void main()
{
  int  x;
  int* xp;
  int  y;
  x = 4;
  y = 5;
  xp = &x;     // value of *xp should be 4
  xp = xp + 2; // what happens?
  *xp = 6;     // puts 6 in memory somewhere, where?
  xp = xp - 2; // what happens?
  *xp = 7;     // puts 7 somewhere in memory, where?
}