Exploding a string into a list of character atoms?

From: Joseph O'Rourke
Subject: Exploding a string into a list of character atoms?
Date: Sat, 21 Sep 1996 00:00:00 +0000
Message-ID: <521lbf$s2u@sylvia.smith.edu>

Is there a function to take a string like "string" and return
the list (S T R I N G)?  (I am using GCL.)  Thanks for any help!