This following is a starting point for your code. You can customize your version as needed. The example below assumes we have defined a Tractor object named "tractor" in TheRobot.tcl. And it assumes we have defined a Canvas object named "led" in the OperatorInterface.

     # @(#) $Header: /home/abrown/public_html/first/first2004/software/SimulatorDocs/Simulator/RCS/Updates.wc,v 1.1 2004/04/26 03:44:15 abrown Exp $
     
     # This file is intended to be customized by the user.  Each
     # object which needs explicit updating should have its update
     # routine called here.
     
       #Tractor_update {TractorName}
       Tractor_update tractor
     
       Canvas_UpdateAll led
     
     # Note that over time this may dwindle to nothing as the library
     # is updated.  Anyway, it may be possible to have the objects
     # self-update at the appropriate times.  We shall see.
     # -----------------------------------------------------------------