Question 1

A class that has a pure virtual member function is called a concrete base class.

Accepted Answer

A) True 
 B)False

Question 2

A derived class destructor always invokes the base class destructor.

Accepted Answer

A) True 
 B)False

Question 3

No objects can be defined of abstract base class type since it is an incomplete definition.

Accepted Answer

A) True 
 B)False

Question 4

Virtual functions are implemented with a table look up that is done at run time.

Accepted Answer

A) True 
 B)False

Question 5

Write a program where the destructors should be virtual.Explain.

Accepted Answer

The requested code and further discussion follow.
#include<iostream>
using namespace std;
class B
{
public:
B():bPtr( new int[5]){ cout << "allocates 5 ints
";}
virtual ~B()
{ delete[] bPtr;cout << "deallocates 5 ints
";}
private:
int * bPtr;
};
class D:public B
{
public:
D():B(),dPtr(new int[1000]){cout << "allocates 1000 ints
";}
~D(){ delete[] dPtr;cout << "deallocates 1000 ints
";}
private:
int * dPtr;
};
int main()
{
for (int i = 0;i < 100;i++)
{
B* bPtr = new D;
delete bPtr;
}
cout << "
Without virtual destructor,
";
cout << "100 * 1000 + 500 ints allocated
"
<< "but only 500 ints deallocated.
";
cout << "
With virtual destructor,
";
cout << "100 * 1000 + 500 ints allocated,and "
<< "100 * 1000 + 500 ints deallocated.
";
}
In this code,if the base class destructor is not virtual,the system must bind the pointer to the destructor at compile time.The pointer in main,bPtr,is of type B*,i.e. ,pointer to B,so it is bound to B's member functions.The destructor for D,~D fails to run.
If the keyword virtual is removed from the destructor in the base class,class B,the derived class destructor ~D is not called.Approximately 400K of memory would then be leaked.

Question 6

A the binding of virtual function is done at runtime if called using an object.

Accepted Answer

A) True 
 B)False

Question 7

It is OK to assign between objects of base type and objects of derived type.

Accepted Answer

A) True 
 B)False

Question 8

It is legal to have all member functions of a class be pure virtual functions.

Accepted Answer

A) True 
 B)False  True

Question 9

Write a class having a public pure virtual method.You need not put any other members in the class.

Accepted Answer

class Figu...

Question 10

Which functions in class D are virtual?
class B
{
public:
virtual void f();
virtual void g();
// ...
private:
//...
};
class D : public B
{
public:
void f();
void g(int);
private:
// ...
};

Accepted Answer

The function void f(...

Question 11

Redefining and overriding are exactly the same thing.

Accepted Answer

A) True 
 B)False

Question 12

Only member functions can be virtual.

Accepted Answer

A) True 
 B)False

Question 13

A pointer to objects of a derived class can be assigned pointers to objects of the base class in the inheritance hierarchy.

Accepted Answer

A) True 
 B)False

Question 14

Upcasting causes no problems

Accepted Answer

A) True 
 B)False

Question 15

Late binding refers to a failure to secure one's ski boots.

Accepted Answer

A) True 
 B)False

Question 16

It is desirable to develop your programs incrementally.Code a little,test a little.If you do this with virtual functions,you get into trouble.Discuss the problem and the (very simple)solution.

Accepted Answer

If you fail to define functions that has...

Question 17

Write a short program that shows how to defeat the slicing problem.

Accepted Answer

// to defeat the slicing problem
#includ...

Question 18

Suppose each of the base class and the derived class has a member function with the same signature.Suppose you have a base class pointer to a derived class object and call the common function member through the pointer.Discuss what determines which function is actually called,whether the one from the base class or the one from the derived class.Consider both the situations where the base class function is declared virtual and where it is not.

Accepted Answer

The non-virtual case: If the base class ...

Question 19

The virtual property is not inherited.

Accepted Answer

A) True 
 B)False

Question 20

Downcasting causes the slicing problem.

Accepted Answer

A) True 
 B)False  False

Exam 15: Polymorphism and Virtual Functions

A class that has a pure virtual member function is called a concrete base class.

Correct Answer
verified

A derived class destructor always invokes the base class destructor.

Correct Answer
verified

No objects can be defined of abstract base class type since it is an incomplete definition.

