8-inch media
''Single density'' (SD or 1D) describes the first generation of floppy disks that use an iron oxide coating. Floppy drives utilize 300-oersted write heads, FM encoding, and a track width of for a density of 48 tracks-per-inch (tpi) and 5876 bits-per-inch (bpi). ''Double density'' (DD or 2D) doubles capacity over SD by replacing FM encoding with an improved5¼-inch media
''SD'' (''1D'') and ''DD'' (''2D'') designations were generally identical to those of 8-inch disks. ''Quad density'' (QD or 4D) doubles capacity over DD by narrowing the width of tracks to for a density of 96 tpi. Some manufacturers ( Micropolis, Tandon, Micro Peripherals (MPI), Teac) used a track density of 100 tpi for quad-density drives, which were incompatible with 96 tpi models. ''High density'' (HD) improves capacity by utilizing a 96 tpi track density in conjunction with improved cobalt disk coating and stronger 600-oersted write heads, allowing 9646 bpi to be written.3½-inch media
''Double density'' (DD) 3½-inch disks use an iron oxide coating, just as with 5¼-inch DD/QD disks. However, drives utilize stronger 670-oersted write heads and a narrower track width of for a density of 135 tpi and 8717 bpi. ''High density'' (HD) 3½-inch disks switch to a cobalt disk coating, just as with 5¼-inch HD disks. Drives use 700-oersted write heads for a density of 17434 bpi. ''Extra-high density'' (ED) doubles the capacity over HD by using a barium ferrite coating and a special write head that allows the use ofOverview
See also
*References
External links
* {{cite web , url=http://www.hardware-bastelkiste.de/floppy.html , title=Floppy-Disketten-Laufwerke , trans-title=Floppy disk drives , access-date=2017-06-19 , author=(M)Tronics SCS , language=German , date=2007-05-20 , url-status=dead , archive-url=https://web.archive.org/web/20170619194609/http://www.hardware-bastelkiste.de/index.html?floppy.html , archive-date=2017-06-19 Floppy disk computer storage