10 ms·
Microsoft open-sources “the earliest DOS source code discovered to date”
https://opensource.microsoft.com/blog/2026/04/28/continuing-the-story-of-early-dos-development/ https://opensource.microsoft.com/blog/2026/04/28/continuing-...
- dang 5mo agoRecent and related: Microsoft open sources DOS 1.00 on 45th anniversary - https://news.ycombinator.com/item?id=47957494 https://news.ycombinator.com/item?id=47957494 - April 2026 (19 comments)
- gnabgib 5mo agoDiscussion, on the source, at the time (79 points, 24 days ago, 19 comments) https://news.ycombinator.com/item?id=47957494 https://news.ycombinator.com/item?id=47957494 Or on the GitHub clone (162 points, 15 comments) https://news.ycombinator.com/item?id=47946813 https://news.ycombinator.com/item?id=47946813
- userbinator 5mo agoI 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.
- teamsolid 5mo agoI am sure that there is a lot good material to take inspiration and learning even from the early Windows 3.11.
- SoftTalker 5mo ago/s ?
- AlecSchueler 5mo agoPretty sure it's a bot or simple karma farming operation.
- mycall 5mo agoDo a deep dive into how OS/360 formalized to having DOS.
- throwaway27448 5mo agoThey waited a couple decades too long for this to be of interest.
- GaryBluto 5mo agoThe day they would make Windows 2000 codebase open source (or source available) would be the day I could die happy (although I'd probably be long dead anyways by the time there's a glimmerof chance of it happening). What a beautiful, smooth-running operating system it was.
- londons_explore 5mo agoThere is a mostly complete leak of it...
- optymizer 5mo agoAgreed. It's still my favorite Windows version.
- NitpickLawyer 5mo agoWasn't there a 2000 source leak a while ago? I remember some exploits coming out after the leak.
- toyg 5mo agoYes but it could not be legally used by anything.
- avadodin 5mo agoOP said source available was acceptable. not even asking for compiler access which is also widely available. Windows has always been more than modular enough for any repurposing and there were licenses that were not tied to specific hardware so you could use them even today. Which is to say no one is stopping you from building a COPILOT.VBX for VisualBasic 3.0.
- greenbit 5mo agoExcept for "the hive". Remember the hive? Sort of an alternate registry, in addition to the actual registry. Granted, it was pretty invisible, until it got corrupted. I had a win2k machine that was my daily (at home) that was fine until idk about 2006, at which point something happened (muons?) and it would go into some kind of panic state just after bringing up the desktop. Hive corruption. I tried on and off for a couple of years to repair it, no luck. It wasn't just about the files on the HD, it was easy enough to transplant the drive and read/write anything, it was that I really liked the way I had the environment configured. Sure, it was all kind of moot, but it became a kind of personal windmill to resurrect this old thing. In the end, I booted an XP CD in it, and selected 'upgrade', and voila, it was Duncan Idaho, back from the dead. Anyway.. loved win2k, but not a fan of the hive.
- protocolture 5mo agoI imagine its not far off. I get the impression they are almost done with windows as a platform.
- WalterBright 5mo agoIt shouldn't be hard to disassemble it.
- teamsolid 5mo agoIt 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.
- dhosek 5mo agoI sometimes think that my mental model of a computer is still an Apple ][+ with 48K of RAM leads to my writing better code.
- stevesimmons 5mo agoAnd mine is a Commodore Vic-20 circa 1981, with 3583 bytes of free RAM. Programmed in 6502 assembler. Can't get much closer to the CPU than that.
- WalterBright 5mo agoWhile I did a few 10 line programs in BASIC in high school on punch cards, when things really started was a freshman class on semiconductors. The class started with diodes and quantum mechanics, then onto transistors, then flip flops, then registers, then ALUs. Then it was on to designing/building a digital clock (which never worked right), and later designing/building/programming single board computers (6802 chip). It was fun knowing everything about a computer. That's long gone!
- aenis 5mo agoFor a very long while now, we had programmers who never understood any low level concepts at all. They have started with js or python, and never looked 'down'. There are no limits to monstrosities they will consider normal. Linus Torvalds, a few months ago, said something to this effect when discussing AI coding tools. That his (also, mine) generation was lucky to have started with low level stuff and managed to retain the understanding of the whole stack - and kids these days don't get that. Good luck acquiring this level of feel for computers, algorithms, data structures today, when a kid's first experience with coding will be a seemingly genius chatbot.
- signa11 5mo agoin the words of mr. mitch-hedburg “here, you throw this away“
- TedDoesntTalk 5mo agoHe could have sold those printouts instead of giving them away.