Correct Answer
verified

Virtual functions are implemented with a table look up that is done at run time.

Correct Answer
verified

Write a program where the destructors should be virtual.Explain.

A the binding of virtual function is done at runtime if called using an object.

Correct Answer
verified

It is OK to assign between objects of base type and objects of derived type.

Correct Answer
verified

It is legal to have all member functions of a class be pure virtual functions.

Correct Answer
verified
True

Write a class having a public pure virtual method.You need not put any other members in the class.

Correct Answer
verified
class Figu...
View Answer

Which functions in class D are virtual? class B { public: virtual void f(); virtual void g(); // ... private: //... }; class D : public B { public: void f(); void g(int); private: // ... };

Correct Answer
verified
The function void f(...
View Answer

Redefining and overriding are exactly the same thing.

Correct Answer
verified

Only member functions can be virtual.

Correct Answer
verified

A pointer to objects of a derived class can be assigned pointers to objects of the base class in the inheritance hierarchy.

Correct Answer
verified

Upcasting causes no problems

Correct Answer
verified

Late binding refers to a failure to secure one's ski boots.

Correct Answer
verified

It is desirable to develop your programs incrementally.Code a little,test a little.If you do this with virtual functions,you get into trouble.Discuss the problem and the (very simple)solution.

Correct Answer
verified
If you fail to define functions that has...
View Answer

Write a short program that shows how to defeat the slicing problem.

Correct Answer
verified
// to defeat the slicing problem
#includ...
View Answer

Correct Answer
verified
The non-virtual case: If the base class ...
View Answer

The virtual property is not inherited.

Correct Answer
verified

Downcasting causes the slicing problem.

Correct Answer
verified
False

Exam 15: Polymorphism and Virtual Functions

A class that has a pure virtual member function is called a concrete base class.

Correct AnswerverifiedShow Answer

A derived class destructor always invokes the base class destructor.

Correct AnswerverifiedShow Answer

No objects can be defined of abstract base class type since it is an incomplete definition.

Correct AnswerverifiedShow Answer

Virtual functions are implemented with a table look up that is done at run time.

Correct AnswerverifiedShow Answer

Write a program where the destructors should be virtual.Explain.

A the binding of virtual function is done at runtime if called using an object.

Correct AnswerverifiedShow Answer

It is OK to assign between objects of base type and objects of derived type.

Correct AnswerverifiedShow Answer

It is legal to have all member functions of a class be pure virtual functions.

Correct AnswerverifiedTrue

Write a class having a public pure virtual method.You need not put any other members in the class.

Correct Answerverifiedclass Figu...View AnswerShow Answer

Which functions in class D are virtual? class B { public: virtual void f(); virtual void g(); // ... private: //... }; class D : public B { public: void f(); void g(int); private: // ... };

Correct AnswerverifiedThe function void f(...View AnswerShow Answer

Redefining and overriding are exactly the same thing.

Correct AnswerverifiedShow Answer

Only member functions can be virtual.

Correct AnswerverifiedShow Answer

A pointer to objects of a derived class can be assigned pointers to objects of the base class in the inheritance hierarchy.

Correct AnswerverifiedShow Answer

Upcasting causes no problems

Correct AnswerverifiedShow Answer

Late binding refers to a failure to secure one's ski boots.

Correct AnswerverifiedShow Answer

It is desirable to develop your programs incrementally.Code a little,test a little.If you do this with virtual functions,you get into trouble.Discuss the problem and the (very simple)solution.

Correct AnswerverifiedIf you fail to define functions that has...View AnswerShow Answer

Write a short program that shows how to defeat the slicing problem.

Correct Answerverified// to defeat the slicing problem#includ...View AnswerShow Answer

Correct AnswerverifiedThe non-virtual case: If the base class ...View AnswerShow Answer

The virtual property is not inherited.

Correct AnswerverifiedShow Answer

Downcasting causes the slicing problem.

Correct AnswerverifiedFalse

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified
True

Correct Answer
verified
class Figu...
View Answer

Correct Answer
verified
The function void f(...
View Answer

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified
If you fail to define functions that has...
View Answer

Correct Answer
verified
// to defeat the slicing problem
#includ...
View Answer

Correct Answer
verified
The non-virtual case: If the base class ...
View Answer

Correct Answer
verified

Correct Answer
verified
False