The following occur to me as possible interpretations of system
mathematica systems -- e.g., non-commutitive algebras
Mathematica's evaluation system -- the kernels and how they work
Mathematica's functions for interacting with the operating system it runs on
Mathematica's own installation structure -- the file architecture of its many components
I think ...
It might help the discussion if I posted a counter-proposal (to mgoldberg's proposal to eliminate the system tag). I think my command of the appropriate jargon is weak, so I welcome criticism, edits, and other constructive action.
I think one thing is clear: The tag was meant to indicate questions related to the CS notion of "system" (if that term is well-...