单词 | Unicode (Universal code) |
释义 | Unicode (Universal code) A set of standard coding schemes intended to replace the multiple coding schemes currently used, worldwide. The Unicode Consortium developed the original standard, Unicode Transformation Format-16 (UTF-16), in 1991 as a standard coding scheme to support multiple complex alphabets such as Chinese, Devanagri (Hindi), Japanese, and Korean. In the Japanese language, for example, even the abbreviated Kanji writing system contains well over 2,000 written ideographic characters; the Hirigana and Katakana alphabets add considerably to the complexity.As 7- and 8-bit coding schemes cannot accommodate such complex alphabets, computer manufacturers traditionally have taken proprietary approaches to this problem through the use of two linked 8-bit values. UTF-16 supports 65,536 (216) characters, which accommodates the most complex alphabets. Unicode accommodates pre-existing standard coding schemes, using the same byte values for consistency. For example, Unicode mirrors ASCII in UTF-7 and EBCDIC in UTF-EBCDIC, specifically for IBM mainframes. UTF-8 supports any universal character in the Unicode range, using one-to-four octets (eight-bit bytes) to do so, depending on the symbol. UTF-32 uses four octets for each symbol, but is rarely used due to its inherent inefficiency.The Unicode Standard has been adopted by most, if not all, major computer manufacturers and software developers, and is required by modern standards such as CORBA 3.0, ECMAScript (JavaScript), Java, LDAP, WML, and XML. Unicode is developed in conjunction with the International Organization for Standardization (ISO) and Internet Engineering Consortium (IEC), which also define the Universal Character Set (UCS), into which the UTF code sets map. UCS-4 is a four-octet code set into which UTF-32 maps and UCS-2 is a two-byte code set into which UTF-16 maps. UCS-1 encodes all characters in byte sequences varying from one to five bytes. See also ASCII, code set, EBCDIC, IEC, and ISO. |
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