Check out your LISP manual. For files, the LISP open function does what you want - see
http://www.lisp.org/HyperSpec/Body/fun_open.html. For example:
Code:
(setf s (open "foobar" :direction :output :if-does-not-exist :create))
For directories, either use LISP's directory command, or one of the file/directory handling functions documented in the Developer's Kit.
Claus