Edit Devices, Continued
Disk drives
Also inside the system unit, there is the disk drive or a combination of disk
drives. A disk drive provides direct access to data on a disk for electronic
storage and retrieval. The two basic types of disk drives are the floppy disk
and the hard disk drive. Hard disk drives can be removable as a
precautionary measure of protection for the data stored on the drive.
Floppy disk
Floppy disk drives play and record on floppy diskettes. There are openings
drive
on the face of the system unit for the insertion of a floppy disk. Inside the
disk drive are electronic heads that read and write. Single-sided disk drives
read/write on one side of the disk. Double-sided disk drives have read/write
heads on both sides. The electronic heads in each floppy disk drive
read/write slower than those of a hard disk drive.
Floppy disks
Floppy disks are round, flexible platters covered with magnetic oxide and
encased in a sturdier plastic envelope. The envelope is lined with a soft
material that continuously cleans the disks, as it spins inside the envelope.
The diskette has a hole in the middle, called a center hub. Also on the
envelope, there is a recording window that allows the read/write heads access
to the disk surface. Disks have a notch in the upper right-hand comer which
is a write protect feature to prevent the user from accidentally recording over
existing data. New disks are blank; therefore, you must initially format
every disk you use in your computer. The diskettes used with a floppy disk
drive come in two sizes: 5 1/4 and 3 ½ inch. The following table explains
other diskette features:
Feature
Meaning
Single-sided
Records on one side only
Single density
256 byte capacity per sector
Double-sided
Records on both sides of disk
Double density
512 byte capacity per sector
Quad density
1,024 byte capacity per sector
Continued on next page
3-15