- froyooh 5mo agoBack when it was all written by hand and optimized well.
- imoverclocked 5mo agoTime to find vulnerabilities! 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?
- FarmerPotato 5mo agoTo see what decisions they made. Like any historical document. Aim to understand the people of the time.
- yjftsjthsd-h 5mo agoIt's a single user OS that runs everything in ring zero by design. I'm not sure, definitionally, that it can have security vulnerabilities. I... guess maybe code execution on exposure to an untrusted floppy disk filesystem?
- aflag 4mo agoEven then, what would that accomplish in most systems? That same disk would most likely be the only permanent storage available to the system when it's inserted. Maybe if you've got two drives and have two floppies inserted at the same time?
- imoverclocked 4mo agoDOS systems often had hard drives. Also, floppy virus propagation is possible (aka: Sneakernet.) It was a different era entirely; Writing a TSR was a right of passage. Sometimes just getting something to work without having any other motive was enough to do it. A clever and small TSR might keep a copy of itself in memory and not require two floppies in the case of no hard drive. In comparison to today’s standards, it’s amazing what we did with 640k (or less!) of ram.
- aflag 4mo ago
- locusofself 5mo agowow, 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.
- SoftTalker 5mo agoYet another case where text printed on paper outlived any digital storage.
- jshier 5mo agoSeems like it was never digitally stored in the first place, and the printed text was barely readable due to age. Not really a big win for paper.
- SoftTalker 5mo agoWell it had to have been on disk or tape at some point. It wasn't all typed in by hand every time they needed to build a new version.
- debesyla 5mo agounless they used punch cards
- andsoitis 5mo ago> unless they used punch cards For MS-DOS?
- WalterBright 5mo agoNot likely. Punch cards disappeared around the end of 1976.
- deleted 5mo ago[deleted]
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- xuzhenpeng 5mo ago[flagged]
- jmward01 5mo agoIt 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]. [1] https://opensource.microsoft.com/blog/2025/09/03/microsoft-open-source-historic-6502-basic/ https://opensource.microsoft.com/blog/2025/09/03/microsoft-o...
- vee-kay 5mo agoWhat's interesting is that Microsoft BASIC itself was derived from BASIC-PLUS which itself was derived from Dartmouth BASIC (which evolved into a structured programming language called SBASIC (Structured BASIC). But the popularity of Microsoft BASIC, actually halted the standardisation of SBASIC as an ANSI standard. https://en.wikipedia.org/wiki/Microsoft_BASIC https://en.wikipedia.org/wiki/Microsoft_BASIC The Altair BASIC interpreter was developed by Microsoft founders Paul Allen and Bill Gates using a self-written Intel 8080 emulator running on a PDP-10 minicomputer.[1] The MS dialect is patterned on Digital Equipment Corporation's BASIC-PLUS on the PDP-10, which Gates had used in high school. https://en.wikipedia.org/wiki/Dartmouth_BASIC https://en.wikipedia.org/wiki/Dartmouth_BASIC Dartmouth BASIC is the original version of the BASIC programming language. It was designed by two professors at Dartmouth College, John G. Kemeny and Thomas E. Kurtz. With the underlying Dartmouth Time-Sharing System (DTSS), it offered an interactive programming environment to all undergraduates as well as the larger university community. Dartmouth also introduced a dramatically updated version known as Structured BASIC (or SBASIC) in 1975, which added various structured programming concepts. SBASIC formed the basis of the American National Standards Institute (ANSI) "Standard BASIC" efforts in the early 1980s. In contrast to the Dartmouth compilers, most other BASICs were written as interpreters. This decision allowed them to run in the limited main memory of early microcomputers. Microsoft's Altair BASIC is one example: it was designed to run in only 4 KB of memory (interestingly, it was delivered on paper tape). Kemeny became involved in an effort to produce an ANSI standard BASIC in an attempt to bring together the many small variations of the language that had developed through the late 1960s and early 1970s. This effort initially focused on a system known as Minimal BASIC that was similar to earliest versions of Dartmouth BASIC, while later work was aimed at a Full BASIC that was essentially SBASIC with various extensions. But by the late 1980s, tens of millions of home computers were running some variant of the MS BASIC interpreter. It had become the de facto standard for BASIC, which eventually led to the abandonment of the ANSI SBASIC efforts. Kemeny and Kurtz, however, decided to continue their efforts to introduce the concepts from SBASIC and the ANSI Standard BASIC efforts. This became True BASIC. https://en.wikipedia.org/wiki/True_BASIC https://en.wikipedia.org/wiki/True_BASIC There are versions of the True BASIC compiler for MS-DOS, Microsoft Windows, and Classic Mac OS. At one time, versions for TRS-80 Color Computer, Amiga and Atari ST computers were offered, as well as a UNIX command-line compiler. After several years of inactivity, as of February 2026, the TrueBASIC website is officially closed.
