void swap(int a, int b) {
   int temp = a;                     // only local "copies" of a and b will swap
   a = b;
   b = temp;
}

int main(void) {
   int a = 5, b = 7;
   swap(a, b);
   printf("a = %d, b = %d\n", a, b); // a and b still have their original values
   return 0;
}