I have a minor question about this diagram I'm hoping someone can clear up for me. The deque has initial capacity 4. The following operations are performed. push_back(1) push_back(2) push_back(3) pop_front() pop_front() push_back(4) push_front(5) push_front(6) push_front(7) final answer: I'm just wondering what the space above the letter 'E' is supposed to signify. I thought there were only 2 empty slots in the deque for the 2 pop_front operations at initial capacity 4.