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diff --git a/man7/unicode.7 b/man7/unicode.7 index ead23a80be..cb12af6847 100644 --- a/man7/unicode.7 +++ b/man7/unicode.7 @@ -35,25 +35,29 @@ The international standard .B ISO 10646 defines the .BR "Universal Character Set (UCS)" . -UCS contains all characters of all other character set standards. It -also guarantees +UCS contains all characters of all other character set standards. +It also guarantees .BR "round-trip compatibility" , i.e., conversion tables can be built such that no information is lost when a string is converted from any other encoding to UCS and back. UCS contains the characters required to represent practically all -known languages. This includes not only the Latin, Greek, Cyrillic, +known languages. +This includes not only the Latin, Greek, Cyrillic, Hebrew, Arabic, Armenian, and Georgian scripts, but also Chinese, Japanese and Korean Han ideographs as well as scripts such as Hiragana, Katakana, Hangul, Devanagari, Bengali, Gurmukhi, Gujarati, Oriya, Tamil, Telugu, Kannada, Malayalam, Thai, Lao, Khmer, Bopomofo, Tibetan, Runic, Ethiopic, Canadian Syllabics, Cherokee, Mongolian, -Ogham, Myanmar, Sinhala, Thaana, Yi, and others. For scripts not yet +Ogham, Myanmar, Sinhala, Thaana, Yi, and others. +For scripts not yet covered, research on how to best encode them for computer usage is -still going on and they will be added eventually. This might +still going on and they will be added eventually. +This might eventually include not only Hieroglyphs and various historic Indo-European languages, but even some selected artistic scripts such -as Tengwar, Cirth, and Klingon. UCS also covers a large number of +as Tengwar, Cirth, and Klingon. +UCS also covers a large number of graphical, typographical, mathematical and scientific symbols, including those provided by TeX, Postscript, APL, MS-DOS, MS-Windows, Macintosh, OCR fonts, as well as many word processing and publishing @@ -69,20 +73,25 @@ made up of 256 8-bit .I rows with 256 .I column -positions, one for each character. Part 1 of the standard +positions, one for each character. +Part 1 of the standard .RB ( "ISO 10646-1" ) defines the first 65534 code positions (0x0000 to 0xfffd), which form the .IR "Basic Multilingual Plane (BMP)" , -that is plane 0 in group 0. Part 2 of the standard +that is plane 0 in group 0. +Part 2 of the standard .RB ( "ISO 10646-2" ) adds characters to group 0 outside the BMP in several .I "supplementary planes" -in the range 0x10000 to 0x10ffff. There are no plans to add characters +in the range 0x10000 to 0x10ffff. +There are no plans to add characters beyond 0x10ffff to the standard, therefore of the entire code space, only a small fraction of group 0 will ever be actually used in the -foreseeable future. The BMP contains all characters found in the -commonly used other character sets. The supplemental planes added by +foreseeable future. +The BMP contains all characters found in the +commonly used other character sets. +The supplemental planes added by ISO 10646-2 cover only more exotic characters for special scientific, dictionary printing, publishing industry, higher-level protocol and enthusiast needs. @@ -111,12 +120,14 @@ Some code points in .B UCS have been assigned to .IR "combining characters" . -These are similar to the non-spacing accent keys on a typewriter. A -combining character just adds an accent to the previous character. The -most important accented characters have codes of their own in UCS, +These are similar to the non-spacing accent keys on a typewriter. +A combining character just adds an accent to the previous character. +The most important accented characters have codes of their own in UCS, however, the combining character mechanism allows us to add accents -and other diacritical marks to any character. The combining characters -always follow the character which they modify. For example, the German +and other diacritical marks to any character. +The combining characters +always follow the character which they modify. +For example, the German character Umlaut-A ("Latin capital letter A with diaeresis") can either be represented by the precomposed UCS code 0x00c4, or alternatively as the combination of a normal "Latin capital letter A" @@ -132,7 +143,7 @@ combining characters, ISO 10646-1 specifies the following three of UCS: .TP 0.9i Level 1 -Combining characters and +Combining characters and .B Hangul Jamo (a variant encoding