this is a gcc file, you can download it and learn its usetility, for further detail please look at t

				jumptab (a)				{				  int b;				  switch (a)				    {				    case 0:				      b = 6;break;				    case 1:				      b = 5;break;				    case 2:				      b = 4;break;				    case 3:				      b = 3;break;				    case 4:				      b = 2;break;				    case 5:				      b = 1;break;				    }				  return b;				}