Suppose an item needs to be dequeued. To calculate the new start location, use the invariant: (start + i) mod cells_length = (start + 1) mod cells_length = (7 + 1) mod 8 = 8 mod 8 = 0
(start + i) mod cells_length = (start + 1) mod cells_length = (7 + 1) mod 8 = 8 mod 8 = 0