of the Korean script, where a Hangul syllable glyph is coded as a triplet or pair of vovel/consonant codes) are not @@ -156,16 +167,19 @@ contains exactly the .B UCS Basic Multilingual Plane at implementation level 3, as described in ISO 10646-1:2000. .B Unicode 3.1 -added the supplemental planes of ISO 10646-2. The Unicode standard and +added the supplemental planes of ISO 10646-2. +The Unicode standard and technical reports published by the Unicode Consortium provide much additional information on the semantics and recommended usages of -various characters. They provide guidelines and algorithms for +various characters. +They provide guidelines and algorithms for editing, sorting, comparing, normalizing, converting and displaying Unicode strings. .SH "UNICODE UNDER LINUX" Under GNU/Linux, the C type .B wchar_t -is a signed 32-bit integer type. Its values are always interpreted +is a signed 32-bit integer type. +Its values are always interpreted by the C library as .B UCS code values (in all locales), a convention that is signaled by the GNU @@ -177,7 +191,8 @@ UCS/Unicode can be used just like ASCII in input/output streams, terminal communication, plaintext files, filenames, and environment variables in the ASCII compatible .B UTF-8 -multi-byte encoding. To signal the use of UTF-8 as the character +multi-byte encoding. +To signal the use of UTF-8 as the character encoding to all applications, a suitable .B locale has to be selected via environment variables (e.g., @@ -185,8 +200,8 @@ has to be selected via environment variables (e.g., .PP The .B nl_langinfo(CODESET) -function returns the name of the selected encoding. Library functions -such as +function returns the name of the selected encoding. +Library functions such as .BR wctomb (3) and .BR mbsrtowcs (3) @@ -199,7 +214,8 @@ tells, how many positions (0\(en2) the cursor is advanced by the output of a character. .PP Under Linux, in general only the BMP at implementation level 1 should -be used at the moment. Up to two combining characters per base +be used at the moment. +Up to two combining characters per base character for certain scripts (in particular Thai) are also supported by some UTF-8 terminal emulators and ISO 10646 fonts (level 2), but in general precomposed characters should be preferred where available @@ -209,11 +225,13 @@ general precomposed characters should be preferred where available In the .BR BMP , the range 0xe000 to 0xf8ff will never be assigned to any characters by -the standard and is reserved for private usage. For the Linux +the standard and is reserved for private usage. +For the Linux community, this private area has been subdivided further into the range 0xe000 to 0xefff which can be used individually by any end-user and the Linux zone in the range 0xf000 to 0xf8ff where extensions are -coordinated among all Linux users. The registry of the characters +coordinated among all Linux users. +The registry of the characters assigned to the Linux zone is currently maintained by H. Peter Anvin <Peter.Anvin@linux.org>. .SH LITERATURE @@ -237,7 +255,8 @@ Reading, MA, 2000, ISBN 0-201-61633-5. S. Harbison, G. Steele. C: A Reference Manual. Fourth edition, Prentice Hall, Englewood Cliffs, 1995, ISBN 0-13-326224-3. -A good reference book about the C programming language. The fourth +A good reference book about the C programming language. +The fourth edition covers the 1994 Amendment 1 to the ISO C 90 standard, which adds a large number of new C library functions for handling wide and multi-byte character encodings, but it does not yet cover ISO C 99, @@ -271,13 +290,15 @@ When this man page was last revised, the GNU C Library support for locales was mature and XFree86 support was in an advanced state, but work on making applications (most notably editors) suitable for use in .B UTF-8 -locales was still fully in progress. Current general +locales was still fully in progress. +Current general .B UCS support under Linux usually provides for CJK double-width characters and sometimes even simple overstriking combining characters, but usually does not include support for scripts with right-to-left writing direction or ligature substitution requirements such as -Hebrew, Arabic, or the Indic scripts. These scripts are currently only +Hebrew, Arabic, or the Indic scripts. +These scripts are currently only supported in certain GUI applications (HTML viewers, word processors) with sophisticated text rendering engines. .SH AUTHOR |