"Special characters" redirects here. For the Wikipedia editor's handbook page, see Help:Special characters. A character encoding system consists of a code that pairs each character from a given repertoire with something else, such as a sequence of natural numbers, octets or electrical pulses, in order to facilitate the transmission of data (generally numbers and/or text) through telecommunication networks or storage of text in computers. Other terms like character encoding, character set (charset), and sometimes character map or code page are used almost interchangeably, but these terms now have related but distinct meanings. See terminology section. Contents 1 History 2 Common character encodings 3 Character encoding translation 4 Terminology 4.1 Unicode encoding model 4.2 General terminology 5 See also 6 References 7 External links // History Common examples of character encoding systems include Morse code, the Baudot code, the American Standard Code for Information Interchange (ASCII) and Unicode. Morse code was introduced in the 1840s and is used to encode each letter of the Latin alphabet and each Hindu-Arabic numeral as a series of long and short presses of a telegraph key. Representations of characters encoded using Morse code varied in length. The Baudot code was created by Émile Baudot in 1870, patented in 1874, modified by Donald Murray in 1901, and standardized by CCITT as International Telegraph Alphabet No. 2 (ITA2) in 1930. ASCII was introduced in 1963 and is a 7-bit encoding scheme used to encode letters, numerals, symbols, and device control codes as fixed-length codes using integers. IBM's Extended Binary Coded Decimal Interchange Code (usually abbreviated EBCDIC) is an 8-bit encoding scheme developed in 1963. The limitations of such sets soon became apparent, and a number of ad-hoc methods were developed to extend them. The need to support more writing systems for different languages, including the CJK family of East Asian scripts, required support for a far larger number of characters and demanded a systematic approach to character encoding rather than the previous ad hoc approaches.

Early binary repertoires include: Braille International maritime signal flags Chinese telegraph code (Hans Schjellerup, 1869, modified 1872 and following) Encoding of Chinese characters as 4-digit decimals. Common character encodings ISO 646 ASCII EBCDIC CP37 CP930 CP1047 ISO 8859: ISO 8859-1 Western Europe ISO 8859-2 Western and Central Europe ISO 8859-3 Western Europe and South European (Turkish, Maltese plus Esperanto) ISO 8859-4 Western Europe and Baltic countries (Lithuania, Estonia and Lapp) ISO 8859-5 Cyrillic alphabet ISO 8859-6 Arabic ISO 8859-7 Greek ISO 8859-8 Hebrew ISO 8859-9 Western Europe with amended Turkish character set ISO 8859-10 Western Europe with rationalised character set for Nordic languages, including complete Icelandic set ISO 8859-11 Thai ISO 8859-13 Baltic languages plus Polish ISO 8859-14 Celtic languages (Irish Gaelic, Scottish, Welsh) ISO 8859-15 Added the Euro sign and other rationalisations to ISO 8859-1 ISO 8859-16 Central, Eastern and Southern European languages (Albanian, Croatian, Hungarian, Polish, Romanian, Serbian and Slovenian, but also French, German, Italian and Irish Gaelic) CP437, CP737, CP850, CP852, CP855, CP857, CP858, CP860, CP861, CP863, CP865, CP866, CP869 MS-Windows character sets: Windows-1250 for Central European languages that use Latin script, (Polish, Czech, Slovak, Hungarian, Slovene, Serbian, Croatian, Romanian and Albanian) Windows-1251 for Cyrillic alphabets Windows-1252 for Western languages Windows-1253 for Greek Windows-1254 for Turkish Windows-1255 for Hebrew Windows-1256 for Arabic Windows-1257 for Baltic languages Windows-1258 for Vietnamese Mac OS Roman KOI8-R, KOI8-U, KOI7 MIK ISCII TSCII VISCII JIS X 0208 is a widely deployed standard for Japanese character encoding that has several encoding forms. Shift JIS (Microsoft Code page 932 is a dialect of Shift_JIS) EUC-JP ISO-2022-JP JIS X 0213 is an extended version of JIS X 0208. Shift_JIS-2004 EUC-JIS-2004 ISO-2022-JP-2004 Chinese Guobiao GB 2312 GBK (Microsoft Code page 936) GB 18030 Taiwan Big5 (a more famous variant is Microsoft Code page 950) Hong Kong HKSCS Korean KS X 1001 is a Korean double-byte character encoding standard EUC-KR ISO-2022-KR Unicode (and subsets thereof, such as the 16-bit 'Basic Multilingual Plane'). See UTF-8 ANSEL or ISO/IEC 6937 Character encoding translation

