Advanced-C++/C2/Function-Overloading-And-Overriding/English

Title of script: Function Overloading and Overriding in C++

Author: Ashwini Patil

Keywords: Overloading, Overriding, Video tutorial.

Visual Cue	Narration
Slide 1	Welcome to the spoken tutorial on function Overloading in C++.
Slide 2	In this tutorial we will learn, Function Overloading. Function Overriding. We will do this with the help of examples.
Slide 3	To record this tutorial, I am using Ubuntu OS version 11.10 g++ compiler v. 4.6.1
Slide 4	Function Overloading means two or more functions can have same name. The number of arguments and the data-type of the arguments will be different. When a function is called it is selected based on the argument list.
Open funoverload.cpp	Let us look at an example In this program we will perform addition operation. I have already typed the code on the editor.
Point the cursor overload.cpp	Note that I have saved the file with the name overload.cpp Let me explain the code now.
Highlight #include<iostream>	This is our header file iostream.
Highlight using namespace std;	This is the using statement.
Highlight int add(int a, int b, int c)	Here we have add function defined as int. In this we have passed three arguments. Then we perform the addition of three numbers.
Highlight	Here we overload the function add. It is declared as float. We pass two arguments. Then we perform the addition of two numbers.
Highlight int main() {	This is our main function.
Highlight int add(int, int, int); float add(float, float); int a,b,c; float d,e,sum;	In main function we declare the add function with different arguments. Then we declare the variables.
Highlight cout << "Enter three integers\n"; cin >> a >> b >>c; sum = add(a, b, c); cout << "Sum of integers: " << sum << "\n";	Now we accept the values from the user. Then we call the function add with three arguments. And store the result in variable sum. And we print the result.
Highlight cout << "Enter two floating point numbers\n"; cin >> d >> e; sum = add(d, e); cout << "Sum of floats: " << sum << "\n";	Here we call the add function with two arguments. The result is stored in sum. And we print the result.
Highlight return 0;	This is the return statement
Click on Save	Now Click on Save
	Let us execute
Open the terminal Ctrl, Alt and Tkeys simultaneously	Open the terminal by pressing Ctrl, Alt and T keys simultaneously
Type g++ overload.cpp -o ovr To execute Type ./ovr	To compile the program type g++ overload.cpp -o ovr To execute type ./ovr
Highlight Output	Here it is displayed as: Enter three integers I will enter as: 10 25 48 The output is displayed as: Sum of integers is 83 Then we see: Enter two floating point numbers I will enter as: 4.5 8.9 Sum of floating point numbers is 13.4
Slide 5	Now we will see function overriding. Redefining a base class function in the derived class. The derived class function overrides the base class function. But the arguments passed are same. And the return-type is also same.
	Let us see an example on Function Overriding I have already typed the code on the editor. Lets take a look.
Highlight #include <iostream> using namespace std;	This is our header file as iostream. This is our std namespace.
Highlight class arithmetic { protected: int a, b, sum, sub, mul, div;	Here we have class arithmetic. In this we have declared integer variables as protected.
Highlight public: void values (int x, int y) { a=x, b=y; }	Then we have function values declared as public.
Highlight virtual int operations () { sum= a + b; cout<< "Addition of two numbers is "<< sum<<"\n"; } };	Then we have virtual function as operations. In this we calculate the addition of two numbers. And print the sum. Here we close the class.
Highlight class Subtract: public arithmetic {	Then we have class Subtract as derived class. This inherits the base class arithmetic.
Highlight public: int operations () { sub= a - b; cout<< "Difference of two numbers is "<<sub <<"\n"; } };	In this we calculate the difference of two numbers.
Highlight class Multiply: public arithmetic { public: int operations () { mul = a * b; cout<< "Product of two numbers is "<< mul<<"\n"; } };	Then we have another derived class as Multiply. This also inherits class arithmetic. In this we calculate the product of two numbers.
Highlight class Divide: public arithmetic { public: int operations () { div = a / b; cout<< "Division of two numbers is "<< div<<"\n"; } };	And here we have class Divide this also inherits the base class arithmetic. In this we calculate the division of two numbers.
Highlight int main() { arithmetic *arith, p; Subtract subt; Multiply mult; Divide divd;	This is our main function. In this we create an object of class arithmetic as p. arith is the pointer to the class arithmetic. Then we have subt object of class Subtract. mult object of class Multiply. And divd object of class Divide.
Highlight arith=&p; arith->values(30,12); arith->operations();	p is set to the address of arith. Here we pass arguments as 30 and 12 in function values. Then we call function operations.
Highlight arith=&subt; arith->values(42,5); arith->operations();	Here we set subt to the address of arith. Then we pass 42 and 5 as arguments. Again we call function operations.
Highlight arith=&mult; arith->values(6,5); arith->operations();	Now we set mult to the address of arith. And pass arguments as 6 and 5. Now we call function operations.
Highlight arith=&divd; arith->values(6,3); arith->operations();	Then we set divd to the address of arith and pass arguments as 6 and 3. Now we call function operations.
Highlight return 0; }	This is our return statement. Now let us execute the program.
On the terminal g++ override.cpp -o over2 ./over2	Come back to our terminal. To execute type: g++ override.cpp -o over2 ./over2
Highlight The output	The output is displayed as: Addition of two numbers is 42 Difference of two numbers is 37 Product of two numbers is 30 Division of two numbers is 2
On the slides	Let us go back to our slides.
Slide 6	Now we will see the difference of overloading and overriding. Overloading can occurs without inheritance. Overriding occurs when one class is inherited from another. In overloading the arguments and the return-type must differ. In overriding the arguments and the return type must be same. In overloading the function name is same. But it behaves differently depending on the arguments passed to them. In overriding the function name, arguments passed and the return type is same. Derived class function can perform different operations from the base class.
	This brings us to the end of this tutorial.
Slide 7 Summary	In this tutorial we have seen Function overloading. eg. int add(int, int, int); float add(float, float); Function Overriding. eg. virtual int operations () int operations () Difference between both.
Slide 8 Assignment	As an assignment Write a program that will calculate the area of rectangle, square and circle. Using function overloading.
Slide 9 About the Spoken Tutorial Project	Watch the video available at the link shown It summarizes the Spoken Tutorial project If you do not have good bandwidth, you can download and watch it
Slide 10 Spoken Tutorial Workshops	The Spoken Tutorial Project Team Conducts workshops using spoken tutorials Gives certificates to those who pass an online test For more details, please write to, contact@spoken-tutorial.org
Slide Number 11 Acknowledgement	Spoken Tutorial Project is a part of the Talk to a Teacher project It is supported by the National Mission on Education through ICT, MHRD, Government of India More information on this Mission is available at: http://spoken-tutorial.org\NMEICT-Intro
	This is Ashwini Patil from IIT Bombay signing off Thank You for joining.

Contributors and Content Editors

Ashwini