The document is a presentation on compiler design, focusing on the relationship between tokens, lexemes, and patterns. It defines tokens as sequences of characters treated as single entities, provides examples like keywords and operators, and explains lexemes as character sequences matched by patterns in the source program. Additionally, it describes patterns as rules that represent all lexemes corresponding to a particular token.

1. Subject: Compiler Design
Presentation On Relationship Among Tokens, Pattern & Lexemes
Submitted To :
Mr. Gaurav Dubey
(Asst. Prof. , Department of
Computer Science & Engineering)
Submitted By :
Bharat Rathore
0905CS191062
Activity - 1

2. OUTLINES
• Token
• Lexeme
• Pattern
• Relationship

3. Tokens
Tokens : A token is sequence of characters that can be treated
as a unit/single logical entity.
Examples
• Keywords
Examples : for, while, if etc.
• Identifier
Examples : Variable name, function name, etc.
• Operators
Examples : '+', '++', '-' etc.
• Separators
Examples : ',' ';' etc.

4. Example on Tokens
int a = 10 ;
Keyword
Constant
Identifier
Separator
Operator

5. Lexeme
It is a sequence of characters in the source program that is matched
by the pattern for a token.
Example : “float”, “=“, “223”, “;”

6. Pattern
Pattern is a rule describing all those lexemes that can represent a
particular token in a source language.

7. Relationship
Relationship Between Token, Pattern & Lexeme