diff --git a/OSN.asd b/OSN.asd
index df8935e..e75277d 100644
--- a/OSN.asd
+++ b/OSN.asd
@@ -43,7 +43,8 @@
                          (:file "osn-to-os10" :depends-on ("pkgdef" "conditions" "osn"))
                          (:file "ui-utils" :depends-on ("pkgdef" "globals" "conditions"))
                          (:file "debugger-ui" :depends-on ("pkgdef" "globals" "conditions" "ui-utils"))
-                         (:file "osn-viewer" :depends-on ("pkgdef" "globals" "conditions" "osn" "osn-parser" "osn-writer" "osn-to-os10" "ui-utils"))
+                         (:file "osn-mode" :depends-on ("pkgdef" "globals" "conditions" "osn" "osn-parser" "osn-writer" "osn-to-os10"))
+                         (:file "osn-viewer" :depends-on ("pkgdef" "globals" "conditions" "osn" "osn-parser" "osn-writer" "osn-to-os10" "ui-utils" "osn-mode"))
                          (:file "xosc-viewer" :depends-on ("pkgdef" "globals" "conditions" "ui-utils"))
                          (:file "win-ui" :depends-on ("pkgdef" "globals" "conditions" "ui-utils" "debugger-ui" "osn-viewer" "xosc-viewer")))
                         :depends-on ("lib")))
diff --git a/src/osn-mode.lisp b/src/osn-mode.lisp
new file mode 100644
index 0000000..b5c63da
--- /dev/null
+++ b/src/osn-mode.lisp
@@ -0,0 +1,75 @@
+;;;; OpenScenarioNext --- OpenScenario Language Design
+;;;; This is copyrighted software.  See documentation for terms.
+;;;; 
+;;;; osn-mode.lisp --- OSN Editor Mode
+
+(cl:in-package "EDITOR")
+
+;;;; %File Description:
+;;;; 
+;;;; OSN Editor Mode
+;;;; 
+
+(defun ensure-osn-mode ()
+  nil)
+
+(defparameter *osn-syntax-table*
+  (create-syntax-table  :string-escape #\\
+			:escape #\\
+			:nested nil
+			:double-comment #\/
+			:second-comment #\*
+			:first-close-comment #\*
+			:second-close-comment #\/
+			:string #\" 
+			:close '(#\))
+			:open '(#\()
+			:whitespace '(#\tab #\space
+					    #\formfeed
+					    #\newline
+					    #\return)))
+
+(defmode "OSN" 
+  :major-p t
+  :vars '((Paren-Pause-Period . nil)
+          (Highlight-Matching-Parens . t)
+	  (Comment-Start . "/*")
+	  (Comment-Begin . "/*")
+	  (Comment-End . "*/"))
+  :syntax-table *osn-syntax-table*)
+
+(defcommand "OSN Mode" (p)
+     "Put current buffer in OSN mode." 
+     "Put current buffer in OSN mode."  
+  (declare (ignore p))
+  (setf (buffer-major-mode (current-buffer)) "OSN"))
+
+(define-editor-mode-variable Compile-Region-Function "OSN" 'region-osn-compile)
+
+(define-editor-mode-variable Compile-Buffer-File-Function "OSN" 
+   'compile-osn-file-internal)
+
+(define-editor-mode-variable Evaluate-Region-Function "OSN" 'region-osn-eval)
+
+(defun region-osn-compile (&rest args)
+  (declare (ignore args))
+  (error "Not available"))
+
+(defun compile-osn-file-internal (&rest args)
+  (declare (ignore args))
+  (error "Not available"))
+
+(defun region-osn-eval (&rest args)
+  (declare (ignore args))
+  (error "Not available"))
+
+(define-editor-mode-variable Find-Dspec-In-Buffer-Function "OSN" nil)
+
+(define-editor-mode-variable Mark-Defun-Possible "OSN" nil
+  "Predicate to determine if valid to mark a defun")
+
+(define-file-type-hook 
+    ("osn")
+    (buffer type)
+  (declare (ignore type))
+  (setf (editor:buffer-major-mode buffer) "OSN"))
diff --git a/src/osn-viewer.lisp b/src/osn-viewer.lisp
index 7aa0a8f..da3f5bb 100644
--- a/src/osn-viewer.lisp
+++ b/src/osn-viewer.lisp
@@ -15,7 +15,8 @@
    (make-instance 'osn-viewer
                   :source nil
                   :osn-buffer
-                  (editor:make-buffer "Unknown" :temporary t))
+                  (editor:make-buffer "Unknown" :temporary t
+                                      :modes '("OSN")))
    :screen
    (derive-main-interface-screen interface)))