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

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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 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 hypheno 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