Tokens are the smallest individual units that make up a program. There are 6 types of tokens: keywords, identifiers, constants, strings, special symbols, and operators. Keywords have fixed meanings and cannot be changed, identifiers name variables and functions, constants are fixed values, strings are sequences of characters in double quotes, special symbols define functions, and operators perform mathematical or logical operations.

1. C TOKENS

2. Tokens
• In a passage of text, individual words and punctuation marks are
called tokens.
• Smallest individual units / smallest element in a program is called
tokens
• There are 6 types of tokens.

3. TYPES OF TOKENS
• Keyword
• Identifier
• Constant
• Strings
• Special symbols
• Operators

4. KEYWORD
• All words have fixed meanings and these meanings cannot be
changed.
• All keywords must be written in lowercase.
• For example : break,if,for,void,while…
if a>b – If(Keyword)

5. IDENTIFIER
• Identifier refers to the names of variables,functions and arrays.
• These are user-defined names and consist of sequence of letters and
digits.
• Both uppercase and lowercase letters are permitted.
• Underscore character are also permitted.

6. RULES FOR IDENTIFIERS
• First character must be an alphabet.
• Must consist of only letters,digits or underscore.
• Only first 31 characters are significant.
• Cannot use a keyword.
• Must not contain white spaces.
For example :
int a;(Valid)
int int;(invalid)

7. Constants
• Constants refers to fixed values that do not change during the
execution of a program.
• These include 2 types
1.Numeric constants
Integer constant
Real constant
2.Character constants
Single character constants
String constant

8. STRINGS
• A string constant is a sequence of characters which are enclosed in
double quotes.
• The characters may be letters,numbers,special characters.
For example : “Hello”, “xyz”, “1234”.

9. SPECIAL SYMBOLS
• Special syumbols are used in programming to define the
characterisric of function.
For example :
() - braces
{} - Paranthesis
; - Semicolon
: - Colon

10. OPERATORS
• An operator is a symbol that tells the computer to perform certain
mathematical or logical manipulations.
• It classified into 8 types of categories.
For example : + - % *
a + b = 5
+ -> Arithmetic perator
= ->Assignment Operator