Output of C++ Program | Set 16

　　Predict the output of following C++ programs.

Question 1

#include<iostream>
using namespace std;

class Base 
{
public:
    int fun()      
    { 
        cout << "Base::fun() called"; 
    }
    int fun(int i) 
    { 
        cout << "Base::fun(int i) called"; 
    }
};

class Derived: public Base 
{
public:
    int fun(char x)   
    { 
        cout << "Derived::fun(char ) called"; 
    }
};

int main() 
{
    Derived d;
    d.fun();
    return 0;
}

　　Output: Compiler Error.
　　In the above program, fun() of base class is not accessible in the derived class. If a derived class creates a member method with name same as one of the methods in base class, then all the base class methods with this name become hidden in derived class.

 

Question 2

#include<iostream>
using namespace std;
class Base 
{
protected:
    int x;
public:
    Base (int i)
    { 
        x = i;
    }
};

class Derived : public Base 
{
public:
    Derived (int i):x(i) 
    { 
    }
    void print() 
    { 
        cout << x ; 
    }
};

int main()
{
    Derived d(10);
    d.print();
}

　　Output: Compiler Error
　　In the above program, x is protected, so it is accessible in derived class. Derived class constructor tries to use initializer list to directly initialize x, which is not allowed even if x is accessible. The members of base class can only be initialized through a constructor call of base class.

　　Following is the corrected program.

#include<iostream>
using namespace std;
class Base 
{
protected:
    int x;
public:
    Base (int i)
    { 
        x = i;
    }
};

class Derived : public Base 
{
public:
    Derived (int i):Base(i) 
    { 
    }
    void print() 
    { 
        cout << x; 
    }
};

int main()
{
    Derived d(10);
    d.print();
}

　　Output:

 　　10

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　　2013-11-27　　16:34:25