Unicode

Source: Wikipedia, the free encyclopedia.

Unicode
New Unicode logo.svg
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

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, 3664 emoji[5] (including in colors), and non-visual control and formatting codes.

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, JSON, and most modern programming languages, sometimes only in UTF-8 form, which is also supported in Microsoft Windows
.

The Unicode character repertoire is synchronized with ISO/IEC 10646, each being code-for-code identical to 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.[6] 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

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 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.[7]

History

Based on experiences with the

Lee Collins and Mark Davis from Apple started investigating the practicalities of creating a universal character set.[9] With additional input from Peter Fenwick and Dave Opstad,[8] 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".[8]

In this document, entitled Unicode 88, Becker outlined a 16-bit character model:[8]

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:[8]

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

In early 1989, the Unicode working group expanded to include Ken Whistler and Mike Kernaghan of Metaphor, Karen Smith-Yoshimura and Joan Aliprand of 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,[10] 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.[11]

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

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

SAP SE.[12]

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.[12]

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

scripts in Unicode, as demonstrated by this screenshot from the OpenOffice.org
application.

Unicode currently covers most major

better source needed
]

As of 2022[update], a total of 161 scripts[14] 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)[15] maintain the list of scripts that are candidates or potential candidates for encoding and their tentative code block assignments on the Unicode Roadmap[16] 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 has been already included in Unicode.

Script Encoding Initiative

The Script Encoding Initiative,[17] 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.[18]

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 a print-on-demand paperback, may be purchased.[19] 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.[20][21]

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.[22]

Version Date Book Corresponding ISO/IEC 10646 edition Scripts Characters
Total[tablenote 1] Notable additions
1.0.0[23] October 1991 (Vol. 1) 24 7,129[tablenote 2] Initial repertoire covers these scripts:
1.0.1[24] 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.[24]
1.1[25] 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.[25]
2.0[26] 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.[26]
2.1[27] 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.[27]
3.0 September 1999 ISBN 0-201-61633-5 ISO/IEC 10646-1:2000 38 49,194
(10,307 added)
Burmese, Ogham, Runic, Sinhala, Syriac, Thaana, Unified Canadian Aboriginal Syllabics, and Yi Syllables added, as well as a set of Braille patterns.[28]
3.1 March 2001 ISO/IEC 10646-1:2000

ISO/IEC 10646-2:2001

41 94,140
(44,946 added)
Old Italic added, as well as sets of symbols for Western music and Byzantine music, and 42,711 additional CJK Unified Ideographs.[29]
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, Hanunoo, Tagalog, and Tagbanwa added.[30]
4.0 April 2003 ISBN 0-321-18578-1 ISO/IEC 10646:2003 52 96,382
(1,226 added)
Tai Le, and Ugaritic added, as well as Hexagram symbols.[31]
4.1 March 2005 ISO/IEC 10646:2003 plus Amendment 1 59 97,655
(1,273 added)
Greek numbers and musical symbols were also added.[32]
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, ʼPhags-pa, and Phoenician added.[33]
5.1 April 2008 ISO/IEC 10646:2003 plus Amendments 1, 2, 3 and 4 75 100,648
(1,624 added)
Capital ẞ.[34]
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.[35]
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)
emoticons and emojis.[36] 222 additional CJK Unified Ideographs (CJK-D) added.[37]
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.[38]
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.[39]
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.[40]
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)
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[42] 129 120,672
(7,716 added)
Old Hungarian, SignWriting, 5,771 CJK Unified Ideographs, a set of lowercase letters for Cherokee, and five emoji skin tone modifiers.[43]
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[44] 135 128,172
(7,500 added)
Adlam, Bhaiksuki, Marchen, Newa, Osage, Tangut, and 72 emoji.[45][46]
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[47] 139 136,690
(8,518 added)
Masaram Gondi, Nüshu, hentaigana (non-standard hiragana), 7,494 CJK Unified Ideographs, 56 emoji, and bitcoin symbol.[48]
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.[49] 146 137,374
(684 added)
Dogra, Georgian Mtavruli capital letters, Gunjala Gondi, Hanifi Rohingya, Indic Siyaq Numbers, Makasar, Medefaidrin, Old Sogdian and Sogdian, Maya numerals, 5 urgently needed CJK Unified Ideographs, symbols for xiangqi (Chinese chess) and star ratings, and 145 emoji.[50]
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.[51] 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.[52]
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.[53]
13.0[54] March 2020 ISBN 978-1-936213-26-9 ISO/IEC 10646:2020[55] 154 143,859
(5,930 added)
Chorasmian, Dhives 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.[54]
14.0[56] 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.[56]
15.0[57] 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.[57]
  1. surrogate code points
    ).
  2. ^ Not counting 'space' or 33 non-printing characters (7,163 total)[23]

