Program for STACKS USING DOUBLE LINKED LISTS

#include<iostream>
#include<conio.h>
#include<stdlib.h>
using namespace std;
class node
{
      public:
             node *next;
    node *prev;
             int data;
};
int n;
class stack : public node
{
     node *head;
        int tos,x;
       public:
             stack()
               {
                 cout<<"\n\t\tSTACKS USING DOUBLE LINKED LISTS\n";
                    tos=-1;
                    cout<<"\nENTER THE STACK SIZE : ";
                    cin>>n;
               }
             void push()
              {
               if(tos < 0 )
                  {
                   cout <<"\n\nenter a element";
                 cin >> x;
                     head =new node;
                     head->prev=NULL;
                     head->next=NULL;
                     head->data=x;
                     tos ++;
                   }
             else
                  {
                     node *temp,*temp1;
                     temp=head;
                     if(tos >= (n-1))
                      {
                        cout <<"\nstack over flow\n";
                         return;
                        }
                     cout <<"\n \nenter a element";
                 cin >> x;
                     while(temp->next != NULL)
                          temp=temp->next;
                     temp1=new node;
                     temp->next=temp1;
                     temp1->next=NULL;
                     temp1->prev=temp;
                     temp1->data=x;
                     tos++;
                   }
            }
             void display()
               {
                  node *temp;
                  temp=head;
                  if (tos < 0)
                    {
                        cout <<"\nSTACK IS EMPTY\n";
                        return;
                    }
                    cout<<"\nthe elements are : ";
      while(temp != NULL)
      {
                        cout <<temp->data<< " ";
                        temp=temp->next;
                     }
                     cout<<"\n";
               }
              void pop()
                {
                   node *temp;
                   temp=head;
                   if( tos < 0 )
                    {
                       cout <<"\n\nstack under flow\n";
                       return;
                    }
     if(tos==0)
     {
      cout<<"\n\nthe removed element is :"<<temp->data<<"\n";
      temp->next=NULL;
      tos--;
      return ;
     }
       if(tos>0)
       {
         while(temp->next->next!=NULL)
                     {
                       temp=temp->next;
                     }
                      if(temp->next->next==NULL)
                     {
       cout<<"\nthe removed element is :"<<temp->next->data;
                     }
                     temp->next=NULL;
                     tos--;
                      return ;
                   }

                }
};
main()
{
 stack s1;
 int x;
 
 while(1)
 {
  cout <<"\n1.PUSH\n2.POP\n3.DISPLAY\n4.EXIT\n enter ur choice:";
  cin>>x;
  switch(x)
     {
  case 1:
                 s1.push();
                  break;

  case 2:    s1.pop();
     break;

  case 3:    s1.display();
                 break;

  case 4:   exit(0);

  default:  cout<<"\ninvalid input..try again\n";
     break;
  }
     }
return 0;
}