Solution

The correct answer is C. B. A. D.

Key Points

• The correct sequence for the tasks of a lexical analyzer is C. B. A. D.
• The lexical analyzer begins by buffering and reading source characters (step C).
• Next, it performs the removal of comments/white spaces to clean up the input (step B).
• Then, it proceeds with token generation, breaking the input into meaningful components (step A).
• Finally, it returns the token stream to the parser for further processing (step D).

Additional Information

• Detailed Explanation of Steps:
  • Step C (Buffering and reading source characters): The lexical analyzer reads the source program character by character, often using a buffering mechanism to manage input efficiently.
  • Step B (Removal of comments/white spaces): Non-essential elements like comments and white spaces are removed to simplify the input for subsequent stages.
  • Step A (Token generation): The cleaned-up input is divided into tokens, which are the smallest units of meaning (e.g., keywords, identifiers, operators).
  • Step D (Return token stream to parser): The generated tokens are passed to the parser, which constructs a syntax tree or other intermediate representation.
• Role of Lexical Analyzer:
  • The lexical analyzer is the first phase of a compiler, responsible for converting source code into a sequence of tokens.
  • It ensures that the input is free of irrelevant characters, simplifying the tasks of subsequent phases like parsing and semantic analysis.
• Additional Considerations:
  • Efficient buffering techniques are crucial for the performance of the lexical analyzer, especially for large programs.
  • Error handling is another important aspect, such as reporting invalid characters or malformed tokens.