Class Access Specifiers public private protected in C++

#include <iostream>
using namespace std;

class MyClass
{
public:
    int i;
    void printMessage()
    {
        cout << "Hello World! : " << i << endl;
    }

private:
    int y;
};

int main()
{
    MyClass m;
    m.i = 500;
    cout << "Value is : " << m.i << endl;
    m.printMessage();
    m.y = 400;
    return 0;
}