 added 5 bidirectional formatting characters 39 7 0 June 2014 ISBN 978 1 936213 09 2 ISO IEC 10646 2012 plus Amendments 1 and 2 as well as the Ruble sign 123 112 956 2 834 added Bassa Vah Caucasian Albanian Duployan Elbasan Grantha Khojki Khudawadi Linear A Mahajani Manichaean Mende Kikakui Modi Mro Nabataean Old North Arabian Old Permic Pahawh Hmong Palmyrene Pau Cin Hau Psalter Pahlavi Siddham Tirhuta Warang Citi and Dingbats 40 8 0 June 2015 ISBN 978 1 936213 10 8 ISO IEC 10646 2014 plus Amendment 1 as well as the Lari sign nine CJK unified ideographs and 41 emoji characters 41 129 120 672 7 716 added Ahom Anatolian hieroglyphs Hatran Multani Old Hungarian SignWriting 5 771 CJK Unified Ideographs a set of lowercase letters for Cherokee and five emoji skin tone modifiers 42 9 0 June 2016 ISBN 978 1 936213 13 9 ISO IEC 10646 2014 plus Amendments 1 and 2 as well as Adlam Newa Japanese TV symbols and 74 emoji and symbols 43 135 128 172 7 500 added Adlam Bhaiksuki Marchen Newa Osage Tangut and 72 emoji 44 45 10 0 June 2017 ISBN 978 1 936213 16 0 ISO IEC 10646 2017 plus 56 emoji characters 285 hentaigana characters and 3 Zanabazar Square characters 46 139 136 690 8 518 added Zanabazar Square Soyombo Masaram Gondi Nushu hentaigana non standard hiragana 7 494 CJK Unified Ideographs 56 emoji and bitcoin symbol 47 11 0 June 2018 ISBN 978 1 936213 19 1 ISO IEC 10646 2017 plus Amendment 1 as well as 46 Mtavruli Georgian capital letters 5 CJK unified ideographs and 66 emoji characters 48 146 137 374 684 added Dogra Georgian Mtavruli capital letters Gunjala Gondi Hanifi Rohingya Indic Siyaq Numbers Makasar Medefaidrin Old Sogdian and Sogdian Mayan numerals 5 urgently needed CJK Unified Ideographs symbols for xiangqi Chinese chess and star ratings and 145 emoji 49 12 0 March 2019 ISBN 978 1 936213 22 1 ISO IEC 10646 2017 plus Amendments 1 and 2 as well as 62 additional characters 50 150 137 928 554 added Elymaic Nandinagari Nyiakeng Puachue Hmong Wancho Miao script additions for several Miao and Yi languages of China hiragana and katakana small letters for writing archaic Japanese Tamil historic fractions and symbols Lao letters for Pali Latin letters for Egyptological and Ugaritic transliteration hieroglyph format controls and 61 emoji 51 12 1 May 2019 ISBN 978 1 936213 25 2 150 137 929 1 added Adds a single character at U 32FF for the square ligature form of the name of the Reiwa era 52 13 0 53 March 2020 ISBN 978 1 936213 26 9 ISO IEC 10646 2020 54 154 143 859 5 930 added Chorasmian Dives Akuru Khitan small script Yezidi 4 969 CJK unified ideographs added including 4 939 in Ext G Arabic script additions used to write Hausa Wolof and other languages in Africa and other 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 from the 1970s and 1980s and 55 emoji 53 14 0 55 September 2021 ISBN 978 1 936213 29 0 159 144 697 838 added Toto Cypro Minoan Vithkuqi Old Uyghur Tangsa Latin script additions at SMP blocks Ext F Ext G for use in extended IPA Arabic script additions for use in languages across Africa and in Iran Pakistan Malaysia Indonesia Java and Bosnia and to write honorifics additions for Quranic use other additions to support languages in North America the Philippines India and Mongolia addition of the Kyrgyzstani som currency symbol support for Znamenny musical notation and 37 emoji 55 15 0 56 September 2022 ISBN 978 1 936213 32 0 161 149 186 4 489 added Kawi and Mundari several new characters including 20 emoji 4 192 CJK ideographs and control characters for Egyptian hieroglyphs 56 The number of characters listed for each version of Unicode is the total number of graphic and format characters i e excluding private use characters control characters noncharacters and surrogate code points Not counting space or 33 non printing characters 7 163 total 22 Architecture and terminology EditSee also Universal Character Set characters Codespace and Code Points Edit The Unicode Standard defines a codespace 57 a set of numerical values ranging from 0 through 10FFFF16 58 called code points 59 and denoted as U 0000 through U 10FFFF U 60 followed by the code point value in hexadecimal which is prepended with leading zeros to a minimum of four digits e g U 00F7 for the division sign but U 13254 not U 013254 for the Egyptian hieroglyph 61 Of these 216 220 defined code points the code points from U D800 through U DFFF which are used to encode surrogate pairs in UTF 16 are reserved by the Unicode Standard and may not be used to encode valid characters resulting in a net total of 216 211 220 1 112 064 assignable code points Code planes and blocks Edit Main article Plane Unicode The Unicode codespace is divided into seventeen planes numbered 0 to 16 Plane 0 is the Basic Multilingual Plane BMP which contains 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 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 Although blocks are an arbitrary size they are always a multiple of 16 code points and often a multiple of 128 code points