A compiler is a software tool that translates source code written in a
high-level programming language into machine code or an intermediate
code. The compilation process is typically divided into several phases,
each responsible for different tasks. The traditional compilation
process consists of the following phases:
Lexical Analysis (Scanning):
- Task:
The source code is broken into tokens (the smallest units of meaning in
a programming language). This phase is carried out by a component
called the lexer or lexical analyzer.
- Output: A stream of tokens with associated lexemes.
Syntax Analysis (Parsing):
- Task: The syntax of the source code is analyzed to determine its grammatical structure. This phase is performed by a parser.
- Output: A parse tree or an abstract syntax tree (AST) that represents the hierarchical structure of the source code.
Semantic Analysis:
- Task:
The meaning of the source code is analyzed, checking for semantic
errors and ensuring that the code adheres to the language's semantics.
- Output: An annotated syntax tree with additional information about types, scope, and other semantic attributes.
Intermediate Code Generation:
- Task:
The compiler generates an intermediate representation of the source
code that is independent of the target machine architecture. This
facilitates optimization and portability.
- Output: Intermediate code (e.g., three-address code or bytecode).
Code Optimization:
- Task:
The intermediate code is optimized to improve the efficiency of the
generated machine code. This phase aims to enhance the performance of
the compiled program.
- Output: Optimized intermediate code.
Code Generation:
- Task: The optimized intermediate code is translated into the target machine code or another intermediate code.
- Output: Target machine code or another intermediate code.
Code Linking and Assembly:
- Task:
If the compilation process involves multiple source files, the
generated machine code is linked together, and additional system
libraries may be included.
- Output: An executable file or another form of output, depending on the target platform.
Code Optimization (Post-Code Generation):
- Task: Additional optimization may be performed on the generated machine code to improve the performance further.
- Output: Further optimized machine code.