Types of constructor

#include <iostream>
using namespace std;

class Rectangle { 
  public:
  int l;
  int b;
  
  Rectangle(){ // Default constructor - no argument passed 
    l=0;
    b=0;
  }
  
  Rectangle (int x,int y){ // parameterise constructor -argument passed 
   l=x;
   b=y; 
  }
  
  Rectangle (Rectangle & r2){ // copy constructor 
   l=r2.l;
   b=r2.b;
 }
  
};

int main(){
  
  Rectangle r1;
  cout<<r1.l<<""<<r1.b<<endl;
  
  Rectangle r2(3,4);
  cout<<r2.l<<""<<r2.b<<endl;
  
  Rectangle r3 = r2;
  cout <<r3.l<<""<<r3.b<<endl;
  
  return 0;
}