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CHARSETS(7)		   Linux Programmers Manual		  CHARSETS(7)

       charsets - programmers view of character sets and internationalization

       Linux is an international operating system.  Various of	its  utilities
       and  device drivers (including the console driver) support multilingual
       character sets including Latin-alphabet letters with diacritical marks,
       accents,  ligatures,  and  entire  non-Latin alphabets including Greek,
       Cyrillic, Arabic, and Hebrew.

       This manual page presents a programmers-eye view of different  charac
       ter-set	standards  and how they fit together on Linux.	Standards dis
       cussed include ASCII, ISO 8859, KOI8-R, Unicode, ISO 2022 and ISO 4873.
       The primary emphasis is on character sets actually used as locale char
       acter sets, not the myriad others that can be found in data from  other

       A  complete  list of charsets used in an officially supported locale in
       glibc  2.2.3  is:  ISO-8859-{1,2,3,5,6,7,8,9,13,15},   CP1251,	UTF-8,
       EUC-{KR,JP,TW},	KOI8-{R,U}, GB2312, GB18030, GBK, BIG5, BIG5-HKSCS and
       TIS-620 (in no  particular  order.)   (Romanian	may  be  switching  to

       ASCII (American Standard Code For Information Interchange) is the orig
       inal 7-bit character set, originally designed for American English.  It
       is currently described by the ECMA-6 standard.

       Various	ASCII  variants  replacing the dollar sign with other currency
       symbols and replacing punctuation with non-English  alphabetic  charac
       ters  to cover German, French, Spanish and others in 7 bits exist.  All
       are deprecated; glibc doesnt  support  locales  whose  character  sets
       arent true supersets of ASCII.  (These sets are also known as ISO-646,
       a close relative of ASCII that permitted replacing these characters.)

       As Linux was written for hardware designed in the US, it natively  sup
       ports ASCII.

   ISO 8859
       ISO  8859  is  a series of 15 8-bit character sets all of which have US
       ASCII in their low (7-bit) half, invisible control characters in  posi
       tions 128 to 159, and 96 fixed-width graphics in positions 160-255.

       Of  these,  the most important is ISO 8859-1 (Latin-1).	It is natively
       supported in the Linux console driver, fairly well supported in	X11R6,
       and is the base character set of HTML.

       Console	support  for  the other 8859 character sets is available under
       Linux through user-mode utilities (such as setfont(8)) that modify key
       board bindings and the EGA graphics table and employ the "user mapping"
       font table in the console driver.

       Here are brief descriptions of each set:

       8859-1 (Latin-1)
	      Latin-1 covers most Western European languages such as Albanian,
	      Catalan,	Danish, Dutch, English, Faroese, Finnish, French, Ger
	      man, Galician, Irish, Icelandic, Italian, Norwegian, Portuguese,
	      Spanish,	and  Swedish.	The  lack  of  the ligatures Dutch ij,
	      French oe and old-style ,,German quotation marks is considered

       8859-2 (Latin-2)
	      Latin-2  supports most Latin-written Slavic and Central European
	      languages: Croatian, Czech, German, Hungarian, Polish, Rumanian,
	      Slovak, and Slovene.

       8859-3 (Latin-3)
	      Latin-3 is popular with authors of Esperanto, Galician, and Mal
	      tese.  (Turkish is now written with 8859-9 instead.)

       8859-4 (Latin-4)
	      Latin-4 introduced letters for Estonian,	Latvian,  and  Lithua
	      nian.   It  is  essentially  obsolete; see 8859-10 (Latin-6) and
	      8859-13 (Latin-7).

       8859-5 Cyrillic letters supporting Bulgarian, Byelorussian, Macedonian,
	      Russian,	Serbian  and  Ukrainian.   Ukrainians  read the letter
	      "ghe" with downstroke  as  "heh"	and  would  need  a  ghe  with
	      upstroke	to  write a correct ghe.  See the discussion of KOI8-R

       8859-6 Supports Arabic.	The 8859-6 glyph table is a fixed font of sep
	      arate  letter  forms, but a proper display engine should combine
	      these using the proper initial, medial, and final forms.

