WHAT KIND OF FLOPPY DISKS DO I NEED FOR MY MAC?  (6.1)
------------------------------------------------------

       There have been three kinds of floppy disks in the history of 
  the Macintosh.  The original 128K Thin Mac (which used to be called 
  a classic Mac before the advent of the much superior Mac Classic) 
  and the subsequent 512K "Fat Mac" used 400K, single-sided 
  double-density diskettes.  These disks are outdated, and it's highly 
  unlikely you'll actually see any.  If you need to exchange data 
  with an older Macintosh, you'll need to use disks formatted as 
  single-sided. Since very few, if any, stores still sell one-sided 
  3.5 inch disks anymore, it's fortunate that all Macs deal quite 
  happily with double-sided disks formatted as single-sided.  Just 
  click the button labeled "One-sided" after you select "Erase Disk" 
  from the Special menu.

       *Neat Trick alert*  Sometimes disks that fail formatting as 
  double-sided can be formatted as single-sided.  Even neater trick: 
  In System 6 the shareware init BAD can map out bad sectors on a 
  floppy disk which lets about 70% of bad disks be formatted. (System 
  7 does this automatically.)  Neatest trick of all:  All name-brand 
  diskettes (SONY, Maxell, etc.) come with lifetime warranties.  A lot 
  of offices keep a bad disk box for everyone to dump their bad disks 
  in and send the disks in for replacement when they collect ten or 
  so; but it's been my experience that if you return just a single bad 
  disk these companies will send a whole ten pack as a replacement.

       With the introduction of the Mac Plus in 1986, Apple also 
  introduced a larger disk drive capable of reading and writing 800K, 
  "Double-Sided Double-Density" disks, DSDD for short.  The only way 
  to tell these disks from the earlier, one-sided diskettes, is by 
  the label on the metal cover.  Unformatted these are identical to 
  the 720K disks common in the IBM world.  With the Mac IIx Apple 
  introduced what's alternately known as the Superdrive or "FDHD," 
  short for "Floppy Drive, High Density."  The FDHD (pronounced 
  Fud-Hud) can read and write all of the previous kinds of diskettes 
  plus double-sided high-density disks which are distinguished by two 
  holes in the disk case rather than the normal one.  The FDHD uses 
  the extra hole to recognize a high-density disk.