Stack Implementation (Linked List)

#include <bits/stdc++.h>
using namespace std;

#define mx 2
int i(0);

class node
{
public:
    int info;
    node *link;
};

class stackk
{
    node *head;
public:
    stackk()
    {
        head = NULL;
    }
    void push(int val)
    {
        node *ptr = new node();
        ptr->info = val;
        ptr->link = head;
        head = ptr;
        i++;
    }

    int pop()
    {
        int val = head->info;
        head = head->link;
        i--;
        return val;
    }

    bool isEmpty()
    {
        if(head == NULL)
        {
            cout<<"\nStack Underflow!!!!\n\n";
            return true;
        }
        return false;
    }

    bool isFull()
    {
        if(i >= mx)
        {
            cout<<"\nStack Overflow!!!\n\n";
            return true;
        }
        return false;
    }

};

int main()
{
    int i, j, k, n;
    stackk stk1;
    while(true)
    {
        cout<<"Stack Operations:\n1. Push\n2. Pop\n0. Exit\nEnter a number from 0 to 2 : ";
        cin>>k;
        if(k == 1)
        {
            if(!stk1.isFull())
            {
                cout<<"\nEnter the value you want to push : ";
                cin>>n;
                stk1.push(n);
                cout<<endl;
            }
        }
        else if(k == 2)
        {
            if(!stk1.isEmpty())
                cout<<"\nThe top of the stack : "<<stk1.pop()<<endl<<endl;;
        }
        else if(k == 0)
            break;
        else
            cout<<"\nEnter correct number!!!\n\n";
    }
}