The Unicode Consortium has warned implementers that the latest version of this Chinese standard, GB 18030-2022, introduces what they describe as "disruptive changes" from the previous version GB 18030-2005 "involving 33 different characters and 55 code positions".[2] GB 18030-2022 was enforced from 1 August 2023.[3] It has been implemented in ICU 73.2; and in Java 21,[4] and backported to older Java 8, 11, 17 (LTS releases) and 20.0.2.[5]
In addition to the encoding method, this standard contains requirements about which additional scripts and languages should be represented, and to whom this standard is applicable.[6] This standard however does not define the official character forms for the Chinese characters; this is standardised in List of Commonly Used Standard Chinese Characters.
The GB18030 character set is formally called "Chinese National Standard GB 18030-2005: Information Technology—Chinese coded character set". GB abbreviates Guójiā Biāozhǔn (国家标准), which means national standard in Chinese. The standard was published by the China Standard Press, Beijing, 8 November 2005. Only a portion of the standard is mandatory.[6] Since 1 May 2006, support for the mandatory subset is officially required for all software products sold in the PRC.
Different Unicode mappings between GB 18030 versions
GB byte sequence
Unicode code point
GB 18030-2000
GB 18030-2005
A8 BC (ḿ)
U+E7C7
U+1E3FḿLATIN SMALL LETTER M WITH ACUTE
81 35 F4 37
U+1E3FḿLATIN SMALL LETTER M WITH ACUTE
U+E7C7
An older version of the standard, known as "Chinese National Standard GB 18030-2000: Information Technology—Chinese ideograms coded character set for information interchange—Extension for the basic set", was published on March 17, 2000. The encoding scheme stays the same in the new version, and the only difference in GB-to-Unicode mapping is that GB 18030-2000 mapped the character A8 BC (ḿ) to a private use code point U+E7C7, and character 81 35 F4 37 (without specifying any glyph) to U+1E3F (ḿ), whereas GB 18030-2005 swaps these two mapping assignments.[7]: 534 More code points are now associated with characters due to update of Unicode, especially the appearance of CJK Unified Ideographs Extension B. Some characters used by ethnic minorities in China, such as Mongolian characters and Tibetan characters (GB 16959-1997 and GB/T 20542-2006), have been added as well, which accounts for the renaming of the standard.
Compared with its ancestors, GB 18030's mapping to Unicode has been modified for the 81 characters that were provisionally assigned a Unicode Private Use Area code point (U+E000–F8FF) in GBK 1.0 and that have later been encoded in Unicode.[8] This is specified in Appendix E of GB 18030.[7]: 534 [9]: 499 There are 24 characters in GB 18030-2005 that are still mapped to Unicode PUA.[10]
In the GB 18030-2022 update, the requirements for characters to be mapped to PUA has been lifted completely and all characters should be mapped to their standard Unicode codepoints. Of these, 18 mappings were updated by position-swapping similar to what happened between GBK and GB 18030. The remaining six kept the two-byte PUA mappings, so that a change to the 4-byte sequence is needed to follow the non-PUA preference.[11]
b.^U+20087𠂇CJK UNIFIED IDEOGRAPH-20087 mapped to 0x95329031 in GB 18030-2022
c.^U+20089𠂉CJK UNIFIED IDEOGRAPH-20089 mapped to 0x95329033 in GB 18030-2022
d.^U+200CC𠃌CJK UNIFIED IDEOGRAPH-200CC mapped to 0x95329730 in GB 18030-2022
e.^U+215D7𡗗CJK UNIFIED IDEOGRAPH-215D7 mapped to 0x9536B937 in GB 18030-2022
f.^U+2298F𢦏CJK UNIFIED IDEOGRAPH-2298F mapped to 0x9630BA35 in GB 18030-2022
g.^U+241FE𤇾CJK UNIFIED IDEOGRAPH-241FE mapped to 0x9635B630 in GB 18030-2022
As a national standard
The first version of GB 18030, designated GB 18030-2000 Information Technology—Chinese coded character set for information interchange — Extension for the basic set, consists of 1-byte and 2-byte encodings, together with 4-byte encoding for CJK Unified Ideographs Extension A matching those in Unicode 3.0. The corresponding Unicode code points of this subset, including provisional private assignments, lie entirely in the BMP. These parts are fully mandatory in GB 18030-2000.[6]: 2 Most major computer companies had already standardized on some version of Unicode as the primary format for use in their binary formats and OS calls. However, they mostly had only supported code points in the BMP originally defined in Unicode 1.0, which supported only 65,536 codepoints and was often encoded in 16 bits as UCS-2. This standard is basically an extension based on GBK with additional characters in CJK Unified Ideographs Extension A.
