Question

In a compiler, which phase is responsible for identifying the token types from the source program's stream of characters?

• A. Syntax Analysis
• B. Semantic Analysis
• C. Lexical Analysis
• D. Intermediate Code Generation

Hint:

A Lexer often uses Regular Expressions to define what constitutes a token and Finite Automata (DFA) to implement the actual scanning logic.

Answer 1

The Correct Option is C

Concept: The compilation process consists of several sequential phases. The first phase interacts directly with the source code string.
• Lexical Analysis (Scanning): Converts characters into tokens.
• Syntax Analysis (Parsing): Checks the grammatical structure.
• Semantic Analysis: Checks for logical meaning (e.g., type checking).

Step 1: Defining the input of the Lexer.
The Lexer takes a stream of characters (raw text) as input. It scans these characters from left to right.

Step 2: The process of Tokenization.
It groups these characters into meaningful sequences called "lexemes." For each lexeme, it identifies a "token" type (Keyword, Identifier, Operator, etc.).

Step 3: Output of the phase.
The output is a sequence of tokens that is then passed to the Parser. Lexical Analysis is the specific phase described in the question.