1 5. Abstract Data Structures & Algorithms 5.1 Data Structure Fundamentals

5.1.3 Queues: Definition

3 Definitions Data are inserted at one end and retrieved from the other. Think of a queue of humans – people arrive at the back and have to work their way to the front.

4 Definitions FIFO structure (First In First Out). Items are dealt with in the order they arrive. This presentation is a queue of slides.

5 Uses Maintaining a list of data to be transferred between the processor and printer (a print queue or print buffer) or other peripheral device. A keyboard queue is similar (characters are buffered in a small amount of memory and then sent to the processor in the order that their keys were pressed).

6 More on printer queues Printers on a LAN buffer jobs in a queue and deal with them in order. This is more obvious with a slower printer or if you watch the print queue on a print server. The print server will also hold a print queue.

7 Uses Queues are more common in real life, so queue simulations are more common than stacks: ‣ supermarket checkouts ‣ traffic lights ‣ air traffic control