Why is Apple DOS source code release important?

Last week, the Computer History Museum released the source code to Apple DOS 3.1:

With thanks to Paul Laughton, in collaboration with Dr. Bruce Damer, founder and curator of the Digibarn Computer Museum, and with the permission of Apple Inc., [the Computer History Museum is] pleased to make available the 1978 source code of Apple II DOS for non-commercial use. This material is Copyright © 1978 Apple Inc., and may not be reproduced without permission from Apple.

This disk operating system has been previously decompiled and the notes published online, which you'd think would make the Computer History Museum's release unimportant. And yet it's been reported far and wide — not just the usual vintage computing sites, but Apple news sites and broader IT outlets as well. Why all the commotion over old news for a 30-year-old machine?

It's not the product, but the process, that's significant. "What is interesting is Apple's agreement to release it," said Dr. Steve Weyhrich of Apple II History. "They never release stuff like this to the world." Agreed David Schmidt: "That is the only thing that is interesting about this: Apple's actual permission to leak any kind of intellectual capital."

However, there is also some original material in this particular offering of the source code. Weyhrich continued: "The code that was released also has that advantage of being scanned from actual printouts of Paul Laughton’s work in progress, with his comments on how the different parts of the system work… I've seen some of these [documents] before, but there are some that not even David Craig has gotten his hands on over the years. Historically, it’s quite interesting, and the Museum has comments from Laughton on the process of the creation of Apple DOS that give details that I didn’t get out of him when [I interviewed him — I guess] I didn’t ask the right questions!"

Click past the jump for an index of sites that have reported the source code's release.


  1. Different versions:

    I read DOS version "3.3" in your article, but the site you link to states: It specified that “Delivery will be May 15?, which was incredibly aggressive. But, amazingly, “Apple II DOS version 3.1? was released in June 1978.

    I think that this is the original source code for Apple II DOS 3.1. The original source code has the 13 sector "3 and 5" encoding used in DOS 3.1, and 3.2.

    DOS 3.3 came later with 16 sectors, and "2 and 6" encoding which you note has been previously decompiled with notes.