Projected versions

Version 15.1, scheduled for publication in Sept. 2023, is a retrenchment, for the consolidation of support and character behaviour. It adds only 5 characters, namely CJK description/formatting characters at the points U+2FFC–2FFF and 31EF. Significant additions of characters will not occur until version 16, in the pipeline for 2024.[58]

Architecture and terminology

Codespace and Code Points

The Unicode Standard defines a codespace:[59] a set of integers called code points[60] and denoted as U+0000 through U+10FFFF.[61]

The first two characters are always "U+" to indicate the beginning of a code point.[62] They are followed by the code point value in hexadecimal. At least 4 hexadecimal digits are shown, prepended with leading zeros as needed.

For example, U+00F7 for the division sign ÷ is padded with two leading zeros, but U+13254 for the

Egyptian hieroglyph
Hiero O4.png
is not padded.[63]

Of these 216 + 220 defined code points,[64] 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 + 220 − 211 = 1,112,064 assignable code points.

Code planes and blocks

The Unicode codespace is divided into seventeen planes, numbered 0 to 16. Plane 0 is the Basic Multilingual Plane (BMP), which contains the most commonly used characters. All code points in the BMP are accessed as a single code unit in UTF-16 encoding and can be encoded in one, two or three bytes in UTF-8. Code points in Planes 1 through 16 (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 the 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 sub-categories. 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
Dz
)
Lm Letter, modifier Graphic Character 397 A modifier letter
Lo Letter, other Graphic Character 131,612 An
unicase alphabet
M, Mark
Mn Mark, nonspacing Graphic Character 1,985
Mc Mark, spacing combining Graphic Character 452
Me Mark, enclosing Graphic Character 13
N, Number
Nd Number, decimal digit Graphic Character 680 All these, and only these, have Numeric Type = De[e]
Nl Number, letter Graphic Character 236 Numerals composed of letters or letterlike symbols (e.g., Roman numerals)
No Number, other Graphic Character 915 E.g.,
subscript
digits
P, Punctuation
Pc Punctuation, connector Graphic Character 10 Includes spacing underscore characters such as "_", and other spacing tie characters. Unlike other punctuation characters, these may be classified as "word" characters by regular expression libraries.[f]
Pd Punctuation, dash Graphic Character 26 Includes several hyphen characters
Ps Punctuation, open Graphic Character 79 Opening bracket characters
Pe Punctuation, close Graphic Character 77 Closing bracket characters
Pi Punctuation, initial quote Graphic Character 12 Opening quotation mark. Does not include the ASCII "neutral" quotation mark. May behave like Ps or Pe depending on usage
Pf Punctuation, final quote Graphic Character 10 Closing quotation mark. May behave like Ps or Pe depending on usage
Po Punctuation, other Graphic Character 628
S, Symbol
Sm Symbol, math Graphic Character 948
≠). Does not include parentheses and brackets, which are in categories Ps and Pe. Also does not include !, *, -, or /
, which despite frequent use as mathematical operators, are primarily considered to be "punctuation".
Sc Symbol, currency Graphic Character 63 Currency symbols
Sk Symbol, modifier Graphic Character 125
So Symbol, other Graphic Character 6,634
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)
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 forms 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.[65] 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[66] 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 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

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 that 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.

