Difference between revisions of "C-and-C++/C3/Loops/English-timed"
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Latest revision as of 14:23, 24 March 2017
| Time | Narration |
| 00:01 | Welcome to the spoken tutorial on Loops in C and C++. |
| 00:06 | In this tutorial we will learn, |
| 00:09 | for loop,while loop and |
| 00:12 | do…while loop. We will do this with the help of some examples. |
| 00:17 | We will also see some common errors and their solutions. |
| 00:21 | To record this tutorial, I am using |
| 00:24 | Ubuntu Operating System version 11.04, |
| 00:28 | gcc and g++ Compiler version 4.6.1 on Ubuntu. |
| 00:34 | Let us start with the introduction to loops. |
| 00:38 | Loops are used to execute a group of instructions repeatedly. |
| 00:44 | Depending on the purpose they are divided into three types: |
| 00:48 | while loop do…..while loop and |
| 00:51 | for loop Let us start with the while loop first. |
| 00:56 | A while loop tests the condition in the beginning. |
| 01:00 | The structure is: while ( condition ) |
| 01:03 | within the bracket statement block. |
| 01:07 | Now move on to do….while loop . |
| 01:09 | A do..while loop is executed at least once before the condition could be validated. |
| 01:15 | The structure is: |
| 01:17 | do (within the brackets) statement block, |
| 01:20 | after the bracket the while ( condition ). |
| 01:23 | You can see that the condition is checked at the end. |
| 01:27 | Now,let us see an example on while loop and do...while loop . |
| 01:32 | I have already typed the code on the editor. |
| 01:35 | Let me open it. |
| 01:37 | Note that our file name is while.c.. |
| 01:41 | Today we are going to learn addition of first 10 numbers using while loop. |
| 01:47 | Let me explain the code now. |
| 01:49 | This is our header file. |
| 01:51 | Inside the main() function we have declared two integer variables x and y and initialized to 0. |
| 01:59 | This is our while loop. |
| 02:02 | The condition of the while loop is x is less than or equal to 10. |
| 02:06 | Here the value of x is added to the value of y. |
| 02:10 | The value obtained after the addition is stored in y. |
| 02:15 | Then we print the value of y. |
| 02:18 | Here x is incremented. |
| 02:20 | That means the variable x is increased by one. |
| 02:25 | And this is our return statement. |
| 02:27 | Now,let us execute the program. |
| 02:30 | Please open the terminal window by pressing Ctrl, Alt and T keys simultaneously on your keyboard. |
| 02:39 | Type gcc space while dot c space hyphen o space while |
| 02:45 | Press Enter. |
| 02:47 | Type ./while (dot slash while). Press Enter. |
| 02:52 | The output is displayed. |
| 02:54 | Now lets us see the working of while loop. |
| 02:57 | Let me resize the window. |
| 03:00 | Here, first the value of x and y is 0. |
| 03:04 | This is our while condition. |
| 03:06 | Here we check whether x is less than or equal to 10 which means the values of x will be from 0 to 10. |
| 03:15 | Then we add y plus x (i.e) 0 plus 0, we get 0. |
| 03:22 | We print the value of y, here we get 0. |
| 03:27 | Then x is incremented which means now the value of x will be 1. |
| 03:33 | Then we will check the condition again, 1 is less than or equal to 10. If the condition is true then we will add the values, |
| 03:44 | y (i.e ) 0 plus x that is 1. 0 plus 1 is 1. |
| 03:50 | We print the value as 1. |
| 03:53 | Again x is incremented. |
| 03:55 | Now the value of x is 2. |
| 03:59 | We check the condition again. |
| 04:01 | 2 is less than or equal to 10, if the condition is true then we will add the values, (i.e ) 1 plus 2 which will give 3. |
| 04:11 | We print the value as 3. |
| 04:13 | Like this, it will go on up to x is less than or equal to 10 (x<=10). |
| 04:20 | Now, we will see the same program using do….while loop . |
| 04:24 | Here is our program. |
| 04:26 | Note that our file name is do hyphen while dot c . |
| 04:31 | This part is already explained in the previous program. |
| 04:35 | So, let us move on to a do...while loop . |
| 04:38 | Here, first the body of the loop will be executed and then the condition is checked. |
| 04:44 | The value of x is added to the value of y and the value obtained after the addition is stored in y. |
| 04:52 | The logic is same as in while program. |
| 04:55 | Now let us execute the program. |
| 04:58 | Come back to our terminal. |
| 05:00 | Type gcc space do hyphen while dot c space hyphen o space do . Press Enter . |
| 05:08 | Type dot slash do (./do). Press Enter . |
| 05:12 | We can see that the output is similar to our while program. |
| 05:16 | Now, let us see the working of do...while loop . |
| 05:20 | Let me resize the window. |
| 05:22 | Here the value x and y is 0. |
| 05:25 | We add those values. Then we will get 0. |
| 05:29 | Now the value of y is 0. |
| 05:31 | We print the value as 0. |
