笨。 一些基本课程在哪里？

I just have started working with codeIgniter and want to know how things in CodeIgniter? such as

1. Where is this extended class located?

   class Mystations extends CI_Controller{
   //--- class content }
   

2. Where can find "load" and "model" ?

   $this->load->model('user_model');
   

3. Though I'm aware of using CI active queries, I don't know how things work in background or where mysql_conect is used in CI.

Since the source is hosted on GitHub, you can search the actual code to find what you're after. For instance:

1. CI_Controller search : result (system/core/Controller.php)

2. function model search : result (system/core/Loader.php)

3. mysqli connnect search : result (system/database/drivers/mysqli/mysqli_driver.php)

1. Your own extended libraries lies in application/libraries. Read about extending here.
2. This question is rather unclear. Your models lies in application/models. Read about models here.
3. You connect to your database through config/database.php by providing your settings. You autoload it in config/autoloads.php.

Note that my answer mostly consists of refering to CodeIgniters User Guide. Their guides are really good and helps you very far on your own.

CodeIgniter + Google + knowing what to search for = Success!