C-and-C++/C2/Functions/English

Title of script: Functions in C and C++

Author: Ashwini R. Patil

Keywords: Functions, return statement, Video Tutorial

Visual Cue	Narration
Slide 1	Welcome to the spoken tutorial on Functions in C and C++
Slide 2	In this tutorial we will learn, What is a function Syntax of function Significance of return statement Few examples on functions We will also see some common errors and their solutions.
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 A function is a self-contained program executing a specific task Every program consists of one or more functions Once it is executed the control will be returned back from where it was accessed
Slide 5	Let us see the syntax for function ret_type fun_name(parameters) Or ret_type fun_name( ) ret-type defines the type of data that the function returns fun_name defines the name of the function parameters is the list of variable names and their types
Slide 6	We can specify an empty parameter list This is called as functions without arguments. This is called as functions with arguments.
	Let us see a program using void I have already typed the program on the editor So i will just open it
Point the cursor on the filename function.c	Please note that our filename is function and I have saved the file with the extentsion .c Let me explain the code now
Highlight #include <stdio.h>	This is our header file
Highlight void add()	Before using any function it must be defined Here we have declared a function called add Note that add function is without any arguments And the return type is void
	There are two types of functions User-defined that is our add function Pre-defined that is printf and main function
Highlight int a = 2; int b = 3;	Here we have initialized a and b by assigning them values as 2 and 3
Highlight int c = a + b;	Here we have declared a variable c Then we add the values of a and b The result is stored in c
Highlight printf("Value of C is %d\n",c);	Then we print the result
Highlight void main()	This is our main function
Highlight add();	Here we call the add function The addition operation will be performed and the result will be printed.
	Now click on Save Now let us execute the program
Press Ctrl, Alt and T keys simultaneously	Please open the terminal window by pressing Ctrl, Alt and T keys simultaneously
Type gcc function.c -o fun Type ./fun	To compile the program, type gcc function.c -o fun To execute, type ./fun
Highlight Output	We see the output is displayed as Sum of a and b is 5
On the editor	Now come back to our program Functions contains special identifiers called as parameters or arguments Let us see the same example with arguments
Type int add(int a, int b)	I will just change a few things here Type int add(int a, int b) Here we have declared a function called add int a and int b are the arguments of the function add
Delete int a=2; int b=3;	Let us delete this No need to initialize a and b here
Type int main()	Then type int main()
Type int sum;	Let us declare a variable sum here type int sum;
Highlight sum = add(5,4);	Then type sum = add(5,4); Here we call the add function Then we pass the parameters as 5 and 4 5 will be stored in a and 4 will be stored in b
	The addition operation will be performed The returned value c will be stored in sum
	Let us now print the result. Hence type here printf(“Sum is %d\n”,sum);
	Delete this as we have already called the function above.
	Type return 0; A non-void function must use a return statement that returns a value.
Click on Save	Click on Save
On the terminal	Let us execute the program Come back to our terminal
Type gcc function.c -o fun Type ./fun	Now compile the program as before, gcc function.c -o fun let us execute ./fun
Highlight Output	We see the output is displayed as The result is 9
	NOW LET US SEE HOW TO EXECUTE THE SAME PROGRAM IN C++ Come back to our program Let me change a few things here
Go to File menu Click on save as option Type cpp	Now click on File menu Click on Save as option Save the file with .cpp extension
Type <iostream>	First we will change the header file <iostream>
Type using namespace std;	We will include the using statement here
	The function declaration is same in C++ So there is no need to change anything here
Type cout<<	Now replace the printf statement with cout statement as we use cout<< function to print a line in C++
%d	We don't need the format specifier and \n here So delete it
Type <<sum <<”\n”	Now type two opening angle brackets here Then type sum two opening angle brackets again and within the double quotes backslash n Delete this closing bracket Click on save
On the terminal	Let us compile the program Come back to the terminal
Type g++ function.cpp -o fun1 Type ./fun1	Type g++ function.cpp -o fun1 Here we have fun1, this is because we don't want to overwrite the output file. press Enter To execute Type ./fun1
Highlight Output	Here the output is displayed as: The result is 9.
Errors Type x	Now we will see the common errors which we can come across. Suppose here we type x in the place of 4. I will retain the rest of the code as it is.
Click on save	Save the program
On the terminal	Let us go to the terminal and compile the program
Highlight error	We see an error at line no. 11 in our function.cpp file x undeclared This is because x is a character variable And our add function has integer variable as an argument So there is a mismatch in return type and return value.
On the editor	Now let's come back to our program Let us fix the error
Type 4	Type 4 here at line no. 11
Click on Save	Click on Save Let us execute this program
On the terminal	Come back to our terminal
	Let us compile and execute as before Yes! it is working
Error 2 Delete 4	Let us see another common error which we can come across. Suppose here we pass only 1 parameter Let us delete 4
Click on Save	Click on Save
On the terminal	Let us compile it Switch to the terminal
Highlight Error	We see an error at line no 11 in our function.cpp file too few arguments to function 'add'
On the editor	Let us switch back to the program
	You can see here we have two parameters int a and int b And here we are passing only one parameter Hence it is giving an error
Click on Save	Let us fix the error Type 4 here Click on Save Switch back to the terminal
On the terminal	Let us compile the program
	Yes it is working! Now let go through a quick summary Come back to our slides
Slide 7	Syntax of function Function without arguments Function with arguements Significance of a return statement
Slide 10 Assignment	As an assignment Write a program to calculate the square of a number using function.
Slide 11 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 12 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 13 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, Nancyvarkey, Priyacst