View source for C-and-C++/C2/Relational-Operators/English-timed

 
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!Time
!Narration

|-
|00:01
| Welcome to the spoken tutorial on '''Relational Operators''' in '''C''' and '''C++'''.

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|00:06
|  In this tutorial, we will learn about:

|-
|00:09  	 	 	
|Relational operators like,

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|00:11
|Less than: e.g.  a < b 

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|00:14
|Greater than: e.g. a > b

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|00:17
|Less than or equal to: e.g.  a <= b 

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|00:22
|Greater than or equal to: e.g. a >= b

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|00:27
|Equal to: e.g. a == b

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|00:30
|Not equal to: e.g. a != b

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| 00:37
| To record this tutorial, I am using: '''Ubuntu 11.10''' as the operating system,        

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|00:42
|'''gcc''' and '''g++ Compiler '''version '''4.6.1 '''in '''Ubuntu.'''

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|  00:50 
|  Let us begin with an introduction.

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|00:53
|Relational operators are used to compare integer and floating point numbers.

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|00:57
|Expressions using relational operators '''return''' '''0''' for false and '''1''' for true. 

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| 01:04
|  Now I will demonstrate the relational operators with the help of a C program.

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|  01:09
|   I have already made the program.

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|01:11
|So, I'll open the editor and explain the code.

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| 01:15
|  First, we declare two variables '''a '''and '''b'''.

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|  01:20
|  This '''printf''' statement prompts the user to enter the values of a and b.

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| 01:26 
|  This '''scanf '''statement takes input for the variables '''a '''and '''b'''.

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|  01:32
|   Now we have the '''greater than (>)''' operator.

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|01:35
|This operator compares the two operands on either side of the operator.

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|01:38
|It returns '''True''' if '''a''' is greater than '''b'''.

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|  01:43
|  This '''printf '''statement is executed if the above condition is true.

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|01:47
|If the above condition is '''false '''then it is skipped.

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|01:50
|The control then jumps to the next statement.

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| 01:53
|  We now have the '''less than (<)''' operator.

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|01:56
|This too compares the operands.

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|01:57
|It returns '''true''' when '''a''' is less than '''b'''.

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| 02:02
|This '''printf''' statement is executed if the above condition is '''true.'''

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|02:06
|It is skipped otherwise.

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|02:09
|  Let's execute the code till here.

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|02:13
|First comment out the following.

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|02:16
|Type '''/* (slash asterisk) 

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|02:21
| */ ''' (asterisk slash).

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| 02:24
|  Click on '''Save'''.

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|02:26
|I have saved my file as '''relational.c'''.

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| 02:29
|   Open the terminal window by pressing '''Ctrl, Alt''' and '''T '''keys simultaneously.

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| 02:35
|  To compile, type the following on the terminal '''gcc space  relational dot c space -o space rel'''.

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| 02:49
|  Press '''Enter'''.

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| 02:51
|  To execute,  type '''./rel''' (dot slash rel). Press '''Enter'''.
 
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| 02:56
|  I enter '''a''' as 8 and '''b '''as 3.

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| 03:01
|  The output is displayed:

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| 03:03
|  '''8 is greater than 3'''.

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| 03:07
|  You can try executing this code with different values of '''a '''and '''b'''.

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|03:11
| Coming back to  the code.

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| 03:14
|  Delete the comment from here  
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| 03:18
|  and  put it here.

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| 03:24
|Now we have the '''less than or equal to (<=) '''operator.

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| 03:28
|  This operator compares the two operands on either side of the operator.

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| 03:33
|  It returns '''true''' if '''a''' is less than or equal to '''b'''.

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|03:38
| This '''printf '''statement is executed if the above condition is true.

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| 03:42
|  If the above condition is '''false '''then it is skipped.

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| 03:45
|  The control then jumps to the next statement.

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| 03:49
| Next comes the '''greater than or equal to (>=) '''operator.

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| 03:52
|  It compares '''a '''and '''b '''and  returns  '''true''' if '''a''' is greater than or equal to '''b'''.

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| 04:00
| If the condition is true then this printf statement will be executed.

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| 04:05
| Now let's execute the code till here.

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| 04:07
|  Click on '''Save'''.

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| 04:09
|  Switch back to the terminal.

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| 04:12
|  Compile and execute as before.
 
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| 04:17
|  I enter '''a''' as 8 and '''b '''as 3.

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| 04:22
|  The output is displayed:

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| 04:25
|  '''8 is greater than or equal to 3'''

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| 04:30
|Now  Coming back to rest of the code.

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| 04:33
|  Delete the multiline comments from here

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| 04:39
|   and here.

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| 04:43
|We now have the '''equal to '''operator.

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| 04:47
|  It is denoted by '''double equal signs (==)'''.

