GB2312 is the registered internet name for a key official character set of the People's Republic of China, used for simplified Chinese characters. GB abbreviates Guojia Biaozhun (国家标准), which means national standard in Chinese.
While GB2312 covers over 99% of the characters of contemporary usage, historical texts and many names remain out of scope. GB2312 includes 6,763 Chinese characters (on two levels: the first is arranged by reading, the second by radical then number of strokes), along with symbols and punctuation, Japanese kana, the Greek and Cyrillic alphabets, Zhuyin, and a double-byte set of Pinyin letters with tone marks. 0.8% of all web pages use GB2312 in April 2016, a drop from 3.5% in January 2010.
There is an analogous character set known as GB/T 12345, closely related to GB2312, but with traditional character forms replacing simplified forms, and some extra 62 supplemental characters.  GB-encoded fonts often come in pairs, one with the GB 2312 (simplified) character set and the other with the GB/T 12345 (traditional) character set.
Characters in GB2312 are arranged in a 94x94 grid (as in ISO 2022), and the two-byte codepoint of each character is expressed in the kuten (or quwei) form, which specifies a row (ku or qu) and the position of the character within the row (cell, ten or wei).
The rows (numbered from 1 to 94) contain characters as follows:
- 01-09, comprising punctuation and other special characters; also Hiragana, Katakana, Greek, Cyrillic, Pinyin, Bopomofo
- 16-55, the first plane for Chinese characters, arranged according to Pinyin. (3755 characters).
- 56-87, the second plane for Chinese characters, arranged according to radical and strokes. (3008 characters).
- 88-89, further Chinese characters. (103 characters). Defined only for GB/T 12345, not GB 2312.
The rows 10-15 and 90-94 are unassigned.
For GB2312-80, it contains 682 signs and 6763 Chinese Charactes.
Encodings of GB2312
EUC-CN is often used as the character encoding (i.e. for external storage) in programs that deal with GB2312, thus maintaining compatibility with ASCII. Two bytes are used to represent every character not found in ASCII. The value of the first byte is from 0xA1-0xF7 (161-247), while the value of the second byte is from 0xA1-0xFE (161-254). Since all of these ranges are beyond ASCII, like UTF-8, it is possible to check if a byte is part of a multi-byte construct when using EUC-CN.
Compared to UTF-8, GB2312 (whether native or encoded in EUC-CN) is more storage efficient: while UTF-8 uses three bytes[a] per CJK ideograph, GB2312 only uses two. However, GB2312 does not cover as many ideographs as Unicode does.
To map the code points to bytes, add 160 (0xA0) to the 1000's and 100's value of the code point to form the high byte, and add 160 (0xA0) to the 10's and 1's value of the code point to form the low byte.
For example, if you have the GB2312 code point 4566 ("外", which means foreign), the high byte will come from 45 (4500), and the low byte will come from 66 (0066). For the high byte, add 45 to 160, giving 205 or 0xCD. For the low byte do the same, add 66 to 160, giving 226 or 0xE2. So, the full encoding is 0xCDE2.
Two implementations of GB2312
There are two implementations of GB2312 which differ in few code points.
|EUC-CN||GBK/GB18030 subset||GB2312.TXT||Character name:3|
|A1A4||U+00B7 · MIDDLE DOT||U+30FB ・ KATAKANA MIDDLE DOT||间隔点; "separator dot"|
|A1AA||U+2014 — EM DASH||U+2015 ― HORIZONTAL BAR||破折号; "em dash"|
The GBK/GB18030 subset is compatible with both GBK and GB18030; GB2312.TXT is the then-official implementation from ftp.unicode.org, which has been obsolete since August 2011 and missing as of September 2016. Even more vendor mappings existed.
As of 2015, Microsoft .Net Framework is using the subset. ICU, iconv-1.14, php-5.6, ActivePerl-5.20, Java 1.7 and Python 3.4 are using GB2312.TXT. Ruby 2.2 is compatible with both implementations; it internally converts the conflictive characters to the subset. W3C's technical recommendation specifies a GBK encoding to be inferred for streams labelled
gb2312, which in turn uses a GB18030 decoder.
- Guobiao code
- Chinese character encoding
- GBK, GB18030 - two extensions of GB 2312
- Big5 - standard used in Taiwan and Hong Kong
- Hannas, William C. (1997). Asia's Orthographic Dilemma. University of Hawai‘i Press. p. 264.
- "Historical trends in the usage of character encodings for websites". W3Techs.
- "GB/T 12345" (PDF).
- "GB 2312-1980: Information technology—Chinese ideogram coded character set for information interchange (basic set)". Retrieved 2 October 2016.
- Haible, Bruno. "GB2312 (Conversion Tables)". Retrieved 29 September 2016.
- "Readme - MAPPINGS/OBSOLETE/EASTASIA". 9 August 2001. Retrieved 29 September 2016.
- "java-EUC_CN-1.3_P.ucm". Retrieved 29 September 2016.
- "libiconv:lib/gb2312.h". GNU Savannah. Retrieved 29 September 2016.
- "Issue 24036". Python Bug Tracker.
- "Encoding § Names and labels". W3C. Retrieved 29 September 2016.
- Only for ideographs covered by GB2312, all of which falls into Unicode BMP.
- Lunde, Ken (2009). "Chinese Character Set Standards—China". CJKV Information Processing (2nd ed.). O'Reilly. ISBN 9780596514471.
- Graphical View of GB2312 in ICU's Converter Explorer
- Unicode to GB2312 or GBK table
- Chinese Character Codes
- Evolution of GBK and GB2312 into GB18030
- GB2312 Character Set for Chinese Characters
- Coded Chinese Graphic Character Set for Information Interchange ISO-IR 58
- C code generates 6367 basic characters with output
- GB2312-80 standard on China-Language.gov.cn