Lecture3

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Dev Bhoomi Group of Institutions
Saharanpur

• Name Saurabh Chauhan
• Class M.C.A. 1ST (2013-15)
• Roll no 1358614017
• Topic Classes and Object.

Sub To Mr. Rakesh Kumar Sub
By Saurabh Chauhan
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C Classes Object

• WELCOME

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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

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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 its 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
  OOPs methodology

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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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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)
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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.

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Classes in C

• Format

class class_name private
public
private members data or variables or
characteristics
Public members or methods Or behavior
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Define a Class Type

• 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()
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Implementing class methods

• Class implementation writing the code of class
  methods.
• There are two ways
• 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 ClassNameMemberFunctionName( )

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Implementing class methods

• Member functions(method) defined inside class
• Do not need scope resolution operator, class
  name

class Circle private double r,ar
public void area ()
cinltltr arrr3.14
coutltlt\n \a area of circle -ltltar
Method Defined inside class
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// 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 coutltlt\n enter the radius of
the circle cingtgtr arrr3.14
coutltltarea of the circle ltltar
Method Defined outside class
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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

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What is an object?
OBJECT
set of methods (public member functions) interna
l state (values of private data members)
Operations Data
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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

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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

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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) coutltltr1.area()ltltendl r2.set(8,
10) coutltltr2.area()ltltendl
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Reasons for OOP

• Simplify programming
• Interfaces
• Information hiding
• Implementation details hidden within classes
  themselves
• Software reuse
• Class objects included as members of other
  classes

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Thank You