CLISP is a program which includes an interpreter, a compiler, a debugger, CLOS, MOP, a foreign language interface, i18n, POSIX and Perl regular expressions, a socket interface, fast bignums, arbitrary precision floats, and more. An X11 interface is available through CLX, Garnet and CLUE/CLIO. Command line editing is provided by readline. CLISP runs Maxima, ACL2 and many other Common Lisp packages.