Simple Queue program in Data Structure

#include<iostream.h>

#include<conio.h>

class queue

{

private:

int data;

queue *prev;

queue *next;

public:

void add(int);

void display(void);

void remove(void);

};

queue *front;

queue *rear;

void queue::add(intnum)

{

if((front==NULL)&&(rear==NULL))

{

front=rear=new queue;

front->data=num;

front->next=NULL;

front->prev=NULL;

}

else

{

rear->next=new queue;

rear->next->data=num;

rear->next->next=NULL;

rear->next->prev=rear;

rear=rear->next;

}}

void queue::display(void)

{

queue *q=front;

if((front==NULL)&&(rear==NULL))

  {

cout<<"Queue is empty";

  }

else

  {

while(q!=NULL)

    {

cout<<q->data<<endl;

      q=q->next;

    }}}

void queue::remove(void)

{

queue *q=front;

if((front==NULL)&&(rear==NULL))

   {

cout<<"Queue is empty"<<endl;

   }

else

   {

front=front->next;

front->prev=NULL;

cout<<q->data<<"/t"<<"is deleted"<<endl;

delete(q);

   }}

void main()

  {

clrscr();

queue q1;

intnum;

int option;

char choice='y';

while(choice=='y')

   {

cout<<"1.ADD"<<endl;

cout<<"2.DISPLAY"<<endl;

cout<<"3.REMOVE"<<endl;

cout<<"Select the option";

cin>>option;

switch(option)

     {

case 1:

       {

cout<<"enter the data";

cin>>num;

q1.add(num);

cout<<"Continue?"<<endl;

break;

       }

case 2:

       {

                q1.display();

                cout<<endl;

                cout<<"Continue?"<<endl;

                break;  }

case 3:

       {

                q1.remove();

                cout<<endl;

                cout<<"Continue?";

                break;}

default:

                {

                cout<<"wrong option";

                cout<<"Continue";

                break;

                 }}

                choice=getch();

     }   }