In C++, there are three levels of relationship between base classes and inherited classes.
1: Overloading. For overloading, the scope must be the same, the function name is the same, and the parameter list of the function is different.
2: Hidden. The so-called hiding is that the derived class hides the function of the same name of the base class. Call this on a derived class object
When a function is used, only functions of derived classes can be called. The functions of the base class are hidden.
3: Overlay. When virtual (that is, virtual) is added in front of the function name of the base class, the function becomes a virtual function.
If the derived class has the same name, the same parameters, and the same return value, the function becomes a virtual function.
This is coverage.
E.g:
#include<iostream>
using namespace std;
class A
{public:
A(int val = 12){}
virtual void show()
{
cout << "A is show()" << endl;
cout << ma <<endl;
}
protected:
int ma;
};
class B:public A
{
public:
B(int size = 10) :mb(size), A(size){}
void show()
{
cout << "B is show()" << endl;
cout << mb << endl;
}
private:
int mb;
};
int main()
{
B b;
A *p =&b;
p->show();
return 0;
}
The memory layout for class A and class B is:
