Compiler diagnostics: Which class of errors can a compiler reliably detect and report during translation of a source program?

Introduction / Context:
Compilers analyze source code to transform it into object code. Along the way, they validate program structure. Understanding what a compiler can and cannot detect helps developers interpret error messages and design tests.

Given Data / Assumptions:

• We distinguish syntax, semantic, and logical errors.
• Syntax concerns grammar of the language (tokens, statements).
• Semantic concerns meaning (types, declarations, compatibility).

Concept / Approach:

All compilers detect syntax errors because parsing requires the program to adhere to grammar rules. Many compilers also detect numerous semantic errors (e.g., type mismatches, undeclared identifiers). Logical errors (algorithmic mistakes) typically compile fine but produce wrong results at runtime. The safest, universally correct answer is that compilers detect syntax errors.

Step-by-Step Solution:

Verification / Alternative check:

Parsing fails immediately on grammar violations; compilers emit errors such as “expected ;” or “unexpected token.”

Why Other Options Are Wrong:

• Semantic errors: often detected, but the question asks which errors the compiler can point out reliably; syntax is the baseline.
• Logical errors: require dynamic knowledge or specifications.
• Internal errors: refer to bugs in the compiler itself, not user code.

Common Pitfalls:

Assuming all meaning-related mistakes are caught at compile time; languages with dynamic typing defer many checks to runtime.

Final Answer:

Syntax errors