Floppy disks

Mylar plastic flexible disk coated with iron oxide coating, in an unsealed, flexible (5.25") or hard (3.5") plastic jacket.
3.5" floppy diskettes are the most common type of storage on a Micro-Computer.
Examples;
- Floppy (or Microfloppy) diskettes
  - Typical capacity(1998): 1.44MB
- SuperDisk (LS-120)
- Zip disk
  - Typical capacity(1998): 100MB

Use

Floppy disks gain rigidity when rotated at speed therefore mimic hard disks closely.
Removable
Cheaper than Hard disks and easy to handle
Transportable (Though removable Disks such as Iomega Zip or LS-120 disks becoming popular)
Less reliable than Hard Disks

3.5" (micro)floppy disks (usually 1.44 Mbytes) - DSHD - most common

5.25" floppy disks (usually 1.2MBytes) DSDD

Flexible mylar diskette coated with iron oxide.
Capacity.
- 3.5"
  DS/DD 720 KBytes
  DS/HD 1.44 MB
  DS/QD 2.88 MB
- 5.25" DS/DD 360 KB - DS/HD 1.2 Mbyte
- Iomega Zip disk 100 MB
- LS-120 "Superdisk" (introduced 1997) 120MB.
Performance
- 3.5
  - 25 millisec access time and data transfer rate of 500 Kbits / sec.
  - Spin at 300 rpm (one revolution in about .2 seconds)
  - Heads move from the center to the outside edge in about 0.17 sec.
  - maximum access time 0.2 sec (larger of the two)
  - Latency (bringing the disk up to speed) can give an access time of 0.5 seconds from a full stop.
Sides : Double sided
Density : double, high, or quad (high) density
Physical organisation:
Data and programs are stored in tracks and sectors where each sector is directly addressable giving fast access.

For 3.5" Microfloppies

Both IBM (and Compatible's) and Apple computers may come with 3.5" Micro-floppies.
Watch when taking IBM formatted floppies to an Apple as on older Apple computers in normal 'Apple' mode, the Apple Operating system will indicate the disk format is invalid and reformat for you!
The Apple "Super-drive" (introduced mid-1993) will accept both Macintosh and IBM DOS format disks.

For 5.25" Diskettes

Drive size	Diskette capacity	Drive Capacity	Transfer rates
3.5	720KB	720KB	250Kbs
		1.44MB	250Kbs (Reading a 720KB disk in a 1.44MB drive)
	1.44MB	1.44MB	500Kbs

5.25	360KB	360KB	250Kbs
	1.2MB	1.2MB	500Kbs
		360KB	300Kbs

Kbs = Kilobits per second.