message "константа сообщения"

program A;

uses Windows.h;

var Wc: TWndClassEx; Msg: TMsg;

function WindowProc(Wnd: HWND; Msg: UINT; wParam: WPARAM; lParam: LPARAM): LRESULT; stdcall;
begin
case Msg of
     WM_DESTROY:
           begin
           PostQuitMessage(0); // PostMessage(Wnd, WM_QUIT, 0, 0);
           Result:=0;
           Exit;
           end;
     else
           begin
           Result:=DefWindowProc(Wnd, Msg, wParam, lParam);
           end;
     end;
end;

begin
Wc.cbSize:=SizeOf(Wc);
Wc.style:=CS_HREDRAW Or CS_VREDRAW;
Wc.lpfnWndProc:=@WindowProc;
Wc.cbClsExtra:=0;
Wc.cbWndExtra:=0;
Wc.hInstance:=hInstance;
Wc.hIcon:=LoadIcon(0, IDI_APPLICATION);
Wc.hCursor:=LoadCursor(0, IDC_ARROW);
Wc.hbrBackground:=COLOR_WINDOW;
Wc.lpszMenuName:=Nil;
Wc.lpszClassName:='A';
RegisterClassEx(Wc);
CreateWindowEx(0, 'A', 'TitleA', WS_VISIBLE Or WS_OVERLAPPEDWINDOW, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, 0, 0, hInstance, Nil);
while GetMessage(Msg, 0, 0, 0) do
     begin
     TranslateMessage(Msg);
     DispatchMessage(Msg);
     end;
end.