Write down about public and private section in a class. Also draw the figure of data hiding facility in a class.

Classes

A class is a summary description of a set of objects. A class thus contains the descriptions of all the behaviours of the objects that it represents.  A class is a collection of data and the various operations that can be performed on that data.

Generally, a class specification has two parts:

1.       Class declaration

2.       Class function definition

The class declaration describes the type and scope of its members. The class function definitions describe how the class functions are implemented.

The general form of a class declaration is:

class class_name

{

private:

 variable declarations;

function declarations;

public:

variable declarations;

function declarations;

};

Private section

A private member variable or function cannot be accessed, or even viewed from outside the class. Only the class and friend functions can access private members.

By default all the members of a class would be private, for example, in the following class width is a private member, which means until we label a member, it will be assumed a private member.

class Box

{

   double width;

   public:

      double length;

      void setWidth( double wid );

      double getWidth( void );

};

Public section

Public members can be accessed from outside the class. The variables inside the class are known as data members and functions are known as member functions. Only the member functions can have access to the private data members and private functions. However, the public members (both function and data) can be accessed from outside the class.  All Objects of same class can access public members with or without using member functions from outside the class.

Data hiding facility in a class

Information hiding is the primary criteria of system and should be concerned with hiding the critical element in system. Information hiding separates the end users from illegal access of the requirement. Encapsulation supports information hiding by making use of the three access specifies of a class.

Accessing class members:

We can access class members like the following way-

Syntax:

object_name.function_name(argument_list);

example:

ob.getdata();

ob.display();