       8859-7 Supports Modern Greek.

       8859-8 Supports modern Hebrew without niqud (punctuation signs).  Niqud
	      and  full-fledged  Biblical Hebrew are outside the scope of this
	      character set; under Linux, UTF-8 is the preferred encoding  for

       8859-9 (Latin-5)
	      This  is	a  variant  of Latin-1 that replaces Icelandic letters
	      with Turkish ones.

       8859-10 (Latin-6)
	      Latin 6 adds the last Inuit  (Greenlandic)  and  Sami  (Lappish)
	      letters  that were missing in Latin 4 to cover the entire Nordic
	      area.  RFC 1345 listed a	preliminary  and  different  "latin6".
	      Skolt Sami still needs a few more accents than these.

	      This  only exists as a rejected draft standard.  The draft stan
	      dard was identical to TIS-620, which is  used  under  Linux  for

	      This  set  does  not exist.  While Vietnamese has been suggested
	      for this space, it does not fit within  the  96  (non-combining)
	      characters  ISO  8859  offers.  UTF-8 is the preferred character
	      set for Vietnamese use under Linux.

       8859-13 (Latin-7)
	      Supports the Baltic Rim languages; in  particular,  it  includes
	      Latvian characters not found in Latin-4.

       8859-14 (Latin-8)
	      This  is	the  Celtic  character set, covering Gaelic and Welsh.
	      This charset also contains the dotted characters needed for  Old

       8859-15 (Latin-9)
	      This adds the Euro sign and French and Finnish letters that were
	      missing in Latin-1.

       8859-16 (Latin-10)
	      This set covers many of the languages  covered  by  8859-2,  and
	      supports Romanian more completely then that set does.

       KOI8-R is a non-ISO character set popular in Russia.  The lower half is
       US ASCII; the  upper  is  a  Cyrillic  character  set  somewhat	better
       designed  than ISO 8859-5.  KOI8-U is a common character set, based off
       KOI8-R, that has better support for Ukrainian.  Neither of  these  sets
       are ISO-2022 compatible, unlike the ISO-8859 series.

       Console	support  for KOI8-R is available under Linux through user-mode
       utilities that modify keyboard bindings and the EGA graphics table, and
       employ the "user mapping" font table in the console driver.

   JIS X 0208
       JIS X 0208 is a Japanese national standard character set.  Though there
       are some more Japanese national standard character  sets  (like	JIS  X
       0201,  JIS  X  0212,  and  JIS X 0213), this is the most important one.
       Characters are mapped into a 94x94 two-byte matrix, whose each byte  is
       in  the	range 0x21-0x7e.  Note that JIS X 0208 is a character set, not
       an encoding.  This means that  JIS  X  0208  itself  is	not  used  for
       expressing  text  data.	JIS X 0208 is used as a component to construct
       encodings such as EUC-JP, Shift_JIS, and ISO-2022-JP.   EUC-JP  is  the
       most important encoding for Linux and includes US ASCII and JIS X 0208.
       In EUC-JP, JIS X 0208 characters are expressed in two  bytes,  each  of
       which is the JIS X 0208 code plus 0x80.

   KS X 1001
       KS  X  1001 is a Korean national standard character set.  Just as JIS X
       0208, characters are mapped into a 94x94 two-byte matrix.  KS X 1001 is
       used  like  JIS	X  0208, as a component to construct encodings such as
       EUC-KR, Johab, and ISO-2022-KR.	EUC-KR is the most important  encoding
       for  Linux  and includes US ASCII and KS X 1001.  KS C 5601 is an older
       name for KS X 1001.

