The BEAM (runtime?) is written in C. There is also an effort to rewrite it in Rust (https://github.com/lumen/lumen). Some functions are built into the VM but most of the supporting 'standard library' (OTP / Open Telecom Platform) is written in Erlang. The (main) compiler is written in C. So it's all C or Erlang afaik.
It is ported to every major flavour of OS.
I don't know what 'back end' means in this context.
It is ported to every major flavour of OS.
I don't know what 'back end' means in this context.