Queue Overview

• A second standard data type is a queue
  • The queue is a homogenious collection of data.
  • It maintains data in the order received
  • It is charactarized by access
    • First in First Out (FIFO)
    • Or last in last out.
  • There are several basic operations
    • Enqueue adds an item to the "tail" or end of the queue
    • Dequeue removes and item from the front of a queue
      • This should produce an error if the queue is empty
      • Some implementations this returns the front item.
    • Front returns the front item on the queue without removing it.
      • This should produce an error if the queue is empty
    • Size returns the number of elements in the queue.
    • IsEmpty returs true if the queue is empty.
    • IsFull returns true if the queue is full.
• Again there are two common implementations.
  • Both maitain a front pointer to the item at the front of the queue
  • And a rear pointer to the item at the back of the queue.
  • The array based implementation
    • This is more difficult as you need to "circle" through the array.
  • The list based implementation is straight forward
    • The head pointer is the front of the queue
    • The last item in the queue is the rear