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.[68]

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.[65] 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 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.[69]

Ready-made versus composite characters

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

canonical equivalence
.

An example of this arises with

Hangul Jamo
. However, it also provides 11,172 combinations of precomposed syllables made from the most common jamo.

The

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

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

Many scripts, including

(by Apple).

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

Standardized subsets

Several subsets of Unicode are standardized: Microsoft Windows since

WGL-4 with 657 characters, which is considered to support all contemporary European languages using the Latin, Greek, or Cyrillic script. Other standardized subsets of Unicode include the Multilingual European Subsets:[71] MES-1 (Latin scripts only, 335 characters), MES-2 (Latin, Greek, and Cyrillic 1062 characters)[72]
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[73] 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 that cannot process a Unicode character appropriately often displays it as an open rectangle, or the Unicode "

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.[74] 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-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-EBCDIC, similar to UTF-8 but designed for compatibility with EBCDIC (not part of The Unicode Standard)

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

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

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

ligatures
).

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

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

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

UTF-6
.

UTF-18
.

Adoption

Unicode, in the form of UTF-8, has been the most common encoding for the World Wide Web since 2008.[76] 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 2023, UTF-8 accounts for on average 97.8% of all web pages (and 987 of the top 1,000 highest-ranked web pages).[77] 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.[78] Over a third of the languages tracked have 100% UTF-8 use.

All internet protocols maintained by

RFC 2277 in 1998, which specified that all IETF protocols "MUST be able to use the UTF-8 charset".[80]

Operating systems

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

UTF-8 (originally developed for Plan 9)[81] has become the main storage encoding on most Unix-like operating systems (though others are also used by some libraries) because it is a relatively easy replacement for traditional extended ASCII character sets. UTF-8 is also the most common Unicode encoding used in HTML documents on the World Wide Web.

Multilingual text-rendering engines which use Unicode include

GTK+ and the GNOME
desktop.

Input methods

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

Online tools for finding the code point for a known character include Unicode Lookup[83] by Jonathan Hedley and Shapecatcher[84] 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

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[85][86] a framework for internationalized email using UTF-8, and has updated[87][88][89][90] several protocols in accordance with that framework.

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

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

Web

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.[91]

Although syntax rules may affect the order in which characters are allowed to appear, XML (including XHTML) documents, by definition,[92] comprise characters from most of the Unicode code points, with the exception of:

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

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

When specifying

percent-encoded
.

Fonts

Unicode is not in principle concerned with fonts per se, seeing them as implementation choices.

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.[94]
The standard does not specify a minimum number of characters that must be included in the font; some fonts have quite a small repertoire.

Free and retail

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

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

Newlines

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

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

Issues

Character unification

Han unification

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.[95]

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). The unification of glyphs leads to the perception that the languages themselves, not just the basic character representation, are being merged.[96][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. The 'locl'

Unicode variation sequences
can also provide in-text annotation of desired glyph selection, but no such sequences for Han characters have been standardized.

Italic or cursive characters in Cyrillic

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

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

Mapping to legacy character sets

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

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

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

ISO 8859-1
, from long before Unicode.

Indic scripts

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

Thai Industrial Standard 620, which worked in the same way, and was the way in which Thai had always been written on keyboards. This ordering problem complicates the Unicode collation process slightly, requiring table lookups to reorder Thai characters for collation.[96] 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

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

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

Anomalies

The Unicode standard has imposed rules intended to guarantee stability.[106] Depending on the strictness of a rule, a change can be prohibited or allowed. For example, a "name" given to a code point cannot and will not change. But a "script" property is more flexible, by Unicode's own rules. In version 2.0, Unicode changed many code point "names" from version 1. At the same moment, Unicode stated that 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,[107] for example:

