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KOI is a family of several code pages for the Cyrillic script.The name stands for Kod obmena informatsiey which means "Code for Information Interchange".
A particular feature of the KOI code pages is that the text remains human-readable when the leftmost bit is stripped, should it inadvertently pass through equipment or software that can only deal with 7 bit wide characters. This is due to characters being placed in a special order , which, however, does not correspond to the alphabetic order in any language that is written in Cyrillic and necessitates the use of lookup tables to perform sorting.
These encodings are derived from ASCII on the base of some correspondence between Latin and Cyrillic , which was already used in Russian dialect of Morse code and in MTK-2 telegraph code. The first 26 characters from А in KOI8-R are А, Б, Ц, Д, Е, Ф, Г, Х, И, Й, К, Л, М, Н, О, П, Я, Р, С, Т, У, Ж, В, Ь, Ы, З.