C-and-C++/C2/Functions/English
Title of script: Functions in C and C++
Author: Ashwini R. Patil
Keywords: Functions, return statement, Video Tutorial
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Slide 1 | Welcome to the spoken tutorial on Functions in C and C++ |
Slide 2
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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
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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 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 |
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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 |
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printf("Value of C is %d\n",c); |
Then we print the result |
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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
./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 |
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Output |
Here the output is displayed as:
The result is 9. |
Errors
x
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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
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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
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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 |