Most Lisp systems, be it Lisp Machines, or modern Common Lisp implementations do the same. The Lisp Machine didn't really have a kernel though, unless you call

Most Lisp systems, be it Lisp Machines, or modern Common Lisp implementations do the same. The Lisp Machine didn't really have a kernel though, unless you call the microcode that implemented the Lisp Machine macrocode "engine". As for I/O, that was just memory mapped .. you write/read to some magic number. What is wild was invisible pointers ... A forwarding pointer specifies that a reference to the location containing it should be redirected to another memory location, just as in postal forwarding. These are also called invisible pointers. (Not a member of the "we wall think we can't implement systems in managed code" club -- there are plenty of such systems dating back to before Unix :-) )