KOI (, from ) is a family of several code pages for the Cyrillic script.

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 (128 codepoints apart from the Latin letter they sound most similar to), 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 (nearly phonetical), which was already used in Russian dialect of Morse code and in MTK-2 telegraph code. The first 26 characters from А (0xE1) 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.

KOI-7

The original KOI encoding (1967) was a 7-bit code page named KOI-7 (КОИ-7), which did not contain lowercase letters.

In KOI-7, the codes of the 31 or 32 Russian letters are ordered according to the Latin letters. Other code points are the same as in ASCII (however, the dollar sign $ (code point 24<sub>hex</sub>) may be replaced by the universal currency sign ¤).

KOI-8

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KOI-8 (КОИ-8), standardized in 1974 as GOST 19768, is an 8-bit extension of ASCII. (FreeDOS Code page 61294)

  • ISO-IR-111 / KOI8-E (ECMA-113 (1st ed., 1986), multilingual for Slavic languages).
  • KOI8-F, KOI-8 Unified. Includes the letter allocations from both KOI8-U and KOI8-E, with a subset of the pseudographics from KOI8-R. (FreeDOS Code page 63342)

Additionally, GOST R 34.303-92 defines "KOI-8 V1" which is ISO-IR-153, and "KOI-8 N1" and "KOI-8 N2" which are variants of Code page 866. These do not follow the KOI-8 layout.

DKOI

DKOI is an EBCDIC-based encoding used in ES EVM mainframes. It has been defined by several standards: GOST 19768-74 / ST SEV 358–76, ST SEV 358-88 / GOST 19768–93, CSN 36 9103.<!-- "charset CSN_369103", "KOI-8_L2", "koi8l2" --> (almost identical to ISO 8859-2 (1987), but has the dollar sign and currency sign swapped)

  • DKOI CS2 (defined in CSN 36 9103)

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Further reading

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