Difference between revisions of "C-and-C++/C2/Scope-Of-Variables/English-timed"
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− | || Time | + | || '''Time''' |
− | || Narration | + | || '''Narration''' |
|- | |- | ||
| 00:01 | | 00:01 | ||
− | | Welcome to the spoken tutorial on Scope of variables in C and C++. | + | | Welcome to the spoken tutorial on '''Scope of variables in C and C++'''. |
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Line 17: | Line 17: | ||
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| 00:13 | | 00:13 | ||
− | | What is a Global variable? | + | |What is a Global variable? |
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Line 37: | Line 37: | ||
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| 00:30 | | 00:30 | ||
− | |'''Ubuntu Operating System''' version 11.04, '''gcc''' and '''g++ | + | |'''Ubuntu Operating System''' version 11.04, '''gcc''' and '''g++ Compiler''' version 4.6.1. |
|- | |- | ||
| 00:41 | | 00:41 | ||
− | | | + | | Let us start with the introduction to the scope of variables. |
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Line 49: | Line 49: | ||
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| 00:54 | | 00:54 | ||
− | |Depending on | + | |Depending on it's type and place of declaration it is divided into two categories: |
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Line 61: | Line 61: | ||
|- | |- | ||
|01:05 | |01:05 | ||
− | | Now we will see an example | + | | Now we will see an example. |
|- | |- | ||
| 01:07 | | 01:07 | ||
− | |I have already typed the program on the editor | + | |I have already typed the program on the editor. |
|- | |- | ||
| 01:10 | | 01:10 | ||
− | |Let me open it | + | |Let me open it. |
|- | |- | ||
Line 85: | Line 85: | ||
|- | |- | ||
|01:26 | |01:26 | ||
− | | Here we have declared two global variables '''a and b.''' | + | |Here we have declared two global variables '''a and b.''' |
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| 01:44 | | 01:44 | ||
− | |These are declared outside any functions above main() | + | |These are declared outside any functions, above main() function. |
|- | |- | ||
| 01:51 | | 01:51 | ||
− | |These have a | + | |These have a '''global scope.''' |
|- | |- | ||
| 01:53 | | 01:53 | ||
− | | | + | |Here we have declared a '''function''' '''add '''without''' arguments.''' |
|- | |- | ||
|01:59 | |01:59 | ||
− | | | + | |Here 'sum' is a local variable, it is declared inside the function '''add'''. |
− | + | ||
− | + | ||
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| 02:19 | | 02:19 | ||
− | |Then sum of a & b will be stored in the variable sum . Here we print the sum | + | |Then sum of a & b will be stored in the variable 'sum'. Here we print the sum. |
|- | |- | ||
| 02:29 | | 02:29 | ||
− | | This is our '''main | + | | This is our '''main()''' function. |
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| 02:38 | | 02:38 | ||
− | | | + | | And this is our '''return''' statement. |
|- | |- | ||
|02:40 | |02:40 | ||
− | | Now | + | |Now click on Save. |
|- | |- | ||
| 02:43 | | 02:43 | ||
− | | Let us execute the program. | + | |Let us execute the program. |
|- | |- | ||
| 02:45 | | 02:45 | ||
− | + | |Please open the terminal window by pressing '''Ctrl, Alt''' and '''T''' keys simultaneously on your keyboard. | |
|- | |- | ||
| 02:55 | | 02:55 | ||
− | | | + | | To compile, type '''gcc space scope.c space hyphen o space sco''' and press Enter. |
− | + | ||
− | + | ||
− | + | ||
− | + | ||
|- | |- | ||
| 03:05 | | 03:05 | ||
− | |To execute | + | |To execute, type '''./sco''' (dot slash sco), press Enter. |
− | + | ||
− | + | ||
− | + | ||
− | + | ||
|- | |- | ||
| 03:10 | | 03:10 | ||
− | | | + | | The output is displayed as |
|- | |- | ||
| 03:13 | | 03:13 | ||
− | |'''Sum of a and b is 7''' | + | |'''Sum of a and b is 7'''. |
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| 03:20 | | 03:20 | ||
− | | | + | | Come back to our program. First press '''Shift, Ctrl''' & '''S''' keys simultaneously on your keyboard. |
|- | |- | ||
| 03:31 | | 03:31 | ||
− | |Now | + | |Now save the file with an extension '''.cpp ''' (dot cpp) and click on Save. |
− | + | ||
|- | |- | ||
| 03:41 | | 03:41 | ||
− | | Let us change the header file as'''iostream | + | | Let us change the header file as '''iostream'''. |
− | + | ||
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| 03:58 | | 03:58 | ||
− | | The declaration of global variable | + | | The declaration of global variable and local variable is same in C++. |
|- | |- | ||
| 04:03 | | 04:03 | ||
− | |So no need to change anything | + | |So, no need to change anything. |
|- | |- | ||
| 04:07 | | 04:07 | ||
− | | | + | | Now replace the '''printf '''statement with the '''cout''' statement. |
− | + | ||
− | + | ||
|- | |- | ||
| 04:13 | | 04:13 | ||
− | | | + | | Delete the '''format specifier''' and '\n'. |
|- | |- | ||
| 04:17 | | 04:17 | ||
− | | | + | |Now delete the comma. |
|- | |- | ||
| 04:19 | | 04:19 | ||
− | | Type two opening angle brackets | + | | Type two opening angle brackets. |
|- | |- | ||
| 04:22 | | 04:22 | ||
