program Swap
// Input:    a, b
// Output:   b, a
// Remarks:  Swaps contents of two registers without using any temporary
//           variables.
// -----------------------------------------------------------------------------

10: 8AFF   read R[A]                     
11: 8BFF   read R[B]                     
12: 4AAB   R[A] <- R[A] ^ R[B]           a ^ b
13: 4BBA   R[B] <- R[B] ^ R[A]           b ^ (a ^ b) = a
14: 4AAB   R[A] <- R[A] ^ R[B]           (a ^ b) ^ a = b
15: 9AFF   write R[A]                    
16: 9BFF   write R[B]                    
17: 0000   halt