# File test/backup/NADOLDisk.rb, line 87
def free_sector_list  
  sector_usage_bitmap=get_sector(0,2)[0x20..0x65]
   free_sectors=[]
    (0..(sector_usage_bitmap.length/2)-1).each do |track|
      track_bitmap_lo=sector_usage_bitmap[track*2]
      track_bitmap_hi=sector_usage_bitmap[1+track*2]
      (0..7).each do |sector|
        if ((track_bitmap_lo & (2**(7-sector)))==0) then
          free_sectors<<DSKTrackSector.new(track,sector)
        end
        if ((track_bitmap_hi & (2**(7-sector)))==0) then
          free_sectors<<DSKTrackSector.new(track,sector+8)
        end        
      end
    end
    free_sectors.sort  
end