It was directly derived from the Greek letter phi (Φ) and has replaced Fita (Ѳ) in the Russian version of the alphabet since 1918. Unlike phi, however, it is transliterated as "f", not "ph".
KOI8-R is defined by RFC1489 (Registration of a Cyrillic Character Set).
KOI8-R was designed for mixed Russian/English texts and covers only Russian Cyrillic characters, so if you’re looking for Ukrainian, Byelorussian, etc. Cyrillic characters, try ISO-IR-111, or KOI8-U (Ukrainian Character Set), or KOI8-C (for ancient Russian texts) instead, which are identical to KOI8-R in the Russian Cyrillic letters area.
A more complete set of Cyrillic characters is also defined by the ISO-8859-5 character set.
The Cyrillic script is used for the Azerbaijani, Bulgarian, Buryat, Byelorussian, Karakalpak, Kazakh, Khalkha, Kirghiz, Macedonian, Moldavian, Russian, Serbian, Tajik, Turkmen, Ukrainian and Uzbek languages.
Characters 1025-1036, 1038-1103, 1105-1116, 1118, 1119, 1168 and 1169 in the Cyrillic range are present in Microsoft’s WGL4 character set, and are therefore included in Microsoft’s core fonts for Windows (Arial, Courier New and Times New Roman).
The characters that appear in the first column of the following table depend on the browser that you are using, the fonts installed on your computer, and the browser options you have chosen that determine the fonts used to display particular character sets, encodings or languages.