I have seen many task killer apps, which claim to kill the apps in background, but once I use them, I find out that what they do is just vanish the apps from their list view and fool the user that they are killed.

If I open the same task killer app again within seconds, the same app will again be there which was claimed to be killed earlier. Now is this a fault of the app or the Android OS?

Not only here, even with apps having an *Exit* option, I have noticed that clicking the exit button does not terminate it. So where is the problem?

Long ago I read that there is no function provided in Android to kill an app (I don't know about current time). So shall the blame be given to the OS? Is there a proper way yet to close an app when we want and make it behave normally?