Magnetic Disk Drive Units
Magnetic disk drive units are storage devices that
read and write information on the magnetized surfaces
of rotating disks. The disks are made of thin metal,
coated on each side so that data can be recorded in the
form of magnetized spots. As the disks spin, characters
can be stored on them or retrieved from them in a
random (direct) manner. This direct accessing of data
has a big advantage over the sequential accessing of
data. You can direct the disk drive to begin reading at
any point.
Floppy Disk Drive Units
Floppy disk drive units consist of a diskette drive
(the mechanism within which the diskette rotates) and a
controller containing the electronic circuitry that feeds
signals into and from the diskette. Diskettes are thin,
flexible platters (floppy disks) coated with magnetic
material so characters can be recorded on the surface in
the form of magnetized spots. Just like hard disks, as the
disk spins, characters can be stored on them or retrieved
from them in a random (direct) manner.
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Computer Consoles
Computer consoles usually include at least a
display and a keyboard.
They may also include a
printer. The main console is located near the CPU and is
used by the computer operator to control the operations
of the computer system. Other consoles maybe used at
the peripheral devices to specify what media to mount,
what forms to use in the printer, what alignment is
required, and so on.
They may also be used by the
peripheral equipment operator to start and stop jobs,
bring up other peripheral devices, requeue jobs, and so
on. Computer consoles are not normally used for
keying data from source documents for production jobs.
Cathode-Ray Tube (CRT) Terminals
A cathode-ray tube (CRT) terminal looks like a
television with a typewriter-like keyboard. It allows
you, the operator, to enter programs and data directly to
the computer. At the same time, it displays the program
or data on the display screen of the CRT. It can also
receive information directly from the computer and
display it on the screen. You can add a printer, a modem,
and adapters to the CRT terminal to provide for printed
output and communications through telephone lines.
Printers
Printers are widely used output devices that express
coded characters as hard (paper document) copy. They
print computer results as numbers, letters, words,