Characters required for a given script may be spread out over several different blocks General Category property Edit Each code point has a single General Category property The major categories are denoted Letter Mark Number Punctuation Symbol Separator and Other Within these categories there are subdivisions In most cases other properties must be used to sufficiently specify the characteristics of a code point The possible General Categories are General Category Unicode Character Property a vteValue Category Major minor Basic type b Character assigned b Count c as of 15 0 Remarks L Letter LC Cased Letter Lu Ll and Lt only d Lu Letter uppercase Graphic Character 1 831Ll Letter lowercase Graphic Character 2 233Lt Letter titlecase Graphic Character 31 Ligatures containing uppercase followed by lowercase letters e g Dž Lj Nj and Dz Lm Letter modifier Graphic Character 397 A modifier letterLo Letter other Graphic Character 131 612 An ideograph or a letter in a unicase alphabetM MarkMn Mark nonspacing Graphic Character 1 985Mc Mark spacing combining Graphic Character 452Me Mark enclosing Graphic Character 13N NumberNd 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 vulgar fractions superscript and subscript digitsP PunctuationPc 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 charactersPs Punctuation open Graphic Character 79 Opening bracket charactersPe Punctuation close Graphic Character 77 Closing bracket charactersPi 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 usagePf Punctuation final quote Graphic Character 10 Closing quotation mark May behave like Ps or Pe depending on usagePo Punctuation other Graphic Character 628S SymbolSm Symbol math Graphic Character 948 Mathematical symbols e g 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 symbolsSk Symbol modifier Graphic Character 125So Symbol other Graphic Character 6 634Z SeparatorZs Separator space Graphic Character 17 Includes the space but not TAB CR or LF which are CcZl Separator line Format Character 1 Only U 2028 LINE SEPARATOR LSEP Zp Separator paragraph Format Character 1 Only U 2029 PARAGRAPH SEPARATOR PSEP C OtherCc Other control Control Character 65 will never change e No name g lt control gt 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 charactersCs Other surrogate Surrogate Not only used in UTF 16 2 048 will never change e No name g lt surrogate gt Co Other private use Private use Character but no interpretation specified 137 468 total will never change e 6 400 in BMP 131 068 in Planes 15 16 No name g lt private use gt Cn Other not assigned Noncharacter Not 66 will never change e No name g lt noncharacter gt Reserved Not 825 279 No name g lt reserved gt Table 4 4 General Category PDF The Unicode Standard Unicode Consortium September 2022 a b Table 2 3 Types of code points PDF The Unicode Standard Unicode Consortium September 2022 DerivedGeneralCategory txt The Unicode Consortium 2022 04 26 5 7 1 General Category Values UTR 44 Unicode Character Database Unicode Consortium 2020 03 04 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 Annex C Compatibility Properties word Unicode Regular Expressions Version 23 Unicode Consortium 2022 02 08 Unicode Technical Standard 18 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 lt control hhhh gt lt control 0088 gt The Name remains blank which can prevent inadvertently replacing in documentation a Control Name with a true Control code Unicode also uses lt not a character gt for lt noncharacter gt Code points in the range U D800 U DBFF 1 024 code points are known as high surrogate code points and code points in the range U DC00 U DFFF 1 024 code points are known as low surrogate code points A high surrogate code point followed by a low surrogate code point form a surrogate pair in UTF 16 to represent code points greater than U FFFF These code points otherwise cannot be used this rule is ignored often in practice especially when not using UTF 16 A small set of code points are guaranteed never to be used for encoding characters although applications may make use of these code points internally if they wish There are sixty six of these noncharacters U FDD0 U FDEF and any code point ending in the value FFFE or FFFF i e 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 62 Like surrogates the rule that these cannot be used is often ignored although the operation of the byte order mark BOM assumes that U FFFE will never be the first code point in a text Excluding surrogates and noncharacters leaves 1 111 998 code points available for use Private use code points are considered to be assigned characters but they have no interpretation specified by the Unicode standard 63 so any interchange of such characters requires an agreement between sender and receiver on their interpretation There are three private use areas in the Unicode codespace Private Use Area U E000 U F8FF 6 400 characters Supplementary Private Use Area A U F0000 U FFFFD 65 534 characters Supplementary Private