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Character encoding is the process of assigning numbers to graphical characters, especially the written characters of human language, allowing them to be stored, transmitted, and transformed using digital computers. The numerical values that make up a character encoding are known as "code points" and collectively comprise a "code space", a "code page", or a "character map".
While Hypertext Markup Language (HTML) has been in use since 1991, HTML 4.0 from December 1997 was the first standardized version where international characters were given reasonably complete treatment. When an HTML document includes special characters outside the range of seven-bit ASCII, two goals are worth considering: the information's integrity, and universal browser display.
Extended Binary Coded Decimal Interchange Code is an eight-bit character encoding used mainly on IBM mainframe and IBM midrange computer operating systems. It descended from the code used with punched cards and the corresponding six-bit binary-coded decimal code used with most of IBM's computer peripherals of the late 1950s and early 1960s. It is supported by various non-IBM platforms, such as Fujitsu-Siemens' BS2000/OSD, OS-IV, MSP, and MSP-EX, the SDS Sigma series, Unisys VS/9, Unisys MCP and ICL VME.
UTF-8 is a variable-length character encoding standard used for electronic communication. Defined by the Unicode Standard, the name is derived from Unicode Transformation Format – 8-bit.
UTF-16 (16-bit Unicode Transformation Format) is a character encoding capable of encoding all 1,112,064 valid code points of Unicode (in fact this number of code points is dictated by the design of UTF-16). The encoding is variable-length, as code points are encoded with one or two 16-bit code units. UTF-16 arose from an earlier obsolete fixed-width 16-bit encoding now known as UCS-2 (for 2-byte Universal Character Set), once it became clear that more than 216 (65,536) code points were needed, including most emoji and important CJK characters such as for personal and place names.
ISO/IEC 8859-7:2003, Information technology — 8-bit single-byte coded graphic character sets — Part 7: Latin/Greek alphabet, is part of the ISO/IEC 8859 series of ASCII-based standard character encodings, first edition published in 1987. It is informally referred to as Latin/Greek. It was designed to cover the modern Greek language. The original 1987 version of the standard had the same character assignments as the Greek national standard ELOT 928, published in 1986. The table in this article shows the updated 2003 version which adds three characters. Microsoft has assigned code page 28597 a.k.a. Windows-28597 to ISO-8859-7 in Windows. IBM has assigned code page 813 to ISO 8859-7. (IBM CCSID 813 is the original encoding. CCSID 4909 adds the euro sign. CCSID 9005 further adds the drachma sign and ypogegrammeni.)
ISO/IEC 2022Information technology—Character code structure and extension techniques, is an ISO/IEC standard in the field of character encoding. It is equivalent to the ECMA standard ECMA-35, the ANSI standard ANSI X3.41 and the Japanese Industrial Standard JIS X 0202. Originating in 1971, it was most recently revised in 1994.
Shift JIS is a character encoding for the Japanese language, originally developed by the Japanese company ASCII Corporation in conjunction with Microsoft and standardized as JIS X 0208 Appendix 1.
Extended Unix Code (EUC) is a multibyte character encoding system used primarily for Japanese, Korean, and simplified Chinese (characters).
Binary Ordered Compression for Unicode (BOCU) is a MIME compatible Unicode compression scheme. BOCU-1 combines the wide applicability of UTF-8 with the compactness of Standard Compression Scheme for Unicode (SCSU). This Unicode encoding is designed to be useful for compressing short strings, and maintains code point order. BOCU-1 is specified in a Unicode Technical Note.
The Compatibility Encoding Scheme for UTF-16: 8-Bit (CESU-8) is a variant of UTF-8 that is described in Unicode Technical Report #26. A Unicode code point from the Basic Multilingual Plane (BMP), i.e. a code point in the range U+0000 to U+FFFF, is encoded in the same way as in UTF-8. A Unicode supplementary character, i.e. a code point in the range U+10000 to U+10FFFF, is first represented as a surrogate pair, like in UTF-16, and then each surrogate code point is encoded in UTF-8. Therefore, CESU-8 needs six bytes for each Unicode supplementary character while UTF-8 needs only four. Though not specified in the technical report, unpaired surrogates are also encoded as 3 bytes each, and CESU-8 is exactly the same as applying an older UCS-2 to UTF-8 converter to UTF-16 data.
