There is a small bug there, should be: Z = .X + .Y Since variables are names of addresses, you have to de-reference the X and Y addresses, add them, and, (cru

There is a small bug there, should be: Z = .X + .Y Since variables are names of addresses, you have to de-reference the X and Y addresses, add them, and, (crucially), the result gets stored: in the place pointed to by Z --- you don't care what .Z is anymore, as you are about to overwrite it. When you think of it that way, z = x + y seems 'wrong' because the meaning of a variable name is different on the LHS and the RHS of '='