classes and objects

Class -A class is an expanded concept of a data structure: instead of holding only data, it can hold both data and functions.

Definition:

A class is a group of objects which show a common property.

OR

A class is a collection of objects of similar type.

Once a class is defined, any number of objects can be created which belong to that class.

For example – Define a class to print the values of two numbers.

Class Helloworld

{

    int one;

    int two;

    public:

    void setdata()

      {

        cout<<”enter two numbers”;

        cin>>one>>two;

      }

     void putdata()

      {

      cout<<one<<endl<<two;

      }

};

int main()

    {

     Hellowrold obj;

     Obj.setdata();

     Obj.putdata();

     return 0;

    }

Classes are generally declared using the keyword class, with the following format:

class class_name

{

access_specifier_1:

   member1;

access_specifier_2:

   member2;

...

};

Object -An object is an instantiation of a class. In terms of variables, a class would be the type, and an object would be the variable.

                               Or

It may be defined as identifiable identity with some characteristics and behavior.

Syntax of creating Object:

Class_name Object_Name

If we have class named AB then the Object of this class can be created using above syntax as

AB Obj;

Abstract class

An abstract class is a class that is designed to be specifically used as a base class. An abstract class contains at least one pure virtual function.

You declare a pure virtual function by using a pure Specifier

(= 0) in the declaration of a virtual member function in the class declaration.

The following is an example of an abstract class:

class AB {

            public:

            virtual void f() = 0; //Pure virtual Function

             };

Concrete class – it is a derived class that implement all the missing functionality of a abstract class is called a concrete class

The following is an example of an concrete class: 

 class CD : public AB //Here class AB is abstract class

{                          // Declare Above
        public:
        CD()

           {   /* set up the CD */  }
       virtual f()   // implementation of f() of class AB

           {
           /* do stuff of f() */
           }
};
Advantages and disadvantages of object oriented programming

Advantages –

1- Reusability of code.

2- Ease of comprehension.

3- Ease of fabrication and maintenance.

4- Ease of redesign and extension.

5- Data can be divided as public and private.(data protection)

6- Program development becomes easy due to increased modularity.(abstraction and encapsulation)

Disadvantages –

1. 1 The relation among classes become artificial at times
2. 2  The object oriented programming design id difficult.
3. 3  OOP is a high level concept so takes more time to execute as many routines run behind at the time of execution.
4. 4  Offers less number of functions as compared to low level programming which interacts directly with hardware.
5. 5  Increased burden on part of OOP developer.