Thanks for that information, Don. I had a Commodore 128 for several years and I would occasionally boot into its CP/M mode. The requirement with PIP to think backwards was the biggest complaint I remember, but it’s good to know the background.

Of course we tend to favor what we already know. Whenever I would telnet into a VMS system, I always wanted to type Unix commands into it because I subconsciously associated telnet with Unix. And when I was learning MS-DOS, I had aliases to translate all of the Amiga equivalent commands on my DOS machine, and vice versa. And Kildall definitely made a practice of copying what he knew, even porting now-obscure mainframe languages to microprocessors.

It’s definitely easier to make improvements on something than to create it from scratch.

No, I wouldn’t say CP/M was overrated. Primitive, yes, but it was one of the first, after all. Attempts to compare it to later developments of MS-DOS and Windows ignore the fact that CP/M grew into CP/M-86, Concurrent CP/M, Concurrent DOS, DR-DOS; and of course that Kildall developed a graphical WIMP interface (GEM) that was every bit as capable as the early Windows. CP/M’s basic problem was not that it wasn’t capable, it was that it missed the wave in a marketing sense, and was forever fighting from behind against MicroSoft products, even when the CP/M products were superior.
Where the CP/M-based products were clearly superior was in multi-tasking, multi-user. However, there they were competing against Unix, Xenix, and ultimately Linux on the one hand; and distributed PC-based networking on the other. They may still have been better from the end-user viewpoint, but the *nix derivatives and PC-networking took enough cream out of the market that they took the profit out of it for Digital Research.

Better or not, Digital Research couldn’t keep that up, and eventually got swamped. But CP/M and its offspring were still at least as good, technically. They just missed the wave in a marketing sense.