Aside from the user interface differences you demonstrated, there was a distinct *nix flavor to the API (i.e programming interface -- using INT 21h) from the CP/M style interface in DOS 1.x. For example, rather than setting up file-control blocks to access with files (this was CP/M style), a new "handle" based system (Unix style) was introduced in DOS 2.x, and this feature was retained in subsequent versions of DOS. Although the ability to change the switch command was dropped for the command shell, the ability to use slash instead of backslash for directory separator IS still available. Where this became important was in the C language -- where backslash has a special meaning (it is an "escape" character that denotes a special sequence to define special characters -- for example \t would represent "carriage return", "newline" and "tab", and \007 would be the ASCII BEL character). To encode a backslash you needed to double it -- so you needed to enter \\ to represent \. Where this makes a *royal mess* was if you needed to access a directory hierarchy -- you'd have to have a separate C program for DOS and UNIX. Fortunately it turns out that within a program you can use "/" for the directory separator (in batch files and CONFIG.SYS you still needed t use backslash however as the forward slash was still the option switch character).

I was part of a team that made an MS-DOS reverse-engineered clone back in 1987. Since no one in the team knew UNIX, we all wondered WT actual F were they thinking when they made these AVAILDEV and SWITCHAR commands and why were they discontinued. A couple of years later I learned UNIX and had the "a-ha" moment.

Forward slashes in MS-DOS...for a brief moment of time, everything was right in the world 😁

*ARE YOU TELLING ME THAT MICROSOFT HAD THE OPTION OF USING SLASHES IN FILE PATHS AND CHOSE NOT TO TAKE IT AND NOW IT'S 2020 AND WE'RE STILL STUCK WITH BACKSLASHES IN WINDOWS PATHS*

I just stumbled into this and it made me almost cry... I started with computers in 1987 as an exchange student at Brown University, literally saving money from my food and housing allowances to buy my first "IBM compatible" with EGA graphics. And digging into all this with MS Microassembler and DOS commands. And suddenly I hear the sounds of the old 360k drives, chirping and humming, listen to the PC's internal workload... And then all the pictures came to my mind, friends in RI, times over there, me, being young and full of expectations and power. And an era of a rising new technology and being part of it. This video is not just tech history, you touched some of my most hidden emotions and memories, thank you so much.

5:33 Remember that DOS carried over the CP/M convention of simply typing a drive letter followed by a colon, with nothing else on the command line, to change the default drive. When the Unix-style “cd” command was introduced for changing the default directory, this interacted with the default-drive-changing function in a surprising way. For example, if your default drive was A:, and you typed “cd B:/test”, this did *not* change the default drive to B: and the directory to /test; instead, it changed the default directory *on drive B:* to /test. It left you in the same default directory you were already in on drive A:. So if you then typed B: to change default drive to B:, *now* you would also find yourself in /test as the default directory.

10:15 Gotta love how the backslash got escaped each time the author tried to use it!

Oh those floppy disc sounds ..sounds so familiar and I did already forgot that sound.

Xenix still is around. Sco licensed it and it was renamed Sco Unixware. Sco licensed Bell Labs Unix Sys V R V and updated it in the late 1980s and still runs on flight computers on 747s. Xenix took off on McDonalds kiosks and Sco made it a terminal OS for fast food and other retail in the 1980s and 90s. In the 2000s some restaurants still used it

This is incredible! I knew of Xenix and how Microsoft originally thought that was the future OS for microcomputers, but I had no idea that XEDOS was a thing or that it was incorporated into MS-DOS 2.0. It would have been cool if you could still use these features in later versions of MS-DOS. Thanks for sharing!

XEDOS sounds like the antagonist AI of a science fiction story

That tandy part reminded of Danooct1

They didn't want 'switchar' to be used because it was not fully implemented. Under MS-DOS each executable command is responsible for parsing its own arguments and not all of them implemented the functionality to look at the operating system for the current switch character and parse their command line appropriately. In other words, trying to do daily activities with the default switchar was consistent, but changing to use the '-' only changed some programs, and you had to remember which was which. It's too bad they didn't provide a standard library like argparse and move the rest of the way to '-' as the default switchar.

