"writing an OS" is a sweeping, unsupported and inaccurate statement. You can be involved in Linux and, say, write the ext4 filesystem or Wifi drivers. Those are pretty low-level. You could also write shell utilities like ls in probably anything where you're just using OS APIs. Is that low-level? I would say not.

My friend, my comrade in arms, I have a link[1] for you. If you read only one of these papers, then please just read the first one, but please note the author credits on almost all of them.

[1] http://doc.cat-v.org/plan_9/4th_edition/papers/

EDIT: In the past half hour, the original website went down, I don't think it is related to my link. Here is a different link with the same contents:

https://9p.io/sys/doc/

The C, Unix and AWK creators know nothing on low-level stuff.

Please, kid.

Oh my god. Can you at least do your research now ? They wrote the core bits and not just userspace utils. Did you read what they wrote before blustering here ?