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

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

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

The KOI8 character sets have the property that the Russian Cyrillic letters are in pseudo-Roman order rather than the natural Cyrillic alphabetical order as in ISO 8859-5. Although this may seem unnatural, it has the useful property that if the 8th bit is stripped, the text can still be read (or at least deciphered) in case-reversed transliteration on an ordinary ASCII terminal. For instance, "Русский Текст" in KOI8-U becomes rUSSKIJ tEKST ("Russian Text") if the 8th bit is stripped.

In the table above, 20 is the regular SPACE character, and 9A is the NO-BREAK SPACE.

The difference with KOI8-R consists of the positions 0xA4; 0xA6; 0xA7; 0xAD; and 0xB4; 0xB6; 0xB7; 0xBD; which consist of extra letters that don't exist in Russian.

Although RFC 2319 says that character 95 should be U+2219 (∙), it may also be U+2022 (•) to match the bullet character in Windows-1251.

Some references have a typo and incorrectly state that character B4 is U+0403, rather than the correct U+0404. This typo is present in Appendix A of RFC 2319 (but the table in the main text of the RFC gives the correct mapping).

See also

• Ukrainian alphabet

External links

• RFC 2319