In computer science, queueing theory is the study of queue as a technique for managing processes and objects in a computer. A queue can be studied in terms of: the source of each queued item, how frequently items arrive on the queue, how long they can or should wait, whether some items should jump ahead in the queue, how multiple queues might be formed and managed, and the rules by which items are enqueued and dequeued.
The queues that a computer manages are sometimes viewed as being in stack. An item is always added to the top of a stack. A process that handles queued items from the bottom of the stack first is known as a first-in first-out (FIFO) process. A process that handles the item at the top of the stack first is known as a last-in first-out (LIFO) process.