[TYPO3-mvc] Class ActionController not found

[B L Praveen]

Yes. I am able to view the new extension.

After changing all the classes extends to path \TYPO3\CMS\Extbase\. I am not getting fatal error

I have one question. When I check the the path specified  there exists no class. Where the class actually resides

In typo3 6 versions Extbase is installed by default in sysext.

When I use the path to sysext. I get fatal errors even though class exists. 

I know about php includes/require but how this in typo3 includes a  class or autloads by giving the path  "\TYPO3\CMS\Extbase\";

Can anybody provide me some documentation on basic concepts,how to autoload,extend core class and sysext class,