As a result of having many character encoding methods in use (and the need for backward compatibility with archived data), many computer programs have been developed to translate data between encoding schemes. Some of these are cited below. Cross-platform: Web browsers - most modern web browsers feature automatic character encoding detection. On Firefox 3, for example, see the View/Character Encoding submenu. iconv – program and standardized API to convert encodings convert_encoding.py – Python based utility to convert text files between arbitrary encodings and line endings.1 decodeh.py - algorithm and module to heuristically guess the encoding of a string.2 International Components for Unicode - A set of C and Java libraries to perform charset conversion. uconv can be used from ICU4C. chardet - This is a translation of the Mozilla automatic-encoding-detection code into the Python computer language. The newer versions of the unix File command attempt to do a basic detection of character encoding. (also available on cygwin and mac) Linux: recode – convert file contents from one encoding to another3 utrac – convert file contents from one encoding to another.4 cstocs – convert file contents from one encoding to another convmv – convert a filename from one encoding to another.5 enca – analyzes encodings for given text files.6 Windows: Encoding.Convert - .NET API7 MultiByteToWideChar/WideCharToMultiByte - Convert from ANSI to Unicode & Unicode to ANSI8 cscvt – character set conversion tool9 Terminology Unicode encoding model Unicode and its parallel standard, the ISO/IEC 10646 Universal Character Set, together constitute a modern, unified character encoding. Rather than mapping characters directly to octets (bytes), they separately define what characters are available, their numbering, how those numbers are encoded as a series of "code units" (limited-size numbers), and finally how those units are encoded as a stream of octets. The idea behind this decomposition is to establish a universal set of characters that can be encoded in a variety of ways.10 To correctly describe this model one needs more precise terms than "character set" and "character encoding". The terms used in the modern model follow:10

A character repertoire is the full set of abstract characters that a system supports. The repertoire may be closed, i.e. no additions are allowed without creating a new standard (as is the case with ASCII and most of the ISO-8859 series), or it may be open, allowing additions (as is the case with Unicode and to a limited extent the Windows code pages). The characters in a given repertoire reflect decisions that have been made about how to divide writing systems into linear information units. The basic variants of the Latin, Greek, and Cyrillic alphabets, can be broken down into letters, digits, punctuation, and a few special characters like the space,citation needed which can all be arranged in simple linear sequences that are displayed in the same order they are read. Even with these alphabets however diacritics pose a complication: they can be regarded either as part of a single character containing a letter and diacritic (known in modern terminology as a precomposed character), or as separate characters. The former allows a far simpler text handling system but the latter allows any letter/diacritic combination to be used in text. Other writing systems, such as Arabic and Hebrew, are represented with more complex character repertoires due to the need to accommodate things like bidirectional text and glyphs that are joined together in different ways for different situations. A coded character set (CCS) specifies how to represent a repertoire of characters using a number of non-negative integer codes called code points. For example, in a given repertoire, a character representing the capital letter "A" in the Latin alphabet might be assigned to the integer 65, the character for "B" to 66, and so on. A complete set of characters and corresponding integers is a coded character set. Multiple coded character sets may share the same repertoire; for example ISO/IEC 8859-1 and IBM code pages 037 and 500 all cover the same repertoire but map them to different codes. In a coded character set, each code point only represents one character, i.e., a coded character set is a function.

