Lunduke
News • Science & Tech
Quick and Dirty: The story of 86-DOS & MS-DOS
The hardware and nerdy details that led to the first release of MS-DOS.
January 19, 2024
post photo preview

MS-DOS is one of the most successful operating systems of all time — absolutely dominating the computer industry for years.

Most of us have heard the tales of how MS-DOS came into existence: How Microsoft purchased it from another company, and how Microsoft licensed it to IBM.

But what are the nerdy details? What is the background? What hardware inspired the development of that MS-DOS precursor… and what did those machines actually look like?

Let’s take a few moments to dive a little deeper into the history of how MS-DOS truly came into existence. To tell this story, we’ll need to go back to the mid 1970s…

1974 - The Altair 8800 & the S-100 BUS

Way back in 1974, the legendary Altair 8800 computer was being designed. And, as part of the system, the S-100 computer bus was designed.

The Altair 8800
 

Fun Factoids: The Altair 8800 was based on an Intel 8080 CPU clocking in at a whopping 2 MHz and sold, as a kit, starting at $439. That base model came packed with 1024 bytes of RAM. Yeah. You read that right. 1k. In order to run the new “Altair BASIC” — which was the first product of Microsoft — you first needed to upgrade to 4k of RAM… which would run another $264.

That S-100 bus — which allowed a number of peripheral cards (memory, drive controllers, etc.) to be inserted into, and used by, the computer — became the first expansion bus standardized across the computer industry.

In fact, usage of the S-100 became incredibly common among a huge number of homebrew computers built far and wide — being the defacto bus type until the IBM PC hit the scene in 1981.

Many of these computer types (using a variety of processors, including the 8080 and Z80) received ports of the CP/M operating system, developed by Gary Kildall’s Digital Research. CP/M was everywhere back then.

1979 - Seattle Computer Product’s S-100 8086 kit

Seattle Computer Products (SCP) (which, as the name would suggest, was based near Seattle, WA) produced a number of S-100 related products — including memory cards such as the 64k RAM board shown below:

Photo courtesy s100computers.com
 

Seattle Computer Products then expanded to produce boards and kits to build S-100 bus based computers using the Intel 8086 CPU (which had just been released by Intel).

SCP’s 8086 S-100 card. This is a later variant (1980 or 1981) of the original 1979 version.
 

There was just one teensy-tiny problem… there was no available operating system to ship with these S-100 based 8086 systems.

Initially these SCP S-100 8086 computers shipped with no full-fledged operating system at all.

But, instead, they worked with another local company — Microsoft — to bundle a version of their BASIC language. The result was known as “BASIC-86” and it was, essentially, a BASIC interpreter and editor, that booted from disk on the new SCP 8086 systems.

This wasn’t the only product that the two companies worked together on. Microsoft had also hired SCP to design their “Z-80 Softcard” for the Apple II platform.

 

This relationship — between Seattle Computer Products and Microsoft — would become critical to the entire computer industry.

Sales of the SCP S-100 8086 boards struggled due to the lack of operating system. Turns out most people want an OS to go with their computer. Who knew?

To remedy this problem, SCP encouraged Gary Kildall to port his wildly popular CP/M operating system to 8086 board (which Kildall had already been working towards anyway). Unfortunately the CP/M port was not shipping fast enough to meet the needs of SCP.

They needed an Operating System. And fast.

1980 - Quick and Dirty DOS

Seattle Computer Products did the only logical thing… they began building their own Operating System.

In April of 1980, Tim Paterson began working on exactly that. Armed with the manuals for CP/M, he began building his own “CP/M-like” operating system — from scratch — in assembly for their 8086 platform.

This effort was called “Quick and Dirty Disk Operating System”… or “QDOS” for short.

QDOS was incredibly similar to CP/M — as the design was done based on the CP/M manuals — and a key goal was to allow easy porting of CP/M software to QDOS. That said, it did differ in some noteworthy ways:

  • CP/M cached file system information, which could cause data loss if an update was not manually performed before a user removed a disk. QDOS changed this by doing disk updates on every write to the drive. This resulted in QDOS disk operations being slower than CP/M… but also protected against data loss.

  • Instead of CP/M’s file system, Tim used the FAT system that Microsoft created for the standalone BASIC-86 that SCP had already been shipping with their S-100 8086 machies.

Fun Factoid: The FAT (File Allocation Table) file system was developed by Marc McDonald — the first full time employee of Microsoft — and first used as the file system for “Microsoft Standalone Disk BASIC-80” (a bootable floppy for 8080 CPU’s that contained a BASIC interpreter). That was later ported to 8086 and was bundled with Seattle Computer Products 8086 systems.

QDOS required the SCP S-100 8086 systems, naturally, with a specific floppy drive controller: the Cromemco 4FDC, as pictured below.

