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C language

Token Types

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                                   Token Types

What is Token
Tokens are the smallest word of a program, which are meaningful for the compiler.
Six types of tokens in C Language. They are

1.   Keywords               (eg: int, while),
2.   Identifiers               (eg: main, total),
3.   Constants              (eg: 10, 20),
4.   Strings                    (eg: “total”, “hello”),
5.   Character set         (eg: A-Z,a-z),
6.   Operators              (eg: +, /,-,*)

 

Keywords

Keywords are reserved words in C and each keyword has specific meaning. 
There are total 32 keywords in C.
Auto
Double
int
struct
Break
Else
long
switch
Case
Enum
register
typedef
Char
Extern
return
union
Continue
For
signed
void
Do
If
static
while
Default
Goto
sizeof
volatile
Const
Float
short
unsigned

Identifier
Every program's element is known as an identifier. They are used for naming of variables, functions, array etc. Identifier are user-defined names which consist of number,alphabets, underscore ‘_’. Identifier’s name should not be same as keywords. Keywords are not used as identifiers.
Rules for naming C identifiers −
·        It must begin with alphabets or underscore.
·   Only numbers, alphabets, underscore can be used, no other special characters, punctuations are allowed.
·        It must not contain white-space.
·        It should not be a keyword.
·        It should be up to 31 characters.

Strings

A string is a collection of characters. This null character indicates that string has ended. Strings are always enclosed with double quotes(“ “).
Example
char string[20] = “demo”;
Here last character of string is '\0'.

Character set

A character set in 'C' is divided into,
  • Letters
  • Numbers
  • Special characters
  • White spaces (blank spaces)
Following is the character set in 'C' programming:
1.   Letters
o   Uppercase characters (A-Z)
o   Lowercase characters (a-z)
2.   Numbers
o   All the digits from 0 to 9
3.   White spaces
o   Blank space
o   New line
o   Carriage return
o   Horizontal tab
4    Special character
o   !@#$%^&*