C++ And Object in lecture3

DEV BHOOMI GROUP OF
INSTITUTIONS
SAHARANPUR
Name : Saurabh Chauhan
Class : M.C.A. 1ST (2013-15)
Roll no : 1358614017
Topic : Classes and Object. 1
Sub To : Mr. Rakesh Kumar
Sub By : Saurabh Chauhan

C++ CLASSES
&
OBJECT
WELCOME :

OUTLINE :
 Introduction of the class :
 Characteristics of the class :
 Format of the class :
 Define a class type :
 Implementing class methods :
 Introduction of an Object :
 Declaration of an object :
 Reasons for OOP :
 Thank you :
3

INTRODUCTION OF THE CLASS :
 A class is binding the data and methods.
 A class is a collection of objects of similar type.
 A class is an object factory (or producer ) that
produces similar objects.
 A class is just like an image and model and can say
a template.
 A class does not exists physically because it’s a
image only in our mind
 But object exists physically because a object is a
real world entity i.e. a pen , a chair , a desk , a dog ,
a bike , a car ,a men etc
 The class and object both are sub method of the
OOP’s methodology
4

WHY DO WE NEED TO HAVE CLASS ?
Characteristics of the class :
 Structures are public by default and classes are
private by default.
 Data more secure in the class.
 Class reduce the complexity.
 We can easy and well programming, if we use the
class in our program .
5

CLASSES IN C++
 A class definition begins with the keyword class.
 The body of the class is contained within a set of
braces, { } ; (notice the semi-colon).
class class_name
{
….
….
….
};
Any valid
identifier
Class body (data member
+ methods)

CLASSES IN C++
 Within the body, the keywords private: and public:
specify the access level of the members of the
class.
 the default is private.
 Usually, the data members of a class are declared
in the private: section of the class and the member
functions are in public: section.

CLASSES IN C++
 Format :
class class_name
{
private:
…
…
…
public:
…
…
…
};
private members data
or variables or
characteristics
Public members or methods
Or behavior

DEFINE A CLASS TYPE
Header
class class_name
{
access specifier :
data ;
access specifier :
methods ;
...
class Rectangle
{
private:
int width;
int length;
public:
void set(int w, int l);
int area();
}; 9
};
Body

IMPLEMENTING CLASS METHODS
 Class implementation: writing the code of
class methods.
 There are two ways:
1. Member functions defined outside class
 Using Binary scope resolution operator (::)
 “Ties” member name to class name
 Uniquely identify functions of particular class
 Different classes can have member functions with
same name
 Format for defining member functions
ReturnType ClassName::MemberFunctionName(
){
…
}

IMPLEMENTING CLASS METHODS
2. Member functions(method) defined inside class
 Do not need scope resolution
operator, class name;
class Circle
{
private:
double r,ar;
public:
void area ()
{
cin<<r ;
ar=r*r*3.14;
}
cout<<“n a area of circle -”<<ar;
};
Method
Defined
inside
class

// this is a program of area of circle
// methods (Defined outside class)
class Circle
{
private:
double r,ar;
public:
void area(); // mehtod
};
void circle ::area
{
cout<<“n enter the radius of the circle :”;
cin>>r;
ar=r*r*3.14;
cout<<“area of the circle :”<<ar;
}
Method
Defined outside class

13
OBJECT
 Object:
 a variable or an instance of a class
 Objects may represent any entity ,such as a person , a cat
a chair , a pen , a place , a bank account , a customer , a table
of data ,etc.
 for ex ,bike is an object .its characteristics are :its color
is black ,Its engine is of 500cc ,Its company is Suzuki .Its
behavior is to starting the engine ,changing the
gear ,using the break, etc.
 Declaration of an Object
 Initiation of an Object

14
WHAT IS AN OBJECT?
OBJECT
Operations
Data
set of methods
(public member functions)
internal state
(values of private data members)

EXAMPLE: A “RABBIT” OBJECT
 You could (in a game, for example) create an object
representing a rabbit
 It would have data:
 How hungry it is
 How frightened it is
 Where it is
 And methods:
 eat, hide, run, dig

CONCEPT: CLASSES DESCRIBE OBJECTS
 Every object belongs to (is an instance of) a class
 An object may have fields, or variables
 The class describes those fields
 An object may have methods
 The class describes those methods
 A class is like a template, or cookie cutter

17
DECLARATION OF AN OBJECT
class Rectangle
{
private:
int width;
int length;
public:
void set(int w, int l);
int area();
};
main()
{
Rectangle r1;
Rectangle r2;
r1.set(5, 8);
cout<<r1.area()<<endl;
r2.set(8,10);
cout<<r2.area()<<endl;
}

REASONS FOR OOP
1. Simplify programming
2. Interfaces
 Information hiding:
 Implementation details hidden within classes
themselves
3. Software reuse
 Class objects included as members of
other classes

C++ And Object in lecture3

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