#ifndef MYTIME_H #define MYTIME_H   class MyTime { private:     int m_hour;     int m_minute; public:     MyTime(int hour,int minute=0);     ~MyTime();       MyTime operator+(const MyTime & time) const;     void Show();       //int GetHour() const;     //int GetMinute() const; };   #endif

#include "MyTime.h" #include 
     
         MyTime::MyTime(int hour,int minute) {     m_hour=hour;     m_minute=minute; };   MyTime::~MyTime() {};   MyTime MyTime::operator+(const MyTime & time) const{     //MyTime sum     //  =MyTime(     //      time.GetHour()+m_hour+(time.GetMinute()+m_minute)/60,     //      (time.GetMinute()+m_minute)%60     //  );     //return sum;     MyTime sum         =MyTime(             time.m_hour+m_hour+(time.m_minute+m_minute)/60,             (time.m_minute+m_minute)%60         );     return sum; };   void MyTime::Show() {     std::cout<<"Hour = "<
      
       <<" , Minute = "<
       
        <
       
      
     

Because that's how it works in c++.In c++ access control works on

per-class basis not on per-object basis.

Access control in c++ is implemented as a static,compile-time feature.I think it is rather obvious that it is not really possible to implement any meaningful per-object access control at compile time.only per-class control can be implemented that way.

some hints of per-object control are present in protected access specification,which is why it even has its own dedicated chapter in the standard(11.5).But still any per-object features described there are rather rudimentary.Again,access control in c++ is meant to work on per-class basis.

Your "it is not really possible to implement any meaningful per-object access control at compile time". Why not? In void X::f(X&x), the compiler is easily capable of distinguishing this->a and x.a. It's not (always) possible for the compiler to know that *this and x are actually the same object if x.f(x) is invoked, but I could very well see a language designer find this OK.