charsets - character set standards and internationalization


   This manual page gives an overview on different character set standards
   and how they were used on Linux before Unicode became ubiquitous.  Some
   of  this  information  is  still helpful for people working with legacy
   systems and documents.

   Standards discussed include such as ASCII,  GB  2312,  ISO  8859,  JIS,
   KOI8-R, KS, and Unicode.

   The  primary  emphasis  is on character sets that were actually used by
   locale character sets, not the myriad others that  could  be  found  in
   data from other systems.

   ASCII  (American  Standard  Code  For  Information  Interchange) is the
   original 7-bit character set, originally designed for American English.
   Also  known as US-ASCII.  It is currently described by the ISO 646:1991
   IRV (International Reference Version) standard.

   Various ASCII variants replacing the dollar sign  with  other  currency
   symbols   and   replacing   punctuation   with  non-English  alphabetic
   characters to cover German, French,  Spanish,  and  others  in  7  bits
   emerged.   All  are  deprecated;  glibc  does not support locales whose
   character sets are not true supersets of ASCII.

   As Unicode, when using UTF-8, is  ASCII-compatible,  plain  ASCII  text
   still renders properly on modern UTF-8 using systems.

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

   Of  these,  the  most important is ISO 8859-1 ("Latin Alphabet No .1" /
   Latin-1).  It was widely adopted and supported  by  different  systems,
   and   is  gradually  being  replaced  with  Unicode.   The  ISO  8859-1
   characters are also the first 256 characters of Unicode.

   Console support for the other 8859 character sets  is  available  under
   Linux  through  user-mode  utilities  (such  as setfont(8)) that modify
   keyboard 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  many  West European languages such as Albanian,
          Basque, Danish, English, Faroese,  Galician,  Icelandic,  Irish,
          Italian,  Norwegian, Portuguese, Spanish, and Swedish.  The lack
          of the ligatures Dutch /, French  ,  and  old-style  German"
          quotation marks was considered tolerable.

   8859-2 (Latin-2)
          Latin-2  supports  many  Latin-written Central and East European
          languages such as Bosnian, Croatian, Czech,  German,  Hungarian,
          Polish,  Slovak,  and  Slovene.  Replacing Romanian / with /
          was considered tolerable.

   8859-3 (Latin-3)
          Latin-3  was  designed  to  cover  of  Esperanto,  Maltese,  and
          Turkish, but 8859-9 later superseded it for Turkish.

   8859-4 (Latin-4)
          Latin-4  introduced letters for North European languages such as
          Estonian, Latvian, and Lithuanian, but was superseded by 8859-10
          and 8859-13.

   8859-5 Cyrillic letters supporting Bulgarian, Byelorussian, Macedonian,
          Russian, Serbian, and (almost  completely)  Ukrainian.   It  was
          never widely used, see the discussion of KOI8-R/KOI8-U below.

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

   8859-7 Was created for Modern Greek in 1987, updated in 2003.

   8859-8 Supports Modern Hebrew without niqud (punctuation signs).  Niqud
          and full-fledged Biblical Hebrew were outside the scope of  this
          character set.

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

   8859-10 (Latin-6)
          Latin-6 added the Inuit (Greenlandic) and Sami (Lappish) letters
          that were missing in Latin-4 to cover the entire Nordic area.

          Supports  the  Thai  alphabet  and  is  nearly  identical to the
          TIS-620 standard.

          This set does not exist.

   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 Old Irish, Manx,
          Gaelic, Welsh, Cornish, and Breton.

   8859-15 (Latin-9)
          Latin-9 is similar to the widely used Latin-1 but replaces  some
          less  common  symbols  with the Euro sign and French and Finnish
          letters that were missing in Latin-1.

   8859-16 (Latin-10)
          This set covers many  Southeast  European  languages,  and  most
          importantly supports Romanian more completely than Latin-2.

   KOI8-R / KOI8-U
   KOI8-R  is  a  non-ISO  character set popular in Russia before Unicode.
   The lower half is ASCII; the upper is a Cyrillic character set somewhat
   better  designed  than ISO 8859-5.  KOI8-U, based on KOI8-R, 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.

   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  ASCII  and  GB
   2312.  Note that EUC-CN is often called as GB, GB 2312, or CN-GB.

   Big5  was  a  popular  character  set  in Taiwan to express traditional
   Chinese.  (Big5 is both a character set and  an  encoding.)   It  is  a
   superset  of  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 were widely used in Taiwan and Hong Kong.  It is
   not ISO 2022 compliant.

   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 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 ASCII and KS X 1001.  KS C 5601 is an older name
   for KS X 1001.

   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
   kernel  and  by  xterm(1).   Several ISO 2022-based character encodings
   have been defined, especially for Japanese.

   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
   (initially 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
   character set, and so on.

   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 be invoked only 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.

   TIS-620 is a Thai national standard character set  and  a  superset  of
   ASCII.  In the same fashion as the ISO 8859 series, Thai characters are
   mapped into 0xa1-0xfe.

   Unicode (ISO 10646) is a standard which aims to unambiguously represent
   every  character  in every human language.  Unicode's structure permits
   20.1 bits to  encode  every  character.   Since  most  computers  don't
   include  20.1-bit  integers,  Unicode  is  usually  encoded  as  32-bit
   integers internally and either a series  of  16-bit  integers  (UTF-16)
   (needing   two   16-bit   integers  only  when  encoding  certain  rare
   characters) or a series of 8-bit bytes (UTF-8).

   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  texts  in  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 texts, 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
   (especially  ISO  8859-1)  to  Unicode,  general  conversion   requires
   carrying  around conversion tables, which can be quite large for 16-bit

   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
   "subfont" 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 the Linux console 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


   iconv(1), ascii(7), iso_8859-1(7), unicode(7), utf-8(7)


   This  page  is  part of release 4.09 of the Linux man-pages project.  A
   description of the project, information about reporting bugs,  and  the
   latest     version     of     this    page,    can    be    found    at


Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.

Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.

Free Software

Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.

Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.

Free Books

The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.

Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.


Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.

Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.