Queue is a linear data structure that follows the FIFO (First In First Out) principle where elements are inserted at the rear and deleted from the front. It has fields for the front and rear pointers and size, and functions to enqueue, dequeue, and display elements. Elements are inserted at the rear if space is available and deleted from the front, maintaining the order they entered the queue.

2. Introduction
Queue is a linear Data Structure in which the
operations are performed based on FIFO (First In
First Out) principle.
In a Queue always the Insertion operation is done at
“rear” and Deletion operation is done at “front”.
In a Queue sequence of elements entered into the
queue is same as the sequence of elements leave
the queue.

3. Queue ADT
Definition
• Queue is a linear Data Structure in which the operations
are performed based on FIFO (First In First Out) principle.
Fields
• rear – used to store the position of insertion
• front – used to store the position of deletion
• size – used to store the size of the queue
• element – used to store the value to be inserted
Functions
• enQueue(element) – to insert into queue
• deQueue( ) – to delete from queue
• display( ) – to display all elements in queue
Condition
• Rear >= size – Queue is full
• Front == rear – Queue is empty

4. class Queue
{
int *Q, front, rear, size;
public:
Queue()
{
cout<<“Enter the Queue size:”;
cin>>size;
Q = new int[size];
front=rear=-1;
}
void qInsert(int);
void qDelete();
void qDisplay();
}

5. f = front
r = rear
f = r = -1
Q
Queue is EMPTY
0 1 2 3 4 5 . . . SIZE-1
When the object of Queue class is created it allocates memory
and executes the constructor

6. Insertion
Q
enQueue( int element )
{
if( rear != size-1)
{
rear ++;
Q[rear] = element;
}
}
else
cout<< “Queue is full !!!”;
0 1 2 3 4 5 6 7 8 9
10 20 30 40

7. Deletion
Q
deQueue( )
{
if( front != rear )
{
front ++;
Cout<<“nElement removed : ”<<Q[front];
}
}
else
cout<< “Queue is empty !!!”;
0 1 2 3 4 5 6 7 8 9
10 20 30 40

8. Display
Q
if( front != rear )
{
for(int i=front+1; i<=rear, i++)
cout<<Q[front]<<“t”;
}
}
else
cout<< “Queue is empty !!!”;
0 1 2 3 4 5 6 7 8 9
10 20 30 40
display( )
{