86-DOS revisited

Recently, the oldest known versions of DOS were uploaded to the internet, and Michal Necasek dove into the floppy images.

Even after more than 40 years(!), old software releases and pre-releases can still surface. In the case of 86-DOS 0.11 and 0.34 it's practically a miracle, since there were probably never very many copies in existence.

For the first time since the early 1980s, FAT formatted floppies with the primordial 16-byte directory entry format have come to light. The old 16-byte directory entries were gone by 86-DOS 1.0 in April 1981 and of course never appeared in any public PC DOS release.

These prehistoric versions of 86-DOS allow us to fill in further missing pieces in the puzzle of DOS origins. It is fascinating to follow how DOS developed from almost nothing to a multi-million dollar business in the course of just a few years.

Michal Necasek

It started out so humbly. Yet, here we are, in 2024, and variants of DOS still have their uses in certain niches. An incredible legacy, for sure.