Chinese Character Encoding for Internet Messages
RFC 1922
Document | Type |
RFC - Informational
(March 1996; No errata)
Was draft-zhu-apng-cc-encoding-v2 (individual)
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Author | Mark Crispin | ||
Last updated | 2013-03-02 | ||
Stream | Legacy stream | ||
Formats | plain text html pdf htmlized (tools) htmlized bibtex | ||
Stream | Legacy state | (None) | |
Consensus Boilerplate | Unknown | ||
RFC Editor Note | (None) | ||
IESG | IESG state | RFC 1922 (Informational) | |
Telechat date | |||
Responsible AD | (None) | ||
Send notices to | (None) |
Network Working Group HF. Zhu Request for Comments: 1922 Tsinghua U Category: Informational DY. Hu Tsinghua U ZG. Wang CITS TC. Kao III WCH. Chang III M. Crispin U Washington March 1996 Chinese Character Encoding for Internet Messages Status of this Memo This memo provides information for the Internet community. It does not specify an Internet standard. Distribution of this memo is unlimited. Abstract This memo describes methods of transporting Chinese characters in Internet services which transport text, such as electronic mail [RFC-822], network news [RFC-1036], telnet [RFC-854] and the World Wide Web [RFC-1866]. Introduction As the use of Internet covers more and more Chinese people in the world, the need has increased for the ability to send documents containing Chinese characters on the Internet. The methods described in this document provide means of transporting existing Chinese character sets as well as leaving space for future extension. This document describes two encodings, ISO-2022-CN and ISO-2022-CN-EXT. These are designed with interoperability in mind and are encouraged in this document for current Chinese interchange; they are 7-bit, support both simplified and traditional characters using both GB and CNS/Big5, and do not impose any unusual quoting requirements on ASCII characters. As important related issues, this document gives detailed descriptions of the two encodings CN-GB and CN-Big5, and a brief description of ISO/IEC 10646 [ISO-10646]. CN-GB and CN-Big5 are Zhu, et al Informational [Page 1] RFC 1922 Chinese Character Encoding March 1996 currently used as the internal codes for Chinese documents. ISO-10646 is the universal multi-octet character set defined by ISO; we feel that in the future it may become the preferred technology for Chinese documents and electronic mail when it is widely available. Specification 1. 7-bit Chinese encodings: ISO-2022-CN and ISO-2022-CN-EXT 1.1. Description ISO-2022-CN is based on ISO 2022 [ISO-2022], similar to earlier work on ISO-2022-JP [RFC-1468] and ISO-2022-KR [RFC-1557] for the Japanese and Korean languages respectively. It is 7-bit, and supports both simplified Chinese characters using GB 2312-80 [GB-2312] and traditional Chinese characters using the first two planes of CNS 11643 [CNS-11643], as well as ASCII [ASCII] characters. ISO-2022-CN-EXT is a superset of ISO-2022-CN that additionally supports other GB character sets and planes of CNS 11643. Since ISO-2022-CN and ISO-2022-CN-EXT are 7-bit encodings, they do not require the 8-bit SMTP extensions. ISO-2022-CN supports all the Chinese characters that appear in Big5 [BIG5]. 1.2. ISO-2022-CN The starting code of ISO-2022-CN is ASCII. ASCII and Chinese characters are distinguished by designations (ESC sequences) and shift functions. Designations define the Chinese character sets used in the text. There are three kinds of designations: SOdesignation, SS2designation and SS3designation. The SOdesignation is in the form ESC $ ) <F>, where <F> is the "final character" assigned to the character set by ISO (refer to the ISO registry [ISOREG] for more details). The SS2designation is in the form ESC $ * <F>, and the SS3designation is in the form ESC $ + <F>. A designation overrides any previous designation for subsequent bytes in the text. There are four kinds of shifts: SI, SO, SS2 and SS3. Shift functions specify how to interpret the subsequent bytes. The shift SI (one byte with hexadecimal value 0F) declares that subsequent bytes are interpreted in ASCII. Zhu, et al Informational [Page 2] RFC 1922 Chinese Character Encoding March 1996 The shift SO (one byte with hexadecimal value 0E) declares that subsequent bytes are interpreted in the character set defined by SOdesignation. The shift SS2 (two bytes with hexadecimal values 1B 4E) declares that the subsequent TWO bytes are interpreted in the character set definedShow full document text