Code page 866 is a code page

Code page

Code page is another term for character encoding. It consists of a table of values that describes the character set for a particular language. The term code page originated from IBM's EBCDIC-based mainframe systems, but many vendors use this term including Microsoft, SAP, and Oracle Corporation...

 used under MS-DOS

MS-DOS

MS-DOS is an operating system for x86-based personal computers. It was the most commonly used member of the DOS family of operating systems, and was the main operating system for IBM PC compatible personal computers during the 1980s to the mid 1990s, until it was gradually superseded by operating...

 to write Cyrillic script. It is based on the "alternative character set" of GOST

GOST

GOST refers to a set of technical standards maintained by the Euro-Asian Council for Standardization, Metrology and Certification , a regional standards organization operating under the auspices of the Commonwealth of Independent States .All sorts of regulated standards are included, with examples...

 19768-87. The code was widely used during MS-DOS era because it preserves the pseudographic symbols (unlike Windows-1251

Windows-1251

Windows-1251 is a popular 8-bit character encoding, designed to cover languages that use the Cyrillic alphabet such as Russian, Bulgarian, Serbian Cyrillic and other languages...

) and maintains alphabetical order (although non-contiguously) of Cyrillic letters (unlike KOI8-R

KOI8-R

KOI8-R is an 8-bit character encoding, designed to cover Russian, which uses the Cyrillic alphabet. It also happens to cover Bulgarian, but is not used since CP1251 is accepted. A derivative encoding is KOI8-U, which adds Ukrainian characters...

).

Code page layout

Each character is shown with its equivalent Unicode

Unicode

Unicode is a computing industry standard for the consistent encoding, representation and handling of text expressed in most of the world's writing systems...

 code point and its decimal code point. Only the second half of the table (code points 128–255) is shown, the first half (code points 0–127) being the same as ASCII

ASCII

The American Standard Code for Information Interchange is a character-encoding scheme based on the ordering of the English alphabet. ASCII codes represent text in computers, communications equipment, and other devices that use text...

.
>