Because it is necessary for applications sharing limited resources to cooperate with one another, Windows CE provides the hibernation message. The H/PC shell sends a WM_HIBERNATE message whenever system resources are low. The hibernation message advises applications to release any resources they do not need to recover their current state when they are reactivated. The release of resources by other applications allows the one currently in the foreground to complete its task. For information on using the WM_HIBERNATE message, see Writing Memory-Efficient Applications.