Magnetic disk basics

• By portability
  1. Removable (exchangable)
     Where drive and disk are separate,
     such as floppy storage.
  2. Fixed
     Where drive and disk are one unit,
     such as Winchester Hard Disk
• By physical features
  1. Flexible (Floppy)
     Where disk is made of a flexible plastic
  2. Hard
     Where disk is made of a rigid metal (eg. Aluminium)
  3. Optical
     Disk is a hard plastic
• By storage technology
  1. Magnetic
     Iron-oxide is magnetised (Floppy disk, Hard disk)
  2. Optical
     Photo-cell with a laser is used to read data.

Magnetic Disk

• Data and Programs stored on Disk are;
  • Easily accessed and modifiable
  • May be accessed randomly
• Some magnetic disks are rigid and called hard disks, others are flexible and are called floppy disks or diskettes.
• Floppy disks gain rigidity when rotated at speed and therefore mimic hard disks very closely.
• Are mainly used to store data and programs in tracks and sectors where each sector is directly addressable giving fast access.
• Where disk and drive are one unit (as in a Winchester unit) the terms may be used interchangably.
• Other forms of magnetic disks include Magneto-optical disks (similar to Compact disks), which provide high density and high accuracy data storage media( in the order of Gigabytes of storage).

Magnetic Disk Drive

• Holds a spinning magnetised disk that stores data.
• Has a moving read/write head to access the disks data
• Given the term Direct Access Devices
• Disk sizes and speed basically depend on how much you wish to pay, from a floppy disk at $2 for 1.44MB, to a fixed hard disk at $450 for 5.2GB plus operating system. (Aug98)
  (Note. The costs of disk storage decreases rapidly. You should check with a current computer publication for an estimate of costs.)