STACK USING CLASS

#include<iostream>
#define MAX 5
using namespace std;
int top=-1;
class stackop
{
int stack[MAX];
public:
void push()
{
int i;
cout<<"\nenter a number to push";
cin>>i;
if (top>=MAX-1)
cout<<"\nstack is full";
else
{
top++;
stack[top]=i;
cout<<"pushed element is"<<stack[top];
}
}
void pop()
{
int b;
if(top==-1)
cout<<"\nstack is empty";
else
{
cout<<"\ndeleted element is "<<stack[top];
top--;
}
}
void display()
{
int i;
if(top>=0)
{
cout<<"\nstack elements are";
for (i=0;i<=top;i++)
cout<<"\t"<<stack[i];
}
else
cout<<"\nno elements";
}
};
int main()
{
stackop s;
int x,y;
while(1)
{
cout<<"\nSTACK OPERATIONS USING C++";
cout<<"\n1.push\n2.pop\n3.display\n4.exit\n enter your choice\n";
cin>>y;
switch(y)
{
case 1:s.push();
       break;
case 2:s.pop();
      break;
case 3:s.display();
       break;
case 4:exit(0);
break;
default:cout<<"wrong choice entered";
}
}
return 0;
}