Back in the day when things like directories and streams were luxuries.

This is cool. I had no idea about the Xenix "heritage" of DOS 2.0! Now that I do know, I'm kinda sad they removed it. Anyway, great video - cheers.

We're still using Xenix in production at my work. There's really old nms for frame-relay equipment that runs on old 486 PC under Xenix.

Ahhhh the good old days, where Unix guarded harems....

I love this arcane DOS history!

There are a number of other 'unix' like features that where hidden in DOS. One example is redirection of STDERR so STDOUT and STDERR could be directed to different pipes or files. Example: some_cmd.exe > normalout.txt 2> errorout.txt some_cmd.exe 2> errorout.txt | some_other_cmd.exe Another feature hardly used (may have shown up in Dos 3.0 rather than 2) was conditional commands some_cmd.exe && some_other_cmd.exe would run some_other_cmd only if some_cmd didn't fail. some_cmd.exe || some_other_cmd.exe would run some_other_cmd only if some_cmd DID fail. example in use dir some_file_name || echo New Data > some_file_name This would create some_file_name and fill it with "New Data" ONLY if it didn't exist already.

Thanks for sharing this! That's some obscure information of something truly forgotten.

So, altering MS-DOS 2.x to use ‘-‘ instead of ‘/‘ would be a great prank back in the days... And more interestingly, you can enter ‘dir /w’ to list the content of the ‘w’ directory 😊

Reverberated statements of grandeur ALWAYS get my attention.

3:42 Available to read online here: archive.org/details/byte-magazine-1983-11-rescan .

7:35 that TIME example made me LOL. Great!

Good catch to add Xenix into your video. Many people don't know about it either.

The fact that DOS and NT based operating systems use "\" as the folder separator instead of "/" like on all POSIX API compliant operating systems (a.k.a. all the others used today) has caused me no end of headaches when trying to write programs that are OS agnostic.

This brings back many Memories. I miss messing with DOS and all those commands I now don’t remember. I was so excited when Windows was introduced. And in color LOL. THANKS.

I knew there was some sort of Microsoft UNIX early on but didn't know it was baked into DOS. Thanks for sharing this interesting bit of IT history.

Fascinating. Used DOS and Xenix but the XEDOS story is new to me.

Omg, subtitles. Thank you very much, Kevin

I imagine Bill Gates finding this video, and thinks to himself with a slight smile: ''Oh, I've completely forgot about this! Incredible what some people dig up after so many years..."

It makes me want to cry when I think of how they could've used the right slash from the start, and if they did, then every major computing environment would by now have compatible naming schemes. The computer I'm using right now is still affected by this decision, and I still type the wrong slashes sometimes because of it.

Damn, wish DOS had kept that, I was right at home seeing it all done that way.

10:12 Rumor has it that the Norton Chronicles typesetters are still trying to find out how to insert a reverse slash \ inside parentheses () in their system...

great work as always.

Am I the only one noticing that that Norton article used around 10:06 seems to have had an escaping problem? Presumably it was typeset using something that uses C style \ escapes, and it took "(\)" to mean "()" :P

The biggest innovations of MS-DOS 2.0 was, by far, the device driver support and subdirectories.

And I thought I knew everything about DOS. VWestlife ROCKS!

The drive sound of a Tandy 1000- I haven't heard that since 1990.

Thanks for the content!

Subtitles again, thank you ^^ Awesome videoman, I clicked right away on it as soon as I saw it :3

Fascinating. I loved DOS. It did what you told it and didn’t ask you stupid questions. I still pop out to the command line on a regular basis.

Thanks for the video! Very interesting! 👍😊

Great video! I remember hearing about something akin to XEDOS way back in the day, but never heard that specific name. I do remember that their long-term plan was to move to Xenix for high-end systems. Of course, this was before they had started collaborating with IBM on what became OS/2. Xenix was a nice UNIX variant, and was the first version of UNIX I ever got to spend time on. Having DOS essentially morph into that would've been nice, but unfortunately that's not how things worked out.

