Which translation method converts all source code into machine code for later execution?

An interpreter translates source code into machine code line by line during execution, rather than producing a standalone machine code file. This means that the source code must be present each time the program runs, resulting in slower execution for repeated runs compared to compiled code.

An assembler converts assembly language, a low-level programming language, into machine code. While it does generate machine code, it operates at a different level than compilers, which work with high-level languages. Therefore, it does not fulfill the criteria of converting all source code from high-level languages into machine code.

The operating system (OS) is responsible for managing hardware and software resources but does not translate source code into machine code. Instead, it provides an environment in which programs execute, and it interacts with compilers and interpreters but is not a translation method itself.