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| 04:50
|  This operator returns '''true''' when both operands are equal to one another.

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| 04:57
|This '''printf''' statement executes when '''a''' is equal to '''b.'''

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| 05:00
|  If not, the control then jumps on to the next statement.

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|05:06
|Similarly, we have the '''not equal to''' operator.

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| 05:08
|  This operator returns '''true''' when the operands are not equal to one another.

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|05:15
| This '''printf''' statement will execute when '''a''' is not equal to '''b'''.

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|  05:20
|Coming to the end of the program. '''return 0;'''

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| 05:24
| Click on '''Save'''.

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|05:26
| Switch back to the terminal.

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| 05:28
|  Compile and execute as before.

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| 05:32
|  Enter '''a''' as 8 and '''b '''as 3.

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| 05:38
|  The output is displayed on the screen:

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| 05:40
|  '''8 is not equal to 3''' 

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| 05:44
|  So, we see how the relational operators work.

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| 05:48
|  Try executing this code with different set of inputs.

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| 05:51
| Now, writing a similar program in '''C++''' is quite easy.

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| 05:56
|  There are a few differences in the syntax.

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| 05:59
|  I have already made the code in '''C++'''.

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|06:04
| Here  is the code for '''relational operators''' in '''C++'''.

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|06:08
|Notice that the header is different.

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| 06:12
|  Also we have the '''using '''statement here.

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| 06:15
|  The output statement in C++ is '''cout'''.

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| 06:19
|  And the input statement in C++ is''' cin.'''

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| 06:22
|  So, apart from these differences, the two codes are very similar.

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|06:26
| Click on Save.

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| 06:28
|  Please make sure the file is saved with the extension '''.cpp'''.

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| 06:32
|  I have saved my file as '''relational.cpp'''.

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| 06:37
| Let's compile the code.

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| 06:39
|  Open the terminal and type '''g++ relational.cpp space minus o space rel1'''

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| 06:50
|  To  execute, type  '''./rel1''' (dot slash rel1), press Enter.
 
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| 06:56
|  I enter '''a''' as 8 and '''b '''as 3.

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| 07:00
|  The output is displayed:

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| 07:02
|  We see that the output is same as  the one in  '''C''' program.

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| 07:07
| Now let us see an error which we can come across.

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| 07:10
|  Come back to the program.

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| 07:13
| Suppose here we replace the 'double equal to' sign with the 'single equal to'.

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| 07:19
|  Click on '''Save.'''

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| 07:21
|  Come back to the terminal.

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| 07:23
|  Compile and execute as before.

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|  07:33
| Here we see it is showing 3 is equal to 3.

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| 07:37
|  Come back to our program.

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| 07:40
|  This is because here we have an assignment operator.

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| 07:43
|  So value of b is assigned to a.

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|  07:46
|Now, let us fix this error.

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| 07:49
|  Type an equal to sign.

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| 07:51
|  Click on '''Save'''.

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|  07:54
|  Switch back to  the terminal.

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| 07:56
|  Compile and execute as before.

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| 08:04
|  The output is now correct.

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|08:06
| Let's summarize the tutorial.

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| 08:08
|  In this tutorial, we learnt

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| 08:10
|  relational operators like:

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| 08:12
|  Less than:  e.g. a <  b 

|-
| 08:14
|  Greater than: e.g. a>b

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| 08:17
|  Less than or equal to:  e.g. a<=b 

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| 08:22
|  Greater than or equal to: e.g. a>=b

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| 08:27
|  Equal to: e.g. a==b

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| 08:29
|  Not equal to: e.g. a!=b

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|  08:34 
|  As an assignment:

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| 08:35
|  Write a program that takes the marks of three students as input.

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| 08:39
|  Compare the marks to see which student has scored the highest.

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| 08:43
|  Check also if two or more students have scored equal marks.

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|  08:48
|  Watch the video available at the following link. 

|-
| 08:51
|  It summarizes the Spoken Tutorial project. 

|-
| 08:54
|  If you do not have good bandwidth, you can download and watch it. 

|-
| 08:58 
|  The Spoken Tutorial Project Team: 

|-
| 09:00
|  Conducts workshops using spoken tutorials. 

|-
| 09:03
|  Gives certificates for those who pass an online test. 

|-
| 09:06
|  For more details, please write to contact at spoken hyphen tutorial dot org.

|-
| 09:14
|   Spoken Tutorial Project is a part of the Talk to a Teacher project. 

|-
| 09:18
|  It is supported by the National Mission on Education through ICT, MHRD, Government of India. 

|-
| 09:24
|   More information on this Mission is available at 

|-
| 09:27
|  spoken hyphen tutorial dot org slash NMEICT hyphen Intro. 

|-
|  09:34
|  This is Ritwik Joshi from IIT Bombay. 

Thank you for joining. 

|}