C++ Classes and Objects

#include <iostream>
using namespace std;

class Rectangle {
private:
    int length, width;
public:
    Rectangle() : length(1), width(1) {}                  // default constructor
    Rectangle(int l, int w) : length(l), width(w) {}     // parameterized
    Rectangle(const Rectangle &r) {                     // copy constructor
        length = r.length; width = r.width;
    }
    ~Rectangle() { cout << "Destroying " << length << "x" << width << endl; }

    int area() const { return length * width; }
};

int main() {
    Rectangle a, b(4, 5), c = b;
    cout << a.area() << " " << b.area() << " " << c.area() << endl;
    return 0;
}

#include <iostream>
using namespace std;

class Counter {
    static int count;              // shared by all objects
    int secret = 42;
public:
    Counter() { count++; }
    static int getCount() { return count; }
    friend void peek(const Counter &c);   // friend can access private members
};
int Counter::count = 0;
void peek(const Counter &c) { cout << "secret = " << c.secret << endl; }

int main() {
    Counter a, b, c;
    cout << Counter::getCount() << endl;
    peek(a);
}