Using the Compatibility Library for Older Devices
The Android platform has gone through an impressive evolution since it was first introduced several years ago. While the intention has always been for Android to power lots of different types of devices, it wasn’t architected from the beginning to meet that goal. Instead, the Google engineers have added, removed, and changed APIs in order to provide new features. One of the biggest changes was the creation of fragments in order to handle larger screen sizes such as on tablets and TVs. But there have been other changes such as with ActionBar and Menus.
The new APIs created a difficult problem for developers who wanted their applications to run on the new devices with the new APIs