The second version designated GB 18030-2005 Information Technology—Chinese coded character set has the same mandatory subset as GB 18030-2000 of 1-, 2- and 4-byte encodings.[7]: 3 This version also includes the full CJK Unified Ideographs Extension B in the 4-byte encoding section which is outside the BMP[10] as a suggestion support requirement.[14] However, as the inclusion of CJK Unified Ideographs Extension B in a 4-byte region is required to be maintained during information processing, software can no longer get away with treating characters as 16-bit fixed width entities (UCS-2). Therefore, they must either process the data as a variable-width format (as with UTF-8 or UTF-16), which is the most common choice, or move to a larger fixed-width format (i.e. UTF-32). Microsoft made the change from UCS-2 to UTF-16 with Windows 2000. This version matches with Unicode 3.1, and also provided support for Hangul (Korean), Mongolian (including Manchu, Clear script, Sibe hergen, Galik), Tai Nuea, Tibetan, Uyghur/Kazakh/Kyrgyz and Yi.
The third and latest version, GB 18030-2022 Information Technology—Chinese coded character set, mandates the suggestion support part of CJK Unified Ideographs Extension B in GB 18030-2005, along with updates up to Unicode 11.0 including Kangxi Radicals and CJK Unified Ideographs URO, Extension C, D, E and F. Additional languages are also recognized by GB 18030-2022 such as part of Arabic, Tai Le, New Tai Lue, Tai Tham, Lisu, and Miao. GB 18030-2022 also introduces three implementation levels, with the requirement of "all products using this standard should implements Implementation Level 1" that includes 66 new BMP characters in the 4-byte encoding region that were added between Unicode 3.1 and Unicode 11.0. Implementation Level 2 requires the support of List of Commonly Used Standard Chinese Characters, and Implementation Level 3 requires all other specified regions in the standard.[11]
From late 2022 to 2023, drafts of a further amendment are to be made to GB 18030-2022 available for public consultation. The current draft updates up to Unicode 15.1 on Ideographic Description Characters, CJK Unified Ideographs URO, Extension A, B, C, G, H and I.[15][16][17] Originally, in late 2022, it would have placed 897 new sinographic characters in Plane 10 (hexadecimal: 0A), a yet-untitled astral Unicode plane, for citizen real-name certification in China, but eventually the repertoire (reduced to 622 characters after expert review) was fast-tracked into Unicode 15.1 in September 2023, as the CJK Unified Ideographs Extension I block.[18] Following this, the amendment draft was modified to use the Extension I code points.[17]
Mapping
GB 18030 defines a one (ASCII), two (extended GBK), or four-byte (UTF) encoding. The two-byte codes are defined in a lookup table, while the four-byte codes are defined sequentially (hence algorithmically) to fill otherwise unencoded parts in UCS. GB 18030 inherits the bad aspects of GBK, most notably needing special code to safely find ASCII characters in a GB18030 sequence.
The one- and two-byte code points are essentially GBK with the euro sign, PUA mappings for unassigned/user-defined points, and vertical punctuations. The four byte scheme can be thought of as consisting of two units, each of two bytes. Each unit has a similar format to a GBK two byte character but with a range of values for the second byte of 0x30–0x39 (the ASCII codes for decimal digits). The first byte has the range 0x81 to 0xFE, as before. This means that a string-search routine that is safe for GBK should also be reasonably[clarification needed] safe for GB18030 (in much the same way that a basic byte-oriented search routine is reasonably safe for EUC).
This gives a total of 1,587,600 (126×10×126×10) possible 4 byte sequences, which is easily sufficient to cover Unicode's 1,112,064 (17×65536 − 2048 surrogates) assigned, reserved, and noncharacter code points.
Unfortunately, to further complicate matters there are no simple rules to translate between a 4 byte sequence and its corresponding code point. Instead, codes are allocated sequentially (with the first byte containing the most significant part and the last the least significant part) only to Unicode code points that are not mapped in any other manner.[h] For example:
An offset table is used in the WHATWG and W3C version of GB 18030 to efficiently translate code points.[20] ICU[19] and glibc use similar range definitions to avoid wasting space on large sequential blocks.
Support
This section needs expansion. You can help by adding to it. (October 2016)
Encoding
GB18030 has been supported on Windows since the release of Windows 95, as code page 54936.[21] Windows 2000 and XP offer a GB18030 Support Package.[22] The open source PostgreSQL database supports GB18030 through its full support for UTF-8, i.e. by converting it to and from UTF-8. Similarly Microsoft SQL Server supports GB18030 by conversion to and from UTF-16.
More specifically, supporting the GB18030 encoding on Windows means that Code Page 54936 is supported by MultiByteToWideChar and WideCharToMultiByte. Due to the backward compatibility of the mapping, many files in GB18030 can be actually opened successfully as the legacy Code Page 936, that is GBK, even if the Code Page 54936 is not supported. However, that is only true if the file in question contains only GBK characters. Loading will fail or cause corrupted result if the file contains characters that do not exist in GBK (see § Technical details for examples).