Thanks Kevin. Way back in '86 I started with MS-Dos 2.1 and you just blew my mind with your legerdemain!. Even when DOS 3.2 came out, I liked 2.1 better. You are a true historian.

A fun fact with Xeninx is that it was sold to a lot of 286 as multiuser system, but at the end it was all just an illusion because the protected mode of the x286 was a total disaster and no one enabled it. You could read everyone passwords by just doing a cat of /dev/ram of any process you want.

I have worked with xenix on a Tandy model 16

it brings me up my childhood memories. good old times.

This is awesome and fascinating, thanks for the video

Very interesting i never heard of this before thanks for the video.

Super interesting video, who have thought that after all these years I'd still be able to learn something new about DOS.

Great video! 👍🏻

Is... Is that a Mac behind Bill at the end? 😃

When will CP/M have it's month?

Thank you for this!

What a fascinating quirk of computer history. My first computer was a Tandy 1000 with MS-DOS 2.11 and I had no idea this was a thing.

This was super interesting.

I read the title as Microsoft Xvideos. Nedless to say, i was hooked on immediately.

Thanks for the awesome video. Never heard the term "XEDOS," and interesting that it was an idea before release of Venix and PC/IX. I could use DOS 2.0's switchar command; I'm typing the wrong thing all through #DOScember. :)

Had only heard of XENIX from the TRS-80 days - thanks for posting!

I was in a lab at the time being a sysadmin for V7 unix and BSD Unix on pdp/11s. We used the MKS toolkit (and switchar) on ibm pc clones, which allowed us to go back and forth easily on the respective command lines. But then Gates saw a Macintosh, decided to commit to Windows, and the moment passed. Luckily, there was BSDI Unix, and later FreeBSD, etc. I personally never saw the need for Linux, but when OSX came out, we all moved to that, and are still there.

I'm glad you demonstrated More's Law.

I knew about switchar, and attempts to make MS-DOS more UNIX like, but didn't know there was a roadmap. Interesting.

Amazing! Never heard about this before.

amazing! Greetings from Argentina!

10:04 Man, I haven't seen prompt $p$g in so long, I had completely forgotten about it 13:00 Funny how he has a Mac SE(/30?) behind him.

Great video. I'd say I never heard of this, but the Like icon is black and scrolling down, I see I left a comment 2 years ago. Nice to see that my memory is so great. Speaking of which, great video. I wonder why they removed the switchvar and that other option in MD-DOS 3.0. BTW, great video.

I used to do support for Xenix on Tandy 16B's. Had one system in a power brownout. All the terminals got kicked off followed by the console then the hard disks (2x 15 MB) stayed that way for about a minute then the power started coming backup and it picked everything backup as if nothing had happened.

I feel like Windows would have been way more solid if it kept its Xenix underpinnings.

Wow, after so long I finally learn something new about MS-DOS :D

SCO - Xenix was also called SystemV (five) We used it in 1993 as a multi-tasking small 5 termimal system for messenger delivery system for billing, ticket generation, and Database.

1982 was the year without Internet and MS-DOS was the new thing. Apple also did the Apple II and Apple IIe are the basic computer system where it does the same as the MS-DOS, but it came with a floppy disk drive. I used to play around with the Apple IIe when I was in school and it was fun. I played “Pick-A-Dilly Pair”, “Oregon Trail”, “Wheel of Fortune”, and other games for the Apple IIe. There was another computer which is quite rare is the Mattel Electronics Aquarius computer which was released in 1983 and it was a huge flop, but you get other features like the basic program like Microsoft did, plus add-ons along with the game like “Snafu” which was a port of the Intellivision game, and a few other games. I remember since I was a kid when Mattel’s Aquarius was the first computer we had at the time, and it was fun. The Aquarius had a data cassette recorder, and a printer. As for the name itself, it has nothing to do with the song by the 5th Dimension.

