class A
 {
 public:
    A(){}
    virtual ~A(){}
    virtual void out(std::ofstream& outFile) = 0;
    virtual void in(std::ifstream& inFile) = 0;
};

class B : public A
{
public:
   B();
   double angle;
   int index;


   virtual void out(std::ofstream& outFile);
   virtual void in(std::ifstream& inFile);

};

virtual void out(std::ofstrea& outFile)
{
    outFile<< index << angle;
}

void B::out(std::ofstrea& outFile)
{
    outFile<< index << angle;
}

void B::out(std::ofstream& outFile)
{
    outFile<< index << angle;
}

void B::out(std::ofstream& out)
{
   out << index << angle;
}

void B::out(std::ofstrea& outFile)  // Virtual keyword is optional in defintion.
{
    // ...
}

void B::out(std::ofstrea& outFile)
{
outFile<< index << angle;
}