Information Technology Reference
In-Depth Information
An
ink jet printer
squirts liquid ink onto paper. The printer is inexpensive to buy, and produces
good quality color graphics, but the cost per page is high because of the cost of the ink cartridges.
A
laser printer
transfers
toner
to a
drum
and then to paper, and then
fuses
the toner to the
paper. It is economical per page and produces good quality output, but is expensive to buy ini-
tially. Specialty printers include
direct thermal
,
thermal wax transfer
,
thermal dye transfer
, and
plotters
.
Audio output comes through speakers and headphones. Speakers designed for computer use are
powered
, and have shielding to prevent
electromagnetic interference (EMI)
.
Choosing Appropriate Storage Devices
Primary storage
is RAM;
secondary storage
is permanent storage, such as a disk. A
disk
is a
platter (or multiple platters) that stores data; a
drive
is the mechanical component that reads and
writes the data. In some storage types, the disk and drive are inseparable.
A
hard disk drive (HDD)
is the most popular type of secondary storage for personal computers.
It is magnetic and mechanical, and usually internal to the system unit. Read/write heads store the
data in
sectors
on
tracks
. A group of sectors is a
cluster
. A group of tracks at a specific read/write
head position is a
cylinder
. HDDs can use either PATA or SATA connectors internally, or USB,
FireWire, or eSATA externally.
An
optical drive
uses a light beam and sensor to read data on
compact discs (CD)
,
digital versa-
tile discs (DVD)
, and/or
Blu-ray discs (BD)
.
A
solid-state drive (SSD)
uses EEPROM to store data in tiny transistors.
Solid-state hard drives
(SSHD)
are a substitute for traditional HDDs as the main secondary storage in a computer.
Local drives are
direct-attached storage (DAS)
. Network-accessible storage is
network-attached
storage (NAS)
.
NAS appliances
are simple computers designed to be used as network storage. A
storage-area network (SAN)
makes remote storage appear as a local volume on each individual
computer.
A
redundant array of inexpensive disks (RAID)
is a system that uses multiple physical HDDs to
increase performance and reliability by spreading the data out across all the disks and implement-
ing schemes for reconstructing the data in the event of one disk's failure.
Cloud storage
is storage that the user accesses online via a
cloud
, which is a secure computing
environment online.
Key Terms
active matrix
aspect ratio
audio adapter
bar code reader
Blu-ray disc (BD)
cathode ray tube (CRT)
charge-coupled device
cloud
cloud storage
cluster
compact disc (CD)
consumables
cost per page
cylinder
digital camera
digital versatile disc (DVD)
digital video camera
digital whiteboard
digitize
direct thermal printer
direct-attached storage (DAS)
disk
display adapter
display screen
dithering
document feeder
