// example: class constructor#include 
     
      using namespace std;class Rectangle {    int width, height;  public:    Rectangle (int,int);    int area () {
    return (width*height);}};Rectangle::Rectangle (int a, int b) {  width = a;  height = b;}int main () {  Rectangle rect (3,4);  Rectangle rectb (5,6);  cout << "rect area: " << rect.area() << endl;  cout << "rectb area: " << rectb.area() << endl;  return 0;}