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WM_POWER Overview  Group

The WM_POWER message is sent when the system, typically a battery-powered personal computer, is about to enter suspended mode.

The WM_POWER message is obsolete. It is provided to simplify porting of 16-bit Windows-based applications. New Win32-based applications should use the WM_POWERBROADCAST message.


fwPowerEvt = wParam;    // power-event notification message 



Value of wParam. Specifies a power-event notification message. This parameter can be one of the following values:




Indicates that the system is resuming operation after entering suspended mode without first sending a PWR_SUSPENDREQUEST notification message to the application. An application should perform any necessary recovery actions.


Indicates that the system is about to enter suspended mode.


Indicates that the system is resuming operation after having entered suspended mode normally ¾ that is, the system sent a PWR_SUSPENDREQUEST notification message to the application before the system was suspended. An application should perform any necessary recovery actions.

Return Values

The value an application returns depends on the value of the wParam parameter. If wParam is PWR_SUSPENDREQUEST, the return value is PWR_FAIL to prevent the system from entering the suspended state; otherwise, it is PWR_OK. If wParam is PWR_SUSPENDRESUME or PWR_CRITICALRESUME, the return value is zero.


This message is sent only to an application that is running on a system that conforms to the Advanced Power Management (APM) basic input/output system (BIOS) specification. The message is sent by the power-management driver to each window returned by the EnumWindows function.

The suspended mode is the state in which the greatest amount of power savings occurs, but all operational data and parameters are preserved. Random-access memory (RAM) contents are preserved, but many devices are likely to be turned off.

See Also


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