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Glossary 65
BTU — British thermal unit — A measurement of
heat output.
bus — A communication pathway between the
components in your computer.
bus speed — The speed, given in MHz, that indicates
how fast a bus can transfer information.
byte — The basic data unit used by your computer. A
byte is usually equal to 8 bits.
C
C — Celsius — A temperature measurement scale
where 0° is the freezing point and 100° is the boiling
point of water.
cache — A special high-speed storage mechanism
which can be either a reserved section of main
memory or an independent high-speed storage device.
The cache enhances the efficiency of many processor
operations.
L1 cache — Primary cache stored inside the
processor.
L2 cache — Secondary cache which can either be
external to the processor or incorporated into the
processor architecture.
carnet — An international customs document that
facilitates temporary imports into foreign countries.
Also known as a merchandise passport.
CD-R — CD recordable — A recordable version of a
CD. Data can be recorded only once onto a CD-R.
Once recorded, the data cannot be erased or written
over.
CD-RW — CD rewritable — A rewritable version of a
CD. Data can be written to a CD-RW disc, and then
erased and written over (rewritten).
CD-RW drive — A drive that can read CDs and write
to CD-RW (rewritable CDs) and CD-R (recordable
CDs) discs. You can write to CD-RW discs multiple
times, but you can write to CD-R discs only once.
CD-RW/DVD drive — A drive, sometimes referred to
as a combo drive, that can read CDs and DVDs and
write to CD-RW (rewritable CDs) and CD-R
(recordable CDs) discs. You can write to CD-RW
discs multiple times, but you can write to CD-R discs
only once.
clock speed — The speed, given in MHz, that
indicates how fast computer components that are
connected to the system bus operate.
COA — Certificate of Authenticity — The Windows
alpha-numeric code located on a sticker on your
computer. Also referred to as the Product Key or
Product ID.
Control Panel — A Windows utility that allows you
to modify operating system and hardware settings,
such as display settings.
controller — A chip that controls the transfer of data
between the processor and memory or between the
processor and devices.
CRIMM — continuity rambus in-line memory
module — A special module that has no memory
chips and is used to fill unused RIMM slots.
cursor — The marker on a display or screen that
shows where the next keyboard, touch pad, or mouse
action will occur. It often is a blinking solid line, an
underline character, or a small arrow.
D
DDR SDRAM — double-data-rate SDRAM — A type
of SDRAM that doubles the data burst cycle,
improving system performance.
DDR2 SDRAM — double-data-rate 2 SDRAM — A
type of DDR SDRAM that uses a 4-bit prefetch and
other architectural changes to boost memory speed to
over 400 MHz.
device — Hardware such as a disk drive, printer, or
keyboard that is installed in or connected to your
computer. device driver — See driver.