GNU glibc's gconv, the character codec library used on most Linux distributions, supports GB 18030-2000 since 2.2,[23] and GB 18030-2005 since 2.14;[24] glibc notably includes non-PUA mappings for GB 18030-2005 in order to achieve round-trip conversion.[25] GNU libiconv, an alternative iconv implementation frequently used on non-glibc UNIX-like environments like Cygwin, supports GB 18030 since version 1.4.[26]
As of 2022, "supporting non-Chinese scripts continues to be optional"[27] (presumably for display/font support only; and in China, since the encoding is a full UTF). The standard is known to support English/ASCII and the "following non-Chinese scripts are recognized by GB 18030-2022: Arabic, Tibetan, Mongolian, Tai Le, New Tai Lue, Tai Tham, Yi, Lisu, Hangul (Korean), and Miao."[27]
Fonts
The GB18030 Support Package for Windows contains SimSun18030.ttc, a TrueType font collection file which combines two Chinese fonts, SimSun-18030 and NSimSun-18030. The SimSun 18030 font includes all the characters[clarification needed] in Unicode 2.1 plus new characters found in the Unicode CJK Unified Ideographs Extension A block although, despite its name, it does not contain glyphs for all characters encoded by GB 18030, as all (about a million) Unicode code points up to U+10FFFF can be encoded as GB 18030. GB 18030 compliance certification only requires correct handling and recognition of glyphs in the mandatory (two-byte, and CJK Ext. A) Chinese part.[6]: 4 Nevertheless, the requirement of PUA characters in the standard have hampered this implementation.[28]
Microsoft YaHei and DengXian provided by Microsoft are updated in 2023 to match GB 18030-2022 implementation level 2, and SimSun is updated to match implementation level 3.[29]
Source Han Sans (and its counterpart Noto Sans CJK) are already compliant with GB 18030-2022 implementation level 2 when the standard update for GB 18030 is announced as of November 2022[update]. Source Han Serif (and its counterpart Noto Serif CJK) however is not compliant at the time, and an update is provided to ensure the font is compliant to implementation level 2. Similarly Microsoft YaHei and PingFang (Apple) require a small number of URO additions that are associated with implementation level 1 in order to become compliant with GB 18030-2022 implementation level 2.[27]
Other CJK font families like HAN NOM[30] and Hanazono Mincho[31] provide wider coverage for Unicode CJK Extension blocks than SimSun-18030 or even SimSun (Founder Extended), but they don't support all code points defined in GB 18030.
^Note that GB18030 omits surrogates; see #Mapping.
^The euro sign is an exception which is given a single byte code of 0x80 in Microsoft's later versions of CP936/GBK and a two byte code of A2 E3 in GB18030.
^The code points include the 66 Unicode noncharacters.
^ICU seems to erroneously consider this code point valid, which is in neither versions of the published standards. WHATWG assigns this byte to U+20AC (GBK euro sign) in its universal gb2312-gbk-gb18030 decoder.
^Some code points are encoded with two bytes (upper row), the others with four bytes (lower row). U+FFFF is encoded as 84 31 A4 39 on page 239 of the 2005 standard, although the standard gives as far as 84 39 FE 39 for BMP mapping.
^Furthermore, due to the encodings of U+E7C7 and U+1E3F having been swapped, U+E7C7 is encoded in the 2005 edition of the standard as 81 35 F4 37, between U+1E3E (81 35 F4 36) and U+1E40 (81 35 F4 38). Hence, only the 2000 edition is entirely sequential in allocating the four-byte codes to otherwise unmapped code points.
^ abcdCESI (2009-07-08). "GB18030 符合性问与答" [GB18030 compliance FAQ]. CESI Certification Center. Archived from the original on 2016-09-28. Retrieved 2016-10-12. Page 4 同时达到以下两个要求的产品，为符合GB 18030-2005强制部分的产品：①产品可以正确输入、输出、处理GB 18030-2005强制部分规定的全部汉字字符；②产品可以正确识别GB 18030-2005强制性部分规定的全部汉字字符对应的编码。 [A product compliant with the mandatory part of GB 18030 must be able to correctly a) input, output and process all Chinese characters defined in the mandatory set; b) recognize encodings for characters in the mandatory set.]Alt URL
^CESI (2009-07-08). "GB18030 符合性问与答" [GB18030 compliance FAQ]. CESI Certification Center. Archived from the original on 2016-09-28. Retrieved 2016-10-12. Page 4 同时达到以下两个要求的产品，为符合GB 18030-2005强制部分的产品：①产品可以正确输入、输出、处理GB 18030-2005强制部分规定的全部汉字字符；②产品可以正确识别GB 18030-2005强制性部分规定的全部汉字字符对应的编码。 [A product compliant with the mandatory part of GB 18030 must be able to correctly a) input, output and process all Chinese characters defined in the mandatory set; b) recognize encodings for characters in the mandatory set.]
^Lunde, Ken. "If gb18030 is revised, consider aligning the Encoding Standard · Issue #27 · whatwg/encoding". GitHub. Besides, supporting PUA code points in the context of the Noto CJK and Source Han fonts is a total non-starter, mainly because they are Pan-CJK typefaces, and PUA usage is extremely dangerous in such contexts.[...] One of my friends at CESI shared with me the text from the final draft a few days ago. This confirmed that the PUA requirement for the 24 characters is being lifted.
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