Introduction to Queues

• The queue data structure keeps lists of elements in a manner where the first item received is the item at the front (or first item out) of the queue.  This servicing scheme is called FIFO (first in-first out), and is the way we we typically expect a line to work.

• In addition to constructors, the destructor, an assignment operator, etc, typically queues have the member functions enqueue() and dequeue().  Enqueue() puts element into the queue, and dequeue() takes one out.

• Examples:  Below is a queue (of characters) with three elements.  It was create with the code:

  myQueue.enqueue('g');

  myQueue.enqueue('y');

  myQueue.enqueue('c');

• The left side of the queue is the front, so if we were to dequeue() from the queue, the 'g' would be the first element removed. 
• Queus can be implemented from an ordinary character array.
  • For example the array above could be declared as:  char storage[6];
• We may also want to keep some other information on the current state of the queue, like how many elements are in the queue (e.g. int num) and how many elements the queue could hold (e.g., int size).
• To get a complete idea of how we might do this, see the queue implementation queue.h and queue.cpp.
  • Test program for queues:  queue_test.cpp