class stringed public Instrument public vitual void play()∥ virtual可省略 i cout<< Stringed play'<<endl void maine Wind flute Stringed violin Percussion drum tune(flute) tune(violin) tune(drum)void main() { } Wind flute; Stringed violin; Percussion drum; tune(drum); tune (flute); tune (violin); class Stringed:public Instrument { }; public: vitual void play() //virtual可省略 { cout<<“Stringed play”<<endl; }