I wonder how long it'll be before they release the source for the earliest Windows versions. The fact that they still have the source for this very old DOS at least gives hope that they also do for old Windows.
It is wonderful how early years of modern computing was brilliant. We treated machines as they really are: machines. Performance, creativity, science..., all possible to make a 386 machine work. Nowadays is all about libraries, virtualization, [bad] code over [bad] code over [bad] code..., I dont like it.
I remember in the naughts, coming across a dos machine that was quite out of time… even for the university basement it was living in next to a pile of lead brick. Its only job was to run an instrument via an home-built ISA card and write data out to 5.25” floppies.
wow, they had to OCR it back in from paper printouts
> This source code is old enough that it hadn’t been stored digitally. “A dedicated team of historians and preservationists led by Yufeng Gao and Rich Cini,” calling itself the “DOS Disassembly Group,” painstakingly transcribed and scanned in code from paper printouts provided by Paterson. This process was made even more difficult because modern OCR software struggled with the quality of the decades-old printout.
It is rare that I say this but, thanks MS! Arguably just as, if not more, important is the BASIC that they wrote. That was what they actually wanted to do. DOS just got them the contract with IBM. For decades MS was really a developer tools company with a side biz of writing operating systems and other misc software. They also open sourced that BASIC code too [1].
I cannot describe to you how jealous I am of the fact that back then writing a few thousand lines of assembly was what it took to launch a successful software company.
I find younger zoomers say this a lot and even to me in my 30s "oh you had it so easy!" because they think the knowledge today, we would have had back then. This is false.
Loser today, you would have been a loser back then too.
No, it wasn't the case then, it's not the case now :
"Beyond the Seattle area, Gates [Bill's mother] was appointed to the board of directors of the national United Way in 1980, becoming the first woman to lead it in 1983. Her tenure on the national board's executive committee is believed to have helped Microsoft, based in Seattle, at a crucial time. In 1980, she discussed her son's company with John Opel, a fellow committee member, and the chairman of International Business Machines Corporation (IBM). Opel, by some accounts, mentioned Mrs. Gates to other IBM executives. A few weeks later, IBM took a chance by hiring Microsoft, then a small software firm, to develop an operating system for its first personal computer." from https://en.wikipedia.org/wiki/Mary_Maxwell_Gates
It's as if your mother now was at the board of NVIDIA (because IBM then was quite the powerhouse). Sure, you still need to write "a few thousands lines of assembly" or equivalent... or find someone else who would, but you still need the connection to sell "it".
So... is your mom at such a famous board? Actually ANY board? If not you might have to write a LOT more and still a successful software company, sorry.
Fascinating piece of computing history. Preserving early DOS source code gives a lot of context to the structural choices that stuck around in x86 architecture for decades.
While oldest source of it, note that the 86-DOS v0.1-C binaries are even earlier (and v0.34 has also been found) than this v1.00 source and can be downloaded and used in an emulator. :-)
43 comments
[ 1.7 ms ] story [ 46.6 ms ] threadMicrosoft open sources DOS 1.00 on 45th anniversary - https://news.ycombinator.com/item?id=47957494 - April 2026 (19 comments)
Or on the GitHub clone (162 points, 15 comments) https://news.ycombinator.com/item?id=47946813
I remember in the naughts, coming across a dos machine that was quite out of time… even for the university basement it was living in next to a pile of lead brick. Its only job was to run an instrument via an home-built ISA card and write data out to 5.25” floppies.
What uses would this code have in 2026?
> This source code is old enough that it hadn’t been stored digitally. “A dedicated team of historians and preservationists led by Yufeng Gao and Rich Cini,” calling itself the “DOS Disassembly Group,” painstakingly transcribed and scanned in code from paper printouts provided by Paterson. This process was made even more difficult because modern OCR software struggled with the quality of the decades-old printout.
[1] https://opensource.microsoft.com/blog/2025/09/03/microsoft-o...
Loser today, you would have been a loser back then too.
"Beyond the Seattle area, Gates [Bill's mother] was appointed to the board of directors of the national United Way in 1980, becoming the first woman to lead it in 1983. Her tenure on the national board's executive committee is believed to have helped Microsoft, based in Seattle, at a crucial time. In 1980, she discussed her son's company with John Opel, a fellow committee member, and the chairman of International Business Machines Corporation (IBM). Opel, by some accounts, mentioned Mrs. Gates to other IBM executives. A few weeks later, IBM took a chance by hiring Microsoft, then a small software firm, to develop an operating system for its first personal computer." from https://en.wikipedia.org/wiki/Mary_Maxwell_Gates
It's as if your mother now was at the board of NVIDIA (because IBM then was quite the powerhouse). Sure, you still need to write "a few thousands lines of assembly" or equivalent... or find someone else who would, but you still need the connection to sell "it".
So... is your mom at such a famous board? Actually ANY board? If not you might have to write a LOT more and still a successful software company, sorry.
https://arstechnica.com/gadgets/2024/01/the-oldest-known-ver...