Dick and Cliff Huston were engineers at Apple who worked on and for the Apple II in the 1970s and early 1980s. They preserved items from their time at the company, and made some of them available to purchase in the past two years. Antoine Vignau of Brutal Deluxe, who is himself an archivist of early Apple history, purchased the Huston’s printout of the source code of the first ProDOS Golden Master. Included with this printout were notes of the development process and preliminary manuals. These notes have been shared with me, and I am grateful to the Huston brothers and to Antoine Vignau for the opportunity to add to the story of ProDOS you can read here. If you’ve never heard of DOS 3.4, DOS 4.0, or XDOS, get the full story!