Queue

In a queue,the elements are inserted from one end and the elements are deleted from the other end.The end from where the elements
are inserted is called REAR end and the end from where the elements are deleted is called FRONT end.Since the first item
inserted is the first item to be deleted from the Queue,Queue is also called First In First Out(FIFO) data structure.In a queue
elements are always inserted from the rear end and elements are deleted from the front end.The pictorial representation of the queue
can be shown as:
                                          
                                              f       r
                                       0   1   2   3   4
                       Delete< -------10  20  30        <----------  Insert
                       
                       FRONT END                                      REAR END
                       
TYPES OF QUEUES
      1. QUEUE(ORDINARY QUEUE)
      2.CIRCULAR QUEUE
      3.DOUBLE ENDED QUEUE
      4.PRIORITY QUEUE