a What is the difference between Classes and Structure in C

a) What is the difference between Classes and Structure in C++?

b) Explain the following with the help of a program in C++?

i) Class

ii) Object

iii) Constructor

c) What is a default constructor in c++?

Solution

a) Answer:

   1) class members have the private access by default,
     structure members have the public access by default.

b) Answer:

   i) Class:

       A class is a collection of data and methods.

       A class is used to specify the collection of an object and it combines data and methods for manipulating that data into single package. The data and functions within a class are called members of the class.

      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:

ii) Object:

    Object is a instance of class, 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:

iii) Constructor:

     A class constructor is a special member function of a class that is executed whenever objects of that class is created.

    A constructor will have same name as the class and it does not have any return type at all.

Example:

Constructors can be defined inside the class definition or outside class definition using class name and scope resolution :: operator.

c)Default Constructor:

    Default constructor is the constructor which doesn\'t take any argument. It has no parameter.

   Example:       

In above example, when the object is created the constructor is called which initializes its data members.