Services are long-living operations, as components of the apps. However, they can be started in isolation each time the device is next started, without the user's acknowledgement. This technique should be discouraged because the accumulation of these silent services results in excessive battery depletion that remains unexplained from the end-user's point of view. In addition, end-users know how to kill applications, but more rarely how to kill services. Thus, any developer should avoid having a call to Context#startService() from a Broadcast Receiver component that has specified an intent-filter for the BOOT_COMPLETED action in the manifest.