Difference between revisions of "C-and-C++/C2/Scope-Of-Variables/English-timed"
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Revision as of 17:46, 9 July 2014
| 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 its 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() funtion. |
| 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), 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 key simultaneously on your keyboard |
| 03:31 | Now Save the file with an extension .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. |
| 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 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
