Editing Extended Unix Code (section)

===Fixed-length format===
[[File:CsEucFixWidJapanese.svg|right|thumb|Layout of the fixed-length format for Japanese]]

The ISO-2022-based [[variable-width encoding|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:<ref name="lunde" />

* Code set 0 as two bytes in the range 0x21–0x7E (except that the first may be 0x00).
* Code set 1 as two bytes in the range 0xA0–0xFF (except that the first may be 0x80).
* Code set 2 as a byte in the range 0x21–0x7E (or 0x00) followed by a byte in the range 0xA0–0xFF.
* Code set 3 as a byte in the range 0xA0–0xFF (or 0x80) followed by a byte in the range 0x21–0x7E.

Initial bytes of 0x00 and 0x80 are used in cases where the code set uses only one byte. There is also a four-byte fixed-length format.<ref name="lunde" /> These fixed-length encoding formats are suited to internal processing and are not usually encountered in interchange.

EUC-JP is registered with the IANA in both formats, the packed format as "EUC-JP" or "csEUCPkdFmtJapanese" and the fixed width format as "csEUCFixWidJapanese".<ref>{{cite web | url=https://www.iana.org/assignments/character-sets/character-sets.xhtml | publisher=IANA | title=Character Sets}}</ref> Only the packed format is included in the [[WHATWG]] Encoding Standard used by [[HTML5]].<ref>{{cite web | url=https://encoding.spec.whatwg.org/#names-and-labels | title=4.2. Names and labels | publisher=WHATWG | work=Encoding Standard}}</ref>