Segment-5
Inheritance
Inheritance:
The capability of a class to derive properties and characteristics from another
classes is called Inheritance. Inheritance is one of the most important features of
Object-Oriented Programming.
Inheritance is a feature in which new classes are created from the existing classes.
The new class created is called “derived class” or “child class” and the existing class
is known as the “base class” or “parent class”.
The derived class inherits all the properties of the base class, without changing the
properties of base class and may add new features to its own. These new features in
the derived class will not affect the base class.
Syntax:
class <derived_class_name> : <access-specifier> <base_class_name>
{
//body
}
Modes of Inheritance: There are 3 modes of inheritance.
1. Public Mode: If we derive a subclass from a public base class. Then the public
member of the base class will become public in the derived class and protected
members of the base class will become protected in the derived class.
2. Protected Mode: If we derive a subclass from a Protected base class. Then both
public members and protected members of the base class will become protected in
the derived class.
3. Private Mode: If we derive a subclass from a Private base class. Then both
public members and protected members of the base class will become Private in the
derived class.
The below table summarizes the above three modes and shows the access specifier
of the members of the base class in the subclass when derived in public, protected
and private modes:
1. Explain the behavior of public and private members when a base class is inherited
publicly by the derived class.[Sp-24]
2. How do the properties of the following two derived class differ? [Sp-23]
Class D1: private B{}
Class D2: public B{}
Sheet for only classes but for exam book is mandatory
Prepared By: Muhammad Nazim Uddin, Lecturer (Adjunct), CSE, IIUC
Types of Inheritance in C++
1. Single Inheritance: In Single Inheritance, one class is derived from another class.
• It represents a form of inheritance where there is only one base and derived class.
Syntax:
class subclass_name : access_mode <base_class>
{
// body of subclass
};
C++ program to explain Single inheritance
#include<iostream>
using namespace std;
// base class
class Vehicle {
public:
Vehicle()
{
cout << "This is a Vehicle\n";
}
};
// sub class derived from a single base classes
class Car : public Vehicle {
//body of this class
};
int main()
{
Car obj;
return 0;
}
Output
This is a Vehicle
2. Multiple Inheritance: Multiple Inheritance is a feature of C++ where a class can
inherit from more than one class. i.e one subclass is inherited from more than
one base class.
Sheet for only classes but for exam book is mandatory
Prepared By: Muhammad Nazim Uddin, Lecturer (Adjunct), CSE, IIUC
Syntax:
class subclass_name : access_mode <base_class1>, access_mode <base_class2>, ....
{
// body of subclass
};
C++ program to explain multiple inheritance
#include <iostream>
using namespace std;
// first base class
class Vehicle {
public:
Vehicle() {
cout << "This is a Vehicle\n";
}
};
// second base class
class FourWheeler {
public:
FourWheeler()
{
cout << "This is a 4 wheeler Vehicle\n";
}
};
// sub class derived from two base classes
class Car : public Vehicle, public FourWheeler {
};
int main()
{
Car obj;
return 0;
}
Output
This is a Vehicle
This is a 4 wheeler Vehicle
3. Multilevel Inheritance: In this type of inheritance, a derived class is created
from another derived class.
Sheet for only classes but for exam book is mandatory
Prepared By: Muhammad Nazim Uddin, Lecturer (Adjunct), CSE, IIUC
C++ program to implement Multilevel Inheritance
#include <iostream>
using namespace std;
// base class
class Vehicle {
public:
Vehicle() {
cout << "This is a Vehicle\n";
}
};
// first sub_class derived from class vehicle
class fourWheeler : public Vehicle {
public:
fourWheeler()
{
cout << "Objects with 4 wheels are vehicles\n";
}
};
// sub class derived from the derived base class fourWheeler
class Car : public fourWheeler {
public:
Car() {
cout << "Car has 4 Wheels\n"; }
};
int main()
{
Car obj;
return 0;
}
Output:
This is a Vehicle
Objects with 4 wheels are vehicles
Car has 4 Wheels
4. Hierarchical Inheritance: In this type of inheritance, more than one subclass is
inherited from a single base class. i.e. more than one derived class is created from a
single base class.
