## Chapter 7. Classes

Class files are used to abstract common functionality and share it amongst multiple `.bb` files. Any metadata usually found in a `.bb` file can also be placed in a class file. Class files are identified by the extension `.bbclass` and are usually placed in a `classes/` directory beneath the `meta*/` directory found in the Source Directory. Class files can also be pointed to by BUILDDIR (e.g. `build/`)in the same way as `.conf` files in the `conf` directory. Class files are searched for in `BBPATH` using the same method by which `.conf` files are searched.

In most cases inheriting the class is enough to enable its features, although for some classes you might need to set variables or override some of the default behaviour.