   GB 2312
       GB 2312 is a mainland Chinese national standard character set  used  to
       express	simplified  Chinese.   Just  like  JIS	X 0208, characters are
       mapped into a 94x94 two-byte matrix used to construct  EUC-CN.	EUC-CN
       is  the	most important encoding for Linux and includes US ASCII and GB
       2312.  Note that EUC-CN is often called as GB, GB 2312, or CN-GB.

       Big5 is a popular character set in Taiwan to express  traditional  Chi
       nese.   (Big5 is both a character set and an encoding.)	It is a super
       set of US ASCII.  Non-ASCII characters  are  expressed  in  two	bytes.
       Bytes  0xa1-0xfe  are  used  as	leading bytes for two-byte characters.
       Big5 and its extension is widely used in Taiwan and Hong Kong.	It  is
       not ISO 2022-compliant.

   TIS 620
       TIS  620 is a Thai national standard character set and a superset of US
       ASCII.	Like  ISO  8859  series,  Thai	characters  are  mapped   into
       0xa1-0xfe.  TIS 620 is the only commonly used character set under Linux
       besides UTF-8 to have combining characters.

       Unicode (ISO 10646) is a standard which aims to unambiguously represent
       every  character  in every human language.  Unicodes structure permits
       20.1 bits to  encode  every  character.	 Since	most  computers  dont
       include	20.1-bit  integers, Unicode is usually encoded as 32-bit inte
       gers internally and either a series of 16-bit integers (UTF-16)	(need
       ing  two 16-bit integers only when encoding certain rare characters) or
       a series of 8-bit bytes (UTF-8).  Information on Unicode  is  available
       at .

       Linux  represents Unicode using the 8-bit Unicode Transformation Format
       (UTF-8).  UTF-8 is a variable length encoding of Unicode.   It  uses  1
       byte  to code 7 bits, 2 bytes for 11 bits, 3 bytes for 16 bits, 4 bytes
       for 21 bits, 5 bytes for 26 bits, 6 bytes for 31 bits.

       Let 0,1,x stand for a zero, one, or arbitrary  bit.   A	byte  0xxxxxxx
       stands for the Unicode 00000000 0xxxxxxx which codes the same symbol as
       the ASCII 0xxxxxxx.  Thus, ASCII goes unchanged into UTF-8, and	people
       using only ASCII do not notice any change: not in code, and not in file

       A byte 110xxxxx is the start of a 2-byte code, and 110xxxxx 10yyyyyy is
       assembled  into	00000xxx  xxyyyyyy.  A byte 1110xxxx is the start of a
       3-byte code, and 1110xxxx 10yyyyyy 10zzzzzz is assembled into  xxxxyyyy
       yyzzzzzz.   (When  UTF-8 is used to code the 31-bit ISO 10646 then this
       progression continues up to 6-byte codes.)

       For most people who use ISO-8859 character sets, this  means  that  the
       characters  outside  of ASCII are now coded with two bytes.  This tends
       to expand ordinary text files by only one or two percent.  For  Russian
       or Greek users, this expands ordinary text files by 100%, since text in
       those languages is mostly outside of ASCII.  For  Japanese  users  this
       means  that  the  16-bit codes now in common use will take three bytes.
       While there are algorithmic conversions from some character sets  (esp.
       ISO-8859-1)  to	Unicode,  general  conversion requires carrying around
       conversion tables, which can be quite large for 16-bit codes.

       Note that UTF-8 is self-synchronizing: 10xxxxxx is a  tail,  any  other
       byte  is  the head of a code.  Note that the only way ASCII bytes occur
       in a UTF-8 stream, is as  themselves.   In  particular,	there  are  no
       embedded NULs ('\0') or '/'s that form part of some larger code.

       Since ASCII, and, in particular, NUL and '/', are unchanged, the kernel
       does not notice that UTF-8 is being used.  It does not care at all what
       the bytes it is handling stand for.

