Compiling

Compiling is the process of transforming source code written in a programming language into a lower-level form that can be executed by a computer, typically machine code or an intermediate representation. A program that performs this translation is called a compiler. Compiling differs from interpretation in that the translation occurs before execution, rather than during runtime.

A typical compiler operates in several stages. The front end performs lexical analysis and parsing to convert source text into a structured representation, while checking syntax and enforcing semantic rules such as types. The middle end carries out optimizations and transforms the program into an intermediate representation that is easier to optimize across architectures. The back end generates target-specific code, which may be machine code, assembly, or bytecode, and may perform additional optimizations. The final output is object code that can be linked with libraries to form an executable.

There are different models of compilation. Ahead-of-Time (AOT) compilation translates the entire program before execution, producing a standalone executable. Just-In-Time (JIT) compilation compiles code at run time, often within a virtual machine, to enable runtime optimization based on actual program behavior. Some languages and environments employ both approaches, depending on deployment or runtime characteristics.

Common outputs of compilation include object files, static or shared libraries, and executables. The performance and portability of compiled programs depend on the compiler, the target architecture, and the available optimizations. Compilation errors are reported during various stages of the process and may include syntax, type, or linkage issues. Debug information can be embedded to map machine code back to source code for troubleshooting.

Examples of languages typically compiled include C, C++, Rust, and Go, whereas languages like Java and C# often rely on managed runtimes with JIT or AOT strategies in different environments.