Difference between revisions of "C-and-Cpp/C2/Scope-Of-Variables/English-USA"
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Revision as of 16:36, 10 April 2015
| 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 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, |
| 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 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. |
