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    "content": [
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            "type": "text",
            "text": "# unicode (man)\n\n## NAME\n\nunicode - universal character set\n\n## DESCRIPTION\n\nThe international standard ISO/IEC 10646 defines the Universal Character Set (UCS).  UCS con‐\ntains  all  characters  of all other character set standards.  It also guarantees \"round-trip\ncompatibility\"; in other words, conversion tables can be built such that  no  information  is\nlost when a string is converted from any other encoding to UCS and back.\n\n## Sections\n\n- **NAME**\n- **DESCRIPTION** (5 subsections)\n- **SEE ALSO**\n\nUse structuredContent.sections for detailed options, examples, and full documentation.\n"
        }
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    "structuredContent": {
        "command": "unicode",
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        "mode": "man",
        "summary": "unicode - universal character set",
        "synopsis": null,
        "tldr_summary": null,
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        "tldr_source": null,
        "flags": [],
        "examples": [],
        "see_also": [
            {
                "name": "locale",
                "section": "1",
                "url": "https://www.chedong.com/phpMan.php/man/locale/1/json"
            },
            {
                "name": "setlocale",
                "section": "3",
                "url": "https://www.chedong.com/phpMan.php/man/setlocale/3/json"
            },
            {
                "name": "charsets",
                "section": "7",
                "url": "https://www.chedong.com/phpMan.php/man/charsets/7/json"
            },
            {
                "name": "utf-8",
                "section": "7",
                "url": "https://www.chedong.com/phpMan.php/man/utf-8/7/json"
            }
        ],
        "section_outline": [
            {
                "name": "NAME",
                "lines": 2,
                "subsections": []
            },
            {
                "name": "DESCRIPTION",
                "lines": 42,
                "subsections": [
                    {
                        "name": "Combining characters",
                        "lines": 13
                    },
                    {
                        "name": "Implementation levels",
                        "lines": 19
                    },
                    {
                        "name": "Unicode under Linux",
                        "lines": 15
                    },
                    {
                        "name": "Private Use Areas (PUA)",
                        "lines": 12
                    },
                    {
                        "name": "Literature",
                        "lines": 26
                    }
                ]
            },
            {
                "name": "SEE ALSO",
                "lines": 3,
                "subsections": []
            }
        ],
        "sections": {
            "NAME": {
                "content": "unicode - universal character set\n",
                "subsections": []
            },
            "DESCRIPTION": {
                "content": "The international standard ISO/IEC 10646 defines the Universal Character Set (UCS).  UCS con‐\ntains  all  characters  of all other character set standards.  It also guarantees \"round-trip\ncompatibility\"; in other words, conversion tables can be built such that  no  information  is\nlost when a string is converted from any other encoding to UCS and back.\n\nUCS  contains the characters required to represent practically all known languages.  This in‐\ncludes not only the Latin, Greek, Cyrillic, Hebrew, Arabic, Armenian, and  Georgian  scripts,\nbut  also  Chinese,  Japanese  and Korean Han ideographs as well as scripts such as Hiragana,\nKatakana, Hangul, Devanagari, Bengali, Gurmukhi, Gujarati,  Oriya,  Tamil,  Telugu,  Kannada,\nMalayalam,  Thai,  Lao, Khmer, Bopomofo, Tibetan, Runic, Ethiopic, Canadian Syllabics, Chero‐\nkee, Mongolian, Ogham, Myanmar, Sinhala, Thaana, Yi, and others.  For scripts  not  yet  cov‐\nered,  research on how to best encode them for computer usage is still going on and they will\nbe added eventually.  