C++练习

#include <iostream>#include <string>using namespace std;class BirthDate{public:    BirthDate(int,int,int);    void display();    void setbirthday(int,int,int);private:    int year;    int month;    int day;};class Teacher{public:    Teacher(int,string,char);    void display();private:   int num;    string name;    char sex;};class Professor:public Teacher{public:    Professor(int,string,char,BirthDate);    void display();    void setbirthday(int,int,int);private:    BirthDate birthday;};/* C++ДњТы */BirthDate::BirthDate(int y,int m,int d):year(y),month(m),day(d){}void BirthDate::display(){    cout<<"birthday:"<<year<<"/"<<month<<"/"<<day;}void BirthDate::setbirthday(int y,int m,int d){year=y;month=m;day=d;}Teacher::Teacher(int nu,string na,char s):num(nu),name(na),sex(s){}void Teacher::display(){    cout<<"num:"<<num<<endl;    cout<<"name:"<<name<<endl;    cout<<"sex:"<<sex<<endl;}Professor::Professor(int nu,string na,char s,BirthDate bbirthday):Teacher(nu,na,s),birthday(bbirthday){}void Professor::display(){    Teacher::display();    birthday.display();}void Professor::setbirthday(int y,int m,int d){    birthday.setbirthday(y,m,d);}int main(){    int num;    string name;    char sex;    int year,month,day;    cin>>num>>name>>sex;    cin>>year>>month>>day;    Professor prof(num,name,sex,BirthDate(year,month,day));    cin>>year>>month>>day;    prof.setbirthday(year,month,day);    prof.display();    return 0;}