Queue: Queue; Post: The queue has been created and is initialized to be empty Error code Queue append (const Queue entry &x) Post: If there is space, x is added to the queue as its rear. otherwise an error code of overflow is returnedQueue :: Queue( ); Post: The Queue has been created and is initialized to be empty. Error_code Queue :: append(const Queue entry &x); Post: If there is space, x is added to the Queue as its rear.Otherwise an Error code of overflow is returned