Some source files begin with a line of this form
;;; -*- Mode: Common-Lisp; Author: m.mouse -*-
;; -*- Mode: Lisp; Author: m.mouse -*-
A buffer is automatically set to be in Lisp mode when such a file is displayed.
Alternatively, if you have files of Common Lisp code with extension other than
.lisp, add the following code to your
.lispworks file, substituting the extensions shown for your own. This ensures that Lisp mode is the major mode whenever a file with one of these extensions is viewed in the editor:
("lispworks" "lisp" "slisp" "el" "lsp" "mcl" "cl")
(declare (ignore type))
(setf (editor:buffer-major-mode buffer) "Lisp"))
Another way to make a Lisp mode buffer is the command New Buffer, and you can put an existing buffer into Lisp mode via the command Lisp Mode.
LispWorks Editor User Guide (Windows version) - 9 Dec 2014