Use Area B U 100000 U 10FFFD 65 534 characters Graphic characters are characters defined by Unicode to have particular semantics and either have a visible glyph shape or represent a visible space As of Unicode 15 0 there are 149 014 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 NON JOINER and U 200D 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 0 Sixty five code points U 0000 U 001F and U 007F U 009F are reserved as control codes and correspond to the C0 and C1 control codes defined in ISO IEC 6429 U 0009 Tab U 000A Line Feed and U 000D Carriage Return are widely used in Unicode encoded texts In practice the C1 code points are often improperly translated mojibake as the legacy Windows 1252 characters used by some English and Western European texts Graphic characters format characters control code characters and private use characters are known collectively as assigned characters Reserved code points are those code points which are available for use but are not yet assigned As of Unicode 15 0 there are 825 279 reserved code points Abstract characters Edit The set of graphic and format characters defined by Unicode does not correspond directly to the repertoire of abstract characters that is representable under Unicode Unicode encodes characters by associating an abstract character with a particular code point 64 However not all abstract characters are encoded as a single Unicode character and some abstract characters may be represented in Unicode by a sequence of two or more characters For example a Latin small letter i with an ogonek a 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 65 All graphic format and private use characters have a unique and immutable name by which they may be identified This immutability has been guaranteed since Unicode version 2 0 by the Name Stability policy 62 In cases where the name is seriously defective and misleading or has a serious typographical error a formal alias may be defined and applications are encouraged to use the formal alias 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 66 Ready made versus composite characters Edit Unicode includes a mechanism for modifying characters that greatly extends the supported glyph repertoire This covers the use of combining diacritical marks that may be added after the base character by the user Multiple combining diacritics may be simultaneously applied to the same character Unicode also contains precomposed versions of most letter diacritic combinations in normal use These make conversion to and from legacy encodings simpler and allow applications to use Unicode as an internal text format without having to implement combining characters For example e can be represented in Unicode as U 0065 LATIN SMALL LETTER E followed by U 0301 COMBINING ACUTE ACCENT but it can also be represented as the precomposed character U 00E9 LATIN SMALL LETTER E WITH ACUTE Thus in many cases users have multiple ways of encoding the same character To deal with this Unicode provides the mechanism of canonical equivalence An example of this arises with Hangul the Korean alphabet Unicode provides a mechanism for composing Hangul syllables with their individual subcomponents known as Hangul Jamo However it also provides 11 172 combinations of precomposed syllables made from the most common jamo The CJK characters currently have codes only for their precomposed form Still most of those characters comprise simpler elements called radicals so in principle Unicode could have decomposed them as it did with Hangul This would have greatly reduced the number of required code points while allowing the display of virtually every conceivable character which might do away with some of the problems caused by Han unification A similar idea is used by some input methods such as Cangjie and Wubi However attempts to do this for character encoding have stumbled over the fact that Chinese characters do not decompose as simply or as regularly as Hangul does A set of radicals was provided in Unicode 3 0 CJK radicals between U 2E80 and U 2EFF KangXi radicals in U 2F00 to U 2FDF and ideographic description characters from U 2FF0 to U 2FFB but the Unicode standard ch 12 2 of Unicode 5 2 warns against using ideographic description sequences as an alternate representation for previously encoded characters 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 lt U 0065 U 0301 gt Ligatures Edit The Devanagari ddhrya ligature द ध र य द ध र य of JanaSanskritSans 67 The Arabic lam alif ligature ل ا لا Many scripts including Arabic and Devanagari have special orthographic rules that require certain combinations of letterforms to be combined into special ligature forms The rules governing ligature formation can be quite complex requiring special script shaping technologies such as ACE Arabic Calligraphic Engine by DecoType in the 1980s and used to generate all the Arabic examples in the printed editions of the Unicode Standard which became the proof of concept for