Exercises while reading the incomplete "Writing a simple operating system from
scratch" by Nick Blundell.
https://www.cs.bham.ac.uk/~exr/lectures/opsys/10\_11/lectures/os-dev.pdf
The name of this directory is a reference to "Bootstrapping a simple compiler
from nothing" by Edmund Grimley-Evans.
https://github.com/certik/bcompiler