Created user controller in 'controllers/admin/user.php'. Created folder in 'views/admin/user' and added view file 'login.php'.
Modified 'controllers/admin/user.php' and added function 'login()'. Modified view 'views/admin/_layout_modal.php' to display subview like login page. Modified file 'views/admin/user/login.php' that's the view for login page. Modified 'config/autoload.php' and autoload the 'html' helper. Modified Admin_Controller.php file to load 'form' helper and 'form_validation' library.
Modified MY_Model.php and set var  to public. Created user model 'models/user_m.php', overrides variables at the model MY_Model.php. Modified Admin_Controller.php and load model 'user_m'.