This might eventually include not only Hieroglyphs and various historic\nIndo-European languages, but even some selected artistic scripts such as Tengwar, Cirth,  and\nKlingon.   UCS also covers a large number of graphical, typographical, mathematical, and sci‐\nentific symbols, including those provided by TeX, Postscript, APL, MS-DOS, MS-Windows, Macin‐\ntosh, OCR fonts, as well as many word processing and publishing systems, and more  are  being\nadded.\n\nThe  UCS standard (ISO/IEC 10646) describes a 31-bit character set architecture consisting of\n128 24-bit groups, each divided into 256 16-bit planes made up of 256  8-bit  rows  with  256\ncolumn  positions,  one for each character.  Part 1 of the standard (ISO/IEC 10646-1) defines\nthe first 65534 code positions (0x0000 to 0xfffd), which form the  Basic  Multilingual  Plane\n(BMP),  that is plane 0 in group 0.  Part 2 of the standard (ISO/IEC 10646-2) adds characters\nto group 0 outside the BMP in several supplementary planes in the range 0x10000 to  0x10ffff.\nThere are no plans to add characters beyond 0x10ffff to the standard, therefore of the entire\ncode  space,  only  a small fraction of group 0 will ever be actually used in the foreseeable\nfuture.  The BMP contains all characters found in the commonly  used  other  character  sets.\nThe  supplemental  planes added by ISO/IEC 10646-2 cover only more exotic characters for spe‐\ncial scientific, dictionary printing, publishing industry, higher-level protocol and enthusi‐\nast needs.\n\nThe representation of each UCS character as a 2-byte word is referred to as  the  UCS-2  form\n(only  for BMP characters), whereas UCS-4 is the representation of each character by a 4-byte\nword.  In addition, there exist two encoding forms  UTF-8  for  backward  compatibility  with\nASCII  processing software and UTF-16 for the backward-compatible handling of non-BMP charac‐\nters up to 0x10ffff by UCS-2 software.\n\nThe UCS characters 0x0000 to 0x007f are identical to those of the classic US-ASCII  character\nset and the characters in the range 0x0000 to 0x00ff are identical to those in ISO/IEC 8859-1\n(Latin-1).\n",
                "subsections": [
                    {
                        "name": "Combining characters",
                        "content": "Some code points in UCS have been assigned to combining characters.  These are similar to the\nnonspacing  accent  keys  on  a typewriter.  A combining character just adds an accent to the\nprevious character.  The most important accented characters have codes of their own  in  UCS,\nhowever,  the  combining  character  mechanism allows us to add accents and other diacritical\nmarks to any character.  The combining characters always follow the character which they mod‐\nify.  For example, the German character Umlaut-A (\"Latin capital letter  A  with  diaeresis\")\ncan  either be represented by the precomposed UCS code 0x00c4, or alternatively as the combi‐\nnation of a normal \"Latin capital letter A\"  followed  by  a  \"combining  diaeresis\":  0x0041\n0x0308.\n\nCombining characters are essential for instance for encoding the Thai script or for mathemat‐\nical typesetting and users of the International Phonetic Alphabet.\n"
                    },
                    {
                        "name": "Implementation levels",
                        "content": "As  not  all  systems  are expected to support advanced mechanisms like combining characters,\nISO/IEC 10646-1 specifies the following three implementation levels of UCS:\n\nLevel 1  Combining characters and Hangul Jamo (a variant encoding of the Korean script, where\na Hangul syllable glyph is coded as a triplet or pair of vowel/consonant codes)  are\nnot supported.\n\nLevel 2  In  addition  to  level  1,  combining characters are now allowed for some languages\nwhere they are essential (e.g., Thai, Lao, Hebrew, Arabic, Devanagari, Malayalam).\n\nLevel 3  All UCS characters are supported.\n\nThe Unicode 3.0 Standard published by the Unicode Consortium contains exactly the  UCS  Basic\nMultilingual  Plane at implementation level 3, as described in ISO/IEC 10646-1:2000.  Unicode\n3.1 added the supplemental planes of ISO/IEC 10646-2.  The Unicode standard and technical re‐\nports published by the Unicode Consortium provide much additional information on  the  seman‐\ntics  and  recommended  usages of various characters.  They provide guidelines and algorithms\nfor editing, sorting, comparing, normalizing, converting, and displaying Unicode strings.\n"
