Users Guide

Glossary 13
• It resides on a physically write-
protected diskette.
• It is located on a network in a
directory to which the system
administrator has assigned read-
only rights to you.
real mode
An operating mode supported by 80286
or higher microprocessors, real mode
imitates the architecture of an 8086
microprocessor. Designed to run in real
mode, MS-DOS (unassisted by additional
software techniques) can address only
640 KB of conventional memory.
refresh rate
The frequency, measured in Hz, at which
the screen’s horizontal lines are re-
charged. A monitor’s refresh rate is also
referred to as its vertical frequency.
REN
Abbreviation for ringer equivalence
number.
RFI
Abbreviation for radio frequency
interference.
RGB
Abbreviation for red/green/blue.
ROM
Acronym for read-only memory. Your
computer contains some programs es-
sential to its operation in ROM code.
Unlike RAM, a ROM chip retains its
contents even after you turn off your com-
puter. Examples of code in ROM include
the program that initiates your computer’s
boot routine and the POST.
rpm
Abbreviation for revolutions per minute.
RTC
Abbreviation for real-time clock. Battery-
powered clock circuitry inside the com-
puter that keeps the date and time after
you turn off the computer.
SCSI
Acronym for small computer system in-
terface. An I/O bus interface with faster
data transmission rates than standard
ports. You can connect up to seven devic-
es to one SCSI interface.
SDMS
Abbreviation for SCSI device management
system.
SDRAM
Abbreviation for synchronous dynamic
random-access memory.
SEC
Abbreviation for single-edge connector
cartridge.
sec
Abbreviation for second(s).
serial port
An I/O port used most often to connect a
modem or a mouse to your computer. You
can usually identify a serial port on your
computer by its 9-pin connector.
shadowing
A computer’s system and video BIOS
code is usually stored on ROM chips.
Shadowing refers to the performance-
enhancement technique that copies BIOS
code to faster RAM chips in the upper
memory area (above 640 KB) during the
boot routine.
SRAM
Abbreviation for static random-access
memory. Because SRAM chips do not
require continual refreshing, they are sub-
stantially faster than DRAM chips. SRAM
is used mostly for external cache
memory.
striping
In composite drivers with two or more
physical drives, the drive array sub-
system uses a method of data storage
called striping. With this method, data is
divided into a series of pieces called
blocks and each data block is stored on a
different physical drive. When each drive
contains a block of data, the process