While Unicode defines the script designator (name) to be "Phags Pa", in that script's character names a hyphen is added: U+A840 PHAGS-PA LETTER KA.[110][111]

Security issues

Unicode has a large number of

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

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

BiDi marks can be used to make large sections of code do something different from what they appear to do. The problem was named "Trojan Source".[116] In response, code editors started highlighting marks to indicate forced text-direction changes.[117]

See also

Notes

  1. ^ "Unicode 15.0.0". unicode.org. Retrieved 2023-03-20.
  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". www.unicode.org.
  4. ^ "Unicode Character Count V15.0". www.unicode.org.
  5. ^ "Emoji Counts, v15.0". unicode.org. Retrieved 2023-01-30.
  6. ^ "The Unicode Standard: A Technical Introduction". Retrieved 2010-03-16.
  7. ^ "Unicode Bulldog Award". www.unicode.org.
  8. ^
    Xerox PARC. Many persons contributed ideas to the development of a new encoding design. Beginning in 1980, these efforts evolved into the Xerox Character Code Standard (XCCS) by the present author, a multilingual encoding that has been maintained by Xerox as an internal corporate standard since 1982, through the efforts of Ed Smura, Ron Pellar, and others.
    Unicode arose as the result of eight years of working experience with XCCS. Its fundamental differences from XCCS were proposed by Peter Fenwick and Dave Opstad (pure 16-bit codes) and by edition=10th anniversary reprint |Lee Collins
    (ideographic character unification). Unicode retains the many features of XCCS whose utility has been proved over the years in an international line of communication multilingual system products.
  9. ^ "Summary Narrative". Retrieved 2010-03-15.
  10. ^ "History of Unicode Release and Publication Dates". unicode.org. Retrieved 2023-03-20.
  11. ^ Searle, Stephen J. "Unicode Revisited". Retrieved 2013-01-18.
  12. ^ a b "The Unicode Consortium Members". Retrieved 2019-01-04.
  13. ^ "Unicode FAQ". Retrieved 2020-04-02.
  14. ^ "Supported Scripts". unicode.org. Retrieved 2022-09-16.
  15. ^ "Roadmap to the BMP". Unicode Consortium. Retrieved 2018-07-30.
  16. ^ "Roadmaps to Unicode". www.unicode.org.
  17. ^ "script encoding initiative". linguistics.berkeley.edu.
  18. ^ "About The Script Encoding Initiative". The Unicode Consortium. Retrieved 2012-06-04.
  19. ^ "Unicode 6.1 Paperback Available". announcements_at_unicode.org. Retrieved 2012-05-30.
  20. ^ "BETA Unicode 15.0.0". unicode.org. Retrieved 2022-07-16.
  21. ^ "Emoji Counts, v15.0β". unicode.org. Retrieved 2022-07-16.
  22. ^ "Enumerated Versions of The Unicode Standard". Retrieved 2016-06-21.
  23. ^ a b c
  24. ^ a b "Unicode Data 1.0.1". Retrieved 2010-03-16.
  25. ^ a b
  26. ^ a b
  27. ^ a b
  28. ^ "Unicode Data-3.0.0". Retrieved 2010-03-16.
  29. ^ "Unicode Data-3.1.0". Retrieved 2010-03-16.
  30. ^ "Unicode Data-3.2.0". Retrieved 2010-03-16.
  31. ^ and "ș" and "ț" characters to support Romanian"Unicode Data-4.0.0". Retrieved 2010-03-16.
  32. ^ "Unicode Data-4.1.0". Retrieved 2010-03-16.
  33. ^ "Unicode Data 5.0.0". Retrieved 2010-03-17.
