Insertion and Deletion in a Queue

Algorithm  (INSERT) :-
Step 1 :- If(rear == maxsize - 1)
                output "Queue overflow and return"
                  else
                   set rear = rear + 1
Step 2 :- [Insert an element]
               queue[rear] = item
Step 3 :- [set front pointer]
                If front == -1
                 then front = 0
Step 4 :- Return 

Algorithm (DELETION) :-

Step 1 :- If (front>rear)|| front == -1
              Output "Queue underflow"
               Exit
Step 2 :-[Remove an element]
              item = queue[front]
Step 3 :-[check for empty queue]
              if(front == rear)
                 front = 0
                 rear = -1
                 else
                  front = front + 1

Disadvantage of Queue:-

 Consider the following queue as show below:-

 0    1    2    3    4  
10  20  30  40  50

• This situation arises when 5 element say 10, 20, 30, 40, 50
• are inserted and then deleting first four element
• If we try to insert an element 60, since rear (r) has value maxsize - 1 we get an overflow condition and it is not possible to insert any element
• Even through queue is not full , in this case it is not possible to insert any item into the queue .
• This disadvantage can over-come if we use the circular queue