Which tool is used to turn assembly language into machine code?

Assembly language is a low-level programming language that closely corresponds to the architecture of a computer's hardware. It uses mnemonics and symbolic names to represent machine-level instructions, making it more readable and easier for humans to understand than binary machine code. However, computers can only execute binary machine code.

An assembler is the tool specifically designed to convert assembly language into machine code. It processes the assembly language instructions and translates them directly into the binary format that the computer's processor can execute. This process allows programmers to write in a more understandable format while still ensuring that their code can run on the hardware.

Compilers, on the other hand, are used to translate high-level programming languages (like C or Java) into machine code, not assembly language. Linkers are responsible for linking different pieces of code and libraries together after they have been compiled. Interpreters execute high-level code directly, without translating it into machine code first, which doesn't apply to assembly language.

Thus, the assembler is the appropriate tool required to transition assembly language into machine code, which makes it the correct answer in this context.