which way to access a base class function or variable

Question

I m a student. Today I Give the Interview and tell me something new about inheritance

 

I said the derived class can not access the base class property or field because below program prove that is why I tell the derived class can not access the base class property or field:

using namespace std;
#include<iostream>

class baseclass
{
  public:
    int a;
    baseclass()
    {
        std::cout << "baseclass\n";
    }
};

class deriveclass: public baseclass
{
 public:
    deriveclass()
    {
        std::cout << "derived class\n";
    }
};


int main()
{
    baseclass * a=new baseclass();  //ok
    deriveclass * b=new deriveclass();  //ok

    baseclass * aa=new deriveclass(); //ok
    deriveclass * bb=new baseclass(); //not ok

    return 0;
}

Link:https://onlinegdb.com/SyfhRDF_U

 

error:

 

main.cpp: In function ‘int main()’: main.cpp:30:36: error: invalid conversion from ‘baseclass*’ to ‘deriveclass*’ [-fpermissive] deriveclass * bb=new baseclass(); //not ok

 

then Interviewer tells me which way to access the base class function or variable?

 

help?