OpenType by Adobe and Microsoft 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 Edit Several subsets of Unicode are standardized Microsoft Windows since Windows NT 4 0 supports 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 68 MES 1 Latin scripts only 335 characters MES 2 Latin Greek and Cyrillic 1062 characters 69 and MES 3A amp MES 3B two larger subsets not shown here Note that MES 2 includes every character in MES 1 and WGL 4 The standard DIN 91379 70 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 specification supports all official languages of European Union countries as well as the official languages of Iceland Liechtenstein Norway and Switzerland and also the German minority languages 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 SpecialsRendering software which cannot process a Unicode character appropriately often displays it as an open rectangle or the Unicode replacement character U FFFD to indicate the position of the unrecognized character Some systems have made attempts to provide more information about such characters Apple s Last Resort font will display a substitute glyph indicating the Unicode range of the character and the SIL International s Unicode Fallback font will display a box showing the hexadecimal scalar value of the character Mapping and encodings Edit 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 71 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 uses one to four bytes for each code point maximizes compatibility with ASCII UTF EBCDIC similar to UTF 8 but designed for compatibility with EBCDIC not part of The Unicode Standard UTF 16 uses one or two 16 bit code units per code point cannot encode surrogates UTF 32 uses one 32 bit code unit per code pointUTF 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 interchange of Unicode text It is used by FreeBSD and most recent Linux distributions as a direct replacement for legacy encodings in general text handling The UCS 2 and UTF 16 encodings specify the Unicode byte order mark BOM for use at the beginnings of text files which may be used for byte order detection or byte endianness detection The BOM code point U FEFF has the important property of unambiguity on byte reorder regardless of the Unicode encoding used U FFFE the result of byte swapping U FEFF does not equate to a legal character and U FEFF in places other than the beginning of text conveys the zero width non break space a character with no appearance and no effect other than preventing the formation of ligatures The same character converted to UTF 8 becomes the byte sequence EF BB BF The Unicode Standard allows that the BOM can serve as signature for UTF 8 encoded text where the character set is unmarked 72 Some software developers have adopted it for other encodings including UTF 8 in an attempt to distinguish UTF 8 from local 8 bit code pages However 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 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 Punycode another encoding form enables the encoding of Unicode strings into the limited character set supported by the ASCII based Domain Name System DNS The encoding is used as part of IDNA which is a system enabling the use of Internationalized Domain Names in all scripts that are supported by Unicode Earlier and now historical proposals include UTF 5 and UTF 6 GB18030 is another encoding form for Unicode from the Standardization Administration of China It is the official character set of the People s Republic of China PRC BOCU 1 and SCSU are Unicode compression schemes The April Fools Day RFC of 2005 specified two parody UTF encodings UTF 9 and UTF 18 Adoption EditSee also UTF 8 Adoption Unicode in the form of UTF 8 has been the most common encoding for the World Wide Web since 2008 73 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 2022 update UTF 8 accounts for on average 97 8 of all web pages and 988 of the top 1 000 highest ranked web pages 74 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 75 Over a third of the languages tracked have 100 UTF 8 use All internet protocols maintained by Internet Engineering Task Force e g FTP 76 have required support for UTF 8 since the publication of RFC 2277 in 1998 which specified that all IETF protocols MUST be able to use the UTF 8 charset 77 Operating systems Edit Unicode has become the dominant scheme for 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 78 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 Uniscribe and DirectWrite for Microsoft Windows ATSUI and Core Text for macOS and Pango for GTK and the GNOME desktop Input methods Edit 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 79 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 in a screen such as with a character map program Online tools for finding the code point for a known character include Unicode Lookup 80 by Jonathan Hedley and Shapecatcher 81 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 Edit 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 82 83 a framework for internationalized email using UTF 8 and has updated 84 85 86 87 several protocols in accordance with that framework The adoption of Unicode in email has been very slow citation needed Some East Asian text is still encoded in encodings such as 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 Edit 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 88 Although syntax rules may affect the order in which characters are allowed to appear XML including XHTML documents by definition 89 comprise characters from most of the Unicode code points with the exception of most of the C0 control codes the permanently unassigned code points D800 DFFF FFFE or FFFF HTML characters manifest either directly as bytes according to 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 amp 916 amp 1049 amp 1511 amp 1605 amp 3671 amp 12354 amp 21494 amp 33865 and amp 47568 or the same numeric values expressed in hexadecimal with amp x as the prefix should display on all browsers as D J ק م 7 あ 叶 葉 and 말 When specifying URIs for example as URLs in HTTP requests non ASCII characters must be percent encoded Fonts Edit Main article Unicode font Unicode is not in principle concerned with fonts per se seeing them as implementation choices 90 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 91 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 fonts based on Unicode are widely available since TrueType and OpenType support Unicode and Web Open Font Format WOFF and 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 Thousands of fonts exist on the market but fewer than a dozen fonts sometimes described as pan Unicode fonts attempt to support the majority of Unicode s character repertoire Instead Unicode based 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 Edit 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 EditHan unification Edit Han unification the identification of forms in the East Asian languages which one can treat as stylistic variations of the same historical character has become one of the most controversial aspects of Unicode despite the presence of a majority of experts from all three regions in the Ideographic Research Group IRG which advises the Consortium and ISO on additions to the repertoire and on Han unification 92 Unicode has been criticized for failing to separately encode older and alternative forms of kanji which critics argue complicates the processing of ancient Japanese and uncommon Japanese names This is often due to the fact that Unicode encodes characters rather than glyphs the visual representations of the basic character that often vary from one language to another Unification of glyphs leads to the perception that the languages themselves not just the basic character representation are being merged 93 clarification needed There have been several attempts to create alternative encodings that preserve the stylistic differences between Chinese Japanese and Korean characters in opposition to Unicode s policy of Han unification An example of one is TRON although it is not widely adopted in Japan there are some users who need to handle historical Japanese text and favor it Although the repertoire of fewer than 21 000 Han characters in the earliest version of Unicode was largely limited to characters in common modern usage Unicode now includes more than 97 000 Han characters and work is continuing to add thousands more historic and dialectal characters used in China Japan Korea Taiwan and Vietnam Modern font technology provides a means to address the practical issue of needing to depict a unified Han character in terms of a collection of alternative glyph representations in the form of Unicode variation sequences For example the Advanced Typographic tables of OpenType permit one of a number of alternative glyph representations to be selected when performing the character to glyph mapping process In this case information can be provided within plain text to designate which alternate character form to select Various Cyrillic characters shown with upright oblique and italic alternate forms Italic or cursive characters in Cyrillic Edit 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 Mapping to legacy character sets Edit 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 combining sequence of already existing characters can no longer be added to the standard in order to preserve interoperability between software using different versions of Unicode Injective mappings must be provided between characters in existing legacy character sets and characters in Unicode to facilitate conversion to Unicode and allow interoperability with legacy software Lack of consistency in various mappings between earlier Japanese encodings such as Shift JIS or 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 94 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 95 This encoding also replaces tilde 0x7E with macron now 0xAF The separation of these characters