- dooosss 5mo agoToo little, too late.
- Tanayk07 5mo ago[flagged]
- deleted 5mo ago[deleted]
- gnarlouse 5mo agoHow about Microsoft fixes npm, github, and vscode
- deleted 5mo ago[deleted]
- theanonymousone 5mo agoI'm wondering whether ReactOS can exploit Claude et. al. to their fullest and "recreate" Windows 2000/95. I may donate some tokens for that cause.
- CursedSilicon 5mo agoThat sounds like a terrifying legal minefield that they would not want to tread
- theanonymousone 5mo agoIs it not safe to assume Window source code is not present in the LLM training data?
- leni536 5mo agoBut surely anything the LLM outputs is clear of licensing requirements /s Or would Microsoft like to argue otherwise in court?
- xandrius 5mo agoSlap a fair use on it and call it a day.
- greenbit 5mo agoWhat's that phrase, "derivative work" or something?
- okandship 5mo agoreadable plain text plus boring metadata still ages better than most clever archival systems
- xandrius 5mo agoIn this case a paper printout.
- hackerqwe 5mo agoMore code that copilot can be trained on.
- nananana9 5mo agoI 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.
- avadodin 5mo agoMore than a few people would rather die in poverty than put in the effort today even if you offered to time-machine them back with their finished product.
- yokoprime 5mo agoTo be fair, i think you needed a cutthroat businessman leading the company. Which i guess is more or less the same today
- justsomehnguy 5mo agoThis too but early MS to their employs was closer to a hipster SV vibe coding in a coffee shop a decade ago.
- themafia 5mo ago> a cutthroat businessman leading the company I'm sure his family connections aided him significantly.
- greenbit 5mo agoAnd for such simple processors and systems no less! No descriptor tables to deal with, no memory management to configure. These days it takes a little processor inside the main processor, just to get things started. Those were golden times.
- embedding-shape 5mo agoReplace Assembly with TypeScript/Rust/Go/whatever and as long as the idea is good and useful, same thing applies today.
- 5mo ago
- danborn26 5mo agoFascinating 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.
- embirdating 5mo ago[dead]
- patrickndaye919 5mo ago[dead]
- jug 5mo agoWhile 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. :-) https://arstechnica.com/gadgets/2024/01/the-oldest-known-version-of-ms-doss-predecessor-has-been-discovered-and-uploaded/ https://arstechnica.com/gadgets/2024/01/the-oldest-known-ver...
- rvnx 5mo agoI’m sure this is better software than Windows Millenium Edition
- acomjean 5mo agoInteresting story of how MS got into the operating system business. IBM wanted the CPM operating system, but Digital Research wouldn’t sign ibms NDA… really a pivot point in computing history. From “Triumph of the Nerds” tv transcript: https://www.pbs.org/nerds/part2.html https://www.pbs.org/nerds/part2.html Jack Sams (IBM) was looking for a package from Microsoft containing both the BASIC computer language and an Operating System. But IBM hadn't done their homework. Steve Ballmer: They thought we had an operating system. Because we had this Soft Card product that had CPM on it, they thought we could licence them CPM for this new personal computer they told us they wanted to do, and we said well, no, we're not in that business. Jack Sams (IBM); When we discovered we didn't have - he didn't have the rights to do that and that it was not...he said but I think it's ready, I think that Gary's got it ready to go. So I said well, there's no time like the present, call up Gary. Steve Ballmer: And so Bill right there with them in the room called Gary Kildall at Digital Research and said Gary, I'm sending some guys down…. Treat them right, they're important guys.
- bragr 5mo agoEh, basically all facts in this story are disputed by all sides. Aside from general gist that there was some meeting that didn't go well.
- chuckadams 5mo agoWhether Kildall actually blew IBM off at that meeting or not, what was definitely the case was that CP/M didn't have a 16-bit version ready to meet IBM's schedule, and that's what ultimately took them out of the running.
