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.
== 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 24hex)
may be replaced by the universal currency sign ¤).
== KOI-8 ==
KOI-8 (КОИ-8), standardized in 1974 by GOST 19768, is a 8-bit extensions of ASCII.
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.
The family members are:
KOI8-B (with Ёё and Ъ)KOI8-R / KOI8-RUSSIA for Russian and Bulgarian (RFC 1489).KOI8-U
/ KOI8-UKRAINE for Ukrainian (RFC 2319).KOI8-RU for Ukrainian, Belorussian and Russian.KOI8-T
for Tajik.KOI8-C, also KOI8-CA, a proposal for Caucasus and Central Asia; hardly ever
been used.ISO-IR-111 / KOI8-E (ECMA-113 (1st ed., 1986), multilingual for Slavic languages).KOI8-F,
United KOI-8.KOI8-K1 "Cyrillic-1" (defined in CSN 36 9103, ST SEV 358-88)KOI8-O (formerly
KOI8-C) for Old Russian orthography.Additionally, GOST R 34.303-92 defines "KOI-8 N1" and "KOI-8
N2" which are, however, variants of Code page 866, not KOI-8.
== 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.There are two variants:
DKOI K1 (ДКОИ К1), each Cyrillic letter is given its own code point.
DKOI K2 (ДКОИ К1), 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 / KOI8-CS2 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 (similar, but not identical to
ISO 8859-2 (1987)) DKOI CS2 (defined in CSN 36 9103)
DKOI L2 (defined in CSN 36 9103)
== References ==
== Further reading == 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.
== External links == "The Home of the KOI8-R since 1995".
Retrieved 2016-12-05.
Hohlov, Yu.
E. "Cyrillic Information Representation in Electronic Form - Character Set (Code Page)
Tables".
Archived from the original on 2016-12-05.
Retrieved 2016-12-05.
Nechayev, Valentin (2013) [2001].
"Review of 8-bit Cyrillic encodings universe".
Archived from the original on 2016-12-05.
Retrieved 2016-12-05.