Consider a double-ended queue (deque) of characters. A deque differs from a standard queue in that it allows objects to be added and deleted from both ends of the queue. Contrast this to a standard queue, where objects can only be added to the end of the queue and removed from the front.

1. What operations would you expect of a deque ADT?
2. What are the pre- and post-conditions of these operations?
3. Fully specify the behaviour of a deque ADT by specifying the complete behaviour of each operation of the deque ADT.
4. Write a non-cyclic block implementation of the deque ADT you specified above.