Class and Objects

Class

A class is a user-defined data type that we can use in our program, and it works as an object constructor, or a "blueprint" for creating objects.

data members -> storage -> variable

member function -> to perform operation -> function

int roll;   //data members
string name;

void display() // member functions
{
    information
}

How to create class?

class <className>
{
    public :   <-//access specifiers
    //data members
    int roll;
    // member functions
    void show(){ }
};

Access Specifiers

• Public
• Private
• Protected

class Student  // create class
{
    public:
    int roll;

    void show () {
        cout<<"Your roll number is : "<<roll<<endl;

    }
}

How to create object ?

classname objectName;

class Student // create class
{
    public:
    int roll;

    void show () {
        cout<<"Your roll number is : "<<roll<<endl;

    }
}
int main(){
    Student s1, s2;  //create object

    s1.roll = 123;
    s2.roll = 567;

    s1.show();
    s2.show();
}

Output :

Your roll number is : 123
Your roll number is : 567

Explanation :

Create a class Student, write access specifier public, declare 1 datamember roll.
create a show() function member and print Your roll number is : and roll variable.
In main function create object of Student class s1 and s2.
pass value in object s1.roll = 123
pass value in object s2.roll = 567
using object call show() function

Example 1:

#include <iostream>
using namespace std;

class Student
{
    public:

    int age;
    string name;

    void getData()
    {
        cout<<"Enter Name :";
        cin>>name;
        cout<<"Enter Your age :";
        cout>>age;
    }
     void showData()
     {
        cout<<"Name  :"<<name<<"Age : "<<age;<<endl;
     }


};
int main() {

    Student s1;
    s1.getData();
    s2.getData();

    s1.showData();
    s2.showData();

    return 0;
}

Output :

Enter Name : Ayesha
Enter Your age :20
Name : Ayesha Age : 20
Enter Name : Harshal
Enter Your age :20
Name : Harshal Age : 20

Explanation :

Create a class Student, write access specifier public, declare 2 datamember age and name.
create a getdata() function and print Enter name and age
create a showData() function and print name and variable, age and variable In main function create object of Student class s1 and s2.
using object call getData() and showData()

Example 2:

#include <iostream>
using namespace std;

class Rectangle
{
    public:

    int length;
    int breadth;

    void getData()
    {
        cout<<"Enter Length and Breadth :";
        cin>>length>>breadth;
        cout<<endl;

    }
    void calculateArea()
    {
        int area = length * breadth;
        cout<<"Area : "<<area;
        cout<<endl;
    }

};
int main() {

    Rectangle r1, r2;

    r1.getData();
    r1.calculateArea();

    r2.getData();
    r2.calculateArea();



    return 0;
}

Output :

Enter Length and Breadth : 20 10
Area : 200
Enter Length and Breadth :10 10
Area : 100

Explanation :

Create a class Rectangle, write access specifier public, declare 2 datamember length and breadth.
create member function calculateArea declare area variable and calulate length * breadth and print area.
In main function create object of Rectangle class r1 and r2.
using object call getData() and calculateArea()