How Compilers and Interpreters Transform Source Code Into Execution

When a programmer writes source code, the computer cannot understand it directly and must process it through a structured pipeline of transformations. The first stage, called lexing or tokenizing, breaks raw characters into meaningful units known as tokens, such as keywords, identifiers, and operators. A parser then takes those tokens and builds an Abstract Syntax Tree, a structured representation that captures the program's meaning, including operator precedence and grouping rules. This pipeline approach — from source code to tokens to AST — forms the foundational mental model behind how both compilers and interpreters work. Understanding each stage as a discrete transformation makes the inner workings of programming language implementations far more approachable for developers.