Photo courtesy s100computers.com
 

By July of 1980, QDOS was functional — with roughly half of the outlined feature set. Then, by August, the famous EDLIN command was added.

Factoid time! The EDLIN program, a simple line editor, is the most enduring portion of this original version of QDOS. Lasting until this day, in various forms and ports, and being the primary text editor for MS-DOS up until the early 1990s. It was inspired by the ED commands of both CP/M and UNIX.

During the summer of 1980, the name QDOS was dropped (as “Quick and Dirty” isn’t the best product name) in favor of the, rather on-the-nose, “86-DOS”. A DOS. On the 8086 platform.

Bellow are a few screenshots of 86-DOS from the 1.0 version, which didn’t ship until 1981 (but still gives a good view of what it looked like back then):

COMMAND.COM and EDLIN
 
A DIR of an 86-DOS system

And, for the sake of posterity, here is the first part of the 86-DOS user manual for version 0.3. This is the very first published description — ever — of the OS that would later become MS-DOS.

At this point, Seattle Computer Products could begin bundling their S-100 8086 systems with the, now functional, 86-DOS.

Below you can see an advertisement of exactly that. A complete computer with an 8086 @ 8 MHz, 128k of RAM, the disk controller mentioned above… and shipping with both 86-DOS and Microsoft’s 86-BASIC. For a mere $3,349.

Ad for the SCP S-100 in the November, 1981 issue of Kilobaud Microcomputing magazine.
 

1981 - The Microsoft Agreement

Remember how Microsoft and Seattle Computer Products had worked together a few times already? Well, they were about to make an agreement that would change all of computing for decades to come.

Starting in November/December of 1980, Microsoft licensed a version of 86-DOS (version 0.3 to be exact) from SCP. This was a non-exclusive deal, meaning SCP could still sell 86-DOS and license to other OEMs.

Amazingly enough, a copy of one of that license — dated January 6th, 1981 — is now available so we can know the exact terms of the deal:

Document copy, courtesy Archive.org
 

That’s when things really took off. At an almost lightning speed.

Just a few short months later — in May — Tim Paterson left SCP and started working directly for Microsoft. His job: to port 86-DOS to the new IBM PC, which had an 8088 processor.

Then, in July of 1981 (just two months later), Microsoft purchased 86-DOS — in entirety — for an additional $50,000 (over the $25,000 MS had previously paid for a non-exclusive license). It was now Microsoft’s to do with as they please… and the original developer now worked for them.

That very next month, in August, Microsoft officially licensed MS-DOS to IBM… who then bundled it with their new IBM Personal Computer (the famous model 5150)… renamed “PC-DOS”.

Something wild to think about: Consider the timeline here.

  • The IBM 5150 PC was announced on August 12th, 1981.

  • The deal between Microsoft and IBM — for MS-DOS, renamed to PC-DOS — was finalized… that same month.

  • Microsoft didn’t actually own MS-DOS… until a few weeks before that.

  • … and Microsoft didn’t even have the developer (Tim Paterson) working for them until two months before that.

That’s right. One of the most important business deals in computer history… came together in a matter of just a few short months… with only days to spare.

Epilogue

There is oh-so-much more to this story. Too much to tell in one sitting.

  • MS-DOS would go on to absolutely dominate the computer industry and set the course of Microsoft for decades to come.

  • That version of CP/M that Seattle Computer Products wanted (before they gave up waiting and built QDOS)? It eventually shipped in November of 1981. CP/M was this close to being shipped with the first IBM PCs. You can mark that moment as the point when CP/M lost its position of market dominance.

  • The relationship with IBM and Microsoft would be a wild and rocky one — involving PC-DOS, OS/2 and many other products over the years.

  • Tim Paterson would end up working at Microsoft, multiple times, on several versions of DOS as well as Visual BASIC.

Fun personal anecdote: As a young man in the 1990s, I started working at Microsoft. One day, it occurred to me: “I wonder if Tim Paterson still works here?”

 

So I looked him up and, turns out, he did. In a building just around the corner from the one I was working in. So I did what any presumptuous, nerdy 19 year old would do… I sent him an email. One where I sounded like a giddy fanboy. Because that’s what I was.

 

Tim was gracious and kind. Taking time out of his schedule to chat with a fan of his work. While we only spoke on a few occasions, those moments meant a great deal to this young nerd.

community logo
Join the Lunduke Community
To read more articles like this, sign up and join my community today
6
What else you may like…
Videos
Podcasts
Posts
Articles
The Apache Software Foundation Drops the "Apache"

“As a non-Indigenous entity, we acknowledge that it is inappropriate for the Foundation to use Indigenous themes or language.”

And, yes. It says “1985” in the date. But, do not be fooled. For it is not actually 1985.

