C-and-C++/C3/Loops/English-timed

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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,
00:10 while loop and
00:12 do…while loop.
00:13 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
00:49 do…..while loop and
00:51 for loop
00:52 Let us start with the while loop first
00:56 A while loop tests the condition in the beginning
01:00 The structure is
01:01 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 atleast 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 upto x is less than or equal to 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 lets 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 lets 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 . Press Enter
05:12 We can see that the output is similar to our while program
05:16 Now, lets 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 lets 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 use 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 .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 .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.
08:42 Let us see what happens
08:44 Come back to the terminal.
08:45 Let me clear the prompt
08:47 Lets us execute the program.
08:50 Press the uparrow key twice.
08:54 Again press the uparrow 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 uparrow key
09:38 Yes, it is working
09:40 This bring 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
09:51 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
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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.

Contributors and Content Editors

PoojaMoolya, Pratik kamble, Priyacst, Sandhya.np14