KOI8-U

KOI8-U (RFC 2319) is an 8-bit character encoding, designed to cover Ukrainian, which uses a Cyrillic alphabet. It is based on KOI8-R, which covers Russian and Bulgarian, but replaces eight box drawing characters with four Ukrainian letters Ґ, Є, І, and Ї in both upper case and lower case.

KOI8-RU is closely related, but adds Ў for Belarusian. In both, the letter allocations match those in KOI8-E, except for Ґ which is added to KOI8-F.

In Microsoft Windows, KOI8-U is assigned the code page number 21866. In IBM, KOI8-U is assigned code page/CCSID 1168.

KOI8 remains much more commonly used than ISO 8859-5, which never really caught on. Another common Cyrillic character encoding is Windows-1251. In the future, both may eventually give way to Unicode.

KOI8 stands for Kod Obmena Informatsiey, 8 bit (Russian: Код Обмена Информацией, 8 бит) which means "Code for Information Exchange, 8 bit".

The KOI8 character sets have the property that the Cyrillic letters are in pseudo-Latin alphabetic order rather than Cyrillic alphabetical order as in ISO 8859-5. This has the useful effect that if the eighth bit is stripped and the text is presented in any character set based on ASCII including the KOI8 sets themselves, the text is still reasonably human readable as a case-reversed transliteration. For instance, the "KOI" acronym "Код Обмена Информацией" becomes kOD oBMENA iNFORMACIEJ.