Source Code : Classes and Objects in C++

Classes and Objects

  The main purpose of C++ programming is to add object orientation to the C  programming language and classes are the central feature of C++ that supports object-oriented programming and are often called user-defined types.

C++ Class Definitions:

  When you define a class, you define a blueprint for a data type. This doesn't actually define any data, but it does define what the class name means, that is, what an object of the class will consist of and what operations can be performed on such an object.

A class definition starts with the keyword class followed by the class name; and the class body, enclosed by a pair of curly braces. A class definition must be followed either by a semicolon or a list of declarations. For example, we defined the Box data type using the keyword class as follows:

class Box

{

public:

double length; // Length of a box

double breadth; // Breadth of a box

double height; // Height of a box

};

Define C++ Objects:

  A class provides the blueprints for objects, so basically an object is created from a class. We declare objects of a class with exactly the same sort of declaration that we declare variables of basic types. Following statements declare two objects of class Box:

Box Box1; // Declare Box1 of type Box

Box Box2; // Declare Box2 of type Box

Both of the objects Box1 and Box2 will have their own copy of data members.

Classes & Objects in Detail

Concept                                                          Description  

Class member functions   A member function of a class is a function that has its definition or its prototype within the class definition like                                        any other variable.  

Class access modifiers   A class member can be defined as public, private or                                           protected. By default members would be .  

Constructor & destructor :  A class constructor is a special function in a class that is   called when a new object of the class is created. A destructor   is also a special function which is called when created object   is deleted.  

C++ copy constructor   The copy constructor is a constructor which creates an   object by initializing it with an object of the same class,   which has been created previously.  

C++ friend functions   A friend function is permitted full access to private   and protected members of a class.  

C++ inline functions   With an inline function, the compiler tries to expand   the code in the body of the function in place of a call   to the function.  

The this pointer in C++   Every object has a special pointer this which points   to the object itself.  

Pointer to C++ classes   A pointer to a class is done exactly the same way a   pointer to a structure is. In fact a class is really just a   structure with functions in it.  

Static members of a class   Both data members and function members of a class   can be declared as static.  

Class Member Functions

  A member function of a class is a function that has its definition or its prototype within the class definition like any other variable. It operates on any object of the class of which it is a member, and has access to all the members of a class for that object.

class Box

{

public:

double length; // Length of a box

double breadth; // Breadth of a box

double height; // Height of a box

double getVolume(void);// Returns box volume

};