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. Despite the more rugged design, 3.5 inch floppy drives tend to to be less reliable due to their compact nature.
3.5 inch floppies came in three different densities (easily distinguished by a second hole on the side) and while only the earliest 3.5in disks were single sided, almost all 3.5 inch floppies can be written to on both sides. The 3 densities are:
- Double density (a.k.a. DD, 720kb)
- High density (a.k.a. HD, 1.44mb)
- Extra high density (a.k.a. ED, 2.88mb)
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 (primarily used in IBM PS/2s) formatted to around 2.76MB. On older Macs the DD disks formatted to around 820KB, and on Amiga 880kb.
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 up to 1.68MB instead of the usual 1.38MB). Most over-formatting utilities don't handle ED disks, as the format never gained much popularity.
