ITPEC FE Morning October 2020 Question 17

Lexical analysis — the compiler first reads the source text as characters and groups them into tokens, which every later phase works on.

The compilation phases run in this order:

1. Lexical analysis: characters into tokens (keywords, identifiers, operators, literals)
2. Syntactic analysis (parsing): tokens into a parse tree, checked against the grammar
3. Semantic analysis: type and declaration checks, meaning of each construct
4. Optimization: improving the intermediate code
5. Code generation: producing the object code

Answer (a)

Why not others:

• •(b) Optimization — works on intermediate code, so it comes after all three analysis phases
• •(c) Semantic analysis — needs the parse tree, so it follows syntactic analysis
• •(d) Syntactic analysis — needs tokens as input, so it follows lexical analysis

Key rule: Each phase consumes the output of the one before: characters, then tokens, then a parse tree, then checked intermediate code, then object code.

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