[userbinator]

Oddly enough, it looks both more and less featured than MS-DOS, and the PDP-11 it ran on was somewhat close to the first IBM PC in memory and CPU speed.

Some comparison points with MS-DOS 1.0:

- 8.3 filenames

- no subdirectories

- single user

- 32-bit file sizes and offsets (64k file size limit was definitely not enough by then)

- FCB-based API (not file handles), FAT12 filesystem with 32MB limit

- Hardcoded device names special-cased

- No pipes nor redirection either

- No multitasking nor TSRs

- No networking at all

- Environment variables present

- Supports dates up to 2099

- Kernel, shell, and utilities written in 100% Asm

- Live debugger (DEBUG.COM)

[kragen]

yeah, i think some of that was cp/m compatibility crap; too bad about 8.3

the other thing is that the pdp-11 had working segmentation, the 8086 didn't, so trapping faults in user processes so they couldn't break the kernel would have required some kind of interpretation or something

did you know microsoft was shipping xenix in 01981 (the same year they started shipping qdos/ms-dos/pc-dos) and shipping xenix for the 8086 in 01982, and that seattle computer products was selling 8086 xenix boxes in 01983

[pjmlp]

According to some sources, which I sadly cannot point out to, just vague memories from somewhere, so take it with a grain of salt.

Early MS-DOS development used to be done from those Xenix environments, they would cross-compile to PCs, until later on, did they migrate to MS-DOS directly.

Most likely around MS-DOS 5, given the MS-DOS 3.3 resources and how MS-DOS 4 development went.

On the other hand, there is the what-if alternative universe of what would have happened had they kept Xenix around.

[dboreham]

Hmm. Wasn't it done on a dec-10?

[kragen]

you're thinking of basic-80, which gates and allen (and davidoff) did (in 01976?) on the dec-10 at harvard, but we're talking about qdos, which tim paterson did in 01981 at seattle computer products before selling it to microsoft

[dboreham]

Ahhh yes. The great distance of time made me forget that DOS is actually relatively new.

[dboreham]

> pdp-11 had working segmentation

The earliest models didn't. See: https://gunkies.org/wiki/PDP-11/20

[kragen]

indeed, and https://www.bell-labs.com/usr/dmr/www/odd.html reminds us that in fact in the time period we're talking about, the pdp-11 that unix was running on didn't have working segmentation, so anyone could crash it easily and people often did so accidentally

this also explains a remark in the manual that puzzled me about the break() system call (p. 43, §A1.17):

> To save time, UNIX does not swap all of the 4K user core area when exchanging core images. The locations swapped are those from the beginning of the core image to the initial program break, and from the top of user core down to the stack pointer. The initial program break is determined by the size of the file containing the program. The system’s idea of how much to swap may be altered by using this call:

    sys break
    newbreak

> newbreak becomes the first location not swapped. If it points beyond the stack, or to the verify first word in the core image, the entire core image is swapped.

in later versions of unix, of course, attempting to access memory after the break would result in a segmentation fault, but evidently in this version whatever you wrote there would just sometimes be lost when 'exchanging core images' — and presumably it wasn't just the segment limit that was missing on the -11/20, but also implicit indexing off the segment base pointer, which would imply that a mere context switch would require swapping the user program out in this way, just as on the pdp-7

i don't suppose anyone else here has knowledge if this inference is correct?

in any case, thank you very much for this correction!

[chungy]

The first time you zero-padded a year to five digits, I thought it was an accident, but there's two more instances of it. Why do you write 1983 as 01983?

[dcminter]

Probably due to this: https://longnow.org/

Personally I think it's a harmless but also not useful affectation (but I also think our chances of making it into the 10,000s as anything still using equivalent dates are slim at best).

[AnimalMuppet]

It's not harmless. 1) It's annoying. 2) It's off-topic - this isn't an article about the long now, or about dating systems. 3) It's inefficient to write dates not in the standard format - it makes everyone waste mental energy trying to figure out how to parse it.

The third point is especially bad for this article, where in context, the assumption should be that 0xxxx is octal, which isn't what he's actually doing at all.

So the upshot is that, rather than efficiently communicate what he's trying to say on this topic, he'd rather grind is axe on an unrelated topic. His choice, I guess, but I think it's a bad one. And an unfortunate one - he's got really good information on this topic, and his choice has hijacked us into talking about his date format.

And, thinking about it, it's not really the "long now". It's more like the "medium now". If it were the long now, he'd have several more zeroes in front.

[billpg]

You'd hate the Holocene Calendar then. (This year is the year 12023.)

[userbinator]

where in context, the assumption should be that 0xxxx is octal

That's what I thought it was too. This convention carried over into C and its derivatives today.

[kragen]

amusingly 8 and 9 would continue to be accepted as octal digits by the c (or b) compiler until ansi c forbid them

a priori, though, '01982' is not very likely to be intended as octal either

[kragen]

the degree to which you are projecting your own antisocial behavior onto me is astounding

i decline to take responsibility for your emotions

i would appreciate it if you would stop harassing people because you don't like the date format they use, their haircut, or their clothes

[cafeinux]

Despite the fact that they've got a point, in my opinion (which I won't try to impose onto others, be reassured), I don't how it could considered harassing. He wrote one comment, that's all. Also, that comment didn't talk about haircuts or clothes, and I don't see how they could be seen as antisocial through that comment.

[AnimalMuppet]

Antisocial? If you do something in public, I can complain about it in public. If the complaining can be antisocial, so can the doing be antisocial. So think well before you throw that charge at me.

[rahen]

That's a bit like his signature but it's also fairly annoying, it doubles the time required to interpret the number as a year, and I usually have to read the number twice.

[chungy]

That's the main reason I asked. It took longer than normal just to read a date, and it apparently has no useful benefit (yes I saw the side-comment about the "Long Now").