Roles of the Lexical analyzer

Lexical analyzer performs below given tasks:

  • Helps to identify token into the symbol table
  • Removes white spaces and comments from the source program
  • Correlates error messages with the source program
  • Helps you to expands the macros if it is found in the source program
  • Read input characters from the source program

Example of Lexical Analysis, Tokens, Non-Tokens

Consider the following code that is fed to Lexical Analyzer

#include <stdio.h>

   int maximum(int x, int y) {

       // This will compare 2 numbers

       if (x > y)

           return x;

       else {

           return y;



Examples of Tokens created

Lexeme Token
int Keyword
maximum Identifier
( Operator
int Keyword
x Identifier
, Operator
int Keyword
Y Identifier
) Operator
{ Operator
If Keyword

Examples of Nontokens

Type Examples
Comment // This will compare 2 numbers
Pre-processor directive #include <stdio.h>
Pre-processor directive #define NUMS 8,9
Macro NUMS
Whitespace /n /b /t

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