SpecOS is a pet project to create a multi-tasking OS for the ZX Spectrum +3 computer.
SpecOS (in a conceptual form) was born around September 1994, and came to life for real sometime around August 2010. The original idea was based on stack-switching, driven by the 50Hz ULA raster interrupt to the cpu.
After a 16-year gap, including University and 10 or so years in the computing industry working with Unix, this developed into a general-purpose Unix-style kernel-based model, striving to implement as much as possible without disabling interrupts, and therefore to reduce the amount of time lost e.g. during disk accesses (which CP/M is documented to suffer from).
Above all, this is a learning exercise, so there is a general policy of "don't copy code from anywhere". Yes it's re-inventing the wheel somewhat, but that's kind of the aim here!