Unicode support in postgresql code

Hi,

Any one could throw some light on how the unicode support is enabled in
the postgresql code? I know that this is a step during the installation
to select the default locale of the postgresql system & other place is
during the creation of a database, there is a option to select the
language (not programming language, human spoken language).

There are a set of C source code available in src/backend/utils/mb.
There are couple of other directories viz., Unicode & conversion_procs
under src/backend/utils/mb. How these code work?

I appreciate & thank for your response in advance.

thanks
kalyan