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,
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 ./ (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