Glossary 179
PIO — programmed input/output — A method of
transferring data between two devices through the
processor as part of the data path.
pixel — A single point on a display screen. Pixels are
arranged in rows and columns to create an image. A video
resolution, such as 800 x 600, is expressed as the number
of pixels across by the number of pixels up and down.
Plug-and-Play — The ability of the computer to
automatically configure devices. Plug and Play provides
automatic installation, configuration, and compatibility
with existing hardware if the BIOS, operating system, and
all devices are Plug and Play compliant.
POST — power-on self-test — Diagnostics programs,
loaded automatically by the BIOS, that perform basic tests
on the major computer components, such as 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.
RAID — redundant array of independent disks — A
method of providing data redundancy. Some common
implementations of RAID include RAID0, RAID 1,
RAID5, 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
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
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
10kHz 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.
SAS — serial attached SCSI — A faster, serial version of
the SCSI interface (as opposed to the original SCSI
parallel architecture). Page 179 Monday, February 6, 2006 2:24 PM