More from The Lunduke Journal:
https://lunduke.com/

00:09:38
September 14, 2025
Microsoft & Red Hat Employees Celebrating Charlie Kirk's Murder

At Microsoft & Red Hat -- and across Big Tech -- many employees are celebrating and encouraging murder. Microsoft has responded... but not Red Hat.

And, yes. The date on the video says 1985. But, no. It's not actually 1985.

More from The Lunduke Journal:
https://lunduke.com/

00:15:26
September 13, 2025
Open Source & Big Tech Leftists Lost Their Minds This Week

Open Source Leftists Celebrate Murder, Censor Conservatives, and say "Free Software is White Supremacy". It's been one of those weeks in the Tech world.

Lunduke's Week in Tech - Sep 13, 2025:
https://lunduke.substack.com/p/lundukes-week-in-tech-sep-13-2025

More from The Lunduke Journal:
https://lunduke.com/

00:21:48
November 22, 2023
The futility of Ad-Blockers

Ads are filling the entirety of the Web -- websites, podcasts, YouTube videos, etc. -- at an increasing rate. Prices for those ad placements are plummeting. Consumers are desperate to use ad-blockers to make the web palatable. Google (and others) are desperate to break and block ad-blockers. All of which results in... more ads and lower pay for creators.

It's a fascinatingly annoying cycle. And there's only one viable way out of it.

Looking for the Podcast RSS feed or other links? Check here:
https://lunduke.locals.com/post/4619051/lunduke-journal-link-central-tm

Give the gift of The Lunduke Journal:
https://lunduke.locals.com/post/4898317/give-the-gift-of-the-lunduke-journal

The futility of Ad-Blockers
November 21, 2023
openSUSE says "No Lunduke allowed!"

Those in power with openSUSE make it clear they will not allow me anywhere near anything related to the openSUSE project. Ever. For any reason.

Well, that settles that, then! Guess I won't be contributing to openSUSE! 🤣

Looking for the Podcast RSS feed or other links?
https://lunduke.locals.com/post/4619051/lunduke-journal-link-central-tm

Give the gift of The Lunduke Journal:
https://lunduke.locals.com/post/4898317/give-the-gift-of-the-lunduke-journal

openSUSE says "No Lunduke allowed!"
September 13, 2023
"Andreas Kling creator of Serenity OS & Ladybird Web Browser" - Lunduke’s Big Tech Show - September 13th, 2023 - Ep 044

This episode is free for all to enjoy and share.

Be sure to subscribe here at Lunduke.Locals.com to get all shows & articles (including interviews with other amazing nerds).

"Andreas Kling creator of Serenity OS & Ladybird Web Browser" - Lunduke’s Big Tech Show - September 13th, 2023 - Ep 044

Car navigation in 1986 from the BBC. Some of the comments are funny.

September 12, 2025

@Lunduke Do the folks behind Matrix.org and Element.io also have crazies that are celebrating recent events?

September 12, 2025

I'm becoming an [doom] emacs fanboy I think...

Anyone else using it? I had it installed for a few months, but never really got into it until yesterday, giving it a real go and already I can see I'm really liking it.

post photo preview
New Lunduke Journal Sub Perks, Lifetime Price Increase Next Week

A quick update: There are some new perks for Lunduke Journal subscribers, and an upcoming price increase for new Lifetime Subscriptions (if you want one of those at the lower price, you have a couple days).

All the details below.

Lifetime Subscription Price Increase

This coming Friday (September 19th), the price of a new Lifetime Subscription to The Lunduke Journal will be increasing from $200 to $300. I wanted to give all of you a few days notice so you could grab one at the lower rate.

If you want to pick up a Lifetime Subscription for the lower price, simply grab one (via Locals, Substack, or Bitcoin) by Thursday night (Sep 18th).

The prices for new Yearly and Monthly subscriptions will remain the same. No changes.

Reminder: The Lunduke Journal has phased out sales and discount promotions. The current price of a subscription is the best price.

New Perks for Lunduke Journal Subscribers

I am working on adding a few new perks for Lunduke Journal subscribers — a way of saying “Thank You” for making this work possible (while still keeping all of the articles and shows free for the world).

Here are the perks as of today.

Perks for all Subscribers (Monthly, Yearly, and Lifetime):

Note: The eBooks & Games are currently only available on Locals & Substack (due to platform features). Those perks will also become available to subscribers on X, YouTube, & Patreon next week. Stay tuned for access details.

Additional (Optional) Perks only for Lifetime Subscribers:

  • The Lunduke Journal will follow your account on X.

  • Your name (real, or internet handle) listed in a special thanks slide at the end of new Lunduke Journal videos.

Both of these perks are 100% optional.

