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

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.
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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.

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PoojaMoolya, Pratik kamble, Priyacst, Sandhya.np14