Definition of Queue A Queue is "an abstract data type in which elements are added to the rear and removed from the front; a 'first in, first out' (FIFO) structure." ( C++ Plus Data Structures , page 226) The main difference between a queue and a stack is that elements in a queue are put on the bottom and taken off the top (remember, in a stack, elements put on the top and taken off the top). For an everyday queue example, consider a line of customers at a bank waiting to be served. Each new customer gets in line at the rear. When the teller is ready to help a new customer, the customer at the front of the line is served. This is a queue--the first customer in line is the first one served. 1.1 Applications of a Queue In general, queues are often used as "waiting lines". Here are a few examples of where queues would be used: In operating systems, for controlling access to shared system resources such as printers, files, communication lines, disks and tapes.A ...