How does the lexical analyzer identify whether given token is Identifier or Keyword?

Question

I have a basic question on Lexical Analysis. As lexical analyzer (which is a DFA which accepts lexemes and produces token) can produce tokens which can be Identifier([a-z]/[A-Z]/[0-9] knowing digit not the first char), Keywords (if, else,..) , Operators & Delimiters.

So if a lexeme like 'whil' comes. Then will it be a lexical error stating Its not a valid keyword or will it be accepted as Identifier(variable), as lexical analyzer do not consider whether the syntax is right or not ?

Does Lexical Analyzer use different DFA for Identifiers, Keywords, Operators ?

Answer 1

Then will it be a lexical error stating Its not a valid keyword

No.

or will it be accepted as Identifier(variable)

Yes, and then there will be a syntax error from the parser.

as lexical analyzer do not consider whether the syntax is right or not ?

The lexical analyser doesn't know anything about syntax. That's the parser's job.

Answer 2

To identify keywords, It uses the same regexp for identifier, and then checks the keyword table, whether it's a keyword. If yes, then keyword, else it is an identifier