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 We will do this through some examples. 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
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 executed, the control will be returned back from where it was accessed.
Slide 5	Let us see the syntax for function. 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 open it.
Point the cursor on the filename function.c	Note that our filename is function. And I have saved the file with the extentsion .c Let me explain the code.
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 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.
Delete printf statement. Type int main()	Delete the printf statement. 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.
	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. Let us execute.
Highlight Output	We see the output is displayed as Sum 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.
Press Shift, Ctrl and S keys >> type function.cpp in Name field >> Click on "Save"	First press Shift, Ctrl and S keys simultaneously. Now save the file with .cpp extension. Click on Save.
Type <iostream>	First we will change the header file as <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. Delete the comma.
Type <<sum <<”\n”	Now, type two opening angle brackets here. After sum , again type two opening angle brackets. Within double quotes, type 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 fun. Press Enter. Type ./fun1
Highlight Output	Here the output is displayed as: Sum 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	Click on Save.
On the terminal	Let us compile the program.
Highlight error	We see an error at line no. 10. x was not declared in this scope. This is because x is a character variable. It was not declared anywhere. 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 at line no. 10.
Click on Save	Click on Save. Let us execute again.
On the terminal	Let me clear the prompt.
	Let us compile the program 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 one parameter. Delete 4.
Click on Save	Click on Save
On the terminal	Switch to the terminal. Let us compile.
Highlight Error	We see an error at line no 10. too few arguments to function 'int add (int, int)'
On the editor	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. Click on Save . Switch back to the terminal.
On the terminal	Let us execute again.
	Yes it is working! Come back to our slides.
Slide 7	To summarise, in this tutorial we have learnt - Function Syntax of function Function without arguments Eg- void add() Function with arguments Eg- int add(int a, int b)
Slide 10 Assignment	As an assignment- Write a program to calculate the square of a number.
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