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

Title of script: Functions in C and C++

Author: Ashwini R. Patil

Keywords: Functions, call by value, call by reference, Video Tutorial, C++

Visual Cue	Narration
Slide 1	Welcome to the spoken tutorial on Function calls in C and C++
Slide 2	In this tutorial we will learn about type of function calls, namely call by value. call by reference. We will do this through an example.
Slide 3	To record this tutorial, I am using Ubuntu Operating system version 11.10 gcc and g++ Compiler version 4.6.1 on Ubuntu
Slide 4	Let us start with the introduction to functions call by value It is a method of passing arguments to the function. When we pass a variable by value it makes a copy of the variable . Changes made to the arguments inside the function will remain in the function. It will not be affected outside the function.
	Let us see a program on function call by value. I have already typed the program on the editor. So i will just open it.
Point the cursor to callbyval.c	Please note that our filename is callbyval.c In this program we will calculate the cube of a number. Let me explain the code now.
Highlight #include <stdio.h>	This is our header file
Highlight int cube(int x) { x=x*x*x; return(x); }	Here we have function cube having an argument as x. In this function, we calculate the cube of x and return the value of x.
Highlight int main()	This is our main function.
Highlight int n=8;	Here we give the value of n as 8.
Highlight printf("Cube of %d is %d\n",n,cube(n));	Then we call the function cube. And print the value of n and the cube of n.
Highlight return 0;	This is our return statement.
	click on Save. Now let us execute the program.
Press Ctrl, Alt and T keys simultaneously	Open the terminal by pressing Ctrl, Alt and T keys simultaneously
Type gcc callbyval.c -o val Type ./val	To compile the program, type gcc callbyval.c -o val To execute, type ./val
Highlight Output	We see the output is displayed as Cube of 8 is 512.
	Now we will see function call by reference. Let us go back to our slides.
Slide 5	It is another method of passing arguments to the function. This method copies the address of the argument instead of the value. Changes made to the arguments inside a function can affect them outside. In this we need to declare the arguments as pointer type.
On the editor	Let us see an example on function call by reference. I have already typed the code on the editor. Lets take a look.
Point to the filename callbyref.c	Note that our filename is callbyref.c Let me explain the code now.
Highlight #include<stdio.h>	This is our headerfile as stdio.h
Highlight int swap(int *a, int *b)	Then we have function swap This function will exchange the values of the variables. You can see that the arguments passed in the function are pointer type.
Highlight int t; t=*a; *a=*b; *b=t;	Here we have declared an integer variable t. First value of *a is stored in t. Then value of *b is stored in *a. Then value of t is stored in *b.
Highlight int main()	This is our main function.
Highlight int i, j;	Here we have declared two integer variables as i and j.
Highlight printf("Enter the values "); scanf("%d%d",&i,&j);	Then we take the values of i and j as user inputs. &i and &j will give the memory address of i and j.
Highlight printf("Before swapping %d and %d\n",i,j);	First we print the values before swapping.
Highlight swap(&i,&j);	Here we call the function swap
Highlight printf("After swapping %d and %d\n",i,j);	Now we print the values after swapping.
Highlight return 0;	This is our return statement.
Click on Save	Click on Save
On the terminal	Let us execute the program Come back to our terminal
Type gcc callbyref.c -o ref Type ./ref	Now compile the program as before, gcc callbyref.c -o ref let us execute ./ref
Highlight Output	We see it is output is displayed as: Enter the values I will enter as 6 and 4 Before swapping 6 and 4 After swapping 4 and 6
	NOW LET US SEE HOW TO EXECUTE THE SAME PROGRAM IN C++ I have the code, lets go through it.
Point cursor callbyref.cpp	Note that our filename is callbyref.cpp Let me explain the code now.
Type <iostream>	First we will change the header file <iostream>
Type using namespace std;	We have used the std namespace
Highlight int swap(int &x, int &y) { int temp; temp = x; x = y; y = temp; }	The function declaration is same in C++. In this we pass the arguments as &x and &y. This will give the memory address of x and y. Here we swap the values.
Highlight The code	Rest of the code is similar to our C code. The printf and scanf statement is replaced by cout and cin statement.
On the terminal	Let us compile the program Come back to the terminal
Type g++callbyref.cpp -o ref1 Type ./ref1	Type g++ callbyref.cpp -o ref1 press Enter To execute Type ./ref1
Highlight Output	Here it is displayed as: Enter values of a and b I will enter 4 3 The output is displayed as Before swapping a and b: 4 and 3 After swapping a and b: 3 and 4
	This brings us to the end of this tutorial. Let us go back to our slides.
Slide 6	Let us summarize, In this tutorial we learn't: Function call by value. Function call by reference.
Slide 7 Assignment	As an assignment Write a similar program to calculate the cube of a number. Using call by value in C++.
Slide 8 About the Spoken Tutorial Project	Watch the video available at http://spoken-tutorial.org /What\_is\_a\_Spoken\_Tutorial It summarises the Spoken Tutorial project If you do not have good bandwidth, you can download and watch it
Slide 9 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 10 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 Thank You for joining

Contributors and Content Editors

Ashwini