Suppose a new item needs to be enqueued. To calculate its location, use the invariant: (start + i) mod cells_length = (start + queue_length) mod cells_length = (7 + 4) mod 8 = 11 mod 8 = 3
(start + i) mod cells_length = (start + queue_length) mod cells_length = (7 + 4) mod 8 = 11 mod 8 = 3