Hi,

Is there a way in context, that for some *text* ascii input (in source .tex
file) define mapping in internal tex system ?

For example, if i put two ascii characters "dj" in .tex file, can i  get
cyrillic character "ђ" in .pdf ?
And so on, for input b, v, g, d, ... to get output б, в, г, д, ...

Or more general, for every letter/string in unicode to define the way that
it should be read.

It's benefit for non ascii language users, because in that case they don't
need to switch keyboard layout all the time between command, math input and
text input.

In Latex, package fontenc(precisely OT2 encoding) do that things.

Minimal example:

\starttext

a, b, v, g, d, dj, e, zh, z

\stoptext

should produce

a, б, в, г, д, ђ, е, ж, з

Best regards,
Sava Maksimovic (Сава Максимовић :) )