Stages of compilation

Question 1

What are the 4 stages of compilation in order?

Answer 1

• Lexical analysis
• Syntax analysis
• Code generation
• Code optimisation

Question 2

What happens in lexical analysis of code?

Answer 2

The lexer analyses lexemes (words) in the source code, checks if it is valid against a pre defined set of rules and identifies the lexeme with a token (e.g. key words, constants, strings, numbers, operators…)
It then puts these tokens into a symbol table

Question 3

What happens in syntax analysis of code?

Answer 3

Tokens from lexical analysis are received as inputs, the structure of the inputs are then analysed to ensure it is syntactically correct.
It then builds a parse tree (syntax tree) and updates the symbol table with data types.

Question 4

What happens in code generation?

Answer 4

Machine code is generated

Question 5

What happens in code optimisation?

Answer 5

The code is analysed to spot:
- Spotting redundant instruction that can be replaced in a more efficient way
- Removing subroutines that are never called
- Removing variables and constants that are never referenced