The operator which is used to operate on the history file. The command format is 'Command, File, Range'. So far, Command can be PURGE, File can be EVENT or DATA, and Range can be ALL or 'mm/dd/year..mm/dd/year'. For example, 'PURGE, EVENT, ALL' tells the UPS software to purge all entries in the event log file. And 'PURGE, DATA, 03/20/1995..07/02/1995' tells the UPS software to purge the entries which are recorded form 03/20/1995 to 07/20/1995 from the event log file.