exists in ISO 8859 1 from long before Unicode Indic scripts Edit Indic scripts such as Tamil and Devanagari are each allocated only 128 code points matching the ISCII standard The correct rendering of Unicode Indic text requires transforming the stored logical order characters into visual order and the forming of ligatures aka 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 96 97 98 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 99 but these were rejected for encoding by the relevant ISO committee ISO IEC JTC 1 SC 2 100 Thai alphabet support has been criticized for its ordering of Thai characters The vowels e ae o i i that are written to the left of the preceding consonant are in visual order instead of phonetic order unlike the Unicode representations of other Indic scripts This complication is due to Unicode inheriting the 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 93 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 aesdng sa dɛːŋ perform starts with a consonant cluster sd with an inherent vowel for the consonant s the vowel ae in spoken order would come after the d but in a dictionary the word is collated as it is written with the vowel following the s Combining characters Edit 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 e e followed by the combining macron above and combining acute above should be rendered identically both appearing as an e with a macron and acute accent but in practice their appearance may vary depending upon what rendering engine and fonts are being used to display the characters Similarly underdots as needed in the romanization of Indic will often be placed incorrectly citation needed Unicode characters that map to precomposed glyphs can be used in many cases thus avoiding the problem but where no precomposed character has been encoded the problem can often be solved by using a specialist Unicode font such as Charis SIL that uses Graphite OpenType or AAT technologies for advanced rendering features Anomalies Edit Main article Unicode alias names and abbreviations The Unicode standard has imposed rules intended to guarantee stability 101 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 from then on an assigned name to a code point would never change anymore 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 102 for example U 2118 SCRIPT CAPITAL P This is a small letter The capital is U 1D4AB 𝒫 MATHEMATICAL SCRIPT CAPITAL P 103 U 034F COMBINING GRAPHEME JOINER Does not join graphemes 102 U A015 ꀕ YI SYLLABLE WU This is not a Yi syllable but a Yi iteration mark U FE18 PRESENTATION FORM FOR VERTICAL RIGHT WHITE LENTICULAR BRAKCET bracket is spelled incorrectly 104 Spelling errors are resolved by using Unicode alias names 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 105 106 Security issues Edit Unicode has a large number of homoglyphs many of which look very similar or identical to ASCII letters Substitution of these can make an identifier or URL that looks correct but directs to a different location than expected 107 and could also be used for manipulating the output of natural language processing NLP systems 108 Mitigation requires disallowing these characters displaying them differently or requiring that they resolve to the same identifier all of this is complicated due to the huge and constantly changing set of characters 109 110 A security advisory was released in 2021 from two researchers one from the University of Cambridge and the other from the same and from the University of Edinburgh in which they assert that the BIDI codes can be used to make large sections of code do something different from what they appear to do 111 See also EditComparison of Unicode encodings Religious and political symbols in Unicode International Components for Unicode ICU now as ICU TC a part of Unicode List of binary codes List of Unicode characters List of XML and HTML character entity references Open source Unicode typefaces Standards related to Unicode Unicode symbols Universal Coded Character Set Lotus Multi Byte Character Set LMBCS a parallel development with similar intentionsNotes Edit The formal version reference is The Unicode Consortium The Unicode Standard Version 15 0 0 Mountain View CA The Unicode Consortium 2022 ISBN 978 1 936213 32 0 Sometimes abbr TUS is used 1 2 References Edit Members of the Unicode Editorial Committee 2002 03 27 Unicode Technical Report 28 Unicode 3 2 Unicode Consortium Retrieved 2022 06 23 a href Template Cite web html title Template Cite web cite web a CS1 maint uses authors parameter link Jenkins John H 2021 08 26 Unicode Standard Annex 45 U source Ideographs Unicode Consortium Retrieved 2022 06 23 2 2 The Source Field Unicode 15 0 0 Unicode Version 15 0 Character Counts The Unicode Standard A Technical Introduction Retrieved 2010 03 16 The Unicode Bulldog Award a b c d e Becker Joseph D 1998 09 10 1988 08 29 Unicode 88 PDF unicode org 10th anniversary reprint ed Unicode Consortium Archived PDF from the original on 