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Glossary 173
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.
ScanDisk — A Microsoft utility that checks files, folders,
and the hard disk’s surface for errors. ScanDisk often runs
when you restart the computer after it has stopped
responding.
SCSI — small computer system interface — A high-speed
interface used to connect devices to a computer, such as
hard drives, CD drives, printers, and scanners. The SCSI
can connect many devices using a single controller. Each
device is accessed by an individual identification number on
the SCSI controller bus.
SDRAM — synchronous dynamic random-access memory
— A type of DRAM that is synchronized with the optimal
clock speed of the processor.
serial connector — An I/O port often used to connect