The document presents an overview of queues, defining them as ordered collections of elements with FIFO (first-in-first-out) processing. It details various types of queues, including linked queues and circular queues, and provides algorithms for insertion and deletion. Additionally, the document discusses practical applications of queues in real-life scenarios and computer science, such as ticket distribution and round-robin scheduling.

1. Presentation on:
QUEUE Presented By:
MAYANK SETH
MCA/25002/18

2. QUEUE

3. Queue
 Ordered collection of homogeneous elements
 Non-primitive linear data structure.
 A new element is added at one end called
rear end and the existing elements are deleted
from the other end called front end.
 This mechanism is called First-In-First-Out
(FIFO).

4. Fig: Models of a Queue

5. Operations On A Queue
To insertion/addition
of element(ENQUEUE)
TO deletion/removal
of element(DEQUEUE)

6. ENQUEUE
Placing an item in a queue is called
“insertion or enqueue”, which is done
at the end of the queue called “rear”.

7. ALGORITHM OF INSERTION
Procedure Insert_Q(Q, n, item, rear)
if(rear=n) then Queue Full
rear=rear+1;
Q[rear]=Item;
end Insert_Q

8. DEQUEUE
Deleting an item in a queue is called
“deletion or dequeue”, which is done at the
beginning of the queue called “front”.

9. ALGORITHM Of DELETION
Procedure Delete_Q(Q, Front, Rear, Item)
if(front=rear)then Queue Empty
front=front+1;
Item=Q[front];
end Delete_Q

10. LINKED QUEUE
• A linked queue is a linear list commonly
implemented as singly link list but two
pointer i.e. Front and Rear.
• The start pointer of singly link list plays the
role of Front while pointer to last node play
role of Rear.

11. ALGORITHM OF INSERTION
Procedure Insert_link_Queue
call getnode(x);
DATA(x)=item;
Link(x)=Nil;
If(front=0)then front=rear=x;
Else
{
Link(rear)=x;
Rear =x;
}
End Insert_link_queue

12. ALGORITHM OF DELETEION
• Procedure delete_link_queue(front, item)
if(front=0)then call link-queue-empty()
Else
{
temp=front;
Item=data(temp);
Front=link(temp)
}
call Return(temp);
End delete_link_queue

13. CIRCULAR QUEUE
• In circular queue, the last position is
connected back to the first position to
make a circle
• The front and rear variable which
displayed a linear movement over a queue
displays a circular movement over the
queue.

14. ALGORITHM OF INSERTION
Procedure InsertCirQ(cirQ,front,rear,n,item)
rear=(rear+1) mod n
If(front=rear)then cirq-full
CirQ[rear]=item;
End InsertCirQ

15. ALGORITHM OF DELETION
Procedure delete-CirQ(cirQ, front, rear, n,
item)
if(front=rear)then cirQ-empty
front=(front+1) mod n
Item=cirQ(front);
End delete-CirQ

16. DEQUEU
 Dequeu i.e double ended queue is a linear list in which
all insertion and deletion are made at both end.
 The end are knows as left end or right end.
Input
restricted
Output
restricted
DEQUEU

17. Queue Applications
 A queue of people at ticket-window: The person who
comes first gets the ticket first. The person who is
coming last is getting the tickets in last. Therefore, it
follows first-in-first-out (FIFO) strategy of queue.
 The Phone answering system: The person who calls first
gets a response first from the phone answering system.
The person who calls last gets the response last.
Therefore, it follows first-in-first-out (FIFO) strategy of
queue.

18. Applications related to Computer
Science
Round Robin Scheduling.
 It is a CPU scheduling algorithm where
each process is assigned a fixed time slot
in a cyclic way.
 The processes (runtime) are to be inserted
into the queue first and then decremented
(by CPU execution time) for each iteration
through the queue until their runtime is
over.

19. • The queue can process only n number of
processes at a time, where n is it's
capacity.
• Only the first n processes need to be
processed, the others are to be ignored.