Corman Common Lisp was designed and implemented by Corman Technologies, since 1995. Previously they developed PowerLisp for the Mac, but Corman CL was a complete rewrite for Windows. (PowerLisp is no longer developed or supported). They developed and maintained Corman CL, with new major releases approximately every 18 months (and minor updates more often), until 2006. The CLOS implementation was originally from Art of the Metaobject Protocol Closette, and then extensively rewritten to add missing Common Lisp features and to improve performance.