C-and-C++/C2/Scope-Of-Variables/English-timed

Time	Narration
00:01	Welcome to the spoken tutorial on Scope of variables in C and C++.
00:08	In this tutorial we will learn,
00:11	* What is the Scope of variable?
00:13	* What is a Global variable?
00:16	* What is a Local variable?
00:19	Few examples.
00:22	We will also see some common errors and their solutions.
00:27	To record this tutorial, I am using
00:30	Ubuntu Operating System version 11.04, gcc and g++ Compiler version 4.6.1.
00:41	Let us start with the introduction to the scope of variables.
00:47	It is the region of code within which the variable can be accessed.
00:54	Depending on it's type and place of declaration it is divided into two categories:
00:59	Global Variable &
01:02	Local Variable.
01:05	Now we will see an example.
01:07	I have already typed the program on the editor.
01:10	Let me open it.
01:14	Note that our file name is scope.c.
01:19	Let me explain the code now.
01:23	This is our header file.
01:26	Here we have declared two global variables a and b.
01:32	And we have initialized them by assigning values as 5 and 2.
01:39	A global variable is available to all functions in your program.
01:44	These are declared outside any functions, above main() function.
01:51	These have a Global scope.
01:53	Here we have declared a function add without arguments.
01:59	Here sum is a local variable, it is declared inside the function add.
02:07	A local variable is available only to the function inside which it is declared.
02:13	These variables are declared inside a block.
02:16	These have local scope.
02:19	Then sum of a & b will be stored in the variable 'sum'. Here we print the sum.
02:29	This is our main function.
02:33	The add function is called and then executed.
02:38	And this is our return statement.
02:40	Now click on save.
02:43	Let us execute the program.
02:45	Please open the terminal window by pressing Ctrl, Alt and T keys simultaneously on your keyboard.
02:55	To compile, type
02:56	gcc space scope.c space hyphen o space sco and press enter.
03:05	To execute,
03:06	type ./sco (dot slash sco), press Enter.
03:10	The output is displayed as
03:13	Sum of a and b is 7.
03:16	Now let us see how to execute the same program in C++.
03:20	Come back to our program. First press Shift, Ctrl & S keys simultaneously on your keyboard.
03:31	Now save the file with an extension .cpp (dot cpp) and click on Save.
03:41	Let us change the header file asiostream.
03:47	Now include the using statement. Click on save .
03:58	The declaration of global variable and local variable is same in C++
04:03	So no need to change anything
04:07	Now replace the printf statement with the cout statement
04:13	Delete the format specifier and '\n'
04:17	now delete the comma .
04:19	Type two opening angle brackets
04:22	Delete the closing bracket, again type two opening angle bracket
04:26	and within the double quotes type backslash n. Now click on save
04:35	Let us execute the program
04:39	Come back to a terminal.
04:42	To compile type, g++ space scope dot cpp space -o space sco1,
04:52	Here we have ,sco1, because We don't want to overwrite output parameter sco for the file scope .c
05:04	now press enter
05:07	To execute type./sco1 and press enter .
05:14	The output is displayed as, Sum of a and b is 7.
05:19	We can see that it is similar to our C code,
05:27	Now we will see some common errors which we can come across.
05:31	Come back to our program, Suppose here I will declare a variable a again,
05:41	Type int a and a semicolon
05:45	Click on save. We have declared the variable a above the main function and after the add function ,
05:55	Let us see what happens.
05:57	Come back to our terminal.
06:01	Now compile as before ,
06:05	We see errors , Redefinition of inta , int a previously defined here. Come back to our program
06:18	a is a global variable.
06:20	It has a global scope.
06:22	We cannot declare the variable twice as it is already declared globally
06:27	We can only declare variable a as a local variable .
06:34	Let us fix the error.
06:36	Delete this .
06:39	Click on save.
06:41	Let us execute again.
06:42	Come back to our terminal.
06:45	Now compile as before, execute as before.
06:49	Yes it is working.
06:52	This brings us to the end of this tutorial.
06:56	let us summarise
06:58	In this tutorial we learn't ,
07:00	Scope of variable,
07:02	Global variable, e.g : int a=5 &
07:07	And local variable ,e.g:int sum
07:12	As an assignment,
07:14	Write a program to print the difference of two numbers.
07:19	Watch the video available at the link shown below .
07:22	It summarises the Spoken Tutorial project.
07:25	If you do not have good bandwidth, you can download and watch it.
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07:40	For more details, please write to,contact@spoken-tutorial.org
07:47	Spoken Tutorial Project is a part of the Talk to a Teacher project.
07:52	It is supported by the National Mission on Education through ICT, MHRD, Government of India.
08:00	More information on this Mission is available at the link shown below
08:04	This is Ashwini Patil from IIT Bombay signing off
08:08	Thank You for watching.

Contributors and Content Editors

Ashwini, Kavita salve, Krupali, PoojaMoolya, Pratik kamble, Sandhya.np14