The other popular data structure is called a queue. The queue is a FIFO $($First In First Out$)$ data structure and you can think of it like standing in line at Disneyland. If you are fortunate enough to be first in line, then you are the first person to get on the ride. You will see the stack and the queue all over computers if you study operating systems. The stack is used to store and keep track of variables and the queue is used to store data that is waiting to be processed. This is just to name a couple ways they are used. In the operating system, tasks that are being scheduled to run are put into the queue. There is a slight difference in that many of these queues are called priority queues in that each task added to the queue is assigned a priority. The higher the priority a task has, the closer it gets to the front of the queue.