12438_classes and objects

7/29/2019 12438_Classes and Objects

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Classes and Objects



Specifying a Class

• A class is an extension of the idea of structure

used in C.

• It is a new way of creating and implementing a

user-defined data type.

• A class is a way to bind the data and its

associated functions together.

• It allows the data and functions to be hidden,

if necessary, from external use.



Class specification

• Class Declaration: - describes the type and scopeof its members.

• Class function definitions: - describes how theclass functions are implemented.

General form of Class Declaration

class class_name

{

Private:

variable declarations;

function declarations;

Public:

variable declarations;

function declarations;

};



• The class declaration is similar to the struct

declaration.

• The keyword class specifies, that what follows

is an abstract data of type class_name.

•

The body of the class is enclosed within braces{} and terminated by a semicolon(;).

• The class body contains the declaration of

variables and functions. These variables and

functions are collectively called class members:

- private and public.



Defining Member Functions

• Outside the class definition: - Member

functions that are declared inside a class have

to be defined separately outside the class.

• Inside the class definition : - Member function

is to replace the function declaration by the

actual function definition inside the class



Syntax

• Outside the class definition: -

Return_type class_name :: function_name (arg){

function body;

}

• Inside the class definition: -

class abc

{ //by default private

Int x,y; //variables declaration

Public:

void getdata(int a, int b); //declarationvoid putdata(void) //definition inside the class

{ cout << x << “\n”;

cout << x << “\n”;

}

};



Accessing Class Members

• The private data of a class can be accessed

only through the member functions of that

class.

• The main() cannot contain statements that

access x and y directly.

• Format for calling a member function:-

object_name.function_name (arg);

eg: - x.avg(100, 65.5);



WAP to find the average of three numbers using classes

#include<iostream.h>

#include<conio.h>

class abc{ //by default private

int x,y,z,a; //variables declaration

public: //member function

void avg(); //function declaration

cout << “ \n Enter the values of x, y, z”; cin >> x >> y >> z;

a = (x+y+z)/3;

cout << “ \n The average is: “ << a;

};

void main() output: Enter the values of x, y, z 3

{ abc btech; 5

btech.avg(); 4

getch(); The average is: 4

}



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12438_classes and objects

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