ANSI-C (and to a lesser extent C99) is pretty much the only language which you can compile anywhere, forever. For this project portability is the #1 requirement.
If he used, say Rust, then the target system needs a rust compiler, and furthermore, the language is not even close to being as standardized a C is at the moment, i.e. who knows if in the future you will still be able to compile your program that you write on 2023's dialect?
If he used, say Rust, then the target system needs a rust compiler, and furthermore, the language is not even close to being as standardized a C is at the moment, i.e. who knows if in the future you will still be able to compile your program that you write on 2023's dialect?