Class and object - Programming

Class and object

Class

A class is use define datatype which bind the data and member function together .

It allows the data and member functions to be hidden if necessary from external use.

The internal data of class is called as data member and functions are called as member function. public member can access outside the class .

The variable or instance of class is called as objects.

The only difference between structur and class is that  by default member of class is private while by default member of structure is public.

Syntax:

Class classname

{

Private:

Datatype declaration ;

Function declaration ;

Public:

data-type declaration ;

Function declaration ;

};

Eg :

class committee

{

int roll no;

char name[20];

public:

void accept(int a, char b);

void display();

};

Access specifiers :

1] Public : -
      
The member which can be declare in public section can access                          from outside the class the public member is an interface                                  between the outside word and private

member, using object of class  we can access the public                            member.

2]Private : -     

The member which can be declare in private section we can                              access that within the class . the private member can not                                access from outside the class.

The member function and friend of this class can access this                            member.

3]Protected :- 

The protected member is same like private member only                                  benefit  is that it  provided one additional benefit that they can                            be accessed in child classes which are  called derived  classes.        

           

Object of class  :-

               The access member of class we required on object by using that we                   can access data member as well as member function.

               When  we create an object of class  memory is allocated ,constructor                  is called implicitly and memory get initialize.

               This process of object creation is called as instantiation .

Syntax:

Int main()

{

Class name object name;

}

Or we can also create object after class end

Class class name {

} object;

Inside the class:

Lets see how to define function inside the class.

class student{

int roll no;

char name[20];

public:

void getdata()

{

Cout<<”enter roll no and name ”;

Cin>>rollno>>name;

}

void putdata()

{

cout<<rollno<<name;

}

};

Outside the class :

The function can be define after the class declaration however the prototype of function should be appear inside the class.

Syntax :

 return type class name :: function name

{

- - - -

- - - -

}

#include <cstdlib>

#include<iostream>

using namespace std;

class student

{

    int roll ;

    char name[20];

public:

    void getdata()

    {

       

        roll=23;

        cout<<"enter roll num and name"<<endl;

        cin>>roll>>name;

    }

        void putdata()

        {

            cout<<roll<<name;

        }

   

};

int main()

{

    student ob;

    ob.getdata();

    ob.putdata();

    return 0;

}

*****************************************************

Output

enter roll num and name

1 rohan

1 rohan

Array of object

The array of variable of class data type is called array of object .

Example :

If class is student in a class so we define array of  student with 10 objects.

class Student

{

Int roll no;

char name[20];

public:

void getdata();

void putdata();

};

The array of object is created as follows s[10];

We can access array of object 

student ob[10];

ob[i].getdata;

ob[i].pudata;

Program for accept and display  student info using array of object.

#include <cstdlib>

#include<iostream>

using namespace std;

class student

{

    int roll;

    char name[100];

public:

    void getdata();

    void putdata();

};

void student::getdata()

{

    cout<<"enter roll number:: ";

    cin>>roll;

    cout<<"enter the name:: ";

    cin>>name;

}

void student::putdata()

{

    cout<<"roll no :: "<<roll<<"\t";

    cout<<"name is :: "<<"\t"<<name<<"\n";

   

}

int main(int argc, char** argv) {

    int i,n;

    student s[10];

    cout<<"enter no of student:";

    cin>>n;

    for(i=0;i<n;i++)

    {

        s[i].getdata();

    }

    for (i=0;i<n;i++)

    {

        s[i].putdata();

    }

    return 0;

}

****************************************

Output

enter no of student:2

enter roll number:: 1

enter the name:: A

enter roll number:: 2

enter the name:: B

roll no :: 1    name is ::      A

roll no :: 2    name is ::      B

So you might think how it sored in array so below is image show  how this information stored in array using object.