Extended Unix Code

The structure of EUC is based on the standard, which specifies a system of graphical character sets that can be represented with a sequence of the 94 7-bit bytes 0x21–7E, or alternatively 0xA1–FE if an eighth bit is available. This allows for sets of 94 graphical characters, or 8836 (942) characters, or 830584 (943) characters. Although initially 0x20 and 0x7F were always the space and and 0xA0 and 0xFF were unused, later editions of allowed the use of the bytes 0xA0 and 0xFF (or 0x20 and 0x7F) within sets under certain circumstances, allowing the inclusion of 96-character sets. The ranges 0x00–1F and 0x80–9F are used for C0 and C1 control codes. EUC is a family of 8-bit profiles of , as opposed to 7-bit profiles such as ISO-2022-JP. As such, only compliant character sets can have EUC forms. Up to four coded character sets (referred to as G0, G1, G2, and G3 or as code sets 0, 1, 2, and 3) can be represented with the EUC scheme. The G0 set is set to an compliant coded character set such as ASCII, () or (the lower half of ) and invoked over GL (i.e. 0x21–0x7E, with the most significant bit cleared). Fixed-length format The ISO-2022-based variable-length encoding described above is sometimes referred to as the EUC packed format, which is the encoding format usually labeled as EUC. However, internal processing of EUC data may make use of a fixed-length transformation format called the EUC complete two-byte format. This represents: Only the packed format is included in the WHATWG Encoding Standard used by HTML5. ==EUC-CN==

EUC-CN which encodes GB 2312 the same way as EUC-CN, but deviates from the EUC structure by extending the lead byte range back to 0x8C, adding 31 IBM-selected characters in 0x8CE0 through 0x8CFE and adding 1880 user-defined characters with lead bytes 0x8D through 0xA0. IBM code page 1383 (CCSID 1383) comprises the single-byte code page 367 and the double-byte code page 1382 (CPGID 1382 as CCSID 1382), which differs by conforming to the EUC structure, adding the 31 IBM-selected characters in 0xFEE0 through 0xFEFE instead, and including only 1360 user-defined characters, interspersed in the positions not used by GB 2312. The alternative CCSID 5479 is used for the pure EUC-CN code page: it uses CCSID 9574 as its double-byte set, which uses CPGID 1382 but excludes the IBM-selected and user-defined characters. GBK and GB 18030 GBK is an extension to . It defines an extended form of the EUC-CN encoding capable of representing a larger array of CJK characters sourced largely from , including traditional Chinese characters and characters used only in Japanese. It is not, however, a true EUC code, because ASCII bytes may appear as trail bytes (and C1 bytes, not limited to the single shifts, may appear as lead or trail bytes), due to a larger encoding space being required. Variants of GBK are implemented by Windows code page 936 (the Microsoft Windows code page for simplified Chinese), and by IBM's code page 1386. The Unicode-based character encoding defines an extension of GBK capable of encoding the entirety of Unicode. However, Unicode encoded as is a variable-length encoding which may use up to four bytes per character, due to an even larger encoding space being required. Being an extension of GBK, it is a superset of EUC-CN but is not itself a true EUC code. Being a Unicode encoding, its repertoire is identical to that of other Unicode transformation formats such as UTF-8. Mac OS Chinese Simplified Other EUC-CN variants deviating from the EUC mechanism include the classic Mac OS Chinese Simplified script (known as Code page 10008 or x-mac-chinesesimp). It uses the bytes 0x80, 0x81, 0x82, 0xA0, 0xFD, 0xFE, and 0xFF for the U with umlaut (ü), two special font metric characters, the non-breaking space, the copyright sign (©), the trademark sign (™) and the ellipsis (...) respectively. This differs in what is regarded as a single-byte character versus the first byte of a two-byte character from both EUC (where, of those, 0xFD and 0xFE are defined as lead bytes) and GBK (where, of those, 0x81, 0x82, 0xFD and 0xFE are defined as lead bytes). This use of 0xA0, 0xFD, 0xFE and 0xFF matches Apple's Shift_JIS variant. Besides these changes to the lead byte range, the other distinctive feature of the double-byte portion of Mac OS Chinese Simplified is the inclusion of two extensions to the basic GB 2312-80 set in rows 6 and 8. and both extensions are included by GB 18030 (the successor to GB 2312). ==EUC-JP==

