BASH/C3/Recursive-function/English-timed
From Script | Spoken-Tutorial
| Time | Narration |
| 00:01 | Dear friends, welcome to the spoken tutorial on Recursive function. |
| 00:07 | In this tutorial, we will learn |
| 00:10 | 'what is a Recursive' function |
| 00:12 | with the help of some examples. |
| 00:15 | To follow this tutorial, you should have knowledge of Shell Scripting in BASH. |
| 00:20 | If not, for relevant tutorials, please visit our website which is as shown.http://www.spoken-tutorial.org |
| 00:27 | For this tutorial, I am using |
| 00:29 | Ubuntu Linux 12.04 Operating System |
| 00:33 | and GNU BASH version 4.2 |
| 00:37 | Please note, GNU Bash version 4 or above is recommended for practice. |
| 00:44 | Let us see what a recursive function is. |
| 00:48 | A recursive function is one which calls itself. |
| 00:52 | Recursion is a useful technique for simplifying complex algorithms. |
| 00:59 | Let me open a file named factorial.sh. |
| 01:04 | I have typed the code in this file. |
| 01:07 | This is the shebang line. |
| 01:10 | factorial() is the function name. |
| 01:12 | Inside this, we print a message “Inside factorial function”. |
| 01:19 | This statement reads user's input and stores the value in variable 'n'. |
| 01:26 | Here, we have 'if-else' condition. |
| 01:30 | If condition checks whether the value of 'n' is equal to zero. |
| 01:36 | If True, it will display the message "factorial value of n is 1". |
| 01:42 | Here is the 'else' part of the 'if' statement. |
| 01:46 | It calls the 'factorial' function. |
| 01:50 | And 'fi' is the end of the 'if-else' statement. |
| 01:55 | Let us run the file "factorial.sh". |
| 01:59 | Open the terminal using CTRL+ALT and T keys simultaneously on your keyboard. |
| 02:07 | Type: chmod space plus x space factorial dot sh |
| 02:15 | Press Enter. |
| 02:17 | Type: dot slash factorial.sh |
| 02:21 | Press Enter. |
| 02:24 | We see "Enter the number:" . |
| 02:26 | I will enter 0. |
| 02:29 | The output is displayed as: |
| 02:31 | "factorial value of 0 is 1". |
| 02:35 | Now press the up-arrow key. Recall the previous command. |
| 02:40 | Press Enter. |
| 02:42 | This time, I will enter 5. |
| 02:45 | Now the output is displayed as: |
| 02:47 | "Inside factorial function". |
| 02:51 | Let us add some more logic to the 'factorial' function. |
| 02:56 | We will calculate the factorial of a number. |
| 03:01 | Come back to our code. |
| 03:03 | Now, let us replace the echo statement "Inside the factorial function" with the code block. |
| 03:10 | Click on Save. |
| 03:13 | temp is a variable and stores the value entered by user. |
| 03:19 | 'If' condition checks whether the variable value is equal to 1. |
| 03:25 | If True, it will print 1. |
| 03:29 | This is the else part of the if statement. |
| 03:33 | This reduces one from the temp variable value |
| 03:37 | and stores the result in a variable 'f'. |
| 03:42 | Variable 'f' stores the output of 'factorial' function. |
| 03:46 | This is a recursive call. |
| 03:50 | Value of variable 'f' and temp are multiplied and stored in 'f'. |
| 03:57 | Then we print the value of 'f'. |
| 04:00 | End of if-else statement and function. |
| 04:05 | Now, come back to our slides. |
| 04:08 | Let us understand the flow of the program. |
| 04:12 | The value of 'n' is taken from the user i.e. 'n'. |
| 04:17 | If the value entered is equal to zero then it prints a message |
| 04:24 | Else it goes to the function factorial. |
| 04:29 | Here, if the value is 'equal to one' then it prints value as 'one'. |
| 04:36 | If not, it makes a recursive call until the value is equal to one. |
| 04:44 | Then, all the values are multiplied and displayed. |
| 04:49 | Now come back to our terminal. |
| 04:52 | Press the up-arrow key. |
| 04:54 | Recall the previous command ./factorial.sh |
| 04:58 | Press Enter. |
| 05:00 | Now I will enter 5 as the input value. |
| 05:05 | We get the factorial of number 5 |
| 05:08 | that is 120. |
| 05:11 | We can see the flow of the program on terminal. Analyze and trace the flow of the program. |
| 05:18 | Come back to our slides. |
| 05:20 | Let us summarize.In this tutorial, we learned |
| 05:23 | Recursive function |
| 05:25 | with the help of some examples. |
| 05:28 | As an assignment,write a program where the recursive function calculates the sum of 'N' numbers. |
| 05:36 | Watch the video available at the link shown below. |
| 05:39 | It summarizes the Spoken-Tutorial project. |
| 05:43 | If you do not have good bandwidth, you can download and watch it. |
| 05:47 | The Spoken Tutorial Project Team: *Conducts workshops using spoken tutorials; |
| 05:53 | Gives certificates to those who pass an online test. |
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| 06:06 | Spoken Tutorial project is a part of the Talk to a Teacher project. |
| 06:10 | It is supported by the National Mission on Education through ICT, MHRD, Government of India. |
| 06:18 | More information on this mission is available at the link shown below. http://spoken-tutorial.org\NMEICT-Intro |
| 06:24 | The script has been contributed by FOSSEE and Spoken-Tutorial teams. |
| 06:29 | This is Ashwini Patil, signing off. |
| 06:33 | Thank you for joining. |
