Difference between revisions of "C-and-Cpp/C2/Scope-Of-Variables/English-USA"

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Latest revision as of 14:20, 23 March 2017

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 gcc space scope.c space hyphen o space sco and press Enter.
03:05 To execute, 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 as iostream.
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 brackets.
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 our 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 'int a', '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 summarize.
06:58 In this tutorial we learnt ,
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, write a program to print the difference of two numbers.
07:19 Watch the video available at the link shown below .
07:22 It summarizes the Spoken Tutorial project.
07:25 If you do not have good bandwidth, you can download and watch it.
07:30 The Spoken Tutorial Project Team-
07:32 Conducts workshops using spoken tutorials,
07:35 Gives certificates to those who pass an online test .
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 Jean Bonnet from IIT Bombay signing off.
08:08 Thank You for watching.

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