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

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

Author: Ashwini Patil

Keywords: Overloading, Overriding, Video tutorial, C++.


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 Let us start with an introduction to function overloading.

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.

Highlight

#include<iostream>

This is our header file iostream.
Highlight

using namespace std;

Here we are using the std namespace.
Highlight

int add(int a, int b, int c)

Please write the function.

Then we have add function defined as int.

In this we have passed three arguments.

Int a, int b and int c;

Then we perform addition of three numbers.

And we return the value.

Highlight

float add(float d, float e)

{

return (d + e);

}Pls indicate the text to be highlighted.

Here we overload the function add.

It is declared as float.

We pass two arguments.

Then we perform the addition operation on 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 function main 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.

Here we print the result.

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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;

And this is the return statement
Let us execute the program
Open the terminal

Ctrl, Alt and Tkeys simultaneously

Open the terminal by pressing Ctrl, Alt and T keys simultaneously on ypur keyboard.
Type

g++ overload.cpp -o ovr

To execute

Type

./ovr

To execute type:

g++ overload.cpp -o ovr

Press Enter

To execute type

./ovr

Press Enter

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

Now we see:

Enter two floating point numbers

I will enter as:

4.5

8.9

The output is displayed as:

Sum of floating point numbers is 13.4

Slide 5 Now we will see function overriding.

Let us switch back to our slides.

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

Here is an example on function Overriding

Note that our filename is override.cpp.

Let us go through the code.

Highlight

#include <iostream>

using namespace std;

This is our header file.

Here we have the std namespace.

Highlight

class arithmetic

{

protected:

int a, b, sum, sub, mul, div;

Then 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.



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virtual int operations ()

{

sum= a + b;

cout<< "Addition of two numbers is "<< sum<<"\n";

}

};

Here we have virtual function as operations.

In this we add the two numbers.

And print the sum.

Here we close the class.

Highlight

class Subtract: public arithmetic

{

Now we have class Subtract as derived class.

This inherits the base class arithmetic.

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public:

int operations ()

{

sub= a - b;

cout<< "Difference of two numbers is "<<sub <<"\n";

}

};

In this we calculate the difference of two numbers.

And we print the difference.

Highlight

class Multiply: public arithmetic

{

public:

int operations ()

{

mul = a * b;

cout<< "Product of two numbers is "<< mul<<"\n";

}

};

Here we have another derived class as Multiply.

This also inherits base class arithmetic.

In this we calculate the product of two numbers.

And display the product.

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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.

And then we display the division.

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int main()

{

arithmetic *arith, p;

Subtract subt;

Multiply mult;

Divide divd;

Now 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.

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arith=&p;

arith->values(30,12);

arith->operations();

Here, p is set to the address of arith.Or arith is set to the address of p?


Reply to Rahul Katarey (15/03/2013, 16:33): "..."

P is set to the address of parallel.



Here we pass arguments as 30 and 12 in function values.

Then we call the function operations.

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arith=&subt;

arith->values(42,5);

arith->operations();

Now here we set subt to the address of arith.

And we pass 42 and 5 as arguments.

Again we call function operations.

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arith=&mult;

arith->values(6,5);

arith->operations();


Now we set mult to the address of arith.

And pass arguments as 6 and 5.

Then we call function operations.

Highlight

arith=&divd;

arith->values(6,3);

arith->operations();

And here again we set divd to the address of arith And pass arguments as 6 and 3.

Then we call function operations.

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return 0;

}

And this is our return statement.

Let us execute the program.

On the terminal


g++ override.cpp -o over2

./over2

Switch back to our terminal.

To execute type:

g++ override.cpp -o over2

Press Enter

Type:

./over2

Press Enter

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 and

Division of two numbers is 2

On the slides Let us go back to our slides.
Slide 6 Let us 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

Let us summarize:

In this tutorial we have seen

Function overloading.

eg. int add(int, int, int);

We have passed three arguments.

float add(float, float);

Here we have passed two arguments.

Function Overriding.

eg. virtual int operations ()

int operations ()

that was overrided.

And then we saw,

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

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Slide 10

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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

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