Which is true for comments?

Question

BlackTom AI · Accepted Answer

Comments are non-executable annotations in source code that programmers use to explain, document, or temporarily disable code. They are intended for humans, not the machine.

1. Relevant knowledge points and concepts
- Purpose of comments: human-readable notes explaining code.
- Compiler pipeline: preprocessing/lexical analysis → parsing → semantic analysis → optimization → code generation.
- Treatment of comments: during lexical analysis or preprocessing, comments are recognized and discarded or turned into tokens that carry no executable semantics. They do not become instructions or occupy runtime memory in the generated machine code.

2. Step-by-step reasoning process
- When source code is fed to the compiler, the lexer scans characters and groups them into tokens. Comments are detected (e.g., //, /* */) and removed or ignored at this stage.
- Since comments have no syntactic or semantic effect on program execution, subsequent compiler phases do not generate code for them.
- The code generation phase emits machine instructions only for tokens that represent executable constructs (variables, expressions, control flow, function calls).

3. Intermediate steps (compilation flow showing comment handling)
- Source text → Lexer finds comment markers → Lexer discards comment text → Parser receives token stream without comment content → Semantic/optimization phases operate on AST → Code generator emits machine code. At no point is comment text converted into machine instructions.

4. Why the correct answer is correct
- Because comments are eliminated before code generation, the compiler does not produce any machine code corresponding to comments. They do not translate to instructions or memory allocations in the executable.

5. Why other options are incorrect
- "Translates comments into ASCII values": incorrect — ASCII conversion applies to character data, not to comments for execution.
- "Allocates memory for comments": incorrect — compilers do not reserve runtime memory for comments; any retained comment-like data (documentation tools) is separate from executable allocation.
- "Converts comments into a series of machine instructions": incorrect — comments are non-executable and are omitted from instruction generation.

6. Conclusion
The correct answer is: The compiler does not generate machine code for comments. This matches the provided answer.

Which is true for comments?单项选择题

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