Which of the following best describes the functionality of a compiler?

The functionality of a compiler is best described as creating executable machine code from source code. This process involves taking high-level programming language code, written by developers, and translating it into machine language that the computer's processor can understand and execute.

Compilers analyze the entire source code to identify and optimize the program's structure, converting it into a binary format that is specific to the computer's architecture. This compiled code can then be run independently of the original source code, typically leading to improved performance compared to interpreted languages, which execute the code line-by-line at runtime.

Other options reflect related concepts but do not encapsulate the primary role of a compiler as effectively. For example, while some compilers may provide user-friendly error messages, their main purpose is not focused on error handling but rather on translation to executable code. Similarly, while compilers can handle portions of code, they typically work on larger segments or entire programs at once rather than small snippets. Finally, immediately running code is characteristic of interpreters, not compilers, since executing is separate from the compilation process.