"Discovery and Upload of the Earliest MS-DOS Ancestor Version"
Originally Published 2 years ago — by Ars Technica
A previously unknown early version (0.1-C) of 86-DOS, the precursor to Microsoft's MS-DOS, has been discovered and uploaded to the Internet Archive by a user named f15sim. This version dates back to August 1980 and is available for download and use with an emulator. It offers a glimpse into the rudimentary beginnings of what would become the foundation for the majority of PCs in the 1980s and the underlying system for Windows in the 1990s. Microsoft later purchased 86-DOS from Seattle Computer Products and developed it into MS-DOS, which, along with its IBM-branded counterpart PC DOS, played a significant role in the rise of the PC market.