2016 11 25 Retrieved 2016 10 25 In 1978 the initial proposal for a set of Universal Signs was made by Bob Belleville at 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 which 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 have been proved over the years in an international line of communication multilingual system products Summary Narrative Retrieved 2010 03 15 History of Unicode Release and Publication Dates on unicode org Retrieved February 28 2017 Searle Stephen J Unicode Revisited Retrieved 2013 01 18 a b The Unicode Consortium Members Retrieved 2019 01 04 Unicode FAQ Retrieved 2020 04 02 Supported Scripts unicode org Retrieved 2022 09 16 Roadmap to the BMP Unicode Consortium Retrieved 2018 07 30 Unicode Roadmap Script Encoding Initiative About The Script Encoding Initiative The Unicode Consortium Retrieved 2012 06 04 Unicode 6 1 Paperback Available announcements at unicode org Retrieved 2012 05 30 BETA Unicode 15 0 0 www unicode org Retrieved 2022 07 16 Emoji Counts v15 0b www unicode org Retrieved 2022 07 16 Enumerated Versions of The Unicode Standard Retrieved 2016 06 21 a b c Unicode version 1 0 1991 1 0 0 UnicodeData txt reconstructed 2004 Retrieved 2010 03 16 a b Unicode Data 1 0 1 Retrieved 2010 03 16 a b Unicode version 1 1 Unicode Data 1995 Retrieved 2010 03 16 a b Unicode version 2 0 0 Unicode Data 2 0 14 Retrieved 2010 03 16 a b Unicode version 2 1 0 Unicode Data 2 1 2 Retrieved 2010 03 16 Unicode Data 3 0 0 Retrieved 2010 03 16 Unicode Data 3 1 0 Retrieved 2010 03 16 Unicode Data 3 2 0 Retrieved 2010 03 16 and ș and ț characters to support Romanian Unicode Data 4 0 0 Retrieved 2010 03 16 Unicode Data 4 1 0 Retrieved 2010 03 16 Unicode Data 5 0 0 Retrieved 2010 03 17 Unicode Data 5 1 0 Retrieved 2010 03 17 Unicode Data 5 2 0 Retrieved 2010 03 17 Unicode 6 0 Emoji List emojipedia org Retrieved 2022 09 21 Unicode Data 6 0 0 Retrieved 2010 10 11 Unicode Data 6 1 0 Retrieved 2012 01 31 Unicode Data 6 2 0 Retrieved 2012 09 26 Unicode Data 6 3 0 Retrieved 2013 09 30 Unicode Data 7 0 0 Retrieved 2014 06 15 Unicode 8 0 0 Unicode Consortium Retrieved 2015 06 17 Unicode Data 8 0 0 Retrieved 2015 06 17 Unicode 9 0 0 Unicode Consortium Retrieved 2016 06 21 Unicode Data 9 0 0 Retrieved 2016 06 21 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 Unicode 10 0 0 Unicode Consortium Retrieved 2017 06 20 Bitcoin symbol Bitcoin Wiki en bitcoin it Retrieved 2021 09 29 The Unicode Standard Version 11 0 0 Appendix C PDF Unicode Consortium Retrieved 2018 06 11 Announcing The Unicode Standard Version 11 0 blog unicode org Retrieved 2018 06 06 The Unicode Standard Version 12 0 0 Appendix C PDF Unicode Consortium Retrieved 2019 03 05 Announcing The Unicode Standard Version 12 0 blog unicode org Retrieved 2019 03 05 Unicode Version 12 1 released in support of the Reiwa Era blog unicode org Retrieved 2019 05 07 a b Unicode 13 0 0 Announcing The Unicode Standard Version 13 0 blog unicode org Retrieved 2020 03 11 The Unicode Standard Version 13 0 Core Specification Appendix C PDF Unicode Consortium Retrieved 2020 03 11 a b Unicode 14 0 0 Announcing The Unicode Standard Version 14 0 a b Unicode 15 0 0 Glossary of Unicode Terms Retrieved 2010 03 16 3 4 Characters and Encoding The Unicode Standard Version 15 0 PDF 2022 p 88 2 4 Code Points and Characters The Unicode Standard Version 15 0 Core Specification PDF 2022 p 29 Re Origin of the U nnnn notation Unicode Mail List Archive Mailing list 2005 11 08 Appendix A Notational Conventions PDF The Unicode Standard Unicode Consortium September 2022 In conformity with the bullet point relating to Unicode in MOS ALLCAPS the formal Unicode names are not used in this paragraph a b Unicode Character Encoding Stability Policy Retrieved 2010 03 16 Properties PDF Retrieved 2022 09 16 Unicode Character Encoding Model Retrieved 2022 09 16 Unicode Named Sequences Retrieved 2022 09 16 Unicode Name Aliases Retrieved 2010 03 16 JanaSanskritSans Archived from the original on 2011 07 16 CWA 13873 2000 Multilingual European Subsets in ISO IEC 10646 1 CEN Workshop Agreement 13873 Multilingual European Character Set 2 MES 2 Rationale Markus Kuhn 1998 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 UTF 8 UTF 16 UTF 32 amp BOM Unicode org FAQ Retrieved 2016 12 12 The Unicode Standard Version 6 2 The Unicode Consortium 2013 p 561 ISBN 978 1 936213 08 5 Davis Mark 2008 05 05 Moving to Unicode 5 1 Retrieved 2021 02 19 Usage Survey of Character Encodings broken down by Ranking w3techs com Retrieved 2022 10 03 Usage Statistics and Market Share of US ASCII for Websites October 2021 w3techs com Retrieved 2020 11 01 B Curtin July 1999 Internationalization of the File Transfer Protocol doi 10 17487 RFC2640 RFC 2640 Retrieved 2022 08 17 H Alvestrand January 1998 IETF Policy on Character Sets and Languages doi 10 17487 RFC2277 BCP 18 RFC 2277 Retrieved 2022 08 17 Pike Rob 2003 04 30 UTF 8 history ISO IEC JTC1 SC 18 WG 9 N PDF Retrieved 2012 06 04 Hedley Jonathan 2009 Unicode Lookup Milde Benjamin 