Family of several code pages for the Cyrillic script
KOI (КОИ) is a family of several
code pages for the
Cyrillic script.
The name stands for Kod obmena informatsiey (
Russian: Код обмена информацией) 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 (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.
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 24hex) may be replaced by the
universal currency sign ¤).
KOI-8 (КОИ-8), standardized in 1974 as
GOST 19768, is an 8-bit
extensions of ASCII.[1][2] Originally it only included 32 lowercase and 31 uppercase Russian letters.
Later derivatives of KOI-8 constitute the family of encodings variously known as KOI8, KOI 8 and KOI-8.
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.[16] These do not follow the KOI-8 layout.
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.[17]
There are two variants:
DKOI K1 (ДКОИ К1), each Cyrillic letter is given its own code point.
DKOI K2 (ДКОИ К2), some Cyrillic letters (А, В, Е, К, М, Н, О, Р, С, Т, Х, а, е, о, р, с, у, х) are merged with visually identical Latin letters.
Latin variants
Some encodings are called KOI, but define Latin alphabets:
KOI8-CS[18] /
KOI8-CS2[17] for
Czech and
Slovak (ČSN (Czech technical standard) 369103, devised by the
Comecon. This encoded Latin with
diacritics, as used in Czech and Slovak, rather than Cyrillic, but the basic idea was the same - text should remain legible with the 8-th bit cleared, thus e.g. Č became C etc.).
KOI8-L2 "Latin-2" (defined in CSN 36 9103), ISO IR 139[19] (almost identical to
ISO 8859-2 (1987), but has the dollar sign and currency sign swapped)
Kornai, Andras; Birnbaum, David J.; da Cruz, Frank; Davis, Bur; Fowler, George; Paine, Richard B.; Paperno, Slava; Simonsen, Keld J.; Thobe, Glenn E.; Vulis, Dimitri; van Wingen, Johan W. (1993-03-13).
"CYRILLIC ENCODING FAQ Version 1.3". 1.3. Retrieved 2017-02-18.
"Kodierungen und Zeichensätze" [Encodings and character sets]. Robotron Technik (Virtual computer museum) (in German). 2016-11-29. ASCII-Code / KOI-Code. Retrieved 2017-02-21.