#include <stdio.h>

struct s{                /*ena struct me ena pedio int*/
  int i;
};

int main()
{
  struct s *p;         /* orizw ena dikth se struct s*/
  int r=5;             /* mia topiki metavlith me timi 5*/

  printf("Memory location: %p\n", (void *)p);
  fflush(stdout);      /* flush content, before it crashes */

  p->i=r;

  printf("%d",p->i);    /* ektyponw to apotelesma tis prakseis^^*/
  return 0;
}


[stathis@netbsd ~] gcc -Wall -W -ansi -pedantic -g kapnos.c -o kapnos 
[stathis@netbsd ~] ./kapnos
Memory location: 0x80487a0
Segmentation fault (core dumped)