Inserting An Element

 void  List::insert_at_front(int  val)  {
     Node  *node  =  new  Node(val);
     node->next  =  head;
     head  =  node;
 }
or more concisely
 void  List::insert_at_front(int  val)  {
     head  =  new  Node(val,  head);
 }