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:

1. 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.

2. 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.

3. 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.

4. 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).

5. 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.

6. 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.

7. 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.

8. 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.

These phases represent the classic structure of a compiler. However, modern compilers may include additional steps or combine certain phases for efficiency. Additionally, Just-In-Time (JIT) compilers, which compile code at runtime, may not follow this exact structure but share similar principles.