- acomjean 5mo agoIf you watch the documentary it’s an interview with the people who were there. There might be some discrepancy but I think the IBM guys were being honest about how it went down. The doc is on the Internet archive and worth a watch. You get the idea that it wasn’t some brilliant business strategy by Microsoft, the deal for the operating system wasn’t that good for them initially. From the transcript: https://www.pbs.org/nerds/part2.html https://www.pbs.org/nerds/part2.html Jack Sams (IBM): Gary had some other plans and so he said well, Dorothy will see you. So we went down the three of us... Gordon Eubanks Former Head of Language Division, Digital Research: IBM showed up with an IBM non-disclosure and Dorothy made what I...a decision which I think it's easy in retrospect to say was dumb. Jack Sams: We popped out our letter that said please don't tell anybody we're here, and we don't want to hear anything confidential. And she read it and said and I can't sign this. Gordon Eubanks: She did what her job was, she got the lawyer to look at the nondisclosure. The lawyer, Gerry Davis who's still in Monterey threw up on this non-disclosure. It was uncomfortable for IBM, they weren't used to waiting. And it was unfortunate situation - here you are in a tiny Victorian House, its overrun with people, chaotic. Jack Sams: So we spent the whole day in Pacific Grove debating with them and with our attorneys and her attorneys and everybody else about whether or not she could even talk to us about talking to us, and we left. ………. Bill Gates: Digital research didn't seize that, and we knew it was essential, if somebody didn't do it, the project was going to fall apart. Steve Ballmer: We just got carried away and said look, we can't afford to lose the language business. That was the initial thought - we can't afford to have IBM not go forward. This is the most exciting thing that's going to happen in PCs. Bill Gates: And we were already out on a limb, because we had licensed them not only Basic, but Fortran, Cobol Assembler er, typing tutor and Venture. And basically every - every product the company had we had committed to do for IBM in a very short time frame.
- 9dev 5mo agoAt some point, we'll probably have a new field in history for digital archeology, and I'm really envious for those future historians! They'll be getting to sleuth around old datasets, trying to reconstruct the history of computing, understand long-forgotten file formats to preserve data, use statistical methods to analyse binary backups, and trace for specific documentation versions to crack old encryption formats...
- giobox 5mo agoThis field already is alive and well in the gaming community. Games companies are notorious for not spending money on keeping their old code around, which is why it's been at the forefront of digital archaeology efforts a lot of the time to preserve the industry's history. I'd also throw the wayback when machine and the internet archive into this bucket.
- EvanAnderson 5mo agoThe term "programmer-archaeologist" was coined by the author Vernor Vinge in his 1999 "A Deepness in the Sky"[0] (a pretty great read and definitely recommended) and the field is arguably a real thing now[1]. [0] https://en.wikipedia.org/wiki/A_Deepness_in_the_Sky https://en.wikipedia.org/wiki/A_Deepness_in_the_Sky [1] https://en.wikipedia.org/wiki/Software_archaeology https://en.wikipedia.org/wiki/Software_archaeology
- 9dev 5mo agoThank you for the recommendation! I'm definitely aware of many initiatives into that direction, but I'm still curious when it'll invariably arrive as a real discipline not in computer science, but humanities.
- dang 5mo agoRelated ongoing thread: Microsoft's 6502 BASIC is now Open Source (2025) - https://news.ycombinator.com/item?id=48257058 https://news.ycombinator.com/item?id=48257058
- lesser-shadow 5mo ago[dead]
- gxd 5mo agoTHANK YOU! Can we now have all the Infocom games owned by Activision (which is yours) now? Pretty please? I know the source is available, but we'd like them with a MIT license (including the manuals, artwork etc). PS: a couple of them could be harder, like Shogun, but it's okay to skip these.
- danborn26 5mo agoLooking through the source is a great reminder of how constrained early computing was. It's amazing how much of this architecture still influences modern systems.
- deleted 5mo ago[deleted]
- chorlton2080 5mo agoThis is nearly a month old
- KellyCriterion 5mo agohaha, rise your hand if you are getting old when reading this :-D
- Ayush_Khati1 5mo ago[flagged]
- wpnx 5mo agoI got it up and running in dos box - it still runs smooth as butter: https://github.com/phyous/DOS-1.0 https://github.com/phyous/DOS-1.0
- deleted 4mo ago[deleted]
- ardev111 5mo ago[flagged]
- yangqing 4mo ago[flagged]
- miohtama 4mo agoAt this stage, was Microsoft already a well-established company if they had money and resources to contract and then license the 86-DOS?
- fredoralive 4mo agoYes, Microsoft had established themselves as supplier of BASIC interpreters to most of the US microcomputer manufacturers. There initial contact with IBM was to provide a version of Microsoft BASIC for the new computer.
- OrangeMusic 4mo agoWait this is from April 30th. Pretty sure this was posted on HN then.