--- a/UserPreferences.st	Thu Nov 19 06:41:24 2015 +0100
+++ b/UserPreferences.st	Fri Nov 20 08:56:52 2015 +0000
@@ -1,5 +1,3 @@
-"{ Encoding: utf8 }"
-
 "
  COPYRIGHT (c) 1998 by eXept Software AG
 	      All Rights Reserved
@@ -843,6 +841,15 @@
 
 
 
+!UserPreferences methodsFor:'accessing-changes & history'!
+
+historyManagerAllowEditOfHistory:aBoolean
+    "useful if you have 'beginner students', to prevent them from changing the history"
+
+    self 
+        at: #'history-manager.allow-edit-of-history'
+        put:aBoolean
+! !
 
 !UserPreferences methodsFor:'accessing-locale'!
 
@@ -899,17 +906,17 @@
      This is rather user setting. To ask whether the selector namespaces
      support should be used, use:
 
-	UserPreferences current selectorNamespacesSupportedAndEnabled
-    "
-
-    ^self at:#selectorNamespacesEnabled ifAbsent:[false].
-
-    "
-	UserPreferences current selectorNamespacesEnabled
-	UserPreferences current selectorNamespacesSupportedAndEnabled
-
-	UserPreferences current selectorNamespacesEnabled: true.
-	UserPreferences current selectorNamespacesEnabled: false.
+        UserPreferences current selectorNamespacesSupportedAndEnabled
+    "
+
+    ^self at:#selectorNamespacesEnabled ifAbsent:false.
+
+    "
+        UserPreferences current selectorNamespacesEnabled
+        UserPreferences current selectorNamespacesSupportedAndEnabled
+
+        UserPreferences current selectorNamespacesEnabled: true.
+        UserPreferences current selectorNamespacesEnabled: false.
     "
 
     "Created: / 19-07-2012 / 15:26:04 / Jan Vrany <jan.vrany@fit.cvut.cz>"
@@ -4609,6 +4616,31 @@
     "Created: / 03-07-2006 / 16:50:20 / cg"
 ! !
 
+!UserPreferences methodsFor:'accessing-prefs-external tools'!
+
+osFileExplorerCommand
+    "return an OS command template to open a finder/explorer or similar"
+
+    ^ self at:#osFileExplorerCommand ifAbsent:nil
+!
+
+osFileExplorerCommand:aString
+    "define an OS command template to open a finder/explorer or similar"
+
+    self at:#osFileExplorerCommand put:aString
+
+    "
+     UserPreferences current osFileExplorerCommand
+     
+     osx:
+     UserPreferences current osFileExplorerCommand:'open %1'
+     
+     linux:
+     UserPreferences current osFileExplorerCommand:'nautilus %1'
+     UserPreferences current osFileExplorerCommand:'dolphin %1'
+    "
+! !
+
 !UserPreferences methodsFor:'accessing-prefs-files and directories'!
 
 changeFileName