bool Extended_queue::full() const/* Post: Return trueif the Extended_queue is full; return false otherwise. */{}void Extended_queue::clear()/*Post: All entries in the Extended_queuehave been deleted; the Extended_queue is empty. */{}Error_code Extended_queue::serve_and_retrieve(Queue_entry &item)/* Post: Return underflow if the Extended_queueis empty.Otherwise remove and copy the item atthe front of the Extended_queue to item. */{ if ( ) return ;else {count--;item = ;front = ( ) ? 0 : (front + 1);}return ;}