Specifications

Glossary
51
CMOS NVRAM is used in IBM-compatible systems
to store configuration information. True NVRAM
often is used in intelligent modems to store a user-
defined default configuration loaded into normal
modem RAM at power-up.
nonvolatile RAM disk A RAM disk powered by
a battery supply so that it continues to hold its
data during a power outage.
North Bridge The Intel term for the main por-
tion of the motherboard chipset that incorporates
the interface between the processor and the rest
of the motherboard. The North Bridge contains the
cache, main memory, and AGP controllers, as well
as the interface between the high-speed (normally
66MHz or 100MHz) processor bus and the 33MHz
PCI (peripheral component interconnect) or 66MHz
AGP (accelerated graphics port) buses. The func-
tional equivalent of the North Bridge on the latest
8xx-series chipsets from Intel is the MCH. See also
chipset, ICH, MCH, and South Bridge.
notebook computer A very small personal
computer approximately the size of a notebook.
NTSC The National Television Standards
Committee, which governs the standard for televi-
sion and video playback and recording in the
United States. The NTSC was originally organized
in 1941 when TV broadcasting first began on a
wide scale in black and white, and the format was
revised in 1953 for color. The NTSC format has 525
scan lines, a field frequency of 60Hz, a broadcast
bandwidth of 4MHz, a line frequency of 15.75KHz,
a frame frequency of 1/30 of a second, and a color
subcarrier frequency of 3.58MHz. It is an interlaced
signal, which means it scans every other line each
time the screen is refreshed. The signal is generated
as a composite of red, green, and blue signals for
color and includes an FM frequency for audio and a
signal for stereo. See also PAL and SECAM, which
are incompatible systems used in Europe. NTSC is
also called composite video.
null modem A serial cable wired so that two data
terminal equipment (DTE) devices, such as personal
computers, or two data communication equipment
(DCE) devices, such as modems or mice, can be con-
nected. Also sometimes called a modem-eliminator or
a LapLink cable. To make a null-modem cable with
DB-25 connectors, you wire these pins together: 1-1,
2-3, 3-2, 4-5, 5-4, 6-8-20, 20-8-6, and 7-7.
numeric coprocessor See math coprocessor.
NVRAM (nonvolatile random access mem-
ory) See nonvolatile memory (NVRAM).
object hierarchy Occurs in a graphical program
when two or more objects are linked and one
object’s movement is dependent on the other
object. This is known as a parent-child hierarchy. In
an example using a human figure, the fingers
would be child objects to the hand, which is a
child object to the arm, which is a child to the
shoulder, and so on. Object hierarchy provides
much control for an animator in moving complex
figures.
OC (optical carrier) rates Various data rates
for optical fiber used in Internet backbones, based
on the OC-1 rate of 51.84Mbps. Multiply the OC
rate by 51.84Mbps to derive the data rate. For
example, OC-12 is 622.08Mbps (51.84×12).
Occam’s Razor Also spelled Ockham’s Razor;
popular name for the principle that the simplest
explanation is usually the correct one—a very use-
ful principle in computer troubleshooting.
OCR (optical character recognition) An
information-processing technology that converts
human-readable text into computer data. Usually a
scanner is used to read the text on a page, and OCR
software converts the images to characters.
Advanced OCR programs, such as OmniPage, can
also match fonts, re-create page layouts, and scan
graphics into machine-readable form.
ODI (Open Data-link Interface) A device dri-
ver standard from Novell that enables multiple pro-
tocols to run on the same network adapter card.
ODI adds functionality to Novell’s NetWare and
network computing environments by supporting
multiple protocols and drivers.
OEM (original equipment manufacturer)
Any manufacturer who sells its product to a reseller.
Usually refers to the original manufacturer of a par-
ticular device or component. Most HP hard disks,
for example, are made by Seagate Technologies,
who is considered the OEM. OEM products often
differ in features from retail products and can have
very short warranty periods if purchased separately
from their intended use.
Appendix A
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