In the early 80's it was Bill Gates who made strategic decisions for MS. That was even before they went public. My wonder is if Gates had ever used Unix. He (personally) developed BASIC for a CPM (I think) machine. I am unaware of any system level skills in his experience. If he had knowledge of or used Unix or XENIX (for which he had a master license from AT&T), why on earth would anyone go down the bazaar path of DOS with lettered drives, tortuous IO interfaces, and assembly language source code? Why didn't he choose a far simpler to support and easier to learn operating system that had 10 years of maturity. I would love to hear Bill Gates' description of the development of a DOS over Unix strategy. My guess is there wasn't enough memory on the first IBM PC's. I worked with LSX while at BTL and forget the memory footprint of LSX. Memory protection was another thing, but LSX looked and felt like UNIX without memory protection. Does anyone recall how much RAM memory could be put on the first IBM PC's? That was probably a major problem. My memory of the LSI-11 architecture has faded. Same for 20286. In the early 1980's I had never heard of Xenix. Ed On Thu, Apr 8, 2021 at 12:22 AM Dan Stromberg <drsalists(a)gmail.com> wrote: -- Advice is judged by results, not by intentions. Cicero

On 4/7/21, Ed Bradford <egbegb2(a)gmail.com> wrote: Limited RAM was probably the main factor keeping Microsoft from replacing DOS with XENIX on early PCs. I think that the main factor after most PCs started to come with sufficient RAM for Unix might have been that the divestiture allowed AT&T to fully commercialize Unix and charge a fortune for licenses. Microsoft did actually talk about gradually phasing out DOS for XENIX before the divestiture happened. I wonder if Microsoft would have actually followed through on replacing DOS with XENIX had the divestiture either not happened at all, or happened in a form that still restricted AT&T from commercializing Unix (maybe a vertical divestiture in which the Bell System continued to exist but was forced to become a wholesaler only). It would probably have been the path of least resistance. History would very likely have gone better than it actually did here, with Unix likely becoming the dominant OS family by the early to mid 90s. With their flagship OS being a Unix, Microsoft would have had a bit harder time being as anti-competitive as they were here, and at least they would have been pushing an OS that was sort of reasonable unlike anything in the DOS-like family. XENIX would probably have gone on to be the dominant implementation of Unix, but it's likely that compatibility layers for it would have been common (as some PC Unices actually did here). I guess things could have also gone a lot worse than they did here though. Linux sucks in quite a few ways, but Microsoft could very well have actually finished winning the Unix wars in the early 2000s had Linux not been there at the right time to emerge as the ultimate victor. At least the possibility of writing a better OS and having it be at least modestly successful by being Linux-compatible still remains here, whereas it would be much harder for a better OS to succeed in a world where Windows was pretty much the only relevant OS.

On Thu, Apr 8, 2021 at 1:58 AM Ed Bradford &lt;egbegb2(a)gmail.com&gt; wrote: I can say I have personally seen him do so ;-) He and Bob Greenberg were at Ricki's Hyatt at the infamous meeting with AT&T in late 1979/early 1980 [I have forgotten the precise date it was early/mid-winter IIRC -- I was there as ½ of Tektronix's reps - this meeting would lead the Sys III license]. Bob and Bill had some sort of PC with them running a pre-Xenix of some type as an example. Please remember that he and his team ran the Seventh edition of UNIX on a PDP-11/70 at Microsoft (called 'kermit' IIRC) and also TOPS-10 on a KL -- I believe that both of these systems are at the LCM in Seattle these days (which is currently in mothballs due to CV-19 and funding which is a real shame). To answer this I have a few educated >>guesses<< which are based on the history of the times and practical reality. Gates (and Paul Allen) had personally grown up TOPS-10 and RSTS in HS and in his 2 semesters at Harvard; so the DEC disk naming scheme for having the system written using assembler was natural to him since DEC did that too. And second, DOS was purchased from Seattle Computer Products (SCP - story told elsewhere and not UNIX history) and it has been written to be modeled after CP/M (which had been modeled at RT/11 and DOS/11 - the last two again using DEC style naming conventions). Interestingly enough, CP/M had been written in PL/M which was Kidall's simplified PL/360 style language for the 8080 that he eventual sold to Intel. I was under the impression SCP used 8086 assembler language for the development of their DOS86 system which was the direct parent to MS/DOS - but they might have used PL/M. So you can add, that an issue at the time was that Intel's PL/M tools were not very portable and since the primary development systems at Microsoft were TOPS-10 and RSTS (and Bob was trying to replace RSTS with UNIX at the time), I don't think there were PL/M tools that ran on them. ᐧ