You write code in Python or C++. The computer understands only binary. A compiler is a program that translates source code into machine code. It reads your entire program, checks for errors, and produces an executable file. Once compiled, the program runs without the compiler.

Compilers do more than translate. They optimize. A good compiler removes redundant instructions, reorders operations, and allocates registers efficiently. The difference between a naive translation and an optimized one can be tenfold in speed.

Stages of compilation

• Lexical analysis: breaks code into tokens
• Parsing: builds a syntax tree
• Semantic analysis: checks types and scope
• Optimization: improves performance
• Code generation: produces machine code

Not all languages use compilers. Interpreted languages like Python execute code line by line. Just-in-time compilers blend both approaches, compiling hot code paths at runtime. Each strategy trades startup speed for execution speed.