981130-1.c

this is a gcc file, you can download it and learn its usetility, for further detail please look at t

struct s { int a; int b;};
struct s s1;
struct s s2 = { 1, 2, };

void
check (a, b)
     int a;
     int b;
{
  if (a == b)
    exit (0);
  else
    abort ();
}

int
main ()
{
  int * p;
  int x;
  
  s1.a = 9;
  p    = & s1.a;
  s1   = s2;
  x    = * p;
  
  check (x, 1);
}