int main() {
   struct Books Book1;        // Declare Book1 of type Book
   struct Books Book2;        // Declare Book2 of type Book
   // book 1 specification
   strcpy( Book1.title, "C Programming");
   strcpy( Book1.author, "Dennis Ritchie"); 
   strcpy( Book1.subject, "C Programming");
   Book1.book_id = 6495407;
   // book 2 specification