I used some Unix OS's on IBM PCs in the late 1980's. ScoUnix and another that slips my mind. Also, I found a bug in DOS 2 ... not sure what subversion ... on my first day using an IBM PC XT back in 1984. I had a 5.25 inch floppy boot disk with a couple of games on it (one was Spacewar ... a classic DOS game), and some other files. And I was typing commands to delete unwanted files, and move some files back to the root dir, and I typed rmdir to remove a subdirectory, but the subdirectory still had files in it. This corrupted the disk and made the disk unusable - iirc, no files would load from it. Had to reformat the disk and and re-copy. The good old days ...

I love this - best #DOScember video, imo. i can't wait to see what you do for #JanuAtari, #Appleril and #JuneCommodore.

great video. it would have been great to keep some of this stuff. as others have mentioned Windows still does support either back-slash or forward-slash for path separators.

Don't forget Tandy and Concurrent DOS.

Very interesting, thanks for sharing that. Microsoft's approach was to augment their existing OS which makes sense from a business standpoint though will prevent disruptive change sometimes needed to create something really unique. Linus started from scratch and focused on the core of the kernel, which went beyond adding piping support. There were other companies also trying to bring the power of Unix to the micro-computer. We may not think of it today, but Unix was no a practical OS for the smaller platform because it required more resources than micro's could provide. In the early 80's Microsoft had meetings with Sinclair Research and wanted to provide and OS for their product line but Sinclair refused and designed their own (initially dubbed DomeOS). There's a nice set of notes published by the author of Sinclair's "workable Unix" OS, which eventually was called QDOS, that highlights their plan. That OS actually did resemble a Linux-like kernel in 1983 and at its core behaved a lot like many modern OS's do today...though it was not file-based, which seemed to be a pet peeve of Linus who really wanted the full Unix experience. I don't think file-based in the early 1980's was that practical for micro computers. Linus actually used that system at a younger age, though before he became interested in OS development, so it likely had little impact, but neat to see his orbit cross that orbit when he eventually went on to build Linux. Interesting tidbit in history.

Fascinating!

Your example of a time in text piping into the real time clock was something we used. We had one server in the main branch and we corrected the time whenever we needed to but we also had servers on different branches. (way before internet) And every night we phoned in to each branch and copied needed files over. I piped the time into one text file, copied it to all branches and there it was piped into the server clock. There was a delay of some minutes but that was acceptable.

5:00 this keyboard is heavenly sounding

XENIX was Microsoft's first OS product, which they licenced from AT&T back in the late 1970s. It initially didn't run on x86 platforms; the first version was designed for the PDP-11 and it was later ported to 68k and ZiLOG's Z8000 architecture. It didn't see an official x86 version until SCO acquired the rights in 1987.

I had heard about the switchar setting but not from official documentation i think it was from microsoft's raymond chen on his the old new thing blog in the last few years. I think that because it only affected msdos commands and not third party software its usefulness was limited. The dev setting would have broken batch files not expecting it so again limited usefulness.

10:44 You can actually create those reserved filenames on later DOS versions via a trick using undelete. For instance, create a file named KON, then delete it, then undelete it, whereupon it will prompt for the first character. In this case, you could give it a C so that it will now be named CON. You’ll need to make use of wildcards to get rid of such files, e.g. DEL ?ON

everyone that operated PCs in the 80s must be so relieved that instead of having to memorize commands all you do nowadays is click a search bar and type out what you want.

What I would give to go back to those times. Things were sooooo much simpler back then.

Grew up on DOS, but never read about this! Thanks..

I worked on Xenix machines. They were monolithically far beyond DOS in terms of stability but not exactly easy to write apps for and hardware at the time (typically PDP boxes) not up to the task other than POS back ends, etc. Think OS/2, but far worse in terms of performance and required specific hardware. Unix on a desktop (XeDOS)might sound cool, but in a tech market where you wanted to push the app market and a PC on every desktop it didn't solve any problems. XeDOS was really a conceptual attempt to get hardware and code compliance. Good luck with that in the 80s.Gates was smart enough to let quick to market DOS apps drive the industry while simultaneously playing IBM while endorsing the clone market. XeDOS was a dead end and Microsoft eventually let Xenix wither.

