# File lib/DSK.rb, line 203
  def set_boot_track(contents)
    sectors_needed=(contents.length / 256)+1
    raise "boot code can't exceed 16 sectors" if sectors_needed>16
    s=sectors_needed.chr+contents
    for sector in 0..sectors_needed-1
      sector_data=s[sector*256..255+sector*256]
      set_sector(0,sector,sector_data)
    end
  end