>>100
Saying that Unix and MS-DOS were non-networked helps explain that they were "secure" because "nobody would try to attack the machine on purpose" when they were created. They were toy OSes, not designed for the real world of the internet and/or multiple users on one machine simultaneously. In the modern world where everything is connected to the internet and there are malware writers, Unix and MS-DOS are inadequate. ``Fixing'' a buffer overflow by writing a note in the man page doesn't work anymore.
Networking was a bolt-on thing for Multics too.
Of course, an OS created before the internet would not be expected to have ARPANET networking until it was actually invented.