Editing Code page 866 (section)

{{Short description|Computer character set for Russian}}
{{Infobox character encoding
|mime = IBM866
|alias = cp866, 866<ref>{{Citation|title=Character Sets|url=https://www.iana.org/assignments/character-sets/character-sets.xhtml|publisher=[[Internet Assigned Numbers Authority]] (IANA)|date=2018-12-12}}</ref>
|image = Octets in conformant CP866 ordered by nibbles.png
|classification = [[OEM code page]], [[extended ASCII]]
|extends = [[US-ASCII]]
|basedon = [[#Alternative code page|Alternative code page]]
|standard = [[WHATWG]] Encoding Standard
|lang = [[Russian language|Russian]], [[Bulgarian language|Bulgarian]]; <br />'''Partial support:''' <br/>[[Ukrainian language|Ukrainian]],{{efn|Includes distinctly Ukrainian and [[Rusyn language|Rusyn]] letters [[Є]] and [[Ї]], but no {{serif|[[І]]}} distinct from Latin {{serif|[[I]]}}, and implements Soviet orthography, i.e. omits [[Ґ]]. These are added in some modifications.|name=ukr}} [[Belarusian language|Belarusian]]{{efn|Includes uniquely Belarusian [[Ў]], but no {{serif|[[І]]}} distinct from Latin {{serif|[[I]]}} (although this is added in some modifications).}}
|otherrelated = [[#Variants|(See below)]]
}}

'''Code page 866''' ([[CCSID]] 866)<ref>{{cite web|title=CCSID 866 information document|archive-url=https://web.archive.org/web/20160327022230/http://www-01.ibm.com/software/globalization/ccsid/ccsid866.html|archive-date=2016-03-27|url=http://www-01.ibm.com/software/globalization/ccsid/ccsid866.html}}</ref> (CP 866, "DOS Cyrillic Russian")<ref name="steele"/> is a [[code page]] used under [[DOS]] and [[OS/2]]<ref name="OS2"/> in [[Russia]] to write [[Cyrillic script]].<ref name="IBMCP866">{{cite web|title=Code page 866 information document|archive-url=https://web.archive.org/web/20160316232819/http://www-01.ibm.com/software/globalization/cp/cp00866.html|archive-date=2016-03-16|url=https://www-01.ibm.com/software/globalization/cp/cp00866.html}}</ref><ref name="OEM"/> It is based on the "alternative code page" ({{langx|ru|Альтернативная кодировка}}) developed in 1984 in IHNA AS USSR and published in 1986 by a research group at the Academy of Science of the USSR.<ref name="Bryabrin1986">{{in lang|ru}} Брябрин В. М., Ландау И. Я., Неменман М. Е. [http://www.wdigest.ru/mpss1986/mpss04_1986.htm О системе кодирования для персональных ЭВМ] // Микропроцессорные средства и системы. — 1986. — № 4. — С. 61–64.</ref> The code page was widely used during the DOS era because it preserves all of the [[Box-drawing characters|pseudographic symbols]] of [[code page 437]] (unlike the "[[Main code page (Russian)|Main code page]]" or Code page 855) and maintains alphabetic order (although non-contiguously) of Cyrillic letters (unlike [[KOI8-R]]). Initially this encoding was only available in the Russian version of MS-DOS 4.01 (1990), but with MS-DOS 6.22 it became available in any language version.

The [[WHATWG]] Encoding Standard, which specifies the character encodings permitted in [[HTML5]] which compliant browsers must support,<ref>{{Cite web |url=https://www.w3.org/TR/html51/syntax.html#character-encodings |title=8.2.2.3. Character encodings |work=HTML 5.1 2nd Edition |publisher=[[W3C]] |quotation=User agents must support the encodings defined in the WHATWG Encoding standard, including, but not limited to […]}}</ref> includes Code page 866.<ref name="lsbe">{{cite web |url=https://encoding.spec.whatwg.org/#legacy-single-byte-encodings |title=Legacy single-byte encodings |work=Encoding Standard |last=van Kesteren |first=Anne |author-link=Anne van Kesteren |publisher=[[WHATWG]]}}</ref> It is the only single-byte encoding listed which is not named as an [[ISO 8859]] part, [[Macintosh operating systems|Mac OS]] specific encoding, [[Microsoft Windows]] specific encoding ([[Windows-874]] or [[Windows code page|Windows-125x]]) or [[KOI-8]] variant.<ref name="lsbe" /> Authors of new pages and the designers of new protocols are instructed to use [[UTF-8]] instead.<ref>{{cite web |url=https://encoding.spec.whatwg.org/#names-and-labels |title=Names and labels |work=Encoding Standard |last=van Kesteren |first=Anne |author-link=Anne van Kesteren |publisher=[[WHATWG]]}}</ref>

Two very similar but not identical encodings are standardised in [[GOST]] R 34.303-92<ref name="gost_r_34.303-92">{{in lang|ru}} ГОСТ Р 34.303-92. [http://docs.cntd.ru/document/gost-r-34-303-92 Наборы 8-битных кодированных символов. 8-битный код обмена и обработки информации.] = 8-bit coded character sets. 8-bit code for information interchange.</ref> as [[#KOI-8 N1|KOI-8 N1]] and [[#KOI-8 N2|KOI-8 N2]] (not  to be confused with the original [[KOI-8]]).