Big O-Notation is a way to measure how long the algorithm runs. O(1) or "constant time" means it takes just one step to run. If you have 1 item or 1000 items O(1) will still run it in one step. Whereas O(n) or "linear time" where "n" is the number of items. So if you have 10 items it will print 10 items, if you have 1000 items it will print 1000 times