Tokens In C Language

Tokens in C Language 

In C Language, Tokens are the part of program which are smallest elements and by collecting these smallest elements every program is designed and developed. 

Types of Tokens in C Language

Tokens in C Language

Keywords- Reserve words, Predefined and having special meaning.

For an example int is a keyword:- 

1. which is already reserved means we can not create it for different purpose.
2. which is predefined means we can not redefined it else program generate error.
3. which is having special meaning to compiler to allocate 2 Byte memory and contain only integer values means we can not create it for floating values.

Here is a List of 32 Keywords in C Language-

auto	break	case	char	const
default storage class for a variable	used to stop the loop or iteration	use to create cases in switch	data type for character values	use to define constant value
continue	default	do	double	else
used to continue the loop or iteration	used for default case in switch	used with do...while loop	data type to store larger value than float	used with if and alone is not allowed
enum	extern	float	for	goto
used for enumeration user defined structure	external or global storage class	data type to store floating values	used to create for loop	used for jumping to label
if	int	long	register	return
used for conditional statement	integer data type to hold integer values	Larger range Modifier	to create register storage class variable	to return value or stop program
short	signed	sizeof	static	struct
smaller range modifier	ability to allow negative and positive values	operator used to show location size of variable	to create single copy of variable	to create structure user defined data type
switch	typedef	union	unsigned	void
used with cases and perform switch statement	define the user defined type name for predefined data type	used to create union user defined data type	ability to allow only positive values	used as nothing return type
volatile		while
value may change at any time		used to create while loop or iteration

Identifiers 

Identifiers used for naming the constant, variable, function, pointer, struct etc. To create an identifiers we must follow some thumb rules otherwise errors will be generated in C Programming these rules are given below- 

1. It should not be reserve word (Keyword).

2. White Space is not allowed in Identifiers.

3. Only alphabets(a-z,A-Z), digits(0-9) and only underscore( _ ) special symbol is allowed.

4. Identifiers not allowed to start with digits.

5. Special symbols are not allowed except underscore( _ ).

Constant/ Literal

constant are the fixed values and it can assigned to other(ex. int a=10;) but can not take other values to assigned ( ex. int 5=20;) otherwise compiler will generate error. It may be numeric or character based. It can also further classified like integer and floating constant values are numeric constants while single character or literal string constant values are character constants.

Numeric Constant 

integer constant- it can be Decimal (example: 5,10 etc.), Octal (starts with 0 example: 010,029 etc.) or Hexadecimal (starts with 0x example: 0x10, 0x30 etc.)
floating constant- with precision values. example: 5.20,8.50, 0.5E-5 where E-5 means 10^-5 etc.  

Character Constant 

Single Character Constant- always used inside single quotes. example: 'A', 'a' etc.
String Constant/ Literal String-always used inside double quotes. example: "abc", "Hello" etc.

Escape Sequence

Escape Sequence are the character combination having special meaning on output without typed display. The list of Escape sequence with their meaning given below:

Escape Sequence	Character	Escape Sequence	Character
\b	Backspace	\n	NewLine
\f	Form Feed	\r	return
\t	Horizontal Tab	\v	vertical Tab
\'	Single Quotation Mark	\"	Double Quotation Mark
\?	Question Mark	\0	Null Character
\\		Backslash

Variable

Variables are the naming words for storing the value in memory. Example: int count=10; where count is a variable of integer type and assigning integer constant 10.

Rules for Naming the Variable in C Language-

1. It should not be reserve word (Keyword like int, float etc are not allowed).

2. White Space is not allowed in Variable naming.

3. Only alphabets(a-z,A-Z), digits(0-9) and only underscore( _ ) special symbol is allowed.

4. Variable name should be of 31 character long and previous limit was 8 characters long.

5. Variable not allowed to start with digits.

6. Special symbols are not allowed except underscore( _ ).

7. Two variables of same name with same letter case(small or capital) in same scope(in curly braces {}) is not allowed.

Examples	Status	Example	Status
count	correct	count_	correct
_count	correct	@count	incorrect, it violates rule 6
max_count	correct	max count	incorrect, it violates rule 2
count20	correct	20count	incorrect, it violates rule 5
INT	correct but not good practice	int	incorrect, it violates rule 1

Special Symbols/ Characters

Special Symbols or Characters used in C Language
+	-	*	/	%	&
!	@	#	$	^	(
)	_	\	~	<	>
?	:	;	"	'	.
{	}	[	]	|

Read Operators in C Language>>