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 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 character map.
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.
ISO/IEC 8859 is a joint ISO and IEC series of standards for 8-bit character encodings. The series of standards consists of numbered parts, such as ISO/IEC 8859-1, ISO/IEC 8859-2, etc. There are 15 parts, excluding the abandoned ISO/IEC 8859-12. The ISO working group maintaining this series of standards has been disbanded.
Unicode, formally The Unicode Standard, is a text encoding standard maintained by the Unicode Consortium designed to support the use of text in all of the world's writing systems that can be digitized. Version 16.0 of the standard defines 154998 characters and 168 scripts used in various ordinary, literary, academic, and technical contexts.
UTF-8 is a character encoding standard used for electronic communication. Defined by the Unicode Standard, the name is derived from Unicode Transformation Format – 8-bit. Almost every webpage is stored in UTF-8.
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.
The byte-order mark (BOM) is a particular usage of the special Unicode character code, U+FEFFZERO WIDTH NO-BREAK SPACE, whose appearance as a magic number at the start of a text stream can signal several things to a program reading the text:
UTF-32 (32-bit Unicode Transformation Format), sometimes called UCS-4, is a fixed-length encoding used to encode Unicode code points that uses exactly 32 bits (four bytes) per code point (but a number of leading bits must be zero as there are far fewer than 232 Unicode code points, needing actually only 21 bits). In contrast, all other Unicode transformation formats are variable-length encodings. Each 32-bit value in UTF-32 represents one Unicode code point and is exactly equal to that code point's numerical value.
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.
Extended Unix Code (EUC) is a multibyte character encoding system used primarily for Japanese, Korean, and simplified Chinese (characters).
A numeric character reference (NCR) is a common markup construct used in SGML and SGML-derived markup languages such as HTML and XML. It consists of a short sequence of characters that, in turn, represents a single character. Since WebSgml, XML and HTML 4, the code points of the Universal Character Set (UCS) of Unicode are used. NCRs are typically used in order to represent characters that are not directly encodable in a particular document. When the document is interpreted by a markup-aware reader, each NCR is treated as if it were the character it represents.
ArmSCII or ARMSCII is a set of obsolete single-byte character encodings for the Armenian alphabet defined by Armenian national standard 166–9. ArmSCII is an acronym for Armenian Standard Code for Information Interchange, similar to ASCII for the American standard. It has been superseded by the Unicode standard.
A wide character is a computer character datatype that generally has a size greater than the traditional 8-bit character. The increased datatype size allows for the use of larger coded character sets.
A variable-width encoding is a type of character encoding scheme in which codes of differing lengths are used to encode a character set for representation, usually in a computer. Most common variable-width encodings are multibyte encodings, which use varying numbers of bytes (octets) to encode different characters.
UTF-EBCDIC is a character encoding capable of encoding all 1,112,064 valid character code points in Unicode using 1 to 5 bytes. It is meant to be EBCDIC-friendly, so that legacy EBCDIC applications on mainframes may process the characters without much difficulty. Its advantages for existing EBCDIC-based systems are similar to UTF-8's advantages for existing ASCII-based systems. Details on UTF-EBCDIC are defined in Unicode Technical Report #16.
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.
This article compares Unicode encodings in two types of environments: 8-bit clean environments, and environments that forbid the use of byte values with the high bit set. Originally, such prohibitions allowed 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. The Standard Compression Scheme for Unicode and the Binary Ordered Compression for Unicode are excluded from the comparison tables because it is difficult to simply quantify their size.
KPS 9566 is a North Korean standard specifying a character encoding for the Chosŏn'gŭl (Hangul) writing system used for the Korean language. The edition of 1997 specified an ISO 2022-compliant 94×94 two-byte coded character set. Subsequent editions have added additional encoded characters outside of the 94×94 plane, in a manner comparable to UHC or GBK.
The Universal Coded Character Set is a standard set of characters defined by the international standard ISO/IEC 10646, Information technology — Universal Coded Character Set (UCS), which is the basis of many character encodings, improving as characters from previously unrepresented typing systems are added.
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.