A character encoding form (CEF) specifies the conversion of a coded character set's integer codes into a set of limited-size integer code values that facilitate storage in a system that represents numbers in binary form using a fixed number of bits (i.e. practically any computer system). For example, a system that stores numeric information in 16-bit units would only be able to directly represent integers from 0 to 65,535 in each unit, but larger integers could be represented if more than one 16-bit unit could be used. This is what a CEF accommodates: it defines a way of mapping a single code point from a range of, say, 0 to 1.4 million, to a series of one or more code values from a range of, say, 0 to 65,535. The simplest CEF system is simply to choose large enough units that the values from the coded character set can be encoded directly (one code point to one code value). This works well for coded character sets that fit in 8 bits (as most legacy non-CJK encodings do) and reasonably well for coded character sets that fit in 16 bits (such as early versions of Unicode). However, as the size of the coded character set increases (e.g. modern Unicode requires at least 21 bits/character), this becomes less and less efficient, and it is difficult to adapt existing systems to use larger code values. Therefore, most systems working with later versions of Unicode use either UTF-8, which maps Unicode code points to variable-length sequences of octets, or UTF-16/UCS-2, which maps Unicode code points to variable-length sequences of 16-bit words. Next, a character encoding scheme (CES) specifies how the fixed-size integer code values should be mapped into an octet sequence suitable for saving on an octet-based file system or transmitting over an octet-based network. With Unicode, a simple character encoding scheme is used in most cases, simply specifying whether the bytes for each integer should be in big-endian or little-endian order (even this isn't needed with UTF-8). However, there are also compound character encoding schemes, which use escape sequences to switch between several simple schemes (such as ISO/IEC 2022), and compressing schemes, which try to minimise the number of bytes used per code unit (such as SCSU, BOCU, and Punycode). See comparison of Unicode encodings for a detailed discussion.

Finally, there may be a higher level protocol which supplies additional information that can be used to select the particular variant of a Unicode character, particularly where there are regional variants that have been 'unified' in Unicode as the same character. An example is the XML attribute xml:lang. The Unicode model reserves the term character map for historical systems which directly assign a sequence of characters to a sequence of bytes, covering all of CCS, CEF and CES layers.10 General terminology In computer science, the terms character encoding, character map, character set or code page were historically synonymouscitation needed, as the same standard would specify a repertoire of characters and how they were to be encoded into a stream of code units — usually with a single character per code unit. The terms now have related but distinct meanings, reflecting the efforts of standards bodies to use precise terminology when writing about and unifying many different encoding systems.10 Regardless, the terms are still used interchangeably, with character set being nearly ubiquitous. A code page usually means a byte oriented encoding, but with emphasis to some suite of encodings (covering different scripts), where many characters share same codes in all these code pages (or most). Well known code page suites are "Windows" (based on Windows-1252) and "IBM"/"DOS" (based on code page 437), see Windows code page for details. Most encodings referred to as code pages, but not all of them, are single byte encodings. IBM's Character Data Representation Architecture (CDRA) designates with coded character set identifiers (CCSIDs) and each of which is variously called a charset, character set, code page, or CHARMAP.10 Contrasted to CCS above, a character encoding is a map from abstract characters to code words. A character set in HTTP (and MIME) parlance is the same as a character encoding (but not the same as CCS).

