C++ Inheritance

Question 1

CPP

#include<iostream>
 
using namespace std;
class Base1 {
 public:
     Base1()
     { cout << \" Base1\'s constructor called\" << endl;  }
};
 
class Base2 {
 public:
     Base2()
     { cout << \"Base2\'s constructor called\" << endl;  }
};
 
class Derived: public Base1, public Base2 {
   public:
     Derived()
     {  cout << \"Derived\'s constructor called\" << endl;  }
};
 
int main()
{
   Derived d;
   return 0;
}

• Compiler Dependent
  
  
• Base1′s constructor called
  Base2′s constructor called
  Derived’s constructor called
  
  
• Base2′s constructor called
  Base1′s constructor called
  Derived’s constructor called
  
  
• Compiler Error

Question 2

Output?

CPP

#include <iostream>  
using namespace std;

class Base1 {
 public:
     ~Base1()  { cout << \" Base1\'s destructor\" << endl; }
};
  
class Base2 {
 public:
     ~Base2()  { cout << \" Base2\'s destructor\" << endl; }
};
  
class Derived: public Base1, public Base2 {
   public:
     ~Derived()  { cout << \" Derived\'s destructor\" << endl; }
};
  
int main()
{
   Derived d;
   return 0;
}

• Base1\'s destructor
  Base2\'s destructor
  Derived\'s destructor

• Derived\'s destructor
  Base2\'s destructor
  Base1\'s destructor
  

• Derived\'s destructor

• Compiler Dependent

Question 3

Assume that an integer takes 4 bytes and there is no alignment in following classes, predict the output.

C

#include<iostream>
using namespace std;

class base {
    int arr[10];
};

class b1: public base { };

class b2: public base { };

class derived: public b1, public b2 {};

int main(void)
{
  cout << sizeof(derived);
  return 0;
}

• 40
• 80
• 0
• 4

Question 4

C

#include<iostream>
 
using namespace std;
class P {
public:
   void print()  { cout <<\" Inside P\"; }
};
 
class Q : public P {
public:
   void print() { cout <<\" Inside Q\"; }
};
 
class R: public Q { };
 
int main(void)
{
  R r; 
  r.print();
  return 0;
}

• Inside P
• Inside Q
• Compiler Error: Ambiguous call to print()

Question 5

Output?

C

#include<iostream>
using namespace std;

class Base {
private:
     int i, j;
public:
    Base(int _i = 0, int _j = 0): i(_i), j(_j) { }
};
class Derived: public Base {
public:
     void show(){
        cout<<\" i = \"<<i<<\"  j = \"<<j;
     }
};
int main(void) {
  Derived d;
  d.show();
  return 0;
}

• i = 0 j = 0
• Compiler Error: i and j are private in Base
• Compiler Error: Could not call constructor of Base

Question 6

C

#include<iostream>
using namespace std;

class Base {};

class Derived: public Base {};

int main()
{
    Base *bp = new Derived;
    Derived *dp = new Base;
}

• No Compiler Error
• Compiler Error in line "Base *bp = new Derived;"
• Compiler Error in line " Derived *dp = new Base;"
• Runtime Error

Question 7

C

#include<iostream>
using namespace std;

class Base
{
public:
    void show()
    {
        cout<<\" In Base \";
    }
};

class Derived: public Base
{
public:
    int x;
    void show()
    {
        cout<<\"In Derived \";
    }
    Derived()
    {
        x = 10;
    }
};

int main(void)
{
    Base *bp, b;
    Derived d;
    bp = &d;
    bp->show();
    cout << bp->x;    
    return 0;
}

• Compiler Error in line " bp->show()"
• Compiler Error in line " cout << bp->x"
• In Base 10
• In Derived 10

Question 8

C

#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() {  cout << \"Derived::fun() called\"; }
};

int main()
{
    Derived d;
    d.fun(5);
    return 0;
}

• Base::fun(int i) called

• Derived::fun() called

• Base::fun() called

• Compiler Error

Question 9

C

#include<iostream>
using namespace std;

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

class Derived: public Base  {
public:
    void fun()   {     cout << \"Derived::fun() called\";   }
};

int main()  {
    Derived d;
    d.Base::fun(5);
    return 0;
}

• Compiler Error
• Base::fun(int i) called

Question 10

Output of following program? 

CPP

#include <iostream>
#include<string>
using namespace std;

class Base
{
public:
    virtual string print() const
    {
        return \"This is Base class\";
    }
};

class Derived : public Base
{
public:
    virtual string print() const
    {
        return \"This is Derived class\";
    }
};

void describe(Base p)
{
    cout << p.print() << endl;
}

int main()
{
    Base b;
    Derived d;
    describe(b);
    describe(d);
    return 0;
}

• This is Derived class
  This is Base class

• This is Base class
  This is Derived class

• This is Base class
  This is Base class

• Compiler Error