Eight primitives and a colon compiler in 512 bytes is a nice demonstration of how much you can bootstrap from almost nothing. The examples building up from there are the best part.
Really shows how approachable it would have been to have just a tiny bit more added to the API of 'PC BIOS' to make for an extremely portable driver platform system to allow OS independent arbitrary hardware drivers as Forth that the system BIOS could compile at boot and run beneath the OS. Though of course the PC BIOS API from when that mattered isn't in anything like a modern protect mode operating profile.
PC BIOS was mostly just for DOS and bringup, it also helped in moving stuff across the barrier during 32 bit boot but afterwards the only thing you would normally use it for is to call hardware specific ROMs for instance for mode changes and such. The rest of the time you'd avoid it like the plague (also because of the expensive switch back to 'real' mode).
