A couple of weeks ago, Microsoft released the source code of MS-/PC-DOS 4.00 to the public.
Due to various bugs, DOS 4.00 was a relatively short-lived release, and it was replaced by DOS 4.01 just a couple of months later.
Howard M. Harte (hharte), who already fixed various flaws in the official source code release of MS-DOS 4.00, managed to figure out the differences between DOS 4.00 and 4.01 — we now have access to the improved version as well!
