Why do website not show after uploaded to host?

I has used FileZilla upload all source code of website to host, has imported database successfully, and deleted file default.php in folder public_html , but when I enter the website address, it only shows file welcome.php like this:
Welcome to CodeIgniter!
The page you are looking at is being generated dynamically by CodeIgniter.
If you would like to edit this page you'll find it located at:
application/views/welcome_message.php
The corresponding controller for this page is found at:
application/controllers/welcome.php
If you are exploring CodeIgniter for the very first time, you should start by reading the User Guide.
After I set ../application/config/routes.php like this :

PHP Code:

$route['default_controller'] = "cHome"; 


cHome is controller of home page of website, it shows error like this :
404 Page Not Found

The page you requested was not found.
I've replaced the other controllers on it but still have the same result, try site_url() or base_url() function, it shows error like this function is not defined. Source I uploaded not to modify configuration anything. I don't understand why. Everybody help me. Thanks!