Advanced-C++/C2/Classes-And-Objects/English-timed

Time	Narration
00:01	Welcome to the spoken tutorial on Classes and Objects in C++.
00:07	In this tutorial, we will learn:
00:09	Classes
00:11	Objects Encapsulation and
00:14	Data abstraction.
00:16	We will do this with the help of an example.
00:20	To record this tutorial, I am using:
00:23	Ubuntu OS version 11.10
00:28	g++ compiler version 4.6.1
00:32	Let us start with the introduction to classes.
00:36	Class is created using a keyword class.
00:39	It holds data and functions.
00:42	Class links the code and data.
00:45	The data and functions of the class are called as members of the class.
00:51	Let us move on to objects.
00:53	Objects are variables.
00:55	They are the copy of a class.
00:58	Each of them has properties and behavior.
01:01	Properties are defined through data elements and
01:06	behavior is defined through member functions called methods.
01:10	Now let us see the syntax for a class.
01:14	Here, class is a keyword used to define a class.
01:18	Class-name is the name of the class.
01:21	public, private and protected are the access specifier.
01:26	And here we have defined the data members and the member functions as public, private and protected.
01:34	This is how we close the class.
01:37	Now let us see an example.
01:39	I have already typed the code on the editor.
01:42	I will open it.
01:44	Note that our filename is class hyphen obj dot cpp
01:50	In this example, we will calculate the area of a square using class.
01:56	Let me explain the code now.
01:58	This is our header file as iostream.
02:02	Here we are using the std namespace.
02:06	This is declaration for a class named square.
02:10	Here, I have not declared any access specifier.
02:14	So, by default it is private.
02:17	Hence, variable x is a private member of class square.
02:22	This is the public specifier.
02:25	Function area is a public function.
02:28	And this is how we close the class.
02:31	Now let us move back to our slides to know more about the access specifiers.
02:36	Public specifier-
02:39	The public specifier allows the data to be accessed outside the class.
02:44	A public member can be used anywhere in the program.
02:49	Private specifier-
02:51	The members declared as private cannot be used or accessed outside the class.
02:57	private members can be used only by the members of the class.
03:03	Protected specifier-
03:05	protected members cannot be accessed from outside the class.
03:10	They can be accessed by a derived class.
03:13	Let us move back to our program.
03:16	Here, in this statement we have the class name,
03:21	the scope resolution operator and the function name.
03:25	We must use this operator.
03:27	It specifies that function area is not a global function.
03:33	It is a member function of class square.
03:36	Here, we have passed an argument as int a.
03:40	Now, let us switch back to our slides to know more about the scope resolution operator.
03:46	It is used to access the hidden data.
03:49	To access the variable or function with the same name, we use the scope resolution operator ::.
03:56	Suppose the local variable and the global variable have same name.
04:01	The local variable gets the priority.
04:05	We can access the global variable using ::(scope resolution operator.)
04:10	Now, switch to our program.
04:12	Here the value of a is stored in x.
04:17	Then we return the area of the square.
04:20	Here x is a private member.
04:22	To access the private parameter, we used the public member a.
04:27	private members are always hidden.
04:30	This is our main function.
04:33	Here, sqr is the object of class square.
04:37	This is how we create an object.
04:40	class-name followed by the object-name.
04:43	Here, we call the function area using the object sqr and a .(dot) operator.
04:50	Then we pass an argument as 4.
04:53	We set the value of x as 4.
04:57	This is our return statement.Now click on Save.
05:00	Let us execute the program.
05:03	Open the terminal window by pressing Ctrl, Alt and T keys simultaneously on your keyboard.
05:11	To compile, type: g++ space class hyphen obj dot cpp space hyphen o space class
05:20	Press Enter.
05:22	Type./class(dot slash class).
05:24	Press Enter.The output is displayed as:
05:28	Area of the square is 16
05:30	Now, let us move back to our program.
05:35	So far now we have seen,
05:37	the data and functions combined together in a class.
05:41	class is a single unit
05:44	in which the data and the function using them is grouped.
05:49	This mechanism is called as Encapsulation.
05:53	Then we have seen class with the private and public members.
05:59	The private data is hidden.
06:02	It cannot be accessed outside the class.
06:05	This mechanism is called as Data abstraction.
06:09	The interface is seen but the implementation is hidden.
06:14	This brings us to the end of this tutorial.
06:17	Let us move back to our slides. Let us summarize.
06:20	In this tutorial, we have learnt:
06:23	Encapsulation Data Abstraction
06:25	Private members
06:27	int x;
06:29	Public functions int area(int);
06:32	'classes'class square
06:35	To create object,
06:37	square sqr;
06:39	To call a function using object sqr dot area();
06:43	As an assignment: write a program to find the perimeter of a given circle.
06:49	Watch the video available at the link shown below.
06:52	It summarizes the Spoken Tutorial project.
06:55	If you do not have good bandwidth, you can download and watch it.
07:00	The Spoken Tutorial Project team:
07:02	Conducts workshops using spoken tutorials.
07:05	Gives certificates to those who pass an online test.
07:09	For more details, please write to: contact@spoken-tutorial.org
07:16	Spoken Tutorial Project is a part of the "Talk to a Teacher" project.
07:20	It is supported by the National Mission on Education through ICT, MHRD, Government of India.
07:26	More information on this mission is available at the link shown below.
07:31	This is Ashwini Patil from IIT Bombay, signing off. Thank You for joining.

Contributors and Content Editors

PoojaMoolya, Pratik kamble, Sandhya.np14