On Tue, 3 May 2016, Al Kossow wrote:
The early BASIC minicomputer timesharing systems (line 2000TSB) had virtual BASIC machines for each user that swapped.
Well, but is this not an software abstraction for a non existing encapsulation feature of the underlying hardware? DGs Extended BASIC also implemented time sharing without the hardware offering this feature and probably many other examples exist (Even if you beat me: Early Windows?)... If the language does not offer any critical commands, this works as well as users can not do nasty things.