Sheet for only classes but for exam book is mandatory
Prepared By: Muhammad Nazim Uddin, Lecturer (Adjunct), CSE, IIUC
C++ program to implement Hierarchical Inheritance
#include <iostream>
using namespace std;
// base class
class Vehicle {
public:
Vehicle() {
cout << "This is a Vehicle\n";
}
};
// first sub class
class Car : public Vehicle {
};
// second sub class
class Bus : public Vehicle {
};
int main()
{
Car obj1;
Bus obj2;
return 0;
}
Output
This is a Vehicle
This is a Vehicle
5. Hybrid (Virtual) Inheritance: Hybrid Inheritance is implemented by combining
more than one type of inheritance. For example: Combining Hierarchical inheritance
and Multiple Inheritance. Below image shows the combination of hierarchical and
multiple inheritances:
Sheet for only classes but for exam book is mandatory
Prepared By: Muhammad Nazim Uddin, Lecturer (Adjunct), CSE, IIUC
C++ program to implement Hybrid Inheritance
#include <iostream>
using namespace std;
// base class
class Vehicle {
public:
Vehicle() { cout << "This is a Vehicle\n"; }
};
class Fare {
public:
Fare() {
cout << "Fare of Vehicle\n";
}
};
class Car : public Vehicle {};
class Bus : public Vehicle, public Fare {};
int main()
{
Bus obj2;
return 0;
}
Output
This is a Vehicle
Fare of Vehicle
1.Write a program to implement multilevel inheritance.[Sp-23]
2.
3.
4.
Sheet for only classes but for exam book is mandatory
Prepared By: Muhammad Nazim Uddin, Lecturer (Adjunct), CSE, IIUC
Key Feature of Hybrid inheritance
Hybrid inheritance is also known as Virtual Inheritance.
It is a combination of two or more inheritance.
In hybrid inheritance, when derived class have multiple paths to a base class, a
diamond problem occurs. It will result in duplicate inherited members of the base
class.
To avoid this problem easily, we use Virtual Base Class. In this case, derived
classes should inherit base class by using Virtual Inheritance
Virtual Base Class
Suppose we have two derived classes B and C that have a common base class A, and
we also have another class D that inherits from B and C. We can declare the base
class A as virtual to ensure that B and C share the same sub object of A.
Diamond Problem Solution
Sheet for only classes but for exam book is mandatory
Prepared By: Muhammad Nazim Uddin, Lecturer (Adjunct), CSE, IIUC
1. What is virtual base class? Explain with writing a program[Aut-22]
2. Describe the diamond problem in the context of multiple inheritance in c++.How
can it be resolved using virtual inheritance? provide an example[Aut-23]
Ambiguity in Multiple Inheritance
When Two base classes have functions with the same name, while a class derived
from both base classes. How do objects of the derived class access the correct base
class function ? The name of the function alone is insufficient, since the compiler
can’t figure out which of the two functions is meant.
Solving Ambiguity in Multiple Inheritance
The problem is resolved using the scope-resolution operator to specify the class in
which the function lies. Thus
objC.A::show(); refers to the version of show() that’s in the A class,
objC.B::show(); refers to the function in the B class
Sheet for only classes but for exam book is mandatory
Prepared By: Muhammad Nazim Uddin, Lecturer (Adjunct), CSE, IIUC
Constructors, Destructors, and Inheritance :
It is possible for the base class, the derived class, or both to have constructor and/or
destructor functions.When a base class and a derived class both have constructor and
destructor functions, the constructor functions are executed in order of derivation. The
destructors functions are executed in reverse order. That is, the base class constructor
is executed before the constructor in the derived class. In Case of destructor functions,
the derived class’s destructor is executed before the base class’s destructor.
