Have a look at Codeigniter URLs
As per your statement, your controller name is index and there would be an index function in your controller which renders the default view. it means you have changed default_controller to index in your Config.php
Now if you read the link above about Codeigniter URLs, there is a way to get data which passed in the URL after "/" You have to load url helper you can either autoload(recommended) it or load it in your constructor or Controller as per your convenience
Then you can just type
$param=$this->uri->segment(2); // in case your URL is http://www.example.com/AALI
The first segment is controller itself, The second is the function if your url is complete and the third is the parameter in CI URL structure but if you are not providing function name the first segment will always be your controller . So the second is your parameter. Just save it in a variable and do what you like.