> How do we actually create a user interface using ada program...??
  What do you mean by a user interface?  Command line?  Dials and
switches?  GUI?  Simple?  Complex?
Others have suggested things for Unix/Windows.  There are also several
Windows bindings (look at www.adapower.com) which fill different needs.
For GUI builders, there are Claw's and Aonix's that I know of.