This article compares Unicode encodings. Two situations are considered: 8-bit-clean environments, and environments that forbid use of byte values that have the high bit set. Originally such prohibitions were to allow for links that used only seven data bits, but they remain in some standards and so some standard-conforming software must generate messages that comply with the restrictions. Standard Compression Scheme for Unicode and Binary Ordered Compression for Unicode are excluded from the comparison tables because it is difficult to simply quantify their size.
Unified Hangul Code (UHC), or Extended Wansung, also known under Microsoft Windows as Code Page 949, is the Microsoft Windows code page for the Korean language. It is an extension of Wansung Code to include all 11172 non-partial Hangul syllables present in Johab. This corresponds to the pre-composed syllables available in Unicode 2.0 and later.
EO, or Eight Ones, is an 8-bit EBCDIC character code represented as all ones.
Extended ASCII is a repertoire of character encodings that include the original 96 ASCII character set, plus up to 128 additional characters. There is no formal definition of "extended ASCII", and even use of the term is sometimes criticized, because it can be mistakenly interpreted to mean that the American National Standards Institute (ANSI) had updated its ANSI X3.4-1986 standard to include more characters, or that the term identifies a single unambiguous encoding, neither of which is the case.
KS X 1001, "Code for Information Interchange ", formerly called KS C 5601, is a South Korean coded character set standard to represent Hangul and Hanja characters on a computer.
The MARC-8 charset is a MARC standard used in MARC-21 library records. The MARC formats are standards for the representation and communication of bibliographic and related information in machine-readable form, and they are frequently used in library database systems. The character encoding now known as MARC-8 was introduced in 1968 as part of the MARC format. Originally based on the Latin alphabet, from 1979 to 1983 the JACKPHY initiative expanded the repertoire to include Japanese, Arabic, Chinese, and Hebrew characters, with the later addition of Cyrillic and Greek scripts. If a character is not representable in MARC-8 of a MARC-21 record, then UTF-8 must be used instead. UTF-8 has support for many more characters than MARC-8, which is rarely used outside library data.
In the C programming language, an escape sequence is specially delimited text in a character or string literal that represents one or more other characters to the compiler. It allows a programmer to specify characters that are otherwise difficult or impossible to specify in a literal.
Several mutually incompatible versions of the Extended Binary Coded Decimal Interchange Code (EBCDIC) have been used to represent the Japanese language on computers, including variants defined by Hitachi, Fujitsu, IBM and others. Some are variable-width encodings, employing locking shift codes to switch between single-byte and double-byte modes. Unlike other EBCDIC locales, the lowercase basic Latin letters are often not preserved in their usual locations.
References
- ↑ "UTR #16: UTF-EBCDIC". www.unicode.org. Retrieved 2021-02-23.
You need to search at most five bytes (seven bytes, if the full range of 31 bits of ISO/IEC 10646 is considered) backwards
- ↑ Baird, Cathy; Chiba, Dan; Chu, Winson; Fan, Jessica; Ho, Claire; Law, Simon; Lee, Geoff; Linsley, Peter; Matsuda, Keni; Oscroft, Tamzin; Takeda, Shige; Tanaka, Linus; Tozawa, Makoto; Trute, Barry; Tsujimoto, Mayumi; Wu, Ying; Yau, Michael; Yu, Tim; Wang, Chao; Wong, Simon; Zhang, Weiran; Zheng, Lei; Zhu, Yan; Moore, Valarie (2002) [1996]. "Appendix A: Locale Data". Oracle9i Database Globalization Support Guide (PDF) (Release 2 (9.2) ed.). Oracle Corporation. Oracle A96529-01. Archived (PDF) from the original on 2017-02-14. Retrieved 2017-02-14.
