# File test/backup/DSK.rb, line 89
        def initialize(file_bytes="\0"*DSK_FILE_LENGTH,sector_order=:physical)
                #file must be a multiple of (16 sectors * 256 bytes) = 4096
                #some dsks on Asimov appear to have an extra byte at the end so allow for 1 extra byte
                if (file_bytes.length%4096>1) then
                        raise "DSK files must be #{DSK_FILE_LENGTH} bytes long (was #{file_bytes.length} bytes)"
                end
                @file_bytes=file_bytes
                @files={}
                @sector_order=sector_order
                @track_count=file_bytes.length/4096
        end