483: Mainline

Once you have introduced enumeration constants, you can improve the clarity of the switch statement by replacing the integers with those enumeration constants:

switch (type_code) { 
  case eng_code: train[n] = new engine;   break; 
  case box_code: train[n] = new box_car;  break; 
  case tnk_code: train[n] = new tank_car; break; 
  case cab_code: train[n] = new caboose;  break; 
}