@VWestlife - I was shocked that I noticed, when booting an old Audix Voicemail system, that the OS was Zenix Copyright Microsoft Corporation! Thanks for the full back story. Gratitude!

I spent the past 2 weeks building and installing the system i had in late 80's/early 90's, with Dos, Windows 3.1, Turbo Pascal 3+4, getting my hands on an Vesa Local Bus board and a Promise 4030-vl cache controller. In some ways it runst both faster and more reliable than most W10 systems :o) A real pleasure to work with, as well as a massive dose of nostalgia! Happy "DOScember"?

I remember working on a Xenix machine in London years ago. I could see it was like Unix but knew nothing about it. I wonder why it never caught on? Instead we were lumbered with desperately slow Windows NT servers because people like clicking mice apparently.

That was a lot of research and very interesting thank you. It was also nice and concise for us young people (we don't like long videos). Oh, I just remembered, I only still feel young, I am not technically young ;}

Very cool! Great video as always and I learned something! I've never heard of this UNIX based OS from Microsoft! It would have been interesting if this OS was still around! Interesting indeed that it was kept hush hush. There has been talk recently that it's possible that later versions of Windows could be based on Linux. I don't want to upset Richard Stallman so I'll say GNU/Linux in case he reads this.. ☺️ There is now a Linux Sub System that can run under Windows 10 where you can run Ubuntu and other distros. The distros can be installed from the Windows Store. I remember the days where Microsoft called Linux a cancer. Things have really changed and I think that's great since I use both operating systems. I've been using and testing the new Microsoft Edge Browser under Linux and I think it's pretty good.. It seems that since it's based on the open source chromium web browser it's not bad. If you would like to try it the Linux version of Microsoft Edge is available here.. blogs.windows.com/msedgedev/2020/10/20/microsoft-edge-dev-linux/

Thanks for the video. So someone at MS did think of an idea to use dashes for switches instead of slashes. I wonder, why they kept using slashes in next versions of DOS ? The use of slashes for switches of DOS commands is only reason Windows is still using backslashes as directory separators today. As for Linux, the main reason why Linux was made was the absence of a free version of Unix. Even if Microsoft's Unix'y DOS would have been released, I don't think it would have satisfied Linus enough to not write Linux. BTW, the Jurrasic Park picture shows IRIX, a Unix OS from SGI.

I'd forgotten about those MS-DOS 2.0 options! Years back I'd discovered the undocumented TRUENAME command in DOS 3.x onward, which shows the actual filename for files redirected or substituted locally or via a network. I later found it mentioned in the book "Voodoo DOS", which was neat because I'd found it on my own. Another quirk I found was in MS-DOS 4.x, where (if I remember the details) I did a directory command to include hidden and system files. Along with COMx, LPTx and CON devices, I found one called CLOCK$. Apparently it was the time of day clock device. I never did much more with it, and it seems to have gone away with DOS 5.0 and later.

How confusing will it be in another 65-years when someone gets a hold of this computer to re-create this video, creating files and directories in 2085 ;)

"a machine on every desktop" sounds just crazy, since we all know "there is a world market for maybe five computers."

I'd like to know where that alternate history timeline woulda taken us.

OH YES! That would make using DOS *SOOOO* much better for me, but I bet it messes things up in software. I always feel dumb and type / for directories and - for switches whenever i'm forced to use a DOS-like system

As I recall, part of the problem with switchar was that many applications did not check for it and would expect a forward slash anyway. It should be noted that there were some interesting third-party packages which tried to bridge the gap between DOS and a true *IX on a PC. Two which come to mind were PC-UNIX (and its sister product PC-VMS) and the MKS Toolkit. The modern equivalent would probably be Cygwin, though Services For Linux may ultimately win the day.

One other bit of trivia for you, In 1995 when I was starting to study computers, I was introduced to the Tech Leviathan called UNIX, and the version they had in the classroom, was supplied by Microsoft. No, this most emphatically was not Linux, it was UNIX, and Microsoft owed a license to it. It was their own bought & paid for version of UNIX. I learned a lot about running a UNIX install from the term that would later become extremely important in Linux.