C++ Program to implement Stacks

Program

#include<iostream>
#include<cstdlib>
#define SIZE 5
int top = -1;
using namespace std;
class stack
{
	int st[SIZE];
	public:
		void push(int);
		void pop();
		void display();
};
void stack::push(int item)
{
	if(top == SIZE - 1)
	{
		cout << "Stack overflow" << endl;
		return;
	}
	top++;
	st[top] = item;
}
void stack::pop()
{
	if(top == -1)
	{
		cout << "Stack underflow" << endl;
		return;
	}
	cout << "Deleted item is:\t" << st[top] << endl;
	top--;
}
void stack::display()
{
	if(top == -1)
	{
		cout << "Stack empty. Nothing to display" << endl;
		return;
	}
	cout << "Contents of stack are:" << endl;
	for (int i = 0; i < top + 1; i++)
		cout << st[i] << endl;
}
int main()
{
	int choice, item;
	stack st;
	while(1)
	{
		cout << "MENU" << endl;
		cout << "1. Push\n2. Pop\n3. Display\n4. Exit" << endl;
		cin >> choice;
		switch(choice)
		{
			case 1:
				cout << "Enter the item to push" << endl;
				cin >> item;
				st.push(item);
				break;
			case 2:
				st.pop();
				break;
			case 3:
				st.display();
				break;
			default:
				exit(0);
		}
	}
	return 0;
}

Output

MENU
1. Push
2. Pop
3. Display
4. Exit
2
Stack underflow
MENU
1. Push
2. Pop
3. Display
4. Exit
1
Enter the item to push
10
MENU
1. Push
2. Pop
3. Display
4. Exit
1
Enter the item to push
20
MENU
1. Push
2. Pop
3. Display
4. Exit
1
Enter the item to push
30
MENU
1. Push
2. Pop
3. Display
4. Exit
3
Contents of stack are:
10
20
30
MENU
1. Push
2. Pop
3. Display
4. Exit
2
Deleted item is:	30
MENU
1. Push
2. Pop
3. Display
4. Exit
2
Deleted item is:	20
MENU
1. Push
2. Pop
3. Display
4. Exit
2
Deleted item is:	10
MENU
1. Push
2. Pop
3. Display
4. Exit
2
Stack underflow
MENU
1. Push
2. Pop
3. Display
4. Exit
1
Enter the item to push
40
MENU
1. Push
2. Pop
3. Display
4. Exit
4