The purpose of this post is to expand on the following sentence [1]:
Russian letters are created by entering [Ctrl-k followed by] a corresponding Latin letter followed by an equals sign -, or, in a few places, a percent sign %.
The Russian alphabet has 33 letters, so there couldn’t be a Latin letter for every Russian letter. Also, there are Latin letters that don’t have a Russian counterpart and vice versa. So the mapping can’t be simple. But still, the above summary is nice: try control-k followed by the English analog and the equal sign. If that doesn’t work, try a percent sign instead.
Which Latin letters does Vim chose as corresponding to Russian letters? Does it go by sound or appearance? For example, the Russian letter Н looks like a Latin H but it sounds like a Latin N. Vim goes by sound. You would enter the Russian letter Н by typing Ctrl-k N =.
For full details, see the Vim documentation :h digraph-table. I give a simplified excerpt from the documentation below. I just look at capital letters because the lower case letters are analogous. All the official Unicode names begin with CYRILLIC CAPITAL LETTER and so I cut that part out.
char digraph hex official name А A= 0410 A Б B= 0411 BE В V= 0412 VE Г G= 0413 GHE Д D= 0414 DE Е E= 0415 IE Ё IO 0401 IO Ж Z% 0416 ZHE З Z= 0417 ZE И I= 0418 I Й J= 0419 SHORT I К K= 041A KA Л L= 041B EL М M= 041C EM Н N= 041D EN О O= 041E O П P= 041F PE Р R= 0420 ER С S= 0421 ES Т T= 0422 TE У U= 0423 U Ф F= 0424 EF Х H= 0425 HA Ц C= 0426 TSE Ч C% 0427 CHE Ш S% 0428 SHA Щ Sc 0429 SHCHA Ъ =" 042A HARD SIGN Ы Y= 042B YERU Ь %" 042C SOFT SIGN Э JE 042D E Ю JU 042E YU Я JA 042F YA
Note that the end of the alphabet is more complicated than simply using a Latin letter and either an equal or percent sign. Also, the table is in alphabetical order, which doesn’t quite correspond to Unicode numerical order because of a quirk with the letter Ё (U+0401) explained here.
[1] Arnold Robbins and Elbert Hannah. Learning the vi & Vim Editors, 8th edition