Compiling and Interpreting
Programming languages need to be transformed into something computers can execute. There are two fundamental approaches: compiling and interpreting. Understanding the difference helps you grasp why different languages behave differently.
Compilation: Translate Everything First
A compiler reads your entire program and translates it into machine code (or an intermediate format) before anything runs. The result is an executable file you can run directly.
Think of it like translating an entire book from English to Spanish. A translator reads the whole book, produces a Spanish version, and then Spanish readers can read it without needing the translator present.
Languages like C, C++, Go, and Rust use compilation. When you compile a program, you wait for the translation to complete, but then the program runs very fast because the translation work is already done.
Interpretation: Translate As You Go
An interpreter reads your code line by line, translating and executing each instruction immediately. There's no separate compilation step — you just run your code directly.
This is like having a live interpreter at a conference. They translate each sentence as the speaker says it. There's no waiting for a complete translation, but the interpreter must be present throughout.
Languages like Python, Ruby, and JavaScript (traditionally) use interpretation. You can run code immediately without a compilation step, which makes development faster and more interactive.
The Tradeoffs
| Aspect | Compiled | Interpreted |
|---|---|---|
| Startup | Slower (must compile first) | Faster (runs immediately) |
| Execution speed | Generally faster | Generally slower |
| Error detection | Many errors caught at compile time | Errors found at runtime |
| Portability | Platform-specific executables | Same code runs anywhere with interpreter |
Modern Reality: It's Complicated
Today's languages often blur these lines. JavaScript engines compile code "just in time" (JIT) for better performance. Java compiles to bytecode that runs on a virtual machine. Python compiles to bytecode internally.
The distinction still matters conceptually, but modern implementations mix both approaches to get the best of both worlds.
Why This Matters
Knowing whether a language is compiled or interpreted helps you understand its development workflow, performance characteristics, and error behavior. It's foundational knowledge for working with any programming language.