What are the main phases of a compiler?
Interviewer Expectations for this Question
01
Core Competency
Assesses fundamental understanding of Compilers & Languages conventions, runtime behavior, and memory/performance considerations.
02
Evaluation Criteria
Hiring managers look for precision, avoidance of ambiguous jargon, and ability to explain trade-offs under real production conditions.
Comprehensive Model Answer
Verified Solution
A typical compiler pipeline has a front end, a middle end and a back end.
- Lexical analysis: turn characters into tokens.
- Syntax analysis: build a parse tree from the token stream using the grammar.
- Semantic analysis: check types, scopes and declarations, and build a symbol table.
- Intermediate representation: lower the tree to a form such as three-address code or SSA.
- Optimisation: improve the IR without changing meaning, for example constant folding and dead code elimination.
- Code generation: emit target machine code or bytecode, including register allocation and instruction selection.
chars -> lexer -> tokens -> parser -> AST -> semantics
-> IR -> optimiser -> codegen -> machine code
Front ends are language-specific, back ends are target-specific, and the shared IR is what lets a compiler support many languages and many CPUs without an explosion of combinations.
Candidate Response Strategy & Interview Tips
- Start with a concise one-sentence summary: Deliver a direct, confident answer first before expanding into nuances.
- Demonstrate real-world trade-offs: Discuss where this approach excels and when you would avoid it in production systems.
- Discuss complexity & edge cases: Proactively explain time/space complexity or boundary conditions (null values, scale limits).
- Prepare for interviewer follow-ups: Technical hiring panels frequently probe deeper into concurrency, backward compatibility, or alternative libraries.