In ACL 4.1, the standard packages are locked--one cannot define or redefine functions named by symbols in these packages. This will prevent the unfortunate behaviour your students found. Kevin Layer, Franz Inc. 1995 University Avenue, Suite 275 layer@Franz.COM (internet) Berkeley, CA 94704 uunet!franz!layer (uucp) Phone: (510) 548-3600; FAX: (510) 548-8253