1. 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
3. 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
4. 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
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5. 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 .
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6. 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)
7. 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.
8. CLASSES IN C++
Format :
class class_name
{
private:
…
…
…
public:
…
…
…
};
private members data
or variables or
characteristics
Public members or methods
Or behavior
9. 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
10. 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(
){
…
}
11. 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
12. // 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. 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. 14
WHAT IS AN OBJECT?
OBJECT
Operations
Data
set of methods
(public member functions)
internal state
(values of private data members)
15. 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
16. 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. 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;
}
18. 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