There is a new feature of Loader Class in this version. That is Application ‘Package’ which allows for the easy distribution of complete sets of resource in a single directory complete with its own libraries, models, helpers, config and language files. It is recommended that these packages be placed in the application/third_party folder. Lets see a sample map of an package directory:
Sample Package named ‘Left Bar’ on a Directory Map:

/application/third_party/foo_bar

config/
helpers/
language/
libraries/
models/

It has it’s own config files, helpers, language files, libraries, and models. How to use this resource in controllers, you can read fully in CodeIgniter 2.0 user_guide/libraries/loader.html.

Core System Classes
Every time CodeIgniter runs there are several base classes that are initialized automatically. It is possible to swap any of the core system classes with your own version. To use your own class please place on local application/core/your_class.php. In 1.7.2 or before you should place on application/libraries/your_class.php.

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