       Rendering  of  Unicode  data streams is typically handled through "sub
       font" tables which map a subset of Unicode to glyphs.   Internally  the
       kernel  uses Unicode to describe the subfont loaded in video RAM.  This
       means that in UTF-8 mode one can use a character set with 512 different
       symbols.   This	is not enough for Japanese, Chinese and Korean, but it
       is enough for most other purposes.

       At the current time, the console driver does not handle combining char
       acters.	 So Thai, Sioux and any other script needing combining charac
       ters cant be handled on the console.

   ISO 2022 and ISO 4873
       The ISO 2022 and 4873 standards describe a font-control model based  on
       VT100  practice.  This model is (partially) supported by the Linux ker
       nel and by xterm(1).  It is popular in Japan and Korea.

       There are 4 graphic character sets, called G0, G1, G2 and G3,  and  one
       of them is the current character set for codes with high bit zero (ini
       tially G0), and one of them is the current character set for codes with
       high  bit  one (initially G1).  Each graphic character set has 94 or 96
       characters, and is essentially a 7-bit character set.   It  uses  codes
       either  040-0177  (041-0176)  or  0240-0377 (0241-0376).  G0 always has
       size 94 and uses codes 041-0176.

       Switching between character sets is done using the shift  functions  ^N
       (SO or LS1), ^O (SI or LS0), ESC n (LS2), ESC o (LS3), ESC N (SS2), ESC
       O (SS3), ESC ~ (LS1R), ESC } (LS2R), ESC | (LS3R).   The  function  LSn
       makes  character  set  Gn the current one for codes with high bit zero.
       The function LSnR makes character set Gn the current one for codes with
       high  bit  one.	The function SSn makes character set Gn (n=2 or 3) the
       current one for the next character only (regardless of the value of its
       high order bit).

       A  94-character	set  is  designated  as  Gn character set by an escape
       sequence ESC ( xx (for G0), ESC ) xx (for G1), ESC * xx (for G2), ESC +
       xx (for G3), where xx is a symbol or a pair of symbols found in the ISO
       2375 International Register of Coded Character Sets.  For example,  ESC
       (  @  selects  the  ISO 646 character set as G0, ESC ( A selects the UK
       standard character set (with pound instead of number  sign),  ESC  (  B
       selects ASCII (with dollar instead of currency sign), ESC ( M selects a
       character set for African languages, ESC ( ! A selects the Cuban  char
       acter set, etc. etc.

       A  96-character	set  is  designated  as  Gn character set by an escape
       sequence ESC - xx (for G1), ESC . xx (for G2) or ESC  /	xx  (for  G3).
       For example, ESC - G selects the Hebrew alphabet as G1.

       A  multibyte  character	set  is  designated  as Gn character set by an
       escape sequence ESC $ xx or ESC $ ( xx (for G0), ESC $ ) xx  (for  G1),
       ESC  $  *  xx  (for  G2),  ESC $ + xx (for G3).	For example, ESC $ ( C
       selects the Korean character set for G0.  The  Japanese	character  set
       selected by ESC $ B has a more recent version selected by ESC & @ ESC $

       ISO 4873 stipulates a narrower use of character sets, where G0 is fixed
       (always	ASCII),  so  that  G1, G2 and G3 can only be invoked for codes
       with the high order bit set.  In particular, ^N and  ^O	are  not  used
       anymore,  ESC  ( xx can be used only with xx=B, and ESC ) xx, ESC * xx,
       ESC + xx are equivalent to ESC - xx, ESC . xx, ESC / xx,  respectively.

       console(4),	console_codes(4),      console_ioctl(4),     ascii(7),
       iso_8859-1(7), unicode(7), utf-8(7)

       This page is part of release 3.05 of the Linux  man-pages  project.   A
       description  of	the project, and information about reporting bugs, can
       be found at http://www.kernel.org/doc/man-pages/.

Linux				  2008-06-03			   CHARSETS(7)

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