A Unicode Technical Standard (UTS) is a specification which has been approved for publication by the Unicode Consortium. It is independent from and does not extend the unicode standard, so conformance to the Unicode Standard does not require conformance with any UTS.
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Unicode, formally The Unicode Standard, is a text encoding standard maintained by the Unicode Consortium designed to support the use of text in all of the world's writing systems that can be digitized. Version 16.0 of the standard defines 154998 characters and 168 scripts used in various ordinary, literary, academic, and technical contexts.
The Unicode Consortium is a 501(c)(3) non-profit organization incorporated and based in Mountain View, California, U.S. Its primary purpose is to maintain and publish the Unicode Standard which was developed with the intention of replacing existing character encoding schemes that are limited in size and scope, and are incompatible with multilingual environments.
The Standard Compression Scheme for Unicode (SCSU) is a Unicode Technical Standard for reducing the number of bytes needed to represent Unicode text, especially if that text uses mostly characters from one or a small number of per-language character blocks. It does so by dynamically mapping values in the range 128–255 to offsets within particular blocks of 128 characters. The initial conditions of the encoder mean that existing strings in ASCII and ISO-8859-1 that do not contain C0 control codes other than NULL TAB CR and LF can be treated as SCSU strings. Since most alphabets do reside in blocks of contiguous Unicode codepoints, texts that use small alphabets and either ASCII punctuation or punctuation that fits within the window for the main alphabet can be encoded at one byte per character, most other punctuation can be encoded at 2 bytes per symbol through non-locking shifts. SCSU can also switch to UTF-16 internally to handle non-alphabetic languages.
The Compatibility Encoding Scheme for UTF-16: 8-Bit (CESU-8) is a variant of UTF-8 that is described in Unicode Technical Report #26. A Unicode code point from the Basic Multilingual Plane (BMP), i.e. a code point in the range U+0000 to U+FFFF, is encoded in the same way as in UTF-8. A Unicode supplementary character, i.e. a code point in the range U+10000 to U+10FFFF, is first represented as a surrogate pair, like in UTF-16, and then each surrogate code point is encoded in UTF-8. Therefore, CESU-8 needs six bytes for each Unicode supplementary character while UTF-8 needs only four. Though not specified in the technical report, unpaired surrogates are also encoded as 3 bytes each, and CESU-8 is exactly the same as applying an older UCS-2 to UTF-8 converter to UTF-16 data.
Letterlike Symbols is a Unicode block containing 80 characters which are constructed mainly from the glyphs of one or more letters. In addition to this block, Unicode includes full styled mathematical alphabets, although Unicode does not explicitly categorize these characters as being "letterlike."
Miscellaneous Technical is a Unicode block ranging from U+2300 to U+23FF. It contains various common symbols which are related to and used in the various technical, programming language, and academic professions. For example:
Miscellaneous Symbols and Arrows is a Unicode block containing arrows and geometric shapes with various fills, astrological symbols, technical symbols, intonation marks, and others.
Ken Roger Lunde is an American specialist in information processing for East Asian languages.
Enclosed Alphanumerics is a Unicode block of typographical symbols of an alphanumeric within a circle, a bracket or other not-closed enclosure, or ending in a full stop.
CJK Unified Ideographs Extension-A is a Unicode block containing rare Han ideographs submitted to the Ideographic Research Group between 1992 and 1998, plus ten ideographs added in Unicode 13.0 which had previously been mistakenly unified with others.
The regional indicator symbols are a set of 26 alphabetic Unicode characters (A–Z) intended to be used to encode ISO 3166-1 alpha-2 two-letter country codes in a way that allows optional special treatment.
Variation Selectors Supplement is a Unicode block containing additional variation selectors beyond those found in the Variation Selectors block.
CJK Unified Ideographs Extension C is a Unicode block containing rare and historic CJK ideographs for Chinese, Japanese, Korean, and Vietnamese submitted to the Ideographic Research Group between 2002 and 2006, plus five "urgently needed" characters added in Unicode versions 14.0 and 15.0, some of which had previously been mistakenly unified with other characters.
CJK Unified Ideographs Extension D is a Unicode block containing uncommon CJK ideographs for Chinese, Japanese, Korean, and Vietnamese, some of which are in current use. Much smaller than most Unicode blocks for CJK unified ideographs, Extension D consists of characters which were submitted to the Ideographic Research Group as "urgently needed characters" between 2006 and 2009. Characters submitted during the same period which were needed less urgently were included in CJK Unified Ideographs Extension E instead.
CJK Compatibility Ideographs is a Unicode block created to contain mostly Han characters that were encoded in multiple locations in other established character encodings, in addition to their CJK Unified Ideographs assignments, in order to retain round-trip compatibility between Unicode and those encodings. However, it also contains 12 unified ideographs sourced from Japanese character sets from IBM.
Enclosed CJK Letters and Months is a Unicode block containing circled and parenthesized Katakana, Hangul, and CJK ideographs. Also included in the block are miscellaneous glyphs that would more likely fit in CJK Compatibility or Enclosed Alphanumerics: a few unit abbreviations, circled numbers from 21 to 50, and circled multiples of 10 from 10 to 80 enclosed in black squares.
Enclosed Ideographic Supplement is a Unicode block containing forms of characters and words from Chinese, Japanese and Korean enclosed within or stylised as squares, brackets, or circles. It contains three such characters containing one or more kana, and many containing CJK ideographs. Many of its characters were added for compatibility with the Japanese ARIB STD-B24 standard. Six symbols from Chinese folk religion were added in Unicode version 10.
Emoticons is a Unicode block containing emoticons or emoji. Most of them are intended as representations of faces, although some of them include hand gestures or non-human characters.
CJK Unified Ideographs Extension E is a Unicode block containing rare and historic CJK ideographs for Chinese, Japanese, Korean, and Vietnamese submitted to the Ideographic Research Group between 2006 and 2013, excluding the characters submitted as "urgently needed" between 2006 and 2009, which were included in CJK Unified Ideographs Extension D.
CJK Unified Ideographs Extension F is a Unicode block containing rare and historic CJK ideographs for Chinese, Japanese, Korean, and Vietnamese, as well as more than a thousand Sawndip characters for writing the Zhuang language, which were submitted to the Ideographic Research Group between 2012 and 2015.