STACK USING LINKED LIST (DYNAMIC STACK)

#include<iostream.h>
#include<stdio.h>
#include<process.h>
struct Book
{
int Bookid;

char BookName[20];
Book *Link;
}*start = NULL;
void Push();
void Pop();
void Display();
void main()
{
int choice;
do
{
cout<<"Enter Your Choice\n1. Push\n2. Pop\n3. Display\n4.Exit\n";
cin>>choice;
switch(choice)
{
case 1: Push();
        break;
case 2: Pop();
        break;
case 3: Display();
        break;
case 4: exit(0);
default:cout<<"Wrong Choice. Try Again\n";
}
}while(1);
}
void Push()
{
Book *b = new Book;
cout<<"Enter the Book Id and Book Name\n";
cin>>b->Bookid;
gets(b->BookName);
b->Link = NULL;
if(start==NULL)
start = b;
else
{
b->Link = start;
start = b;
}
}
void Pop()
{
if(start == NULL)
cout<<"Empty Stack\n";
else
{
Book *n = start;
start = start->Link;
cout<<n->Bookid<<" deleted\n";
delete n;
}
}
void  Display()
{
if(start == NULL)
cout<<"Empty Stack\n";
else
{
Book *s = start;
while(s!=NULL)
{
cout<<"Book Id : "<<s->Bookid<<"\n";
cout<<"Book Name : "<<s->BookName<<"\n";
s=s->Link;
}
}
}