为何mfc使用MAKEINTRESOURCE

LPCTSTR xx = MAKEINTRESOURCE(IDD_DIALOG1);
hwnd=CreateDialog(hInstance,MAKEINTRESOURCE(IDD_DIALOG1),NULL,(DLGPROC )WindowProc);//主对话框
ShowWindow(hwnd,SW_SHOWNORMAL);
UpdateWindow(hwnd);
SendMessage(hwnd, WM_SETICON, (WPARAM)TRUE, (LPARAM)LoadIcon(GetModuleHandle(NULL), (LPCTSTR)IDI_SMALL));//添加窗口小图标
MSG msg;
while(GetMessage(&msg,NULL,0,0))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}