Difference between revisions of "C-and-C++/C2/Tokens/English-timed"

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Revision as of 16:52, 8 March 2017

Time Narration
00:01 Welcome to the spoken tutorial on Tokens in C and C Plus Plus.
00:06 In this tutorial we will learn ,
00:09 How to define and use tokens.
00:12 We will do this with the help of an example.
00:15 We will also see some common errors and their solutions.
00:20 To record this tutorial, I am using Ubuntu Operating system version 11.10,
00:26 gcc and g++ Compiler version 4.6.1.
00:33 Let us start with an introduction.
00:36 Token is a generic word for data types, variables, constants and identifiers.
00:46 Let us start with our program.
00:49 I have already typed the code on the editor.
00:53 Let me open it.
00:56 Note that our file name is 'tokens.c'.
01:04 In this program we will initialize the variables and print their values.
01:09 Let me explain the code now.
01:12 This is our header file.
01:16 This is our main function.
01:20 Here, int is a keyword.
01:22 The compiler knows the meaning of keyword.
01:26 a is an integer variable.
01:28 We have assigned a value of 2 to it.
01:32 This is called as initialization.
01:35 If a value is not assigned to a variable then it is called as declaration of the variable.
01:43 Here, b is a constant.
01:46 We have initialized 'b' by assigning a value of 4 to it.
01:53 const keyword is used to create 'read only' variable.
01:58 Let us switch back to our slides to know more about keywords and constant.
02:06 Keywords have fixed meanings that cannot be changed.
02:11 Keywords cannot be used as variable names.
02:15 There are 32 keywords in C.
02:18 To name some, auto, break, case, char, enum, extern, etc.
02:28 Constants: constants are fixed values.
02:33 They do not change during the execution of a program.
02:38 There are two types of constants, Numeric constants and Character constants.
02:45 Now come back to our program.
02:47 Here, float is a data type of variable c.
02:52 We have assigned it a value of 1.5.
02:56 Data type is a finite set of values along with a set of rules.
03:04 Here, d is a variable.
03:07 char and single quotes suggest that we are dealing with a character.
03:12 As a result, d is a character variable storing the value A.
03:20 It is easy to see that int, double, float and char are data types.
03:30 a, c and d are variables.
03:35 Now come back to our slides.
03:37 We will know more about data types and variables.
03:48 Data types: Let us begin with integer data type.
03:50 It is declared as int.
03:53 If we want to print an integer data type , we will use %d as the format specifier.
04:01 Similarly, we will use float and %f for floating point numbers.
04:09 For character data type, we will use char and %c.
04:15 And For double data type, we will use double and %lf as the format specifier.
04:24 Now we will see the range of data types.
04:29 Integer data type has a range of this
04:34 Floating point has a range of this
04:39 Character has a range of this
04:42 And Double has a range of this
04:47 The values stored in the variable must not be greater or less than this range.
04:56 Now we will move on to variables.
05:00 Variable is a data name.
05:02 It may be used to store a data value .
05:06 The values can change when a program runs.
05:10 Before using a variable it must be declared.
05:14 We should try to give meaningful names to variables.
05:18 example john, marks, sum etc.
05:24 Now we will move back to our program.
05:27 Here, printf is the identifier name for this function.
05:32 Come back to our slides.
05:35 Let us know about identifiers.
05:38 Identifiers are user defined names.
05:41 An identifier consists of letters and digits.
05:46 Both uppercase and lowercase letters are permitted.
05:51 First character must be an alphabet or underscore.
05:55 Now Come back to our program.
05:58 Here we have initialized the variables and constants.
06:02 Here we print them.
06:05 And this is our return statement.
06:08 Now click on Save.
06:10 Let us execute the program.
06:12 Please open the terminal window by pressing Ctrl, Alt and T keys simultaneously on your keyboard.
06:21 To compile, type gcc space tokens dot c space hyphen o tok. Press Enter.
06:30 To execute, type ./tok (dot slash tok).
06:35 The output is displayed.
06:39 We can see that here we have six values after the decimal point.
06:44 And here we have two values.
06:48 Now let us find out how this happened. Come back to our program.
