Q:

How do I check the character set used by ubuntu and probably change it

As the subject says, I am curious to know what character-set is used by Ubuntu, is it ASCII or something else like utf-8/utf-16 etc. And  if possible how can i change the default character set.

A:

Locales customize programs to your language and country. When you
  installed Ubuntu, you answered some simple questions such as
  specifying your country and language. Ubuntu used the answers to those
  questions, in part, to choose a suitable locale for your installation.
The basic functionality is provided by the locale package, which is
  installed by default. Actual locales are installed separately via the
  language-pack-* packages.

Most users want a single locale to be used for all aspects of their
  session. In this case, the GUI provided by System Settings -> Language
  Support does the right thing. 
Below are some of the things that you can do:

List installed locales
List current settings
Changing settings temporarily
Changing settings permanently
(Re-)Generating locales1

Read On
1Source:Ubuntu Documentations

