Difference between revisions of "Advance-C/C2/Storage-class-specifiers/English-timed"

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* '''static''' keyword  
 
* '''static''' keyword  
 
* '''extern''' keyword
 
* '''extern''' keyword
−
* '''register''' keyword, with the help of examples.
+
* '''register''' keyword, with the help of an example.
  
 
|-
 
|-
 
| 00:22
 
| 00:22
 
| For this tutorial, I am using:
 
| For this tutorial, I am using:
−
* '''Ubuntu Operating system version 11.10''' and  
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* '''Ubuntu Operating system''' version '''11.10''' and  
−
* '''gcc Compiler version 4.6.1 on Ubuntu'''.
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* '''gcc Compiler''' version '''4.6.1''' on Ubuntu.
  
 
|-
 
|-
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|-
 
|-
 
| 00:57
 
| 00:57
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|* How to store the '''variable'''
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|* How to store the variable
  
 
|-
 
|-
 
| 00:59
 
| 00:59
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|* What is the initial value of the '''variable'''
+
|* What is the initial value of the variable
  
 
|-
 
|-
 
| 01:03
 
| 01:03
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|* Life time of the '''variable'''.
+
|* Life time of the variable.
  
 
|-
 
|-
 
| 01:06
 
| 01:06
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| The Syntax is: '''storage_specifier data_type variable _name'''
+
| The Syntax is: '''storage_specifier data_type variable _name'''.
  
 
|-
 
|-
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|-
 
|-
 
| 01:39
 
| 01:39
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| Storage space of '''keywords''' is '''CPU memory'''.
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| Storage-space of '''keywords''' is '''CPU memory'''.
  
 
|-
 
|-
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|-
 
|-
 
| 02:26
 
| 02:26
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| Value of '''i''' is incremented here.
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| Value of 'i' is incremented here.
  
 
|-
 
|-
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|-
 
|-
 
| 03:22
 
| 03:22
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| We get an error: '''"file-scope declaration of 'i' specifies 'auto'" '''.
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| We get an error: "file-scope declaration of 'i' specifies 'auto'".
  
 
|-
 
|-
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|-
 
|-
 
| 03:47
 
| 03:47
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| Click on '''Save '''and execute on the '''terminal'''.
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| Click on '''Save '''and execute on the terminal.
  
 
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|-
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|-
 
|-
 
| 04:16
 
| 04:16
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| Although we have studied about '''static variable '''in the previous tutorials, I will explain it here briefly.
+
| Although we have studied about '''static variable''', in the previous tutorials, I will explain it here briefly.
  
 
|-
 
|-
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|-
 
|-
 
| 04:41
 
| 04:41
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| Storage space is '''CPU memory'''.
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| Storage-space is '''CPU memory'''.
  
 
|-
 
|-
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|-
 
|-
 
|05:23
 
|05:23
−
| Let us see what happens.  Execute the file on the '''terminal'''.
+
| Let us see what happens.  Execute the file on the terminal.
  
 
|-
 
|-
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|-
 
|-
 
| 05:51
 
| 05:51
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| This is because, '''static''' variables are '''global''' variables.
+
| This is because '''static''' variables are '''global''' variables.
  
 
|-
 
|-
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|-
 
|-
 
| 06:42
 
| 06:42
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|Note that our filename is '''"extern.c"'''.
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|Note that our filename is "extern.c".
  
 
|-
 
|-
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|-
 
|-
 
|07:03
 
|07:03
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| Using the '''printf''' statements, we will display the values of '''x''' and '''y.'''
+
| Using the '''printf''' statements, we will display the values of 'x' and 'y'.
 
This is the '''return''' statement.
 
This is the '''return''' statement.
  
