Difference between revisions of "Advanced-C++/C2/Abstract-Class/English-timed"

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Revision as of 15:04, 9 October 2014


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 v. 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 upto 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 filename 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 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 eg. class abstractinterface
04:09 Pure virtual function eg. 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 class 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, 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