2011 Unicode Character Recognition J Klensin Y Ko July 2007 Overview and Framework for Internationalized Email doi 10 17487 RFC4952 RFC 4952 Retrieved 2022 08 17 J Klensin Y Ko February 2012 Overview and Framework for Internationalized Email doi 10 17487 RFC6530 RFC 6530 Retrieved 2022 08 17 J Yao W Mao February 2012 SMTP Extension for Internationalized Email doi 10 17487 RFC6531 RFC 6531 Retrieved 2022 08 17 A Yang S Steele N Freed February 2012 Internationalized Email Headers doi 10 17487 RFC6532 RFC 6532 Retrieved 2022 08 17 C Newman A Gulbrandsen A Melnikov June 2008 Internet Message Access Protocol Internationalization doi 10 17487 RFC5255 RFC 5255 Retrieved 2022 08 17 R Gellens C Newman February 2010 POP3 Support for UTF 8 doi 10 17487 RFC5721 RFC 5721 Retrieved 2022 08 17 Wood Alan Setting up Windows Internet Explorer 5 5 5 and 6 for Multilingual and Unicode Support Alan Wood Retrieved 2012 06 04 Extensible Markup Language XML 1 1 Second Edition Retrieved 2013 11 01 Bigelow Charles Holmes Kris September 1993 The design of a Unicode font PDF Electronic Publishing 6 3 292 Fonts and keyboards Unicode Consortium 2017 06 28 Retrieved 2019 10 13 A Brief History of Character Codes Steven J Searle originally written 1999 last updated 2004 a b The secret life of Unicode A peek at Unicode s soft underbelly Suzanne Topping 1 May 2001 Internet Archive AFII contribution about WAVE DASH An Unicode vendor specific character table for japanese web archive org 2011 04 22 Archived from the original on 2011 04 22 ISO 646 Problem Section 4 4 3 5 of Introduction to I18n Tomohiro KUBOTA 2001 Arabic Presentation Forms A PDF Retrieved 2010 03 20 Arabic Presentation Forms B PDF Retrieved 2010 03 20 Alphabetic Presentation Forms PDF Retrieved 2010 03 20 China 2002 12 02 Proposal on Tibetan BrdaRten Characters Encoding for ISO IEC 10646 in BMP PDF V S Umamaheswaran 2003 11 07 Resolutions of WG 2 meeting 44 PDF Resolution M44 20 Unicode stability policy a b Unicode Technical Note 27 Known Anomalies in Unicode Character Names unicode org 2021 06 14 Unicode chart actually this has the form of a lowercase calligraphic p despite its name PDF Misspelling of BRACKET in character name is a known defect PDF Unicode Standard Annex 24 Unicode Script Property The Unicode Consortium 2021 2 2 Relation to ISO 15924 Codes Retrieved 2022 04 29 Scripts 15 0 0 txt The Unicode Consortium 2022 Retrieved 2022 09 16 UTR 36 Unicode Security Considerations unicode org Boucher Nicholas Shumailov Ilia Anderson Ross Papernot Nicolas 2022 Bad Characters Imperceptible NLP Attacks 2022 IEEE Symposium on Security and Privacy SP San Francisco CA USA IEEE 1987 2004 arXiv 2106 09898 doi 10 1109 SP46214 2022 9833641 ISBN 978 1 6654 1316 9 Wheeler David A 2020 Countermeasures Initial Analysis of Underhanded Source Code 4 1 UTR 36 Unicode Security Considerations unicode org Retrieved 2022 06 27 Nicholas Boucher Ross Anderson Trojan Source Invisible Vulnerabilities PDF Retrieved 2021 11 02 Further reading EditThe Unicode Standard Version 3 0 The Unicode Consortium Addison Wesley Longman Inc April 2000 ISBN 0 201 61633 5 The Unicode Standard Version 4 0 The Unicode Consortium Addison Wesley Professional 27 August 2003 ISBN 0 321 18578 1 The Unicode Standard Version 5 0 Fifth Edition The Unicode Consortium Addison Wesley Professional 27 October 2006 ISBN 0 321 48091 0 Julie D Allen The Unicode Standard Version 6 0 The Unicode Consortium Mountain View 2011 ISBN 9781936213016 1 The Complete Manual of Typography James Felici Adobe Press 1st edition 2002 ISBN 0 321 12730 7 Unicode A Primer Tony Graham M amp T books 2000 ISBN 0 7645 4625 2 Unicode Demystified A Practical Programmer s Guide to the Encoding Standard Richard Gillam Addison Wesley Professional 1st edition 2002 ISBN 0 201 70052 2 Unicode Explained Jukka K Korpela O Reilly 1st edition 2006 ISBN 0 596 10121 X Yannis Haralambous Martin Durst 2019 Unicode from a Linguistic Point of View In Haralambous Yannis ed Proceedings of Graphemics in the 21st Century Brest 2018 Brest Fluxus Editions pp 167 183 doi 10 36824 2018 graf hara1 ISBN 978 2 9570549 1 6 External links EditUnicode at Wikipedia s sister projects Definitions from Wiktionary Media from Commons Textbooks from Wikibooks Discussions from Meta Wiki Official website Official technical site Latest Unicode Standard The Unicode Character Database a text document listing the names code points and properties of all Unicode characters Unicode at Curlie Alan Wood s Unicode Resources contains lists of word processors with Unicode capability fonts and characters are grouped by type characters are presented in lists not grids The World s Writing Systems all 294 known writing systems with their Unicode status 131 not yet encoded Unicode BMP Fallback Font displays the Unicode 6 1 value of any character in a document including in the Private Use Area rather than the glyph itself Retrieved from https en wikipedia org w 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