# File lib/DOSDisk.rb, line 294
  def set_sector(track,sector,contents)
  super(track,sector,contents)  
  
  #now mark sector as used in sector usage list  
  if ((track!=0x11) || (sector!=00)) then #don't bother marking the VTOC sectors used
    sector_usage_bitmap_sector=get_sector(0x11,0)  
    offset_of_byte_containing_this_sector=0x38+(track*4)
    if sector<8 then 
        offset_of_byte_containing_this_sector+=1
    end
    byte_containing_this_sector=sector_usage_bitmap_sector[offset_of_byte_containing_this_sector]
    byte_containing_this_sector=byte_containing_this_sector&(0xff-(2**(sector%8)))
    sector_usage_bitmap_sector[offset_of_byte_containing_this_sector]=byte_containing_this_sector
    set_sector(0x11,0,sector_usage_bitmap_sector)
  end
end