public、potected 、private继承下的子类对父类成员的访问情况

#include<iostream>
   #include<string>
   using namespace std;
   class parent{
   protected:
           int m_a;
           int m_b;
   public:
           int m_c;
          void set(int a,int b,int c){
                  m_a = a;
                  m_b = b;
                  m_c = c;
          }
  };
  class child_A:public parent{
  public:
          void print(){
                  cout << "m_a=" << m_a << endl;
                  cout << "m_b=" << m_b << endl;
                  cout << "m_c=" << m_c << endl;
          }
  };
  class child_B:protected parent{
  public:
          void print(){
                  cout << "m_a=" << m_a << endl;
                  cout << "m_b=" << m_b << endl;
                  cout << "m_c=" << m_c << endl;
                                                                                                                                   ,          顶端
          }

  };
  class child_C:private parent{
  public:
          void print(){
                  cout << "m_a=" << m_a << endl;
                  cout << "m_b=" << m_b << endl;
                  cout << "m_c=" << m_c << endl;
          }

  };
  int main(){
          child_A a;//public继承
          child_B b;//protected 继承
          child_C c;//private继承
          a.m_c = ;//
          //b.m_c = 100;//
          //c.m_c = 100;
          return ;
          a.print();
          b.print();
          c.print();
          cout << endl;
          a.set(,,);
          b.set(,,);
          c.set(,,);
  }
//结果

class.cpp:10:7: error: ‘void parent::set(int, int, int)’ is inaccessible
void set(int a,int b,int c){
^
class.cpp:54:13: error: within this context
b.set(2,2,2);
^
class.cpp:54:13: error: ‘parent’ is not an accessible base of ‘child_B’
class.cpp:10:7: error: ‘void parent::set(int, int, int)’ is inaccessible
void set(int a,int b,int c){
^
class.cpp:55:13: error: within this context
c.set(3,3,3);
^
class.cpp:55:13: error: ‘parent’ is not an accessible base of ‘child_C’