A queue is an ordered collection of items from which items may be deleted at one end(called front and head of the queue) and into which items may be inserted at the other end (called the rear end on tail of the queue). It is First-In-First-Out(FIFO).There are two types of queue-Linear Queue and Circular Queue.
En-queue is the process of appending data to queue.
De-queue is the process of removing data from queue.
1)Both the head and tail pointer vary
a)Declare and initialize necessary variables
front=0,rear=-1,Max_size
b)For En-queue operation
IF rear>=Max_Size-1
Print”Queue is Full !”
ELSE
rear=rear+1
queue[rear]=item
c)For next En-queue operation go to step2
d)For De-queue operation
IF front>rear
Print “Queue is Empty!”
ELSE
Item=queue[front]
front=front+1
e)For De-queue of next data items go to step 4
f)Stop
2)Head pointer fixed tail pointer vary
a)Declare and initialize necessary variables
rear=-1
b)For en-queue operation
IF rear>=Max_Size-1
Print “Queue is Full !”
ELSE
rear=rear+1
queue[rear]=item
c)For En-queue of next data item go to step 2
d)For De-queue operation
IF rear=-1
Print “ queue is Empty”
ELSE
Item=queue[rear]
swap the elements from upper to one step lower
rear=rear-1
e)For De-queue for next data item go to step 4
f)Stop
CIRCULAR QUEUE
a)Declare and initialize necessary variables such as head=0,tail=0
b)For En-queue operation
IF head==(tail+1)%Max_Size
Print” Queue is Full !”
ELSE
queue[tail+1]=item
Tail=(tail+1)%Max_Size
c)For En-queue of next data item go to step 2
d)For De-queue operation
IF head =tail
Print “Queue is Empty!”
ELSE
remove item i.e. item =queue[head]
set head=(head+1)%Max_Size
e)For De-queue of next data item goto step 4
f)Stop
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