Introduction to C++ Programming, Y. Daniel Liang
Chapter 11 Inheritance and Polymorphism
Section 11.2 Base classes and Derived classes
1
Object-oriented programming allows you to derive new classes from existing classes. This is called ____________.
A.
encapsulation
B.
inheritance
C.
abstraction
D.
generalization
2
Which of the following statements are true?
A.
A derived class is a subset of a base class.
B.
A derived class is usually extended to contain more functions and more detailed information than its base class.
C.
"class A: public B" means A is a derived class of B.
D.
"class A: public B" means B is a derived class of A.
Section 11.3 Generic Programming
3
Suppose Circle and Rectangle classes are derived from GeometricObject and you declared
void displayGeometricObject(GeometricObject shape)
{
cout << shape.toString() << endl;
}
Which of the following function call is correct?
A.
displayGeometricObject(GeometricObject("black", true));
B.
displayGeometricObject(Circle(5));
C.
displayGeometricObject(Rectangle(2, 3));
D.
displayGeometricObject(string());
Section 11.4 Constructors and Destructors
4
Are the constructors inherited by the derived class?
A.
Yes
B.
No
5
Are the destructors inherited by the derived class?
A.
Yes
B.
No
6
Suppose class A is derived from B and both A and B have no-arg constructors. To invoke B's constructor from A, use ________.
A.
A(): B() { ... }
B.
A(): { B(); ... }
C.
B(): A() { ... }
D.
B(): { A(); ... }
7
What is the output of the following code?
#include <iostream>
using namespace std;
class B
{
public:
~B()
{
cout << "B";
}
};
class A: public B
{
public:
~A()
{
cout << "A";
}
};
int main()
{
A a;
return 0;
}
A.
AB
B.
BA
C.
A
D.
B
E.
AA
8
What is wrong in the following code?
class Fruit
{
public:
Fruit(int id)
{
}
};
class Apple: public Fruit
{
public:
Apple()
{
}
};
A.
The program will compile if you add a no-arg constructor for Fruit.
B.
The program has a syntax error because Fruit does not have a no-arg constructor.
C.
The program will compile if you delete the constructor in Fruit.
D.
The program will compile if you replace Apple() by Apple(): Fruit(4).
Section 11.5 Redefining Functions
9
Which of the following statements are true?
A.
To redefine a function, the function must be defined in the derived class using the same signature and return type as in its base class.
B.
Overloading a function is to provide more than one function with the same name but with different signatures to distinguish them.
C.
It is a compilation error if two functions differ only in return type.
D.
A private function cannot be redefined. If a function defined in a derived class is private in its base class, the two functions are completely unrelated.
10
Which of the following statements are true?
A.
A function can be overloaded in the same class.
B.
A function can be redefined in the same class.
C.
If a function overloads another function, these two functions must have the same signature.
D.
If a function redefines another function, these two functions must have the same signature.
11
To invoke the toString() function defined in GeometricObject from a Circle object c, use __________.
A.
super.toString()
B.
c.super.toString()
C.
c.GeometricObject::toString()
D.
c->GeometricObject::toString()
Section 11.6 Polymorphism and Virtual Functions
12
What is the printout of the following code?
#include <iostream>
using namespace std;
class C
{
public:
string toString()
{
return "C";
}
};
class B: public C
{
string toString()
{
return "B";
}
};
class A: public B
{
string toString()
{
return "A";
}
};
void displayObject(C *p)
{
cout << p->toString();
}
int main()
{
displayObject(&A());
displayObject(&B());
displayObject(&C());
return 0;
}
A.
ABC
B.
CBA
C.
AAA
D.
BBB
E.
CCC
13
What is the printout of the following code?
#include <iostream>
using namespace std;
class C
{
public:
virtual string toString()
{
return "C";
}
};
class B: public C
{
string toString()
{
return "B";
}
};
class A: public B
{
string toString()
{
return "A";
}
};
void displayObject(C *p)
{
cout << p->toString();
}
int main()
{
displayObject(&A());
displayObject(&B());
displayObject(&C());
return 0;
}
A.
ABC
B.
CBA
C.
AAA
D.
BBB
E.
CCC
14
What is the printout of the following code?
#include <iostream>
using namespace std;
class C
{
public:
string toString()
{
return "C";
}
};
class B: public C
{
string toString()
{
return "B";
}
};
class A: public B
{
virtual string toString()
{
return "A";
}
};
void displayObject(C *p)
{
cout << p->toString();
}
int main()
{
displayObject(&A());
displayObject(&B());
displayObject(&C());
return 0;
}
A.
ABC
B.
CBA
C.
AAA
D.
BBB
E.
CCC
15
What is the printout of the following code?
#include <iostream>
using namespace std;
class C
{
public:
virtual string toString()
{
return "C";
}
};
class B: public C
{
string toString()
{
return "B";
}
};
class A: public B
{
string toString()
{
return "A";
}
};
void displayObject(C p)
{
cout << p.toString();
}
int main()
{
displayObject(A());
displayObject(B());
displayObject(C());
return 0;
}
A.
ABC
B.
CBA
C.
AAA
D.
BBB
E.
CCC
16
If A is derived from B, and B is derived from C, B has a virtual function, will this function be dynamically binded?
A.
Yes
B.
No
17
If the variable that references the object for the function is not the address of the object, will this function be dynamically binded?
A.
Yes
B.
No
18
Which of the following statements are true?
A.
If a function is defined virtual in a base class, it is automatically virtual in all its derived classes. It is not necessary to add the keyword virtual in the function declaration in the derived class.
B.
If a function will not be redefined, it is more efficient without declaring it virtual, because it takes more time and system resource to bind virtual functions dynamically at runtime.
C.
A virtual function may be implemented in several derived classes. C++ dynamically binds the implementation of the function at runtime, decided by the actual class of the object referenced by the variable.
D.
The compiler finds a matching function according to parameter type, number of parameters, and order of the parameters at compile time.
19
Which of the following statements are true?
A.
Private members can only be accessed from the inside of the class and public members can be accessed from any other classes.
B.
A protected data field or a protected function in a base class can be accessed by name in its derived classes.
C.
A public data field or function in a class can be accessed by name by any other program.
Section 11.8 Abstract Classes and Pure Virtual Functions
20
Which of the following is an abstract function?
A.
virtual double getArea();
B.
virtual double getArea() = 0;
C.
double getArea() = 0;
D.
virtual double getArea();
21
Which of the following statements are true?
A.
An abstract class is declared using a keyword abstract.
B.
A class is abstract if it contains a pure virtual function.
C.
An abstract class is like a regular class except that you cannot create objects from it.
D.
You can declare a class abstract even though it does not contain abstract functions.
Section 11.9 Dynamic Casting
22
Which of the following statements are true?
A.
Assigning a pointer of a derived class type to a pointer of its base class type is called upcasting.
B.
Assigning a pointer of a base class type to a pointer of its derived class type is called downcasting.
C.
Upcasting can be performed implicitly without using the dynamic_cast operator.
D.
downcasting must be performed explicitly using the dynamic_cast operator.
23
Suppose you declared GeometricObject *p = &object. To cast p to Circle, use ___________.
A.
Circle *p1 = dynamic_cast<Circle>(p);
B.
Circle *p1 = dynamic_cast<Circle*>(p);
C.
Circle p1 = dynamic_cast<Circle*>(p);
D.
Circle p1 = dynamic_cast<Circle>(p);