EUC-JP is a variable-length encoding used to represent the elements of three Japanese character set standards, namely , , and . Other names for this encoding include Unixized JIS (or UJIS) and AT&T JIS. Less than 0.1% of all web pages use EUC-JP as of February 2026, while 2.1% of websites written with Japanese use this second-most popular (for Japanese) encoding (which is more than for Shift JIS less used than , --> both are much less used that UTF-8). It is called Code page 954 by IBM. Microsoft has two code page numbers for this encoding (51932 and 20932). This encoding scheme allows the easy mixing of 7-bit ASCII and 8-bit Japanese without the need for the escape characters employed by ISO-2022-JP, which is based on the same character set standards, and without ASCII bytes appearing as trail bytes (unlike Shift JIS). A related and partially compatible encoding, called EUC-JISx0213 or EUC-JIS-2004, encodes and (similarly to , its Shift_JIS-based counterpart). Compared to EUC-CN or EUC-KR, EUC-JP did not become as widely adopted on PC and Macintosh systems in Japan, which used or its extensions (Windows code page 932 on Microsoft Windows, and MacJapanese on classic Mac OS), although it became heavily used by Unix or Unix-like operating systems (except for HP-UX). Therefore, whether Japanese websites use EUC-JP or Shift_JIS often depends on what OS the author uses. Characters are encoded as follows: • As an EUC/ISO 2022 compliant encoding, the C0 control characters, space, and DEL are represented as in ASCII. • A graphical character from ASCII (code set 0) is represented as its usual one-byte representation, in the range 0x21 – 0x7E. While some variants of EUC-JP encode the lower half of here, most encode ASCII, including the W3C/WHATWG Encoding standard used by HTML5, and so does EUC-JIS-2004. • A character from JIS X 0208 (code set 1) is represented by two bytes, both in the range 0xA1 – 0xFE. This differs from the ISO-2022-JP representation by having the high bit set. This code set may also contain vendor extensions in some EUC-JP variants. In EUC-JIS-2004, the first plane of is encoded here, which is effectively a superset of standard . In EUC-JIS-2004, the second plane of is encoded here, Some implementations of EUC-JIS-2004, such as the one used by Python, allow both and plane 2 characters in this set. It also allows the entire user defined code set, and the unused rows at the ends of the JIS X 0208 and JIS X 0212 code sets (rows 85–94 and 78–94 respectively), to be used for user-defined characters. Also similarly to KEIS, codes are represented the same as in EUC-JP. The lead byte range is extended back to 0x41, with 0x80–0xA0 designated for user definition; lead bytes 0x41–0x7F are assigned row numbers 101 through 163 for kuten purposes, although row 162 (lead byte 0x7E) is unused. Rows 101 through 148 are used for extended kanji, while rows 149 through 163 are used for extended non-kanji. ==EUC-KR==

EUC-KR is a variable-length encoding to represent Korean text using two coded character sets, (formerly KS C 5601) and either (, formerly ) or ASCII, depending on variant. (formerly ) stipulates the encoding and dubbed it as EUC-KR. A character drawn from KS X 1001 (G1, code set 1) is encoded as two bytes in GR (0xA1–0xFE) and a character from or ASCII (G0, code set 0) takes one byte in GL (0x21–0x7E). It is usually referred to as Wansung () in the Republic of Korea. IBM refers to the double-byte component as Code page 971, and to EUC-KR with ASCII as Code page 970. It is implemented as Code page 20949 ("Korean Wansung") and Code page 51949 ("EUC Korean") by Microsoft. , less than 0.06% of all web pages globally declare using EUC-KR, but 3.8% of South Korean web pages use EUC-KR. Including extensions, it is the most widely used legacy character encoding in Korea on all three major platforms (macOS, other Unix-like OSes, and Windows), but its use has been very slowly shifting to UTF-8 as it gains popularity, especially on Linux and macOS. As with most other encodings, UTF-8 is now preferred for new use, solving problems with consistency between platforms and vendors. Unified Hangul Code A common extension of EUC-KR is the Unified Hangul Code (, or ), which is the default Korean codepage on Microsoft Windows. It is given the code page number 949 by Microsoft, and 1261 or 1363 by IBM. IBM's code page 949 is a different, unrelated, EUC-KR extension. Unified Hangul Code extends EUC-KR by using codes that do not conform to the EUC structure to incorporate additional syllable blocks, completing the coverage of the composed syllable blocks available in Johab and Unicode. The W3C/WHATWG Encoding Standard used by HTML5 incorporates the Unified Hangul Code extensions into its definition of EUC-KR. Mac OS Korean (HangulTalk) Other encodings incorporating EUC-KR as a subset include the Mac OS Korean script (known as Code page 10003 or x-mac-korean), Many of these characters do not have exact Unicode mappings, and Apple software maps these cases variously to combining sequences, to approximate mappings with an appended private-use character as a modifier for round-trip purposes, or to private-use characters. Apple also uses certain single-byte codes outside of the EUC-KR plane for additional characters: 0x80 for a required space, 0x81 for a won sign (₩), 0x82 for an en dash (–), 0x83 for a copyright sign (), 0x84 for a wide underscore () and 0xFF for an ellipsis (...). Although none of these additional single-byte codes are within the lead byte range of plain EUC-KR (unlike Apple's extensions to EUC-CN, see above), some are within the lead byte range of Unified Hangul Code (specifically, 0x81, 0x82, 0x83 and 0x84). ==EUC-KP==

Similarly to KS X 1001, the North Korean KPS 9566 standard is typically used in EUC form; in these contexts, it is sometimes referred to as EUC-KP. More recent editions of the standard extend the EUC representation with characters using non-EUC two-byte codes, in a similar manner to Unified Hangul Code. ==EUC-TH==

Although certain single-byte encodings such as the ISO/IEC 8859 series technically conform to the EUC structure, they are rarely labeled as EUC. However, is used on Solaris as a label for TIS-620. ==EUC-TW==

EUC-TW is a variable-length encoding that supports ASCII and 16 planes of , each of which is 94×94. It is a rarely used encoding for traditional Chinese characters as used in Taiwan. Variants of Big5 are much more common than EUC-TW, although Big5 only encodes the first two planes of CNS 11643 hanzi, while UTF-8 is becoming more common. • As an EUC/ISO 2022 encoding, the C0 control characters, ASCII space, and DEL are encoded as in ASCII. • A graphical character from ASCII (G0, code set 0) is encoded in GL as its usual single-byte representation (0x21–0x7E). • A character from CNS 11643 plane 1 (code set 1) is encoded as two bytes in GR (0xA1–0xFE). • A character in planes 1 through 16 of CNS 11643 (code set 2) is encoded as four bytes: • The first byte is always 0x8E (Single Shift 2). • The second byte (0xA1–0xB0) indicates the plane, the number of which is obtained by subtracting 0xA0 from that byte. • The third and fourth bytes are in GR (0xA1–0xFE). Note that plane 1 of CNS 11643 is encoded twice as code set 1 and a part of code set 2. ==See also==