> Big computers and little computers are completely different beasts created by radically different groups of people. It's logical, I know, to assume that the personal computer came from shrinking a mainframe, but that's not the way it happened. This seems off. Those little computers in your phones run a flavor of Unix, just like the mainframes did (besides VMS, etc). Also, those little computers connect to the cloud…
When he talks about "little computers," he's talking about the microcomputers of the '70s and '80s, like the IBM PC, Apple II and Macintosh, Commodore 64 and Amiga, etc. And he wasn't wrong. Those machines were completely different than the "big iron" of the day -- they were single-user, single-tasking systems with no meaningful memory protection or other features to protect the system against poorly written or malic…
The PDP-7 and PDP-11 were also like that. (And yes, they were used for multi-user scenarios, but even an early micro could be so used, if you e.g. ran a BBS on it.) Memory protection and the like are important features to be sure, but they don't define a segment class. And the micros quickly gained these features anyway, with machines like the Motorola 68020 and the Intel i386. The early OS's like MS-DOS/Win 9x and Classic Mac OS didn't make use of them, but this was entirely due to performance concerns, combined with running a CPU-intensive GUI. The transition to a memory-protected, secure-by-default OS was entirely foreseeable, even aside from the sensible concerns about an "internetworked world".