c++ - C ++ Child class cannot inherit private member from Father class? -

i using win8 vc++2012.

the code above show child class b under no circumstances can access a::a. neither can change access attribute of a::a a::b , a::c.

so a::c not inherited b. sizeof(a) , sizeof(b) 12 , 24 respectively, means a::a occupy memory in b.

1. how b stores a::a in memory while never access it?
2. the book c++ primer says, can restore access attribute of base class member can not change it. here code shows can change access attributes of a::b protected public in b. why?

here's code:

#include <iostream> using namespace std;  class { private:     int a; protected:     int b; public:     int c;      a(int a, int b, int c): a(a), b(b), c(c)     {         cout << "a: ";         cout << << " ";         cout << b << " ";         cout << c << endl;     } };  class b: protected { private:     int d; protected:     int e;     //using a::a; compile error public:     int f;     //a::a;  compile error     using a::c; //restore a::c public access     a::b; // change a::b protected public      b(int d, int e, int f): a(d, e, f), d(d), e(e), f(f)     {         cout << "b\n";         //cout << << endl; compile error         cout << b << " ";         cout << c << " ";         cout << d << " ";         cout << e << " ";         cout << f << endl;     } }; int main() {     a(1,2,3);     b b(4,5,6);      cout << "sizeof(a)=" << sizeof(a) << endl; //output 12     cout << "sizeof(b)=" << sizeof(b) << endl; //output 24     return 0; } 

children inherit parent's private members, can not access them. access make them protected

class { protected: // <<------------ make `a` protected in parent     int a;