C++ (Object and Class)

The major purpose of C++ programming is to introduce the concept of object orientation to the C programming language.

Object Oriented Programming is a paradigm that provides many concepts such as inheritance, data binding, polymorphism etc.

The programming paradigm where everything is represented as an object is known as truly object-oriented programming language. Smalltalk is considered as the first truly object-oriented programming language.

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OOPs (Object Oriented Programming System)

Object means a real word entity such as pen, chair, table etc. Object-Oriented Programming is a methodology or paradigm to design a program using classes and objects. It simplifies the software development and maintenance by providing some concepts:

• Object
• Class
• Inheritance
• Polymorphism
• Abstraction
• Encapsulation

C++ Object

In C++, Object is a real world entity, for example, chair, car, pen, mobile, laptop etc.

In other words, object is an entity that has state and behaviour. Here, state means data and behaviour means functionality.

Object is a runtime entity, it is created at runtime.

Object is an instance of a class. All the members of the class can be accessed through object.

Let's see an example to create object of employee class using e1 as the reference variable.

1. Employee e1;  //creating an object of Employee      

In this example, Employee is the type and e1 is the reference variable that refers to the instance of Employee class.

C++ Class

In C++, class is a group of similar objects. It is a template from which objects are created. It can have fields, methods, constructors etc.

Let's see an example of C++ class that has three fields only.

1. class Employee   
2.  {    
3.      public:  
4.      int id;  //field or data member     
5.      float salary; //field or data member  
6.      String name;//field or data member    
7.  }    

C++ Object and Class Example

Let's see an example of class that has two fields: id and name. It creates instance of the class, initializes the object and prints the object value.

1. #include <iostream>  
2. using namespace std;  
3. class Employee {  
4.    public:  
5.       int id;//data member (also instance variable)      
6.       string name;//data member(also instance variable)      
7. };  
8. int main() {  
9.     Employee e1; //creating an object of Employee   
10.     e1.id = 201;    
11.     e1.name = "Anurag Rana";   
12.     cout<<e1.id<<endl;  
13.     cout<<e1.name<<endl;  
14.     return 0;  
15. }  

C++ Class Example: Initialize and Display data through method

Let's see another example of C++ class where we are initializing and displaying object through method.

1. #include <iostream>  
2. using namespace std;  
3. class Employee {  
4.    public:  
5.        int id;//data member (also instance variable)      
6.        string name;//data member(also instance variable)      
7.        void insert(int i, string n)    
8.         {    
9.             id = i;    
10.             name = n;    
11.         }    
12.        void display()    
13.         {    
14.             cout<<id<<"  "<<name<<endl;    
15.         }    
16. };  
17. int main(void) {  
18.     Employee e1; //creating an object of Employee   
19.     Employee e2; //creating an object of Employee 
20.     e11.insert(1101, "Anurag");    
21.     e2.insert(1102, "Pankaj");    
22.     e1.display();    
23.     e2.display();  
24.     return 0;  
25. }  

C++ Class Example: Store and Display Employee Information

Let's see another example of C++ class where we are storing and displaying employee information using method.

1. #include <iostream>  
2. using namespace std;  
3. class Employee {  
4.    public:  
5.        int id;//data member (also instance variable)      
6.        string name;//data member(also instance variable)  
7.        float salary;  
8.        void insert(int i, string n, float s)    
9.         {    
10.             id = i;    
11.             name = n;    
12.             salary = s;  
13.         }    
14.        void display()    
15.         {    
16.             cout<<id<<"  "<<name<<"  "<<salary<<endl;    
17.         }    
18. };  
19. int main(void) {  
20.     Employee e1; //creating an object of Employee   
21.     Employee e2; //creating an object of Employee  
22.     e1.insert(201, "Sonoo",990000);    
23.     e2.insert(202, "Nakul", 29000);    
24.     e1.display();    
25.     e2.display();    
26.     return 0;  
27. }  

Anurag Rana