From Just Solve the File Format Problem
KOI8-R (Код Обмена Информацией, 8 бит, русский) is an 8-bit character encoding including the Cyrillic alphabet, intended for use with the Russian language. It dates to the Soviet era, and is the most commonly encountered of the KOI8 family of encodings. Character codes 32-126 are identical with the corresponding ASCII characters. Cyrillic characters are ordered in phonetic correspondence to ASCII characters in the bottom half of the code table, not in native alphabetical order. This order is designed to maximize legibility if the 8th bit is stripped.