SET(MODIFIED)
  Turns on or turns off DECTPU'S internal marker indicating that the
  specified buffer has been modified.
  Syntax
     SET (MODIFIED, buffer, {OFF | ON})
  Parameters
     buffer               The buffer whose marker you want to set.
     OFF                  A keyword that turns off DECTPU's internal
                          modified-status marker.
     ON                   A keyword that turns on DECTPU's internal
                          modified-status marker.