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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|---|---|---|---|
| Last updated | 2013-03-02 | ||
| Stream | Legacy | ||
| Formats | plain text pdf 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 defined
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