What is the Output of above Program ?

It all depends on swap2 function definition. If, for instance, the swap2 function is defined for destroying the Universe then the program would abruptly terminate.


The following C program

#include <stdio.h>
int main()
{
  int x = 5, y = 10;
  swap2(x, y);
  printf("%d, %d\n", x, y);
  swap2(x, y);
  printf("%d, %d\n", x, y);
  return 0;
}

Will always output

5, 10
5, 10

for any correct implementation of the swap2 function, since the swap2 prototype must be

void swap(int x, int b);

(actually you can use another type for return value).


In C++ programming language the scenario may change, defining, for instance, swap2 this way

void swap2( int & a, int & b)
{
  int t = a;
  a = b;
  b = t;
}

Could you guess the actual output?