where is Controller class in CI

[eluser]Zorancho[/eluser]
It goes by the MVC pattern. First the index.php file, constants are being defined and paths of the system and application folders, then system/codeigniter/CodeIgniter.php file is being called and on line 148 in it the Controller class is being called. Have a look at the CodeIgniter.php file and all the files that it includes there and what those files do.