Legacy encoding is a cliché used sometimes to characterize old character encoding, but with an ambiguity of sense. Most of its use is in the context of Unicodification, where it refers to encodings that do not cover all Unicode code points, or, more generally, using somewhat different character repertoire: several code points representing one Unicode character11, or versa (see e.g. code page 437). Some sources declare an encoding to be legacy only because it preceded Unicode.12 All Windows code pages are usually referred to as legacy. See also Alt code Character encoding — articles related to character encoding in general Character sets — articles detailing specific character encodings Code page — various character set encodings used by IBM, Microsoft, SAP… Mojibake — character set mismap. Mojikyo - a system ('glyph set') that includes over 100,000 Chinese character drawings, modern and ancient, popular and obscure.1314 TRON, part of the TRON Project, is an encoding system that does not use Han Unification, instead it uses 'control codes' to switch between 16bit 'planes' of characters.1415 Universal Character Set characters Windows code page — various character set encodings used by Microsoft Windows References Mackenzie, Charles E. (1980). Coded Character Sets, History and Development. Addison-Wesley. ISBN 0-201-14460-3.  ^ Homepage of Michael Goerz - convert_encoding.py ^ Decodeh - heuristically decode a string or text file ^ Recode - GNU Project - Free Software Foundation (FSF) ^ Utrac Homepage ^ Convmv - converts filenames from one encoding to another ^ Extremely Naive Charset Analyser ^ Microsoft .NET Framework Class Library - Encoding.Convert Method ^ MultiByteToWideChar/WideCharToMultiByte - Convert from ANSI to Unicode & Unicode to ANSI ^ Character Set Converter ^ a b c d e "Unicode Technical Report #17: Unicode Character Encoding Model". 2008-11-11. http://www.unicode.org/reports/tr17/. Retrieved 2009-08-08.  ^ "Processing database information using Unicode, a case study" ^ Constable, Peter (2001-06-13). "Character set encoding basics". Implementing Writing Systems: An introduction. SIL International. http://scripts.sil.org/cms/scripts/page.php?site_id=nrsi&item_id=IWS-Chapter03#79e846db. Retrieved 2010-03-19.  ^ "Mojikyo English page". mojikyo.org. http://www.mojikyo.org/html/abroad/abroad_top.html. Retrieved 2009 11 07. dead link ^ a b "Character Set List". jbrowse.com. http://www.jbrowse.com/text/unij.html. Retrieved 2009 11 07.  ^ "TRON code website". tron.org. http://www2.tron.org/troncode.html. Retrieved 2009 11 07.  External links Character sets registered by Internet Assigned Numbers Authority Unicode Technical Report #17: Character Encoding Model v · d · eCharacter encodings Category:Character sets Early telecommunications ASCII · ISO/IEC 646 · ISO/IEC 6937 · T.61 · sixbit code pages · Baudot code · Morse code ISO/IEC 8859 -1 · -2 · -3 · -4 · -5 · -6 · -7 · -8 · -9 · -10 · -11 · -12 · -13 · -14 · -15 · -16 Bibliographic use ANSEL · ISO 5426 / 5426-2 / 5427 / 5428 / 6438 / 6861 / 6862 / 10585 / 10586 / 10754 / 11822 · MARC-8 National standards ArmSCII · CNS 11643 · GOST 10859 · GB 2312 · HKSCS · ISCII · JIS X 0201 · JIS X 0208 · JIS X 0212 · JIS X 0213 · KPS 9566 · KS X 1001 · PASCII · TIS-620 · TSCII · VISCII · YUSCII EUC CN · JP · KR · TW ISO/IEC 2022 CN · JP · KR · CCCII MacOS codepages ("scripts") Arabic · CentralEurRoman · ChineseSimp / EUC-CN · ChineseTrad / Big5 · Croatian · Cyrillic · Devanagari · Dingbats · Farsi · Greek · Gujarati · Gurmukhi · Hebrew · Icelandic · Japanese / ShiftJIS · Korean / EUC-KR · Roman · Romanian · Symbol · Thai / TIS-620 · Turkish · Ukrainian DOS codepages 437 · 720 · 737 · 775 · 850 · 852 · 855 · 857 · 858 · 860 · 861 · 862 · 863 · 864 · 865 · 866 · 869 · Kamenický · Mazovia · MIK · Iran System Windows codepages 874 / TIS-620 · 932 / ShiftJIS · 936 / GBK · 949 / EUC-KR · 950 / Big5 · 1250 · 1251 · 1252 · 1253 · 1254 · 1255 · 1256 · 1257 · 1258 · 1361 · 54936 / GB18030 EBCDIC codepages 37/1140 · 273/1141 · 277/1142 · 278/1143 · 280/1144 · 284/1145 · 285/1146 · 297/1147 · 420/16804 · 424/12712 · 500/1148 · 838/1160 · 871/1149 · 875/9067 · 930/1390 · 933/1364 · 937/1371 · 935/1388 · 939/1399 · 1025/1154 · 1026/1155 · 1047/924 · 1112/1156 · 1122/1157 · 1123/1158 · 1130/1164 · JEF · KEIS Platform specific ATASCII · CDC display code · DEC-MCS · DEC Radix-50 · Fieldata · GSM 03.38 · HP roman8 · PETSCII · TI calculator character sets · ZX Spectrum character set Unicode / ISO/IEC 10646 UTF-8 · UTF-16/UCS-2 · UTF-32/UCS-4 · UTF-7 · UTF-EBCDIC · GB 18030 · SCSU · BOCU-1 Miscellaneous codepages APL · Cork · HZ · IBM code page 1133 · KOI8 · TRON Related topics control character (C0 C1) · CCSID · charset detection · Han unification · ISO 6429/IEC 6429/ANSI X3.64 · mojibake