C and C++ define a special type for pointer arithmetic, namely ptrdiff_t, which is a typedef of a platform-specific signed integral type. You can use a variable of type ptrdiff_t to store the result of subtracting and adding pointers. For example:

Code:
#include <stdlib.h>
int main()
{
  int buff[4];
  ptrdiff_t diff = (&buff[3]) - buff; // diff = 3
  diff = buff -(&buff[3]); //  -3
}
What are the advantages of using ptrdiff_t? First, the name ptrdiff_t is self-documenting and helps the reader understand that the variable is used in pointer arithmetic exclusively. Secondly, ptrdiff_t is portable: its underlying type may vary across platforms, but you don't need to make changes in the code when porting it.