> SYS(2015)is guaranteed to be unique within the same PC.

Are you sure about that? This would require (inter-process) communication between all instances of Fox runtimes on a machine. There seems to be such communication of sorts - a busy Fox can keep other Foxen from closing for a while - but I don't think that IPC is involved in SYS(2015).

> AFAIK, nobody proved otherwise yet.

Might be a nice Sunday morning exercise. Should be easy enough to prove what's up one way or another. *g*