Stack using array

#include <iostream>
using namespace std;
class Stack
{
private:
    int arr[100]; 
    int top;        
public:
    Stack()
    {
        top = -1;
    }
    // check if empty
    bool isEmpty()
    {
        return top == -1;
    }
    // check if full
    bool isFull()
    {
        return top == 99;
    }
    // push
    void push(int val)
    {
        if (isFull())
        {
            cout << "Stack Overflow\n";
            return;
        }
        arr[++top] = val;
    }
    // pop
    void pop()
    {
        if (isEmpty())
        {
            cout << "Stack Underflow\n";
            return;
        }
        top--;
    }
    // peek (top element)
    int peek()
    {
        if (isEmpty())
        {
            cout << "Stack is empty\n";
            return -1;
        }
        return arr[top];
    }
    // display stack
    void display()
    {
        if (isEmpty())
        {
            cout << "Stack is empty\n";
            return;
        }
        for (int i = top; i >= 0; i--)
        {
            cout << arr[i] << " ";
        }
        cout << endl;
    }
};
int main()
{
    Stack s;
    s.push(10);
    s.push(20);
    s.push(30);
    s.display();
    cout << "Top = " << s.peek() << endl;
    s.pop();
    s.display();
    return 0;
}