MS-DOS has been Open-Sourced! We Build and Run it!

For Clarity on the timeline:
- Microsoft licensed (non-exclusively) 86-DOS in Dec 1980 for $25,000
- Paterson left SCP in April 1981 and worked for Microsoft from May 1981 to April 1982.
- 86-DOS was purchased outright by Microsoft and renamed to MS-DOS on 27 July 1981 for $50,000
- In March 1982, MarkZ became the dev mgr for MS-DOS 2

The Code:

Remember that the code is open-sourced, but trademark law still applies!

Any requests to contact me on Telegram, etc, are scams...

Follow me on Twitter at @davepl1968

[PeterRichardsandYoureNot]

To this day I still laugh at the fact that Unix, macOS and dos all treat end of line differently. It has become a universal pain in the butt for developers.

[koopak]

only 6 years left until we'll be watching Dave compiling the ultimate MSDOS 6.22

[dixie_rekd]

"my code is immortalised in the last major release"

Dave, you've already immortalised your code and yourself through this channel. In 1000 years historians will turn to these videos to see what was really happening in the world of computer OS development during the era.

and so the legend lives on.

[paulscarlett]

As a graduate of Waterloo in 79, I first saw a hierarchical file system on the Honeywell system operated by the Math faculty in my first year - 1974. The OS was GECOS -- and it had implemented the file system from Multics. I had heard of a system used by the grad students call Unix, but it was considered a toy compared to the Honeywell system. I believe this aspect of Multics, the file system, was it's greatest gift to the history of computer development.

[spitefulwar]

Marty! Fire up the DeLorean. We've got a date with history!

[gdauch]

'So, depending on who you believe - you cannot do this. But, I assure you that it works fine.'

As I was listening to this while getting started with my day, it gave me a little chuckle. Can 100% appreciate the very gentle way of translating "hold my beer." Kudos sir.

[bigal]

MSDOS 2.11 was what I cut my teeth on. Making an empty boot disk with the 4.0 boot sector wasn't cheating IMO. Here's your commendation for original thinking.

[YdenPL]

I'm still not fully through the video but I saw Mark Zbikowski mentioned and haven't heard Dave mention that basically every .exe file there is, even today, starts with the magic number "MZ", Mark's initials. What a legacy, to be remembered in every piece of software for DOS and Windows to ever exist!

[deevs]

That takes me back to my old DOS (yes MS-DOS, but also PC-DOS as well, so I'm calling it just DOS LOL) programming days. I started doing network related programming, and was very dependant on the functions defined in "Share", which I'm sure you already know, wasn't added to DOS till version 3.10. The old INT 21 calls in DOS calls still seems as fresh as when I did assemble programming using MASM and later, Borland's Turbo Assembler back on the early to mid 80s. I was very dependant on the DOS technical reference manual (actually IBM's PC-DOS manual, since I worked in a mostly IBM facility), and other programming books, especially a book called "Undocumented DOS". I later became an IBM employee, mostly working their midrange systems, but that's another story for another day. In any case, thanks for the trip down memory lane. Love your content.

[brian]

Sweet! I will have to build this. I had to learn MS-DOS, CP/M and DR-DOS as a teenager while working at a computer shop on the weekends. It was an odd time in the 80s as there was an equal demand for all three. Now in 2024 I see allot of interest in MS-DOS again with people wanting to build DOS only retro machines. Exciting times ahead, anxious to see what the community does with the code. Thanks for the video!

[Epsilonsama]

Hopefully Microsoft releases 6.2 source code for preservation purposes. While this days DOSbox and FreeDOS are easier to work with from a user perspective this is still important for preserving history.

[robspiess]

@8:29 oops, looks like you forgot to remove the "Title Text" from your onscreen animation. Love the video! Super interesting looking back at how MSDOS operated!

[alisharifian]

The MZ magic code that you see in the beginning of every MS-DOS executable (when opening them in a hex editor) is the initials of Mark Zbikowski.

[KYMarty]

Love the stories. Takes me back to my early tinkering days. I started when everything was still DOS. I had an IBM PCjr. It was just enough different than an original PC that it forced me to learn a lot. I still have the original CPU that I swapped out for a V20 chip to double the CPU speed. Those were the days!

[mitchellstl]

That PS2 looks like it just came out of the box from IBM. thanks for sharing your unique history perspective! Really cool!

[JamieStuff]

The 360K floppy in a 1.2M drive was a thing. While it generally worked, the problem arose if you used the 1.2 to overwrite a track already written by a 360 drive, then read it back on a 360 drive. The narrower 1.2 track would not completely erase the 360 track, and that "leftover" signal would appear as noise to the 360 drive. I never ran into the problem, but then I had both drives in my computer.

BTW, formatting and writing a bulk erased disk on a 1.2 drive would read just fine on a 360 drive.

[toddhill]

IBM PC-DOS 3.11 was the gold standard when I was in college and also working at our local DuPont plant. They hesitated on 4.0 due to bad press and didn't advance until DOS 5.0 was released. We started using Windows 3.1 at the same time.

[stefanbuscaylet]

XOR BX, BX was one clock cycle faster and one byte shorter than MOV BX, 0 in the 8080 days. Great to see you MSFT guys knew this. I was using MASM pretty much the same time you were. I just didn’t work for Microsoft. Great job and thanks for posting this.

[matt_b...]

I seem to remember MSDOS4.0 being somewhat plagued with issues, with folks rolling back to 3.3.

I am already subscribed to the channel. You're welcome!

[juanmacias]

This was awesome, I had heard how uploading the files to Github messed up the formatting as it was upgraded to UTF-8.