Queues (using arrays)

•Queues are a familiar aspect of everyday life: people often wait in-line for a bus or to be served in a bank.

•Queues are commonplace in computing: in a real-time system, there are queues of processes waiting to use processor(s), queues of jobs waiting to use a computing resource, e.g., a printer, etc.

•The general concept of a queue is a line of objects that has a front and a rear: the first object in the queue is at the front of the queue and the last object is at the rear of the queue; objects join at the rear and leave from the front

•Queues operate on a First In First Out (FIFO) basis

•A queue is a commonly occurring data structure with the properties that we can:

•Add a value to the back of the queue

•Remove the value from the front of the queue

•Discover the Size of the queue

•A queue needs to keep track of the front (head) and back (tail) positions.

The applet represents the more abstract representation of a queue. The code based representation is shown in this applet.

The following applet represents a simple queue at a shop. You just enter a customers name and click Add to add him to the queue. Suppose each customer is new information in a system. The first information going in is the first one to leave.

* Code taken from Lecture 2 in Data Structures Semester 2 2005 by Mr. Chris Cox for Oxford Brookes University.