Advanced-C++/C2/Abstract-Class/English-timed

Time	Narration
00:01	Welcome to the spoken-tutorial on abstract class and pure virtual function in C++.
00:08	In this tutorial, we will learn:
00:10	* Abstract Classes
00:11	* Pure virtual function.
00:13	We will do this through an example.
00:16	To record this tutorial, I am using:
00:19	*Ubuntu OS version 11.10
00:23	*g++ compiler version 4.6.1
00:27	Let us start with an introduction to abstract class.
00:31	Abstract class is always a base class.
00:35	It contains at least one pure virtual function.
00:39	We cannot create an instance of abstract class.
00:43	Let us see pure virtual function.
00:45	A pure virtual function is a function with no body.
00:49	It is not defined in the base class.
00:52	It is declared as:
00:54	virtual void virtualfunname()=0;
01:00	A derived class must override the function.
01:04	Otherwise the compiler will give an error.
01:07	It is up to a derived class to implement the function.
01:11	Let us look at an example.
01:13	I have already typed the code on the editor.
01:16	I will open it.
01:18	Note that our file name is abstract.cpp.
01:22	This example involves addition and subtraction of two numbers.
01:28	Let us go through the code.
01:30	This is our header file as iostream.
01:33	Here we are using the std namespace.
01:36	This is declaration for a class named abstractinterface.
01:41	Then we have public specifier.
01:44	In this, we have declared a virtual function named numbers().
01:49	It is initialized to 0.
01:51	Then we have a non-virtual function.
01:55	And two integer variables as 'a' and 'b'.
01:59	Here, we access the input function.
02:01	In this, we accept the numbers 'a' and 'b'.
02:05	This is a derived class named add.
02:09	It inherits the properties of the base class "abstractinterface".
02:14	Here we override the function numbers().
02:18	In this, we perform addition of two numbers 'a'and 'b'
02:21	and store the result in integer variable "sum".
02:25	Then we print the result.
02:27	Here we have another derived class as sub.
02:31	This also inherits the base class "abstractinterface".
02:35	In this, again we override the function numbers().
02:39	And here we calculate the difference of two numbers 'a' and 'b'.
02:43	Then we print the difference.
02:45	This is our main() function.
02:48	Here we create an object of class "add" as obj1.
02:53	Then we call both the functions input() and numbers() using the object obj1.
02:59	Then we create another object of class "sub" as obj2.
03:04	Again, we call the two functions using the object obj2.
03:08	And this is our 'return' statement.
03:10	Now let us execute the program.
03:13	Open the terminal window by pressing Ctrl, Alt and T keys simultaneously on your keyboard.
03:21	To compile, type: g++ space abstract dot cpp space hyphen o space abs
03:31	press Enter.
03:32	Type: dot slash abs
03:34	press Enter.
03:36	It is displayed as Enter the numbers.
03:38	I will enter as 9 and 4.
03:42	The output is displayed as Sum is 13.
03:46	Again we see Enter the numbers.
03:49	I will enter as 8 and 3.
03:52	The output is displayed as diff is 5.
03:56	This brings us to the end of this tutorial.
03:59	Come back to our slides.
04:01	Let us summarize.
04:03	In this tutorial, we learnt:
04:04	Abstract class e.g. class abstractinterface.
04:09	Pure virtual function e.g. virtual void numbers()=0;
04:14	As an assignment- Create an abstract class student.
04:17	* Create a pure virtual function as Info.
04:20	* Accept the name and roll no of the student in the function.
04:25	* Create two derived classes marks and sports.
04:29	* In marks, accept marks of three subjects.
04:32	* In sports, enter marks scored in sports.
04:35	* Calculate the total marks.
04:38	* Then create another derived class as result.
04:41	* In this, display the name, roll-no and total marks of the student.
04:47	Watch the video available at the link shown below.
04:50	It summarizes the Spoken-Tutorial project.
04:53	If you do not have good bandwidth, you can download and watch it.
04:58	The Spoken Tutorial Project team: Conducts workshops using spoken tutorials.
05:03	Gives certificates to those who pass an online test.
05:07	For more details, please write to: contact@spoken-tutorial.org
05:14	Spoken-Tutorial Project is a part of the "Talk to a Teacher" project.
05:18	It is supported by the National Mission on Education through ICT, MHRD, Government of India.
05:25	More information on this mission is available at the link shown below: http://spoken-tutorial.org/NMEICT-Intro
05:30	This is Ashwini Patil from IIT Bombay, signing off. Thank You for watching.

Contributors and Content Editors

Gaurav, PoojaMoolya, Pratik kamble, Sandhya.np14