@theruran @janneke Here's a project of mine where I simply print "Hello world" without relying on glibc: https://github.com/bugaevc/hello-hurd — but that too is written in C, imagine writing it all in hex.

2. Linux is huge, but you can build it in a minimal configuration (see https://tiny.wiki.kernel.org/). Mach may be a microkernel, but it's minimal in functionality, not size. In fact it's a meme in the microkernel community just how large for a microkernel Mach is. But I don't have any numbers to quantify this.