C++ casting type question?

Your question is not clear to me. Can you try explaining again what you are trying to do? What do you want to be recognised as an int? The pointer to num or the value contained in num? If it's the value contained in num, do you expect it to be interpreted as an integer with value 12345? If so, that's not going to happen. You need to find another way to convert from a character string to an integer, e.g. using sscanf(), itoa() or something.