class Complex                  //Definitiong of class complex

     {

      public:

               Complex(double r=0,double i=0){ mRel = r; mImag = i;}//constructor

               Complex operator +(Complex c);  //Reuse operator '+'

              Complex operator -(Complex c);  //Reuse operator '-'

              void Display();                //Output complex

     private:

              double mRel,mImag;

     };

     Complex Complex::operator +(Complex c)

    {

       //Complex cc;

       //cc.mRel = mRel + c.mRel;

       //cc.mImag = mImag + c.mImag;

      double a = mRel + c.mRel;

      double b = mImag + c.mImag;

      return Complex(a,b);

    }

     Complex Complex::operator -(Complex c)

   {

     Complex cc;

     cc.mRel = mRel - c.mRel;   //why can access private member declared in class 'Complex'*********

     cc.mImag = mImag - c.mImag;

     return Complex(cc.mRel,cc.mImag);

   }

   void Complex::Display()

   {

    cout<<"("<<mRel<<" "<<mImag<<")"<<endl;

   }

   void main()

   {

     Complex c1(5,4),c2(2,10),c3;

     cout<<"c1=";  c1.Display();

     cout<<"c2=";  c2.Display();

     c3 = c1 - c2;

     cout<<"c3=c1-c2=";

    c3.Display();

    c3 = c1 + c2;

    cout<<"c3=c1+c2=";

    c3.Display();

    //cout<<c3.mImag<<endl;   //***********

   }

大家看有**********的两个注释行，问题就在注释行里！！！