| 05:33 | Then x is incremented by 1 which means now the value of x is 1, then the condition will be checked. |
| 05:42 | You can see that the body of loop is executed first. |
| 05:45 | Anyhow, if the condition is false then also we will get a value that is 0. |
| 05:52 | Now, here we will check whether 1 is less than or equal to 10. |
| 05:56 | The condition is true. Again we will add the values. |
| 06:00 | Now 0 plus 1. |
| 06:02 | Then we will print the value of y as 1. |
| 06:05 | Again x will be incremented. |
| 06:08 | Now the value of x is 2. |
| 06:11 | Then we check 2 is less than or equal to 10. |
| 06:15 | We will go back here. |
| 06:17 | Then we will add the values. 1 plus 2 is 3. |
| 06:20 | We print the value of y as 3. |
| 06:23 | Like this, the conditions will be checked till the value of x will be less than or equal to 10. |
| 06:30 | And this is our return statement. |
| 06:33 | Note that here the while condition ends with the semicolon. |
| 06:38 | In while loop the condition does not end with the semicolon. |
| 06:43 | Now let us see how to execute these programs in C++. |
| 06:48 | This is our while program in C++. |
| 06:52 | The logic and implementation are same as in our C program. |
| 06:56 | There are a few changes like the header file as iostream in place of stdio.h. |
| 07:04 | We have included the 'using' statement here using namespace std and here we have used the cout function in place of printf function. |
| 07:16 | The structure of while loop is same as in our C program. |
| 07:21 | Lets us execute the program. |
| 07:23 | Come back to a terminal. |
| 07:25 | Let me clear the prompt. |
| 07:28 | To execute, type g++ space while dot cpp space hyphen o space while1 . Press Enter . |
| 07:38 | Type dot slash while1 (./while1). Press Enter . |
| 07:43 | You can see that the output is similar to our while program in C. |
| 07:48 | Now let us see the do... while program in C++. |
| 07:52 | Come back to the text editor. |
| 07:54 | Here also there are similar changes like the header file , the using statement and the cout function. |
| 08:03 | Rest of the things are similar. |
| 08:06 | Lets us execute the program. |
| 08:08 | Come back to our terminal. |
| 08:10 | Type g++ space do hyphen while dot cpp space hyphen o space do1 . Press Enter . |
| 08:19 | Type dot slash do1 (./do1). Press Enter . |
| 08:23 | We can see that the output is similar to our do...while program in C. |
| 08:28 | Now we will see some common errors and their solutions. |
| 08:32 | Come back to our text editor. |
| 08:35 | Suppose, here I will not increment the value of x. |
| 08:41 | Click on Save Let us see what happens. |
| 08:44 | Come back to the terminal Let me clear the prompt. |
| 08:47 | Lets us execute the program. |
| 08:50 | Press the up-arrow key twice. |
| 08:54 | Again press the up-arrow key. |
| 08:57 | The output is displayed. |
| 08:59 | We can see number of zeros, this is because the loop does not have the terminating condition . |
| 09:07 | It is known as infinite loop. |
| 09:10 | Infinite loop can cause the system to become unresponsive. |
| 09:14 | It causes the program to consume all the processors time but it can be terminated. |
| 09:21 | Come back to our program, let us fix the error. |
| 09:25 | Type x++ and a semicolon. |
| 09:28 | Click on Save. Let us execute again. |
| 09:31 | Come back to terminal. |
| 09:33 | Press the up-arrow key. |
| 09:38 | Yes, it is working. |
| 09:40 | This brings us to the end of this tutorial. |
| 09:43 | We will move back to our slides. |
| 09:45 | Let us summarize. |
| 09:47 | In this tutorial we learned, |
| 09:50 | while loop example. while(x is less than or equal to 10) |
| 09:54 | do….while loop . |
| 09:56 | example. do statement block and |
| 09:59 | while condition at the end. |
| 10:01 | As an assignment, |
| 10:03 | write a program to print the following, using for loops. |
| 10:07 | 0 to 9. |
| 10:10 | The syntax of the for loop is |
| 10:12 | for (variable initialization; variable condition; and variable increment or decrement) |
| 10:20 | and here will be the body of the loop. |
| 10:24 | Watch the video available at the link shown below. |
| 10:27 | It summarizes the Spoken Tutorial project. |
| 10:30 | If you do not have good bandwidth, you can download and watch it. |
| 10:33 | The Spoken Tutorial Project Team: |
| 10:35 | Conducts workshops using spoken tutorials. |
| 10:38 | Gives certificates to those who pass an online test. |
| 10:42 | For more details, please write to contact@spoken-tutorial.org. |
| 10:47 | Spoken Tutorial Project is a part of Talk to a Teacher project. |
| 10:51 | It is supported by the National Mission on Education through ICT, MHRD, Government of India. |
| 10:58 | More information on this mission is available at the link shown below. |
| 11:02 | This script as been contributed by Dhawal Goyal. This is Ashwini Patil from IIT Bombay, signing off. |
| 11:08 | Thank You for joining. |