                    },
                    {
                        "name": "Unicode under Linux",
                        "content": "Under GNU/Linux, the C type wchart is a signed 32-bit integer type.  Its values  are  always\ninterpreted  by  the C library as UCS code values (in all locales), a convention that is sig‐\nnaled by the GNU C library to applications by defining  the  constant  STDCISO10646  as\nspecified in the ISO C99 standard.\n\nUCS/Unicode  can  be  used  just  like ASCII in input/output streams, terminal communication,\nplaintext files, filenames, and environment variables in the ASCII compatible UTF-8 multibyte\nencoding.  To signal the use of UTF-8 as the character encoding to all applications, a  suit‐\nable locale has to be selected via environment variables (e.g., \"LANG=enGB.UTF-8\").\n\nThe  nllanginfo(CODESET)  function returns the name of the selected encoding.  Library func‐\ntions such as wctomb(3) and mbsrtowcs(3) can be used to transform the internal wchart  char‐\nacters  and strings into the system character encoding and back and wcwidth(3) tells how many\npositions (0–2) the cursor is advanced by the output of a character.\n"
                    },
                    {
                        "name": "Private Use Areas (PUA)",
                        "content": "In the Basic Multilingual Plane, the range 0xe000 to 0xf8ff will never  be  assigned  to  any\ncharacters  by the standard and is reserved for private usage.  For the Linux community, this\nprivate area has been subdivided further into the range 0xe000 to 0xefff which  can  be  used\nindividually  by  any  end-user and the Linux zone in the range 0xf000 to 0xf8ff where exten‐\nsions are coordinated among all Linux users.  The registry of the characters assigned to  the\nLinux  zone is maintained by LANANA and the registry itself is Documentation/admin-guide/uni‐\ncode.rst in the Linux kernel sources (or Documentation/unicode.txt before Linux 4.10).\n\nTwo other planes are reserved for private usage, plane 15 (Supplementary Private Use  Area-A,\nrange  0xf0000  to 0xffffd) and plane 16 (Supplementary Private Use Area-B, range 0x100000 to\n0x10fffd).\n"
                    },
                    {
                        "name": "Literature",
                        "content": "•  Information technology — Universal Multiple-Octet Coded Character Set (UCS) — Part 1:  Ar‐\nchitecture and Basic Multilingual Plane.  International Standard ISO/IEC 10646-1, Interna‐\ntional Organization for Standardization, Geneva, 2000.\n\nThis is the official specification of UCS.  Available from \u001b]8;;http://www.iso.ch/\u001b\\http://www.iso.ch/\u001b]8;;\u001b\\.\n\n•  The  Unicode  Standard, Version 3.0.  The Unicode Consortium, Addison-Wesley, Reading, MA,\n2000, ISBN 0-201-61633-5.\n\n•  S. Harbison, G. Steele. C: A Reference Manual. Fourth edition,  Prentice  Hall,  Englewood\nCliffs, 1995, ISBN 0-13-326224-3.\n\nA  good  reference  book  about the C programming language.  The fourth edition covers the\n1994 Amendment 1 to the ISO C90 standard, which adds a large number of new C library func‐\ntions for handling wide and multibyte character encodings, but it does not yet  cover  ISO\nC99, which improved wide and multibyte character support even further.\n\n•  Unicode Technical Reports.\n\u001b]8;;http://www.unicode.org/reports/\u001b\\http://www.unicode.org/reports/\u001b]8;;\u001b\\\n\n•  Markus Kuhn: UTF-8 and Unicode FAQ for UNIX/Linux.\n\u001b]8;;http://www.cl.cam.ac.uk/~mgk25/unicode.html\u001b\\http://www.cl.cam.ac.uk/~mgk25/unicode.html\u001b]8;;\u001b\\\n\n•  Bruno Haible: Unicode HOWTO.\n\u001b]8;;http://www.tldp.org/HOWTO/Unicode-HOWTO.html\u001b\\http://www.tldp.org/HOWTO/Unicode-HOWTO.html\u001b]8;;\u001b\\\n"
                    }
                ]
            },
            "SEE ALSO": {
                "content": "locale(1), setlocale(3), charsets(7), utf-8(7)\n\nLinux man-pages 6.7                          2024-01-28                                   unicode(7)",
                "subsections": []
            }
        }
    }
}