3.5 inch floppy disk
This format was designed to be smaller then the 5.25in floppydrive and it's media and fixed some of the 5.25in floppies design problems. The disks are housed in a stiff housing, opposed to the "floppy" housing the 5.25in floppy was made in.
3.5in floppies came in 3 different densities (easily distinguished by a second hole on the side) and while only the earliest 3.5in disks were single sided, almost all 3.5in floppies can be written to on both sides. The 3 densities are:
- Double density (a.k.a. DD)
- High density (a.k.a. HD)
- Extra high density (a.k.a. ED)
Like earlier floppies, there were many different ways to format a disk, often depending on what type of computer the disk was formatted with. On PC's, DD disks were usually (DOS-)formatted to 720KB (though in practice it had about 714KB of usable space), HD disks formatted to 1.44MB (in practice it was around 1.38MB) and the uncommon 2.88MB disks formatted to around 2.76MB. On older Macs the DD disks formatted to around 820KB.
In addition to the standard DOS formatting utility, there are several other 3rd party formatting utilities around (Winimage is one of them) which can overformat disks to hold more space (even Microsoft used it's DMF format to distribute media, which could hold upto around 1.68MB instead of the usual 1.38MB). Most overformatting utilities won't overformat ED disks though but as these disks and it's drives are very hard to come by, this is hardly significant.
