write a program to demonstrate constructor overloading.

 Here's an example program that demonstrates constructor overloading in C++:

#include <iostream>

using namespace std;

class Rectangle {

   private:

    int length, width;

   public:

    // Default constructor

    Rectangle() {

        length = 0;

        width = 0;

    }

    // Parameterized constructor with one argument

    Rectangle(int l) {

        length = l;

        width = l;

    }

    // Parameterized constructor with two arguments

    Rectangle(int l, int w) {

        length = l;

        width = w;

    }

    // Method to calculate and return the area of the rectangle

    int area() {

        return length * width;

    }

};

int main() {

    // Create objects of Rectangle class with different constructors

    Rectangle rect1;

    Rectangle rect2(5);

    Rectangle rect3(4, 6);

    // Print the area of each rectangle

    cout << "Area of rect1: " << rect1.area() << endl;

    cout << "Area of rect2: " << rect2.area() << endl;

    cout << "Area of rect3: " << rect3.area() << endl;

    return 0;

}

In this program, we define a 'Rectangle' class that has three constructors: a default constructor that sets both 'length' and 'width' to 0, a parameterized constructor with one argument that sets both 'length' and 'width' to the same value, and a parameterized constructor with two arguments that sets 'length' and 'width' separately.

We then create three objects of the "Rectangle" class using each of the three constructors, and calculate and print the area of each rectangle using the 'area()' method.

This program demonstrates how constructor overloading can provide flexibility and convenience when creating objects of a class.