What is a inheritance in C++?

Iwe3official

9 Nov, 2022

INHERITANCE

(Concept)

Existing class are main components of inheritance
New classes can be derived from existing class
The properties of existing class are simply extended to new class
The new class created using such methods are called as derived class and the existing classes are known as base classes. The relationship between new class and existing class are known as kind of relationship.
The programmer can define new member variables and functions in derived class but the base class remain unchanged.
The object of derived class can access members of base class as well as derived class. On the other hand the base class cannot access members of derived class. The base classes do not know about their sub classes.

Q)Write a program to derive a class publically from base class. Declare the base class member under private section.

Explanation: Class B is derived publically from base class A. The private members of the base class can be accessed by using public member functions of the base class. The object b invokes the member function show() of the derived class. The function show() invokes show_x() function of base class. The object b can access member function defined in both base class and derived class. i.e

b.show() //invoke member function of the derived class.

b.show_x() // invokes member function of base class.

(2) PRIVATE INHERITANCE

The object of privately derived class cannot access the public members of base class under public section.

Q.) Write a program to derive a class privately. Declare the member of base class under public section.

#include<iostream.h>
#include<conio.h>
class A {
public :
int X;
};
class B : private A {
public :
int Y;

B() {

X=20;

Y=40; }

void show() {
cout<<“X=“<<X;
cout<<“Y=“<<Y;
}
};
void main() {
clrscr();
B b;
b.show();
}

OUTPUT

X=20
Y=40

Explanation: class B is a derived class from class A. The member variable X is a public member of base class. The object b of derived class cannot access variable x directly.
b.X// cannot access
Member function of derived class can access members of base class. i.e the function show() does the same.

Protected inheritance

Why??
The member functions of derived class cannot access the private member variables of base class. The private members of base class can be accessed using public member functions of same class. This approach makes a program lengthy. To overcome the problem associated with private data another access specifier called protected was introduced.

Q) Write a program to declare protected data in base class. Access data of base class declared under protected section using member functions of derived class.

Types of inheritance

The process of inheritance depends on (1)number of base classes (i.e program can use one or more base class to derive a single class)
(2)Nested derivation (the derived class can be used as base class and new class can be derived from it.

Different types of inheritance are:

Single
Multiple
Hierarchical
Multilevel
Hybrid
Multipath

Single inheritance

When only one base class is used for derivation of a class and derived class is not used as base class, such type of inheritance between one base and derived class is known as single inheritance.