  34. ^ "Unicode Data 5.1.0". Retrieved 2010-03-17.
  35. ^ "Unicode Data 5.2.0". Retrieved 2010-03-17.
  36. ^ "Unicode 6.0 Emoji List". emojipedia.org. Retrieved 2022-09-21.
  37. ^ "Unicode Data 6.0.0". Retrieved 2010-10-11.
  38. ^ "Unicode Data 6.1.0". Retrieved 2012-01-31.
  39. ^ "Unicode Data 6.2.0". Retrieved 2012-09-26.
  40. ^ "Unicode Data 6.3.0". Retrieved 2013-09-30.
  41. ^ "Unicode Data 7.0.0". Retrieved 2014-06-15.
  42. ^ "Unicode 8.0.0". Unicode Consortium. Retrieved 2015-06-17.
  43. ^ "Unicode Data 8.0.0". Retrieved 2015-06-17.
  44. ^ "Unicode 9.0.0". Unicode Consortium. Retrieved 2016-06-21.
  45. ^ "Unicode Data 9.0.0". Retrieved 2016-06-21.
  46. ^ Lobao, Martim (2016-06-07). "These Are The Two Emoji That Weren't Approved For Unicode 9 But Which Google Added To Android Anyway". Android Police. Retrieved 2016-09-04.
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  48. ^ "Bitcoin symbol - Bitcoin Wiki". en.bitcoin.it. Retrieved 2021-09-29.
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  51. ^ "The Unicode Standard, Version 12.0.0 Appendix C" (PDF). Unicode Consortium. Retrieved 2019-03-05.
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  53. ^ "Unicode Version 12.1 released in support of the Reiwa Era". blog.unicode.org. Retrieved 2019-05-07.
  54. ^ a b
  55. ^ "The Unicode Standard, Version 13.0– Core Specification Appendix C" (PDF). Unicode Consortium. Retrieved 2020-03-11.
  56. ^ a b
  57. ^ a b
  58. ^ "Unicode 15.1.0". www.unicode.org.
  59. ^ "Glossary of Unicode Terms". Retrieved 2010-03-16.
  60. ^ "2.4 Code Points and Characters". The Unicode Standard Version 15.0 – Core Specification (PDF). 2022. p. 29.
  61. ^ "3.4 Characters and Encoding". The Unicode Standard, Version 15.0 (PDF). 2022. p. 88.
  62. ^ "Re: Origin of the U+nnnn notation". Unicode Mail List Archive (Mailing list). 2005-11-08.
  63. MOS:ALLCAPS
    , the formal Unicode names are not used in this paragraph.
  64. ^ 220 from U+0000 through U+FFFFF and 216 from U+100000 through U+10FFFF
  65. ^ a b "Unicode Character Encoding Stability Policy". Retrieved 2010-03-16.
  66. ^ "Properties" (PDF). Retrieved 2022-09-16.
  67. ^ "Unicode Character Encoding Model". Retrieved 2022-09-16.
  68. ^ "Unicode Named Sequences". Retrieved 2022-09-16.
  69. ^ "Unicode Name Aliases". Retrieved 2010-03-16.
  70. ^ "JanaSanskritSans". Archived from the original on 2011-07-16.
  71. ^ CWA 13873:2000 – Multilingual European Subsets in ISO/IEC 10646-1 CEN Workshop Agreement 13873
  72. ^ "CEN Multilingual European Character Set 2 (MES-2) Rationale". University of Cambridge. Retrieved 2023-03-20.
  73. ^ "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.
  74. ^ "UTF-8, UTF-16, UTF-32 & BOM". Unicode.org FAQ. Retrieved 2016-12-12.
  75. .
  76. ^ Davis, Mark (2008-05-05). "Moving to Unicode 5.1". Retrieved 2021-02-19.
  77. ^ "Usage Survey of Character Encodings broken down by Ranking". w3techs.com. Retrieved 2023-01-16.
  78. ^ "Usage Statistics and Market Share of US-ASCII for Websites, October 2021". w3techs.com. Retrieved 2020-11-01.
  79. RFC 2640
    . Retrieved 2022-08-17.
  80. . Retrieved 2022-08-17.
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Further reading

External links