CodeIgniter是否始终将控制器与URI的一部分相关联？

This is my first attempt to work/learn CodeIgniter. However, I'm struggling in understanding the "C".

1) Does CodeIgniter always associate a controller to a segment of a URI?

2) What are the best practices to work with controllers? I mean, how can I avoid dumping all my methods in a single controller? Can I split a controller in several files without creating unnecessary URI.

1.Yes controller always associate to segment of a URI. If your controller is under some directory like

controllers 
    search ---------------------directory inside controller
       search ------------------controller
           stock_search -------------------method

then it will add whole path in the uri segment e.g :basepath.'search/search/stock_search/';

But you can route it your custom path using routes.php $route['search'] = 'search/search/stock_search/';

2.You can create different controllers (name should be different) with the different methods or you can say you can split controller methods in different files and customise their url accordingly in routes.php and can create parent controller to use methods in any controller by extending through it.

If you want to get something in codeigniter then codeigniter send the request to a controller. URI must have a controller if no controller in uri then the reguest is goes to default controller which is tell in application/config/routes.php in this code $route['default_controller'] = 'welcome';

And will not be able to split a controller in several files without creating more than one URI.

Controller is associated to url segments.

Url used in Codeigniter is as follows: http://example.com/index.php/projname/controller/method/params.

If you dont specify controller in uri, default controller is called specified in routes.php $route['default_controller'] = 'welcome';