06:54 This is because we have % point 2f here.
06:59 It denotes that we can print only two values after the decimal point.
07:04 Suppose here I want an output with three decimal places.
07:09 Let us replace % point 2f with % point 3f.
07:16 Now click on Save.
07:19 Come back to our terminal.
07:22 Compile as before, execute as before.
07:28 We see here three values after the decimal point.
07:33 Now we will execute the same program in c++.
07:36 Come back to our program.
07:40 I will change a few things here.
07:42 First press Shift+Ctrl+s keys simultaneously on your keyboard.
07:50 Now save the file with an extension .cpp and click on Save.
07:58 Let us change the header file as iostream
08:03 Now include the using statement.
08:08 And click on Save.
08:11 Now replace the printf statement with the cout statement
08:15 since we use cout<< function to print a line in C++.
08:21 Click on Search for and replace text option.
08:27 Type here printf opening bracket “(”
08:33 And here in this column type, cout and two opening angle brackets “<<”.
08:40 Now click on Replace All and click on Close.
08:45 We don't need the format specifier and '\n'
08:50 Let us delete them.
08:52 Now delete the comma and type two opening angle brackets.
09:01 Click on Save. Now delete the closing bracket.
09:04 Type two opening angle brackets again.
09:09 And within the double quotes type \n.
09:16 Now Click on Save.
09:20 Let us execute the program. Come back to our terminal.
09:24 To compile, type g++ space tokens dot cpp space hyphen o space tok1.
09:35 Here we have tok1 because we don't want to overwrite the output parameter tok for the file tokens.c.
09:46 Now press Enter.
09:48 To execute, type ./tok1 . Press Enter.
09:55 The output is displayed.
09:59 Now let us move on to some common errors which we can come across.
10:03 Come back to our program.
10:05 Suppose here I will reassign a new value to b as 8.
10:12 Now click on Save. Let us see what happens.
10:15 Come back to our terminal.
10:17 Let me clear the prompt.
10:22 Now compile as before.
10:26 We see an error at line no.7 in our tokens. cpp file.
10:32 "Assignment of read only variable 'b' ".
10:36 Come back to our program.
10:39 This is because 'b' is a constant. Constants are fixed values.
10:45 They do not change during the execution of program.
10:49 Hence it is giving an error. Let us fix the error.
10:54 Delete this. Click on Save.
10:57 Let us execute again. Come back to our terminal.
11:01 Compile as before.
11:03 Execute as before. Yes, it is working.
11:09 Now we will see another common error.
11:12 Switch back to our program.
11:15 Suppose here I will miss the single quotes. Click on Save.
11:21 Let us execute. Come back to our terminal.
11:25 Compile as before.
11:28 We see an error at line no.9 in our tokens dot cpp file.
11:34 " 'A' was not declared in the scope". Come back to our program.
11:40 This is because anything within the single quotes is considered as a character value.
11:47 And here we have declared 'd' as a character variable.
11:53 Let us fix the error. Type single quotes at line no.9 here.
11:59 Now Click on Save. Let us execute.
12:02 Come back to our terminal.
12:04 Now Compile as before.
12:06 Execute as before. Yes it is working.
12:13 Now switch back to our slides.
12:15 Let us summarize.In this tutorial we learnt,
12:18 Data types eg. int, double, float etc.
12:24 Variables eg. int a=2;
12:29 Identifiers eg. printf() and
12:34 Constant eg. double const b=4;
12:40 As an assignment,Write a program to calculate the simple interest.
12:45 Hint: principal * rate * time upon 100.
12:50 Watch the video available at the link shown below.
12:54 It summarizes the Spoken Tutorial project.
12:56 If you do not have good bandwidth, you can download and watch it.
13:01 The Spoken Tutorial Project Team:
13:03 Conducts workshops using spoken tutorials,
13:07 Gives certificates to those who pass an online test.
13:10 For more details, please write to contact @spoken-tutorial.org
13:19 Spoken Tutorial Project is a part of the Talk to a Teacher project.
13:24 It is supported by the National Mission on Education through ICT, MHRD, Government of India.
13:30 More information on this Mission is available at the link shown below.
13:35 Ashwini Patil from IIT Bombay signing off .Thank You for joining.

Contributors and Content Editors

Jyotisolanki, Krupali, PoojaMoolya, Pratik kamble, Sandhya.np14, Sneha

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