How does C++ get compiled?

C++ compilation is a multi-stage process that transforms human-readable source code into executable machine code. Here's a breakdown:

1. Preprocessing

The C++ compiler begins by running the preprocessor.
The preprocessor handles directives that start with a # symbol (e.g., #include, #define).
#include directives insert the contents of specified header files into the source code. This allows you to use pre-written code from libraries or other parts of your project.
#define directives create macros, which are simple substitutions of text. They can be used to define constants or create shorthand notations.
Conditional compilation directives (#ifdef, #ifndef, #else, #endif) allow parts of the code to be included or excluded based on certain conditions.
The preprocessor outputs a modified source code file that no longer contains preprocessor directives.

The core compiler takes the preprocessed C++ code as input.
It parses the code, performs syntax and semantic analysis, and checks for errors.
It translates the C++ code into assembly code, which is a low-level representation of the program's instructions specific to the target processor architecture.
This assembly code is still human-readable, but it's much closer to machine code than C++.

The assembler takes the assembly code generated by the compiler and converts it into machine code, also known as object code.
Machine code consists of binary instructions that the processor can directly execute.
The output of the assembler is an object file (e.g., .o on Unix-like systems, .obj on Windows). This file contains the machine code for your program, but it's not yet an executable.

The linker combines one or more object files and resolves references between them.
If your program uses external libraries (e.g., standard C++ library, third-party libraries), the linker includes the necessary code from these libraries into the final executable.
The linker also handles memory layout, assigns addresses to variables and functions, and performs other necessary tasks to create a self-contained executable file.
The output of the linker is the final executable file (e.g., .exe on Windows, no extension on Unix-like systems).

In essence, C++ compilation involves:

Preprocessing: Handling # directives.
Compilation: Translating C++ to assembly code.
Assembly: Converting assembly code to machine code (object files).
Linking: Combining object files and libraries to create the final executable.