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| 07:40
 
| 07:40
 
| The output is displayed as:
 
| The output is displayed as:
−
'''The value of x is 10 '''
+
"The value of x is 10"
−
'''The value of y is 50'''
+
"The value of y is 50"
  
 
|-
 
|-
 
| 07:48
 
| 07:48
−
| As we studied, the value of the '''extern''' keyword is through out the main program.
+
| As we studied, the value of the '''extern''' keyword is through out the '''main''' program.
  
 
|-
 
|-
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|-
 
|-
 
| 08:37
 
| 08:37
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|Note that the file name is''' register.c'''
+
|Note that the filename is "register.c".
  
 
|-
 
|-
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|-
 
|-
 
| 09:25
 
| 09:25
−
| You can see, the output is displayed as: '''"Values stored in register memory 1 2 3 4 5"'''.
+
| You can see, the output is displayed as: "Values stored in register memory 1 2 3 4 5".
  
 
|-
 
|-
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* '''static''' keyword
 
* '''static''' keyword
 
* '''extern''' keyword
 
* '''extern''' keyword
−
* '''register''' keyword
+
* '''register''' keyword.
  
 
|-
 
|-
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|-
 
|-
 
| 09:59
 
| 09:59
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|Declare both the keywords '''auto''' and '''static''' in the program.  
+
| Declare both the keywords '''auto''' and '''static''' in the program.  
  
 
|-
 
|-
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|-
 
|-
 
| 10:45
 
| 10:45
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|More information on this mission is available at:
+
|More information on this mission is available at the link shown below:
 
http://spoken-tutorial.org\NMEICT-Intro.
 
http://spoken-tutorial.org\NMEICT-Intro.
  
 
|-
 
|-
 
| 10:52
 
| 10:52
−
| This is Ashwini Patil from IIT Bombay. Thank you for joining.
+
| This is Ashwini Patil from IIT Bombay, signing off. Thank you for joining.
  
 
|}
 
|}

Revision as of 11:48, 10 December 2015

Time
Narration
00:01 Welcome to the Spoken Tutorial on Storage class specifiers.
00:07 In this tutorial, We will learn about:
  • Storage class specifiers
  • auto keyword
  • static keyword
  • extern keyword
  • register keyword, with the help of an example.
00:22 For this tutorial, I am using:
  • Ubuntu Operating system version 11.10 and
  • gcc Compiler version 4.6.1 on Ubuntu.
00:34 To follow this tutorial, you should be familiar with 'C' tutorials.
00:41 If not, for relevant tutorials, please visit our website which is as shown.
00:47 I will start with an introduction to storage class specifiers.
00:52 Specifiers tell the compiler- * where to store a variable
00:57 * How to store the variable
00:59 * What is the initial value of the variable
01:03 * Life time of the variable.
01:06 The Syntax is: storage_specifier data_type variable _name.
01:13 Types of storage class specifiers are:
  • auto
  • static
  • extern
  • register .
01:21 Let us start with auto keyword.
01:24 auto keyword declares an automatic variable.
01:28 It has a local scope.
01:30 Keywords are not initialized automatically.
01:34 You should explicitly initialize keywords while declaring.
01:39 Storage-space of keywords is CPU memory.
01:43 Let us see an example. I have a code file; let us go through it.
01:49 Note that our filename is auto.c.
01:54 We have declared a function as “increment()”.
01:58 This is the main() function.
02:00 In the main() function, increment() function is called 4 times.
02:06 Then we have the return 0 statement.
02:10 Let us see the function definition.
02:14 Here, we have declared variable 'i' as auto int. It has a local scope.
02:21 Then we display value of 'i' using printf.
02:26 Value of 'i' is incremented here.
02:30 Let us open the terminal by pressing Ctrl+Alt+T keys simultaneously on your keyboard.
02:38 Type: gcc space auto.c space hyphen o space auto. Press Enter.
02:48 Type: dot slash auto
02:51 The output is zero.
02:54 Now come back to our program.
02:57 Let us initialize the auto variable i above the main() function.
03:02 I will cut this declaration and initialization from here and paste it over here.

Click on Save.

03:14 Let us execute on the terminal. Press the up-arrow key twice.

Press Enter.

