Code page 866 is a code page used under DOS and OS/2 in Russia to write Cyrillic script. It is based on the "alternative code page" published in 1986 by a research group at the Academy of Science of the USSR. The code page was widely used during the DOS era because it preserves all of the pseudographic symbols of code page 437 and maintains alphabetic order of Cyrillic letters. Initially, this encoding was only available in the Russian version of MS-DOS 4.01 and since MS-DOS 6.22 in any language version. The WHATWG Encoding Standard, which specifies the character encodings permitted in HTML5 which compliant browsers must support, includes Code page 866. It is the only single-byte encoding listed which is not named as an ISO 8859 part, Mac OS specific encoding, Microsoft Windows specific encoding or KOI-8 variant. Authors of new pages and the designers of new protocols are instructed to use UTF-8 instead. Not identical, but two very similar encodings are standardised in GOST R 34.303-92 as KOI-8 N1 and KOI-8 N2.
Character set
Each character is shown with its equivalent Unicode code point. Only the second half of the table is shown, the first half being the same as code page 437.
Variants
There existed a few variants of the code page, but the differences were mostly in the last 16code points.
Alternative code page
The original version of the code page by Bryabrin et al. is called the "Alternative code page", to distinguish it from the "Main code page" by the same authors. It supports only Russian and Bulgarian. It is mostly the same as code page 866, except for codes F2hex through F7hex and codes F8hex through FBhex. The differing row is shown below.
Modified code page 866
An unofficial variant with code points 240–255 identical to code page 437. However, the letter Ёё is usually placed at 240 and 241. This version supports only Russian and Bulgarian. The differing row is shown below.
The KBL code page, unofficially known as Code page 771, is the earliest DOS character encoding for Lithuanian. It mostly matches code page 866 and the Alternative code page, but replaces the last row and some block characters with letters from the Lithuanian alphabet not otherwise present in ASCII. The Russian Ё/ё is not supported, similarly to KOI-7. A modified version, Code page 773, which replaces the Cyrillic letters with Latvian and Estonian letters, also exists.
LST 1284
Lithuanian Standard LST 1284:1993, known as Code page 1119 or unofficially as Code page 772, mostly matches the "modified" Code page 866, except for the addition of quotation marks in the last row and the replacement of the mixed single-double box drawing characters with Lithuanian letters. Unlike KBL, the Russian Ё/ё is retained. It accompanies LST 1283, which encodes the additional Lithuanian letters at the same locations as LST 1284, but is based on Code page 437 instead. It was later superseded by LST 1590-1, which encodes these Lithuanian letters in the same locations, but does not include Cyrillic letters, replacing them with Latvian and Estonian letters.
Code page/CCSID 1125 matches the original Alternative code page for all points except for F2hex through F9hex inclusive, which are replaced with Ukrainian letters. Code page/CCSID 1131 matches code page 866 for all points except for F8hex, F9hex, and FChex through FEhex inclusive, which are replaced with otherwise-missing Ukrainian and Belarusian letters, in the process displacing the bullet character from F9hex to FEhex. The differing rows are shown below.
Euro sign updates
IBM code page/CCSID 808 is a variant of code page/CCSID 866; with the euro sign in position FDhex, replacing the universal currency sign. IBM code page/CCSID 848 is a variant of code page/CCSID 1125 with the euro sign at FDhex, replacing ¤. IBM code page/CCSID 849 is a variant of code page/CCSID 1131 with the euro sign at FBhex, replacing ¤.
The GOST R 34.303-92 standard defines two variants. The more extensive variant, KOI-8 N2, matches code page 866 and the Alternative code page until the last row. For the last row, it supports letters for Belarusian and Ukrainian in addition to Russian, but in a layout unrelated to code page 866 or 1125. Notably, even the Russian Ё/ё is in a different location. The differing row is shown below. The other variant, KOI-8 N1, is a subset of KOI-8 N2 which omits the non-Russian Cyrillic letters and mixed single/double lined box drawing characters, leaving them empty for further internationalization. The affected rows are shown below.
Lehner–Czech modification
An unofficial modification used in software developed by Michael Lehner and Peter R. Czech. It replaces three mathematic symbols with guillemets and the section sign which are commonly used in the Russian language. (Lehner and Czech created a number of alternative character sets for other European languages as well, including one based on CWI-2 for Hungarian, a Kamenicky-based one for Czech and Slovak, a Mazovia variant for Polish and a seemingly-unique encoding for Lithuanian. The modified row is shown below.
Latvian variant
A Latvian variant, supported by Star printers and FreeDOS, is code page 3012. This encoding is nicknamed "RusLat".
FreeDOS
provides additional unofficial extensions of code page 866 for various non-Slavic languages:
Before Microsoft's final code page for Russian MS-DOS 4.01 was registered with IBM by Franz Rau of Microsoft as CP866 in January 1990, draft versions of it developed by Yuri Starikov of Dialogue were still called code page 900 internally. While the documentation was corrected to reflect the new name before the release of the product, sketches of earlier draft versions still named code page 900 and without Ukrainian and Belarusian letters, which had been added in autumn 1989, were published in the Russian press in 1990. Code page 900 slipped through into the distribution of the Russian MS-DOS 5.0 LCD.CPI codepage information file.
