The document discusses the applications of queues in operating systems, particularly in multi-user and multitasking environments, as well as in communication software for holding incoming information. It explains two types of queue implementations: static (using a fixed-size array) and dynamic (using a linked list that can change in size). Additionally, it describes a pointer implementation for managing queues with front and rear pointers for enqueuing and dequeuing operations.

1. Applications of Queues
 Operating system
multi-user/multitasking environments, where
several users or task may be requesting the same
resource simultaneously.
 Communication Software
queues to hold information received over networks
and dial up connections. (Information can be
transmitted faster than it can be processed, so is
placed in a queue waiting to be processed)
 Some other?

2. Implementation
 Static
Queue is implemented by an array, and size
of queue remains fix
 Dynamic
A queue can be implemented as a linked
list, and expand or shrink with each enqueue
or dequeue operation.

4. A pointer Implementation of
Queues
Keep two pointers:
 FRONT: A pointer to the first element of the queue.
 REAR: A pointer to the last element of the queue.
x y .
z
Front
Rear

5. A pointer Implementation of
Queues
Q.front
Q.Rear
MAKENULL(Q)
Q.front
Q.Rear
ENQUEUE(x,Q)
.
x
NULL

6. Q.front
Q.Rear
ENQUEUE(y,Q)
x .
y
Q.front
Q.Rear
DEQUEUE(Q)
.
y
A pointer Implementation of
Queues