Surely you misspelt PC-DOS 2.11, as released by IBM.
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For most of their lives, PC-DOS and MS-DOS were nearly interchangeable, with fairly minor differences, so I omitted the prefix. And while XX-DOS 2.11 was quite fine, the 3.1 version was also quite reliable, too. 4.0, of course, was a disaster, but 5 fixed most of the bugs of 4 and was almost there ...
Ah, the good old days!
I have a friend who owned a two-digit serial number copy of MS-DOS 1.0.
I guess I'll have to stop wet-coating my own glass plates pretty soon and join the 20th century. Hmm. I wonder if there's a website that will tell me how I can coat my own digital sensors?