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Guójiā Biāozhǔn Kuòzhǎn (GBK)

Layout of GBK (see below for a larger copy of this diagram)
MIME / IANA	GBK
Alias(es)	CP936, MS936, windows-936, csGBK
Languages	Web browsers, decode asGB 18030, supporting all languages, while the encoding (and other software decoders) is primarily used forSimplified Chinese, but also supportsTraditional Chinese,Japanese,English,Russian and (partially)Greek.
Standard	GBK 1.0
Classification	Extended ASCII,[a]variable-width encoding,CJK encoding
Extends	EUC-CN
Preceded by	GB 2312
Succeeded by	GB 18030
^Not in the strictest sense of the term, as ASCII bytes can appear as trail bytes.

GBK is an extension of theGB 2312character set forSimplified Chinese characters, used in thePeople's Republic of China. It includes all unifiedCJK characters found inGB 13000.1-93, i.e. ISO/IEC 10646:1993, or Unicode 1.1. Since its initial release in 1993, GBK has been extended by Microsoft inCode page 936/1386, which was then extended intoGBK 1.0.GBK is also the IANA-registered internet name for the Microsoft mapping,^[1] which differs from other implementations primarily by the single-byteeuro sign at 0x80.

GB abbreviatesGuójiā Biāozhǔn, which meansnational standard in Chinese, whileK stands forExtension (扩展kuòzhǎn). GBK not only extended the old standardGB 2312 with Traditional Chinese characters, but also with Chinese characters that were simplified after the establishment ofGB 2312 in 1981. With the arrival of GBK, certain names with characters formerly unrepresentable, like the 镕 (róng) character in former Chinese PremierZhu Rongji's name, are now representable.^[2]

As of October 2022^[update], GBK is the third-most popular encoding served from China and territories (afterUTF-8 and the subsetGB 2312), with 1.9% of web servers serving a page that declares GBK.^[3] However, all major web browsers decode GB2312-marked documents as if they were marked GBK, except for Safari and Edge on the labelGB_2312.^[4] Together, GBK andGB 2312 encodings have a combined 5.5% presence in China and territories.^[3] Globally, GBK accounts for less than 0.07% of all web pages and GBK+GB2312 for 0.2%.^[5]

In 1993, the Unicode 1.1 standard was released, including 20,902 characters used inmainland China,Taiwan,Japan andKorea. Following this, China releasedGB 13000.1-93, theGuobiao standard equivalent of Unicode 1.1.

TheGBK character set was defined in 1993 as an extension ofGB 2312-80, while also including the characters of GB 13000.1-93 through the unused codepoints available in GB 2312. Hence GBK is backward compatible with GB 2312. GBK was defined in a normative annex to GB 13000.1-93.^[6]

Microsoft implemented GBK inWindows 95 andWindows NT 3.51 asCode Page 936. While GBK was never an official standard, widespread usage of Windows 95 led to GBK becoming thede facto standard. While GBK included all the Chinese characters defined in Unicode 1.1 and GB 13000.1-93, these standards used different code tables. The primary reason for its existence was simply to bridge the gap between GB 2312-80 and GB 13000.1-93.

In 1995, China National Information Technology Standardization Technical Committee set down the Chinese Internal Code Extension Specification (Chinese:汉字内码扩展规范 (GBK);pinyin:Hànzì Nèimǎ Kuòzhǎn Guīfàn (GBK)), Version 1.0, known asGBK 1.0, which is a slight extension of Codepage 936. The newly added 95 characters were not found in GB 13000.1-1993, and were provisionally assigned UnicodePUA code points.^[7]: 534

Microsoft later added theeuro sign to Code page 936 and assigned the code 0x80 to it. This is not a valid code point in GBK 1.0.

In 2000, theGB 18030-2000 standard was released, superseding yet maintaining compatibility with GBK 1.0. It increased the number of definitions of Chinese characters and extended the number of possible characters through the implementation of four-byte character spaces. The subset of GB 18030 consisting of one-byte and two-byte characters is sometimes also referred to asGBK. Mapping to Unicode has been slightly changed, though, as some characters are now defined in Unicode. In the most up-to-date form of the standard, GB 18030-2005, only 24^[8] characters are still mapped to Unicode PUA (seeGB 18030#PUA.)

In 2002,GBK was registered as an IANA charset; the registration uses code page 936 mapping as well as CP936/MS936 aliases, but refers to GBK 1.0 specification.^[1]W3C's technical recommendation published in 2015^[9] defines aGBKencoder as a GB 18030 encoder with a single-byte euro sign and without four-byte sequences (while W3C'sGBKdecoder specification has no such limitation, decodes asGB 18030, i.e. with same range of letters as all ofUnicode).

A character is encoded as 1 or 2 bytes. A byte in the range00–7F is a single byte that means the same thing as it does inASCII. Strictly speaking, there are 95 characters and 33 control codes in this range.

A byte with the high bit set indicates that it is the first of 2 bytes. Loosely speaking, the first byte is in the range81–FE (that is, never80 orFF), and the second byte is40–A0 except7F for some areas andA1–FE for others.

More specifically, the following ranges of bytes are defined:

In graphical form, the following figure shows the space of all 64K possible 2-byte codes. Green and yellow areas are assigned GBK codepoints, red are for user-defined characters. The uncolored areas are invalid byte combinations.

The areas indicated in the previous section as GBK/1 and GBK/2, taken by themselves, is simplyGB 2312-80 in its usual encoding, GBK/1 being the non-hanzi region and GBK/2 the hanzi region. GB 2312, or more properly the EUC-CN encoding thereof, takes a pair of bytes from the rangeA1–FE, like any 94² ISO-2022 character set loaded into GR. This corresponds to the lower-right quarter of the illustration above. However, GB 2312 does not assign any code points to the rows located atAA–B0 andF8–FE, even though it had staked out the territory. GBK added extensions to these rows. You can see that the two gaps were filled in with user-defined areas.

More significantly, GBK extended the range of the bytes. Having two-byte characters in the ISO-2022 GR range gives a limit of 94²=8,836 possibilities. Abandoning the ISO-2022 model of strict regions for graphics and control characters, but retaining the feature of low bytes being 1-byte characters and pairs of high bytes denoting a character, you could potentially have 128²=16,384 positions. GBK takes part of that, extending the range fromA1–FE (94 choices for each byte) to81–FE (126 choices) for the first byte and40–FE (191 choices) for the second byte, for a total of 24,066 positions.

Microsoft's Code Page 936 is generally thought of as being GBK.^[1] However, the95 PUA characters added in GBK 1.0 are not included in Code Page 936. Code Page 936 also has a single-byteeuro sign at 0x80 which GBK 1.0 doesn't have.^[10]

GBK's successor,GB 18030-2000, uses the remaining range available to the second byte (30–39) to further expand the number of possibilities while retaining GBK as a subset.

• A scan of the GBK 1.0 specification provided by theIdeographic Research Group
• ICU's Authoritative GBK mapping - part ofGB18030 dataArchived 2016-10-31 at theWayback Machine
• Microsoft Reference page for GBK
• Mapping of GBK to Unicode N.B.: this is Microsoft code page 936, which contains entries for 21791 double-byte code points, 96 single-byte graphic characters, and 33 control characters. This is not exactly the same as GBK which has 21886 characters.
• GBK Code Table N.B. This gbk-encoded page shows the available coding space totally populated except for 2 places, for a total of 32256 glyphs (32352 with the implied single-byte ASCII codes not illustrated), which is more than 23940 or 21886. Actual rendering of this table depends on your browser's GBK decoder.

• Windows code pages
• Chinese character encodings

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