Inheritance and Memory Allocation in Object-Oriented Programming (OOP) using C++, Slides of Object Oriented Programming

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Object-Oriented Programming

(OOP)

Lecture No. 22

Inheritance in Classes

► If a class B inherits from class A, then B contains all the characteristics (information structure and behavior) of class A

► The parent class is called base class and the

child class is called derived class

► Besides inherited characteristics, derived class may have its own unique characteristics

Inheritance in C++

►There are three types of inheritance in C++

 Public  Private  Protected

“IS A” Relationship

► IS A relationship is modeled with the help of public inheritance

► Syntax

class ChildClass : public BaseClass{ ... };

Accessing Members

►Public members of base class become

public member of derived class

►Private members of base class are not

accessible from outside of base class, even in the derived class (Information Hiding)

Example

class Person{

char *name; int age; ...

public:

const char *GetName() const; int GetAge() const; ...

};

Example

void Student::Print()

{

cout << name << “ is in” << “ semester ” << semester;

}

ERROR

Example

void Student::Print()

{

cout << GetName() << “ is in semester ” << semester;

}

Allocation in Memory

►The object of derived class is represented

in memory as follows

Data members of

base class

Data members of

derived class

base member base member ...

derived member derived member ... docsity.com

Allocation in Memory

►Every object of derived class has an

anonymous object of base class

Constructors

Base class constructor initializes the anonymous object

Derived class constructor initializes the derived class object

base member base member ...

derived member

derived member

...

class Parent{

public:

Parent(){ cout << “Parent Constructor...”;}

};

class Child : public Parent{

public:

Child(){ cout << “Child Constructor...”;}

};

Example

Constructor

►If default constructor of base class does

not exist then the compiler will try to generate a default constructor for base class and execute it before executing constructor of derived class

Constructor

►If the user has given only an overloaded

constructor for base class, the compiler will not generate default constructor for base class