Data abstraction and encapsulation

       The wrapping up of data and functions into a single unit is called encapsulation.This single unit is called the class.The data is not accessible to the outside world,and only those functions which are wrapped inside the class are capable of accessing the data directly.This gives rise to the data hiding or information hiding concept which is an essential feature of OOP language.

      Abstraction refers to the task of representing the essential featues without getting into the background details or explanations.Classes use the concept of abstraction and are defined as a list of attributes such as size,weight etc and functions to operate on these attributes.These attributes define the properties of the objects that are to be created and are called the “data members” and functions are called “member functions” of the object.Since classes use the concept of data abstraction the are known as ABSTRACT-DATA-TYPES or simply ADT.