How Source Code Becomes Machine Instructions: A Step‑by‑Step Overview of the Compilation Process

In this tutorial the author walks through the journey of a program from human‑readable source code to binary machine instructions that a CPU can execute.

The compilation process begins with lexical analysis, where the compiler scans the source string, discards whitespace and line breaks, and groups characters into meaningful tokens such as keywords (e.g., int , main ) and literals (e.g., numbers).

After tokenization, the compiler parses the token stream according to the language grammar. For example, when it encounters an if token, it applies the if statement syntax, building a hierarchical structure known as an abstract syntax tree (AST).

Once the AST is constructed, the compiler traverses it to generate intermediate or target‑specific instructions. In many real compilers the generated code is first emitted as assembly, which is then assembled into binary machine code.

Compilers also perform optimizations; for instance, dead code such as an unused variable assignment can be eliminated before the final machine code is emitted.

Finally, a linker combines the generated object files into a single executable program that the operating system can load and run.

The article also mentions that targeting multiple CPU architectures (e.g., x86, ARM) requires separate backend implementations, and that using an intermediate representation such as LLVM IR allows a compiler to generate code for many targets by delegating the low‑level details to LLVM.