For example, an application built in BlackBerry JDE 6.0 runs on a BlackBerry smartphones running BlackBerry Device Software 6.0 and later. It does not run on a BlackBerry smartphones running BlackBerry Device Software 5.0 and prior. Thus, when building applications, you should use a BlackBerry JDE version that matches the lowest version of BlackBerry Device Software you want to support.
Newer versions of the JDE provide additional APIs and features. The APIs and features which were introduced with each BlackBerry Java OS version are described here.
Additional information regarding BlackBerry OS usage can be found here.