03:22 We get an error: "file-scope declaration of 'i' specifies 'auto'".
03:29 This is because an auto variable is local to the function.
03:34 We cannot initialize it globally.
03:37 Let us fix the error. Come back to our program.
03:42 Delete this; paste it over here.
03:47 Click on Save and execute on the terminal.
03:52 Press the up-arrow key. Recall the previous command.
03:57 Press Enter. Type: dot slash auto. Press Enter.
04:03 Yes, it is working! The output is zero.
04:07 This is because we have initialized the value of 'i' as zero.
04:13 Now, let us see static variable.
04:16 Although we have studied about static variable, in the previous tutorials, I will explain it here briefly.
04:24 'static' variables are initialized to zero.
04:28 They are not destroyed even after program control exits from the block.
04:35 Value of the variable persists between different function calls.
04:41 Storage-space is CPU memory.
04:45 Let us see an example. I will edit the same code file.
04:51 Come back to our program.
04:54 Press Ctrl + Shift + S keys simultaneously.
05:01 Now, I will just change the filename as static. Click on Save.
05:10 Now, I will change the initialization of the variable 'i' to static int i equal to zero

Click on Save.

05:23 Let us see what happens. Execute the file on the terminal.
05:30 Type: gcc space static.c space hyphen o space stat. Press Enter.
05:41 Type: dot slash stat. Press Enter.
05:46 The output is displayed as: "0, 1, 2, 3"
05:51 This is because static variables are global variables.
05:56 The scope of static variable is local to the function, they are defined in.
06:03 They do not lose their value between function calls.
06:08 Now, let us learn about extern keyword.
06:12 Scope of extern variable is throughout the main program.
06:17 Definition for extern variable might be anywhere in the 'C' program.
06:23 extern variables are initialized to zero, by default.
06:28 They can be accessed by all functions in the program.
06:33 These are stored in CPU memory.
06:36 Let us see an example.
06:38 I have a code file; let us go through it.
06:42 Note that our filename is "extern.c".
06:47 I have initialized a variable as integer variable 'x' to 10.
06:54 This is the main() function. In the main() function, I have declared an extern integer variable y.
07:03 Using the printf statements, we will display the values of 'x' and 'y'.

This is the return statement.

07:12 We will initialize 'y' to 50 after the main() function close.
07:18 Now, switch to the terminal and let us see what will be the output.
07:24 Type: gcc space extern.c space hyphen o space ext. Press Enter.
07:35 Type: dot slash ext. Press Enter.
07:40 The output is displayed as:

"The value of x is 10" "The value of y is 50"

07:48 As we studied, the value of the extern keyword is through out the main program.
07:55 We can define it anywhere in the program.
07:59 Both the statements are justified.
08:02 Now, let us move on to register keyword.
08:06 register variables will be accessed faster than normal variables.
08:13 They are stored in register memory rather than main memory.
08:19 Limited number of variables can be used since register size is very low.
08:25 16 bits, 32 bits or 64 bits.
08:30 Let us see an example now. I have a code file. Let us go through it.
08:37 Note that the filename is "register.c".
08:42 Here, we have declared register integer variable.
08:47 This variable will be directly stored in the register memory.
08:53 This is the 'for' loop that displays the value of 'i' from 1 to 5.
08:59 This will display the value of 'i'.
09:03 Let us execute the program and see.
09:07 On the terminal, type: gcc space register.c space hyphen o space register
09:17 Press Enter. Type: dot slash register. Press Enter.
09:25 You can see, the output is displayed as: "Values stored in register memory 1 2 3 4 5".
09:34 This brings us to the end of this tutorial. Let us summarize.
09:39 In this tutorial, we learnt-
  • Storage class specifiers
  • auto keyword
  • static keyword
  • extern keyword
  • register keyword.
09:52 As an assignment, write a program to print the sum of first 5 numbers.
09:59 Declare both the keywords auto and static in the program.
10:04 Watch the video available at the link shown below.
10:07 It summarizes the Spoken Tutorial project.
10:11 If you do not have good bandwidth, you can download and watch it.
10:16 The Spoken Tutorial project team: * Conducts workshops using spoken tutorials.
10:22 * Gives certificates to those who pass an online test.

For more details, please write to contact@spoken-tutorial.org

10:33 Spoken Tutorial project is a part of the Talk to a Teacher project.
10:38 It is supported by the National Mission on Education through ICT, MHRD, Government of India.
10:45 More information on this mission is available at the link shown below:

http://spoken-tutorial.org\NMEICT-Intro.

10:52 This is Ashwini Patil from IIT Bombay, signing off. Thank you for joining.

Contributors and Content Editors

PoojaMoolya, Pratik kamble, Sandhya.np14

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