“Despite this reduction in scope for MS-DOS 2.0, it did carry many bits of XENIX. The system adopted I/O redirection via less-than and greater-than symbols, piping, a hierarchical directory tree, file handles […]”
The source code for MSDOS 2 is available and the file descriptor stuff appears to be in https://github.com/microsoft/MS-DOS/blob/master/v2.0/source/... and XENIX2.ASM. It stands in contrast to the File Control Block API which MSDOS 1 (née 86-DOS) modeled after CP/M’s API.
In The History of Xenixmicrosoft
MS-DOS
Assembly2018–2026
microsoft / MS-DOS · Archived
MS-DOS
The original sources of MS-DOS 1.25, 2.0, and 4.0 for reference purposes
68Distinct people
79Mentions
0Explicit recommenders
32.3KGitHub stars
What to know before exploring
What it is
The original sources of MS-DOS 1.25, 2.0, and 4.0 for reference purposes
GitHub
Where it is used
No documented product use was verified in the last source check.
What people are saying
No recommendation phrase was found in the indexed comments.
No classified warning is attached to this page. Read the discussions before treating silence as approval.
Also in these discussions
- ownedbywuigi/dos · linked in 2 of the same discussions
Mentioned in the same Hacker News threads. That is not proof they are substitutes.
This week on Hacker News
Nov 8–Nov 15 UTC · Direct repository links and separately labeled related project stories. Indexed through 11/15/2026, 8:01:28 AM UTC.
No direct repository links were found in the indexed HN discussions over the past seven days. Older discussions are available below.
Mentions over time
HN mentions by year79 dated mentions
Observed mentions: 2018-09-28 22:44:43 UTC to 2026-09-20 23:50:56 UTC.
* An incomplete calendar period is marked with an outlined bar. Its count is not directly comparable with a full period.
Counts come from the repository’s dated source evidence. Index cutoff: 2026-11-02 08:16:59 UTC.
View mention counts and date ranges
| Period | Start (UTC) | End (exclusive, UTC) | Mentions | Submissions | Comments |
|---|---|---|---|---|---|
| 2018 | 2018-01-01 00:00:00 UTC | 2019-01-01 00:00:00 UTC | 8 | 2 | 6 |
| 2019 | 2019-01-01 00:00:00 UTC | 2020-01-01 00:00:00 UTC | 5 | 0 | 5 |
| 2020 | 2020-01-01 00:00:00 UTC | 2021-01-01 00:00:00 UTC | 10 | 0 | 10 |
| 2021 | 2021-01-01 00:00:00 UTC | 2022-01-01 00:00:00 UTC | 6 | 0 | 6 |
| 2022 | 2022-01-01 00:00:00 UTC | 2023-01-01 00:00:00 UTC | 10 | 0 | 10 |
| 2023 | 2023-01-01 00:00:00 UTC | 2024-01-01 00:00:00 UTC | 6 | 1 | 5 |
| 2024 | 2024-01-01 00:00:00 UTC | 2025-01-01 00:00:00 UTC | 22 | 2 | 20 |
| 2025 | 2025-01-01 00:00:00 UTC | 2026-01-01 00:00:00 UTC | 7 | 0 | 7 |
| 2026 (partial) | 2026-01-01 00:00:00 UTC | 2027-01-01 00:00:00 UTC | 5 | 0 | 5 |
From the project README
An excerpt from the repository, fetched Nov 12, 2026.
Read the project’s introduction
MS-DOS v1.25, v2.0, v4.0 Source Code
This repo contains the original source-code and compiled binaries for MS-DOS v1.25 and MS-DOS v2.0, plus the source-code for MS-DOS v4.00 jointly developed by IBM and
Microsoft.
The MS-DOS v1.25 and v2.0 files were originally shared at the Computer History Museum on March 25th, 2014 and are being (re)published in this repo to make them easier to find, reference-to in external writing and works, and to allow exploration and experimentation for those interested in early PC Operating Systems.
License
All files within this repo are released under the MIT License as per the LICENSE file stored in the root of this repo.
For historical reference
The source files in this repo are for historical reference and will be kept static, so please don’t send Pull Requests suggesting any modifications to the source files, but feel free to fork this repo and experiment 😊.
This project has adopted the Microsoft Open Source Code of Conduct. For more information see the Code of Conduct FAQ or contact opencode@microsoft.com with any additional questions or comments.
Trademarks
This project may contain trademarks or logos for projects, products, or services. Authorized use of Microsoft
trademarks or logos is subject to and must follow
Microsoft's Trademark & Brand Guidelines.
Use of Microsoft trademarks or logos in modified versions of this project must not cause confusion or imply Microsoft sponsorship.
Any use of third-party trademarks or logos are subject to those third-party's policies.
Read the full README on GitHubWhat Hacker News says
6 sourcesAsynchronous I/O figures in prominently in Windows NT but I just assumed it wasn't ever thought about in DOS (being single-tasking and single-user). I was really surprised to see[0]:
Each driver in the chain defines two entry points; the strategy routine and the interrupt routine. The 2.0 DOS does not really make use of two entry points (it simply calls strategy, then immediately calls interrupt). This dual entry point scheme is designed to facilitate future multi-tasking versions of MS-DOS. In multi-tasking environments I/O must be asynchronous, to accomplish this the strategy routine will be called to queue (internally) a request and return quickly. It is then the responsibility of the interrupt routine to perform the actual I/O at interrupt time by picking requests off the internal queue (set up by the strategy routine), and process th
Read the rest
em. When a request is complete, it is flagged as "done" by the interrupt routine. The DOS periodically scans the list of requests looking for ones flagged as done, and "wakes up" the process waiting for the completion of the request.
I didn't realize that kind of forwarding-looking perspective was going into the design of MS-DOS.
[0] https://github.com/microsoft/MS-DOS/blob/master/v2.0/source/...
Not gonna lie, a small part of me misses smashing the caps lock key when coding back in the day. :)
Example: https://github.com/microsoft/MS-DOS/blob/master/v2.0/source/...
In MS-DOS v1.25 and v2.0 is now open-source (2014)Not just "open-source", but actual MIT-licensed (aka Expat-licensed) Free Software:
https://github.com/microsoft/MS-DOS/blob/master/LICENSE.md
https://directory.fsf.org/wiki/License:Expat
Huh. Was not expecting that. Nice.
Edit: Of course they won't actually mention Free Software, because they don't want to acknowledge Free Software. smh
In MS-DOS v1.25 and v2.0 is now open-source (2014)MS-DOS v1.25 and v2.0 is now open-source (2014)
207 points · Open discussion>Any others I'm missing?
I would suggest MS-DOS: https://github.com/microsoft/MS-DOS
In Exploring the Internals of Linux v0.01