Post Message

Places (posts) a message in the message queue associated with the thread that created the specified window and returns without waiting for the thread to process the message.

Syntax:

BOOL WINAPI PostMessage(

  opt_  HWND hWnd,

        UINT Msg,

        WPARAM wParam,

        LPARAM lParam

);

Parameters

hWnd [in, optional]

Type: HWND

A handle to the window whose window procedure is to receive the message. The following values have special meanings.

HWND_BROADCAST : The message is posted to all top-level windows in the system, including disabled or invisible unowned windows, overlapped windows, and pop-up windows. The message is not posted to child windows.

NULL: The function behaves like a call to "PostThreadMessage" with the dwThreadId parameter set to the identifier of the current thread.

Msg [in]

Type: UINT

The message to be posted.

wParam [in]

Type: WPARAM

Additional message-specific information.

lParam [in]

Type: LPARAM

Additional message-specific information.




Source:MSDN