KOI8-U
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KOI8-U is an 8-bit character encoding, designed to cover Ukrainian, which uses the Cyrillic alphabet. It is based on KOI8-R, which covers Russian and Bulgarian, but replaces eight graphic characters with four Ukrainian letters Ґ, Є, І, and Ї in both upper case and lower case.
KOI8 remains much more commonly used than ISO 8859-5, which never really caught on. Another common Cyrillic character encoding is Windows-1251. In recent times, both might eventually give way to Unicode.
In Russian, KOI8 stands for Kod Obmena Informatsiey, 8 bit (Код Обмена Информацией, 8 бит) which means "Code for Information Exchange, 8 bit".
The KOI8 character sets have the property that the Russian Cyrillic letters are in pseudo-Roman order rather than the natural Cyrillic alphabetical order as in ISO 8859-5. Although this may seem unnatural, it has the useful property that if the 8th bit is stripped, the text can still be read (or at least deciphered) in case-reversed transliteration on an ordinary ASCII terminal. For instance, "Русский Текст" in KOI8-U becomes rUSSKIJ tEKST ("Russian Text") if the 8th bit is stripped.
| KOI8-U | ||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| x0 | x1 | x2 | x3 | x4 | x5 | x6 | x7 | x8 | x9 | xA | xB | xC | xD | xE | xF | |
| 0x | unused | |||||||||||||||
| 1x | ||||||||||||||||
| 2x | SP | ! | " | # | $ | % | & | ' | ( | ) | * | + | , | - | . | / |
| 3x | Template:Num | Template:Num | Template:Num | Template:Num | Template:Num | Template:Num | Template:Num | Template:Num | Template:Num | Template:Num | : | ; | < | = | > | ? |
| 4x | @ | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O |
| 5x | P | Q | R | S | T | U | V | W | X | Y | Z | [ | \ | ] | ^ | _ |
| 6x | ` | a | b | c | d | e | f | g | h | i | j | k | l | m | n | o |
| 7x | p | q | r | s | t | u | v | w | x | y | z | { | | | } | ~ | |
| 8x | ─ | │ | ┌ | ┐ | └ | ┘ | ├ | ┤ | ┬ | ┴ | ┼ | ▀ | ▄ | █ | ▌ | ▐ |
| 9x | ░ | ▒ | ▓ | ⌠ | ■ | ∙ | √ | ≈ | ≤ | ≥ | NBSP | ⌡ | ° | ² | · | ÷ |
| Ax | ═ | ║ | ╒ | ё | є | ╔ | і | ї | ╗ | ╘ | ╙ | ╚ | ╛ | ґ | ╝ | ╞ |
| Bx | ╟ | ╠ | ╡ | Ё | Є | ╣ | І | Ї | ╦ | ╧ | ╨ | ╩ | ╪ | Ґ | ╬ | © |
| Cx | ю | а | б | ц | д | е | ф | г | х | и | й | к | л | м | н | о |
| Dx | п | я | р | с | т | у | ж | в | ь | ы | з | ш | э | щ | ч | ъ |
| Ex | Ю | А | Б | Ц | Д | Е | Ф | Г | Х | И | Й | К | Л | М | Н | О |
| Fx | П | Я | Р | С | Т | У | Ж | В | Ь | Ы | З | Ш | Э | Щ | Ч | Ъ |
In the table above, 20 is the regular SPACE character, and 9A is the NO-BREAK SPACE.
The difference with KOI8-R consists of the positions 0xA4; 0xA6; 0xA7; 0xAD; and 0xB4; 0xB6; 0xB7; 0xBD; which consist of extra letters that don't exist in Russian.
Although RFC 2319 says that character 95 should be U+2219 (∙), it may also be U+2022 (•) to match the bullet character in Windows-1251.
Some references have a typo and incorrectly state that character B4 is U+0403, rather than the correct U+0404. This typo is present in Appendix A of RFC 2319 (but the table in the main text of the RFC gives the correct mapping).