CWindow( HWND hWnd = NULL );
Parameters
hWnd
[in] The handle to a window.
Remarks
The constructor. Initializes the m_hWnd member to hWnd, which by default is NULL.
Note CWindow::CWindow does not create a window. Classes CWindowImpl, CContainedWindow, and CDialogImpl (all of which derive from CWindow) provide a method to create a window or dialog box, which is then assigned to CWindow::m_hWnd. You can also use the CreateWindow Win32 function.