High Quality Content by WIKIPEDIA articles! Hemlock is a free Emacs-style text editor for most POSIX-compliant Unix systems. It follows the tradition of the Lisp Machine editor ZWEI and the ITS/TOPS-20 implementation of Emacs, but differs from many other Emacs variants in that is written in Common Lisp rather than the usual Emacs Lisp — that is, the Lisp machine and ITS Emacs have largely been rewritten in Common Lisp, borrowing features from later variants of Emacs like XEmacs or GNU Emacs.