C-and-C++/C2/Tokens/Gujarati

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,
00.21	I am using Ubuntu Operating system version 11.10gcc and g++ Compiler version 4.6.1.
00.33	Let us start with an introduction
00.37	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. 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. This is our header file.
01.16	This is our main functions.
01.20	Here, int is a keyword
01.22	The compiler knows the meaning of keywords.
01.26	a is an integer variable
01.29	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, const, default, enum extern, etc.
02.28	Constants are fixed values.
02.34	They do not change during the execution of a program. 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
02.57	Data type is a finite set of values along with a set of rules
03.05	Here, d is a variable
03.07	Char and single quotes suggest that we are dealing with a character
03.13	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 datatypes.
03.30	a, c and d are variables
03.36	Now come back to our slides.
03.38	We will know more about datatypes and variable
03.48	Let us begin with integer data type
03.51	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 use double and %lf as the format specifier.
04.25	Now we will see the range of data types
04.29	Integerdata type has a range of this -32,768 to 32,767
04.34	Floating point has a range of this 3.4E +/-38
04.39	Character has a range of this -128 to 127
04.42	And Double has a range of this 1.7E +/-308
04.48	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.
05.03	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
05.15	We should try to give meaningful names to variables
05.19	example john, marks, sum etc.
05.24	Now move back to our program.
05.27	Here, printf is the identifier name for this function
05.32	Come back to our slides. 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. Here we print them.
06.05	And this is our return statement. Now click on save.
06.10	Let us execute the program
06.12	Please open the terminal by pressing Ctrl, Alt and T keys simultaneously on your keyboard.
06.21	To compile ,Type gcc tokens.c -o tok press Enter
06.30	To execute type./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 %.2f here.
06.59	It denotes that we can print only two values after the decimal point.
07.04	here I want an output with three decimal places.
07.09	Let us replace %.2f with %.3f
07.16	Now Click on Save
07.20	Come back to the terminal. compile as before, execute as before.
07.29	We can see here three values after the decimal point.
07.33	NOW WE WILL EXECUTE THE SAME PROGRAM IN C++
07.37	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 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
08.28	Type here printf opening bracket “(”
08.33	And here in this column type,
08.35	cout and two opening angle brackets “<<”. Now click on Replace All and click on Close.
08.45	We don't need the format specifier /n
08.50	Let us delete them.Now delete the comma.
08.54	And type two opening angle brackets.
09.01	Click on Save. Now delete the closing bracket
09.06	Type two opening angle brackets again.
09.09	And within the double quotes type \n. Now Click on Save
09.20	Let us execute the program.Come back to the terminal.
09.24	To compile , type g++ tokens.cpp -o tok 1
09.35	Here we have tok1
09.36	Because we don't want to overwrite the output parameter tok for the file tokens.c . 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.Suppose here I will reassign a new value to b as 8.
10.13	now Click on Save. Let us see what happens.
10.15	Come back to our terminal.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
10.40	This is because b is a constant. Constants are fixed values.
10.46	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.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. 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.
12.14	Now switch back to our slides.
12.15	Let us summarize
12.16	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
12.41	Write a C program to calculate the simple interest.
12.45	Hint: Simple Interest = principal * rate * time / 100
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13.35	Ashwini Patil from IIT BombayThank You for joining

Contributors and Content Editors

Jyotisolanki, Krupali, PoojaMoolya, Pratik kamble