As stated by other members that not every framework has an Autoloader but I believe that every framework should.
If you can understand what a framework does than you should understand that there designed to be modular, being able to add and remove components easily, if you was to hard code all your libraries models, controllers etc then when you add new libraries you would have to recode for the library to work.
So that's the convenience part of the autoloader, the other part is the performance and resource management side of it, The base idea of the autoloader is to load the files only when required.
so on your index.php page you may need 5 libraries, but on your register.php you may only need 2 libraries, so that using an autoloader will save you 3 includes on your register page.
It also allows a better file structure as your components are separated and organized.
as you may be looking into placing an autoloader into your framework i strongly recommend you look at the *PSR-0* standards that is currently in use in Zend and many other high end framework, the link can be found below:
[To see links please register here]