Class and object program in c++

Class and object program in c++ is simple and basic program in object oriented programming concept.

In this tutorial we will see C++ classes and objects, simple class program in c++.

First we will see what is class, how to define class and how to create object in c++.

What is class ?

Class definition : Class is a user defined data type. It encloses data members and member functions.

By default all the members of the class are private.

Syntax for class

How to define class

class class_name {

<visibility mode>:

Datatype mem1;


Datatype memN;

<visibility mode>:

return_type function_name(arguments);



return_type class_name :: function_name(arguments)


//body of function


How to create object

Class_name object_name1,…..object_nameN ;

Algorithm for simple class and object in c++

  1. Start
  2. Write class with member function and declare functions. class circle.
  3. Define function outside of class using scoe resolution operator
  4. Write a main function
  5. Create object
  6. Call function using objects.
  7. End

Area of circle program in c++ using class

12345678910111213141516171819202122232425262728293031#include <iostream>using namespace std;class circle{        float radius, area;   //data members    public:        circle()        {                cout<<“\n Enter the value of Radius : “;                cin>>radius;        }        void calculate();   //member function        void display();     //member function};void circle :: calculate()  //accessing data members of a class circle{        area = 3.14 * radius * radius;}void circle :: display(){        cout<<“\n Area of Circle : “<<area;}int main(){        circle cr;   //object created        cr.calculate();   //calling function        cr.display();  //calling function        return 0;}

Output :

classes and objects
classes and objects

Explanation :

1. Execution starts with main method.

2. First we create object of class

circle cr; => object created.

and default constructor get executed.

circle() {

cout<<“\n Enter the value of Radius : “;

cin>>radius;  => radios = 5


3. Next we call function in class circle using object

cr.calculate(){ => function get call and function executed.

area = 3.14 * radius * radius;  => area= 78.5

} => returns to main method

4. Next we call function display()  in class circle using object

cr.display(){ => function get call and function executed.

cout<<“\n Area of Circle : “<<area;  => Area of Circle : 78.5

}  => returns to main method

5. End with the program.