Here is a short program that illustrates when base class and derived class
constructor and destructor functions are executed:
# include <iostream >
using namespace std;
class base
{
public :
base () { cout << " Constructing base class \n"; }
~ base () { cout << " Destructing base class \n"; }
};
class derived
: public base
{
public :
derived () { cout << " Constructing derived class \n"; }
~ derived () { cout << " Destructing derived class \n"; }
Sheet for only classes but for exam book is mandatory
Prepared By: Muhammad Nazim Uddin, Lecturer (Adjunct), CSE, IIUC
};
int main ()
{
derived o;
return 0;
}
This program displays the following output:
Constructing base class
Constructing derived class
Destructing derived class
Destructing base class
Constructors in derived classes
1. How to invoke Base class parameterized constructor inside derived class
parameterized constructor? Give example.[Sp-23]
Nesting of Classes
A nested class is a class which is declared in another enclosing class.
A nested class is a member and as such has the same access rights as any other
member.
A nested class is declared within the scope of another class.
Sheet for only classes but for exam book is mandatory
Prepared By: Muhammad Nazim Uddin, Lecturer (Adjunct), CSE, IIUC
Output:
Previous Question Answer:
Q1. How to invoke Base class parameterized constructor inside derived class
parameterized constructor?Give example.
Answer:
# include <iostream >
using namespace std;
class base
{
int i;
public :
base (int n)
{
cout << " Constructing base class \n";
i = n;
}
~ base () { cout << " Destructing base class \n"; }
void showi () { cout << i << ’\n’; }
};
class derived : public base
{
int j;
public :
derived (int n) : base (n) // pass arg to base class .
{
cout << " Constructing derived class \n";
j = n;
}
Sheet for only classes but for exam book is mandatory
Prepared By: Muhammad Nazim Uddin, Lecturer (Adjunct), CSE, IIUC
~ derived () { cout << " Destructing derived class \n"; }
void showj () { cout << j << ’\n’; }
};
int main () {
derived o (10) ;
o. showi ();
o. showj ();
return 0;
}
Q2. write the output of this code
#include<bits/stdc++.h>
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(){
R r;
r.print();
return 0;
}
Output:
The output of the code will be
"inside Q”
Explanation:
The code defines three classes - P, Q, and R. Class P has a public member function
print(), which outputs the text "inside P". Class Q is a derived class of P and overrides
the print() function to output "inside Q". Class R is a derived class of Q but doesn't
define its own print() function, so it inherits the one from Q
In the main() function, an object of class R is created, and its print() function is called.
Since R doesn't define its own print() function, it uses the one from Q, which outputs
"inside Q". Therefore, the output of the program is "inside Q"
Sheet for only classes but for exam book is mandatory
Prepared By: Muhammad Nazim Uddin, Lecturer (Adjunct), CSE, IIUC
Correct Answer:
Int main()
{
V obc;
obc.A::cheers();
obc.B::cheers();
}
Output:
Class A: Hip-hip-hooray
Class B: Hip-hip-hooray
Answer:
#include <iostream>
using namespace std;
class vehicle{
public:
int wheels, speed;
void getvehicle(){
cout<<"wheels = " << wheels << endl;
cout<<"speed = " << speed << endl;
}
};
class car:public vehicle{
public:
Sheet for only classes but for exam book is mandatory
Prepared By: Muhammad Nazim Uddin, Lecturer (Adjunct), CSE, IIUC
int passengers;
void getcar(){
cout<<"Passengers = " << passengers << endl;
}
};
class truck: public vehicle{
public:
int load_lim;
void gettruck(){
cout<<"Load Limit = " << load_lim << endl;
}
};
int main() {
car car_obj;
truck truck_obj;
car_obj.wheels = 4;
car_obj.speed = 180;
car_obj.passengers = 5;
truck_obj.wheels = 6;
truck_obj.speed = 90;
truck_obj.load_lim = 500;
car_obj.getvehicle();
car_obj.getcar();
truck_obj.getvehicle();
truck_obj.gettruck();
return 0;
}
Prepared By
Muhammad Nazim Uddin,
Lecturer(Adjunct), CSE, IIUC
Sheet for only classes but for exam book is mandatory
Prepared By: Muhammad Nazim Uddin, Lecturer (Adjunct), CSE, IIUC