− | |Delete the closing bracket, again type two opening | + | |Delete the closing bracket, again type two opening angle brackets. |
|- | |- | ||
| 04:26 | | 04:26 | ||
− | | | + | |And within the double quotes type backslash n. Now click on Save. |
|- | |- | ||
| 04:35 | | 04:35 | ||
− | |Let us execute the program | + | |Let us execute the program. |
− | + | ||
|- | |- | ||
| 04:39 | | 04:39 | ||
− | |Come back to | + | |Come back to our terminal. |
|- | |- | ||
| 04:42 | | 04:42 | ||
− | | To compile | + | | To compile, type '''g++ space scope dot cpp space -o space sco1 ''' |
− | + | ||
|- | |- | ||
| 04:52 | | 04:52 | ||
− | | Here we have | + | | Here we have '''sco1''' because we don't want to overwrite output parameter '''sco''' for the file 'scope.c'. |
|- | |- | ||
| 05:04 | | 05:04 | ||
− | | | + | | Now press Enter. |
− | + | ||
|- | |- | ||
| 05:07 | | 05:07 | ||
− | | | + | | To execute type '''./sco1''' and press Enter. |
|- | |- | ||
|05:14 | |05:14 | ||
− | |The output is displayed as | + | |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 | + | | 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. | |Now we will see some common errors which we can come across. | ||
|- | |- | ||
| 05:31 | | 05:31 | ||
− | |Come back to our program | + | |Come back to our program. Suppose here I will declare a variable '''a''' again. |
|- | |- | ||
| 05:41 | | 05:41 | ||
− | |Type '''int a ''' and a semicolon | + | |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. | | Let us see what happens. | ||
− | |||
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|06:01 | |06:01 | ||
− | | Now compile as before | + | | Now compile as before. |
− | + | ||
|- | |- | ||
|06:05 | |06:05 | ||
− | |We see errors , | + | |We see errors, '''redefinition of 'int a' ''' , ''' 'int a' previously defined here'''. Come back to our program. |
|- | |- | ||
|06:18 | |06:18 | ||
|'''a''' is a global variable. | |'''a''' is a global variable. | ||
− | |||
|- | |- | ||
|06:20 | |06:20 | ||
|It has a '''global scope.''' | |It has a '''global scope.''' | ||
− | |||
|- | |- | ||
|06:22 | |06:22 | ||
− | |We cannot declare the variable twice as it is already declared globally | + | |We cannot declare the variable twice as it is already declared globally. |
− | + | ||
|- | |- | ||
|06:27 | |06:27 | ||
|We can only declare '''variable a''' as a local variable . | |We can only declare '''variable a''' as a local variable . | ||
− | |||
− | |||
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− | | | + | | 06:36 |
− | | Delete | + | | Delete this . |
|- | |- | ||
| 06:39 | | 06:39 | ||
− | | Click on | + | | Click on Save. |
|- | |- | ||
| 06:41 | | 06:41 | ||
− | | | + | | Let us execute again Come back to our terminal. |
− | + | ||
− | + | ||
− | + | ||
− | + | ||
− | + | ||
|- | |- | ||
| 06:45 | | 06:45 | ||
− | | Now | + | | Now compile as before, execute as before. |
|- | |- | ||
| 06:49 | | 06:49 | ||
− | | | + | | Yes, it is working. |
− | + | ||
|- | |- | ||
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| 06:56 | | 06:56 | ||
− | | | + | | Let us summarize. |
|- | |- | ||
| 06:58 | | 06:58 | ||
− | | In this tutorial we | + | | In this tutorial we learnt , |
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| 07:07 | | 07:07 | ||
− | | | + | | and local variable ,e.g:int sum |
|- | |- | ||
| 07:12 | | 07:12 | ||
− | | | + | | As an assignment, |
− | + | ||
|- | |- | ||
|07:14 | |07:14 | ||
− | | | + | |write a program to print the difference of two numbers. |
|- | |- | ||
| 07:19 | | 07:19 | ||
| Watch the video available at the link shown below . | | Watch the video available at the link shown below . | ||
− | |||
|- | |- | ||
|07:22 | |07:22 | ||
− | |It | + | |It summarizes the Spoken Tutorial project. |
− | + | ||
|- | |- | ||
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| 07:30 | | 07:30 | ||
− | | The Spoken Tutorial Project Team | + | | The Spoken Tutorial Project Team: |
− | + | ||
|- | |- | ||
|07:32 | |07:32 | ||
− | |Conducts workshops using spoken tutorials | + | |Conducts workshops using spoken tutorials, |
− | + | ||
|- | |- | ||
|07:35 | |07:35 | ||
|Gives certificates to those who pass an online test . | |Gives certificates to those who pass an online test . | ||
− | |||
|- | |- | ||
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| 07:47 | | 07:47 | ||
− | | | + | | Spoken Tutorial Project is a part of the Talk to a Teacher project. |
− | + | ||
|- | |- | ||
|07:52 | |07:52 | ||
|It is supported by the National Mission on Education through ICT, MHRD, Government of India. | |It is supported by the National Mission on Education through ICT, MHRD, Government of India. | ||
− | |||
|- | |- | ||
|08:00 | |08:00 | ||
|More information on this Mission is available at the link shown below | |More information on this Mission is available at the link shown below | ||
+ | |||
|- | |- | ||
| 08:04 | | 08:04 | ||
− | | | + | | This is Ashwini Patil from IIT Bombay signing off. |
− | + | ||
|- | |- |
Latest revision as of 12:57, 24 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 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 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