Queues

Abstract

Aqueueis a sequential, homogeneous, variable-sized, possibly empty collection of objects whose attributes and operations satisfy the following:

• 1. A queue is said to beemptywhen it contains no objects.

• 2. A queue has two ends, called thefrontand therear.

• 3. The only object in a queue that is visible is the object at the front of the queue.

• 4. The Dequeue operation removes the object currently at thefrontof the queue. All remaining objects in the queue, if any, move one position forward toward the front of the queue. The object immediately following the front object becomes the new front of the queue. If there are no other objects in the queue, the queue becomesempty.

• 5. The Enqueue operation inserts new objects at therearof the queue. If the queue was empty, the enqueued object becomes the front object in the queue. At any time, new objects may be enqueued. When an object is enqueued, it becomes the rear object in the queue.