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There are six stages of compiling a program:

1. lexical analysis
2. symbol table construction
3. syntax analysis
4. semantic analysis
5. code generation
6. optimisation

Lexical analysis

• Comments and unnecessary spaces are removed.
• Keywords, constants and identifiers are replaced by 'tokens', which are symbolic strings to identify what the elements are.

Symbol table construction

• A table stores the names and addresses of all variables, constants and arrays.
• Variables are checked to make sure they have been declared and to determine the data types used.

Syntax analysis

• Tokens are checked to see if they match the syntax of the programming language.
• If syntax errors are found, error messages are produced.

Semantic analysis

• Variables are checked to make sure they have been correctly declared and contain the correct data type.
• Operations are checked to ensure that they are appropriate for the type of variable being used.

Code generation

• Machine code is generated in this stage.

Optimisation

• Code optimisation makes the program more efficient so it runs faster and uses fewer resources.