The _("Multipop Timesharing System" | http://www-robotics.cs.umass.edu/~pop/OS.html) was an *(OS), first operational in late 1967, which was based on the concurrently developed implemenation of POP-2, a member of the POP family of languages by _(Robin Popplestone) (see _(Poplog)).

Multipop employed no conventional hardware _(protection) mechanisms; instead its _(security) was guaranteed by the fact that access to system resources was obtained via _(closure)s of device access functions, and on built in restrictions on _(code generation) embodied in the _(compiler) (an ancient example of a _(no-kernel) system).