If you are a Lifetime Subscriber, and would like to take advantage of either (or both), simply email “bryan at lunduke.com” with the subject line “Lifetime Perk” (that part is important, I get so many emails this will help me see yours) and include a link to your X profile and/or the way you want your name to appear at the end of videos.

One of the nice parts of having Lunduke Journal follow your X account… is it will make it far easier (and more likely) for me to see your comments.

Thank You

I am working to expand all of the regular perks (books, etc.) to subscribers across all platforms (which was a little tricky, considering the differences in each platform, but I managed to figure out how to do it) — while adding a few new ones as well.

Nothing crazy, just a way of saying “Thank You”.

Seriously.

From the bottom of my heart, thank you for your support. The Lunduke Journal is only possible thanks to each and every one of you.

-Lunduke

Read full Article
September 13, 2025
post photo preview
Lunduke's Week in Tech - Sep 13, 2025
Open Source Leftists Celebrate Murder, Censor Conservatives, and say "Free Software is White Supremacy".

So many stories this week about Leftist Activists, within Open Source and Big Tech, going absolutely insane.

From celebrating the murder of Charlie Kirk to censoring Conservatives and even equating Free and Open Source Software with White Supremacy. And there’s more.

What’s truly crazy to me, is that most of these cases of Leftist insanity are from leaders within Open Source. These are the people running projects and representing companies.

Seriously. It’s wild.

Here are the stories of the week, presented in reverse chronological order.

All of these links are to Substack (where you can watch the video or listen to the audio podcast) — but all of these stories are available for free on every platform which The Lunduke Journal publishes to. Use whichever platform works for you.

Only The Lunduke Journal Told These Stories

This week I am reminded why The Lunduke Journal is important.

Over the last 7 days, we published 13 stories.

Of those 13 stories only 2 were covered by any other Tech News outlet. Two.

And, in both of those 2 stories, The Lunduke Journal is the only Tech News outlet that covered them accurately — and without a pro-Big-Tech, Left Wing bias.

If we didn’t exist, the other 11 stories wouldn’t get told at all. How crazy is that?

Thankfully the stories are spreading — with people seeing them over 9 million times last month alone.

If you want to be part of making The Lunduke Journal possible, consider becoming a subscriber. Lots of options, big and small. And all go directly towards daily operations.

Might I make a suggestion?

The Lifetime Subscription (which counts towards both Substack and Locals — and last for life) is a marvelous, one time, way to show support. And it comes with all of the perks (access to the Locals community as well as the official Lunduke Journal forum, & DRM-free eBooks).

You can snag a Lifetime Subscription via Locals, Substack, or with Bitcoin.

But, heck, any type of subscription (via any platform) is appreciated! Choose whichever works best for you!

Then be sure to go to Lunduke.com and choose the platforms which are the most convenient for you to use — The Lunduke Journal publishes all over the Inter-Tubes!

And, once again, thank you to every subscriber. This work is only possible because of you. You rule.

-Lunduke

Read full Article
September 11, 2025
Keep The Lunduke Journal Free!

So far, in 2025, The Lunduke Journal has published 246 shows — being the only Tech News outlet covering the vast majority of those stories.

All without even the slightest influence from Big Tech. No sponsorships, no ad reads, not a penny taken from any company.

And every single story — every article, podcast, & video — is free to share far and wide.

In order for The Lunduke Journal to continue doing this unique work — to keep the lights on well into the future — we need your help.

If you haven’t yet become a subscriber to The Lunduke Journal, doing so today makes a big impact. Pick one of the options below. Big or small. Monthly, Yearly, or Lifetime subscriptions — or even simply one-time donations — all make a huge difference.

Support The Lunduke Journal

Monthly or Yearly Subscriptions:
Locals, Substack, X, YouTube, or Patreon

Lifetime Subscriptions:
Pay Once, For Life (Locals & Substack)

One-Time Donations:
Locals or Bitcoin

You Make The Lunduke Journal Possible

Seriously. This is all possible because of you.

We are able to make all of this free to share with the world because of you.

Might I make a suggestion?

The Lifetime Subscription (which counts towards both Substack and Locals) is a marvelous, one time, way to show support. And it comes with all of the perks (access to the Locals community as well as the official Lunduke Journal forum, & DRM-free eBooks).

You can snag a Lifetime Subscription via Locals, Substack, or with Bitcoin. Lots of options.

But, heck, any type of subscription (via any platform) is appreciated! Choose whichever works best for you!

Then be sure to go to Lunduke.com and choose the platforms which are the most convenient for you to use — The Lunduke Journal publishes all over!

And, once again, thank you for making The Lunduke Journal possible.

-Lunduke

Read full Article
See More
Available on mobile and TV devices
google store google store app store app store
google store google store app tv store app tv store amazon store amazon store roku store roku store
Powered by Locals