Compiler Phase and Grammar Checking: Correct Answer Explanation
In a traditional compiler, the compiler checks grammar (syntax rules) during the syntax analysis phase (often called parsing). Syntax analysis uses a context-free grammar (CFG) to verify that the token sequence produced by lexical analysis matches the language’s grammatical structure. This contrasts with semantic analysis, which validates meaning (e.g., type correctness), and with code generation/optimization, which occur after a valid parse is obtained.
Key concepts: Syntax analysis , Parsing , Semantic analysis , Code generation , Code optimization.
Compiler Phases (Lexical, Syntax/Parsing, Semantic, IR, Codegen)
How the compiler uses phases to reach a correct result
- 1Step 1
Source code is converted into tokens (e.g., identifiers, keywords, operators).
- 2Step 2
The parser checks whether tokens follow the grammar rules; incorrect structure is a syntax error.
Mermaid view of the flow: - 3Step 3
After the syntax is valid, meanings are checked (e.g., type consistency).
- 4Step 4
Valid intermediate representation is translated into target machine/assembly code.
- 5Step 5
Machine/IR code is improved for performance/size while preserving behavior.
Visualizing what each option corresponds to
The question asks: “Grammar of the programming is checked in ____ phase of compiler.”
- (iii) syntax analysis is the phase that checks grammar/structure using the grammar rules (i.e., parsing).
- (i) semantic analysis checks meaning, not grammar.
- (ii) code generation translates representation to target code after correctness of syntax/semantics.
- (iv) code optimization improves efficiency after code generation.
Exam shortcut
If the question says grammar or syntax rules, the answer is almost always syntax analysis (parsing)—semantic analysis is for meaning.
Common confusion
Students often confuse grammar errors (e.g., missing semicolon, wrong token order) with semantic errors (e.g., adding int + string, undeclared variables). Grammar → syntax analysis; meaning → semantic analysis.
Typical compiler pipeline (high level)
Lexical Analysis
Phase 1Converts characters into tokens."
Syntax Analysis
Phase 2Checks grammar using parsing; builds parse structure."
Semantic Analysis
Phase 3Checks meaning (types, declarations, scope)."
Code Generation
Phase 4Produces target code from intermediate representation."
Code Optimization
Phase 5Improves efficiency without changing behavior."
Quick Reference: What each phase checks
Knowledge Check
Grammar of the programming is checked in ......... phase of compiler.