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Time' 'Narration
00:02 Welcome to the spoken tutorial on Polymorphism in C++.
00:07 In this tutorial we will learn,
00:10 Polymorphism.
00:11 Virtual members.
00:13 We will do this through an example.
00:16 To record this tutorial, I am using Ubuntu OS version 11.10 gcc g++ compiler v. 4.6.1
00:27 Let us start with the introduction to polymorphism.
00:31 Polymorphism is the ability to take different forms.
00:36 It is the mechanism to use a function with same name in different ways.
00:42 Let us see virtual functions.
00:45 Virtual function is the member function of a class.
00:49 It can be overriden in its derived class.
00:53 It is declared with virtual keyword.
00:57 Virtual function call is resolved at run-time.
01:01 Now let us see an example on virtual functions.
01:06 I have already written the code.
01:08 Let us go through it.
01:10 Note that our filename is virtual.cpp
01:15 In this program:
01:16 We will calculate the area of a rectangle, parallelogram and traingle.
01:22 This is our header file as iostream.
01:25 Here we are using std namespace.
01:29 Then we have a class parallelogram
01:33 This is the base class.
01:35 In this we have declared integer variables as width, height and ar.
01:42 These are declared protected.
01:45 Then we have function set_values declared as public.
01:50 Here we have passed two arguments as a and b.
01:55 Then we access the protected members using the public members.
02:00 This is our virtual function area.
02:04 Here we calculate the area of parallelogram.
02:07 Then we have class Rectangle as derived class.
02:12 It inherits the properties of base class parallelogram.
02:17 Here we override the function area.
02:21 Then we calculate the area of the rectangle.
02:23 And print the value.
02:25 Here we have another derived class as triangle.
02:29 This also inherits properties of the base class parallelogram.
02:35 Here again we override the function area.
02:39 Then we calculate the area of the triangle.
02:41 And print the value.
02:43 This is our main function.
02:46 Here we create an object of class parallelogram as p.
02:52 We can see here pointer parallel.
02:56 This is the pointer of class parallelogram.
03:00 This is called as Base pointer.
03:03 Pointer of base class can point to the object of the derived class.
03:08 Here we create objects of class Rectangle and Triangle.
03:14 Here, Parallel is assigned to the address of p.
03:18 Then we pass arguments as 3 and 2.
03:23 Then we call function area.
03:26 Here, Parallel is assigned to the address of rect
03:30 rect is the object of class Rectangle.
03:33 Again we pass arguments as 4 and 5.
03:37 And we call the function area.
03:40 And at last we assign Parallel is assigned to the address of Triangle
03:45 trgl.
03:47 This is the object of class Triangle.
03:51 Here we pass arguments as 6 and 5.
03:54 And call function area.
03:56 This is our return statement
03:59 Now let us execute the program
04:02 open the terminal by pressing Ctrl, Alt and T keys simultaneously on your keyboard.
04:09 To compile type:
04:10 g++ virtual.cpp -o vir Press Enter
04:20 Type: ./vir Press Enter
04:24 We can see that, The output is displayed as:
04:27 Area of parallelogram is 6
04:29 Area of rectangle is 20
04:31 and Area of triangle is 15
04:34 Come back to our slides.
04:36 Let us summarize.
04:37 In this tutorial, we learnt
04:39 Polymorphism.
04:41 Virtual functione.g. Virtualint area
04:45 As an assignment
04:46 Calculate the perimeter of rectangle, square and triangle.
04:50 Create perimeter as a virtual function.
04:54 Watch the video available at the link shown below
04:57 It summarizes the Spoken Tutorial project
05:00 If you do not have good bandwidth, you can download and watch it
05:04 The Spoken Tutorial Project Team
05:06 Conducts workshops using spoken tutorials
05:09 Gives certificates to those who pass an online test
05:14 For more details, please write to,
05:21 Spoken Tutorial Project is a part of the Talk to a Teacher project
05:25 It is supported by the National Mission on Education through ICT, MHRD, Government of Indiaabout:startpage
05:32 More information on this Mission is available at:\NMEICT-Intro
05:37 This is Ashwini Patil from IIT Bombay signing off

Thank You for joining.

Contributors and Content Editors

PoojaMoolya, Pratik kamble, Ranjana, Sandhya.np14, Sneha