継承？

#include 
typedef struct _parent {

  int x;

} parent;
typedef struct _child {

  int x;

  int y;

} child;
int main() {

  parent *p;

  child c;
  c.x = 10;

  c.y = 20;
  p = (parent*) &c;
  printf("%d\n", p->x);

  return 0;

}

継承になるのかなぁ…