A queue is another linear data structure which follows the FIFO principle. A queue allows two basic operations on the collection. The first one is enqueue which allows us to add an item to the back of the queue. The second one is dequeue which allows us to remove an item from the front of the queue. A queue is another of the most used data structures in computer technology. We will learn details about queues in Chapter 4, Consrtucting Stacks and Queues.