class C
 {
   private:
    string A;
    double B;
   public:
   //empty constructor
   C();
   C(string, double);
 }

//this is how I declare the empty constructor
 C::C()
  {

  }


  C::C(string a, double b)
  {
         A = a;
         B = b;
  }

C::C() : B() {} // zero-initializes B

C::C(const string& a, double b) : A(a), B(b) {}

C::C()
:B(0.0)
{
}

C(const string& a= "", double b= 0.0)
: A(a),
  B(b)
{
}

class Bar{
    private:
        Bar(); //Explicitly private;
};
Bar b;

C::C(string a, double b):A(a), b(b)
{
}

C() = default;

int m_member = 0; // this is a class member