Microsoft creates updated builds of the Windows Mobile operation system called Adaptation Kit Updates (AKU). These releases are rarely intended directly for consumers, and are usually a result of some extra features or fixes required by a particular Windows Mobile device. For example, if an OEM (Original Equipment Manufacturer) decides to add a new kind of external keyboard to a Windows Mobile Pocket PC, then some extra driver code will be required - in that case, Microsoft creates an AKU to drive the hardware.

Developer impact

It is rarely the case that developers need to know which device is running which AKU. The goal is that every device running Windows Mobile 5 runs every application. When a developer takes into account different screen sizes and orientations, either by design or programmatically, then the application should run on all Windows Mobile hardware.

End user impact

The end user of a device doesn't need to know anything about AKU builds. Perhaps a particular model of device will be updated to have new features (for example, push email) but that depends on whether the OEM and the operators decide to implement those features.

For more details, see ListOfAKUs