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Glossary 71
memory, hard drives, and video. If no problems are
detected during POST, the computer continues the
start-up.
processor — A computer chip that interprets and
executes program instructions. Sometimes the
processor is referred to as the CPU (central processing
unit).
PS/2 — personal system/2 — A type of connector for
attaching a PS/2-compatible keyboard, mouse, or
keypad.
PXE — pre-boot execution environment — A WfM
(Wired for Management) standard that allows
networked computers that do not have an operating
system to be configured and started remotely.
R
RAID — redundant array of independent disks — A
method of providing data redundancy. Some
common implementations of RAID include RAID 0,
RAID 1, RAID 5, RAID 10, and RAID 50.
RAM — random-access memory — The primary
temporary storage area for program instructions and
data. Any information stored in RAM is lost when you
shut down your computer.
readme file — A text file included with a software
package or hardware product. Typically, readme files
provide installation information and describe new
product enhancements or corrections that have not
yet been documented.
read-only — Data and/or files you can view but
cannot edit or delete. A file can have read-only status
if:
• It resides on a physically write-protected floppy disk,
CD, or DVD.
• It is located on a network in a directory and the
system administrator has assigned rights only to
specific individuals.
refresh rate — The frequency, measured in Hz, at
which your screen's horizontal lines are recharged
(sometimes also referred to as its vertical frequency).
The higher the refresh rate, the less video flicker can
be seen by the human eye.
resolution — The sharpness and clarity of an image
produced by a printer or displayed on a monitor. The
higher the resolution, the sharper the image.
RFI — radio frequency interference — Interference
that is generated at typical radio frequencies, in the
range of 10 kHz to 100,000 MHz. Radio frequencies
are at the lower end of the electromagnetic frequency
spectrum and are more likely to have interference
than the higher frequency radiations, such as infrared
and light.
ROM — read-only memory — Memory that stores
data and programs that cannot be deleted or written
to by the computer. ROM, unlike RAM, retains its
contents after you shut down your computer. Some
programs essential to the operation of your computer
reside in ROM.
RPM — revolutions per minute — The number of
rotations that occur per minute. Hard drive speed is
often measured in rpm.
RTC — real time clock — Battery-powered clock on
the system board that keeps the date and time after
you shut down the computer.
RTCRST — real-time clock reset — A jumper on the
system board of some computers that can often be
used for troubleshooting problems.
S
SAS — serial attached SCSI — A faster, serial version
of the SCSI interface (as opposed to the original SCSI
parallel architecture).
SATA — serial ATA — A faster, serial version of the
ATA (IDE) interface.