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178 Glossary
suppression and may also provide voltage regulation.
Small UPS systems provide battery power for a few
minutes to enable you to shut down your computer.
USB — universal serial bus — A hardware interface for a
low-speed device such as a USB-compatible keyboard,
mouse, joystick, scanner, set of speakers, printer,
broadband devices (DSL and cable modems), imaging
devices, or storage devices. Devices are plugged directly in
to a 4-pin socket on your computer or in to a multi-port
hub that plugs in to your computer. USB devices can be
connected and disconnected while the computer is turned
on, and they can also be daisy-chained together.
UTP — unshielded twisted pair — Describes a type of
cable used in most telephone networks and some
computer networks. Pairs of unshielded wires are twisted
to protect against electromagnetic interference, rather
than relying on a metal sheath around each pair of wires to
protect against interference.
UXGA — ultra extended graphics array — A video
standard for video cards and controllers that supports
resolutions up to 1600 x 1200.
V
video controller — The circuitry on a video card or on the
system board (in computers with an integrated video
controller) that provides the video capabilities—in
combination with the monitor—for your computer.
video memory — Memory that consists of memory chips
dedicated to video functions. Video memory is usually
faster than system memory. The amount of video memory
installed primarily influences the number of colors that a
program can display.
video mode — A mode that describes how text and
graphics are displayed on a monitor. Graphics-based
software, such as Windows operating systems, displays in
video modes that can be defined as x horizontal pixels by y
vertical pixels by z colors. Character-based software, such
as text editors, displays in video modes that can be
defined as x columns by y rows of characters.
video resolution — See resolution.
virus — A program that is designed to inconvenience you
or to destroy data stored on your computer. A virus
program moves from one computer to another through an
infected disk, software downloaded from the Internet, or
e-mail attachments. When an infected program starts, its
embedded virus also starts.
A common type of virus is a boot virus, which is stored in
the boot sectors of a floppy disk. If the floppy disk is left in
the drive when the computer is shut down and then
turned on, the computer is infected when it reads the
boot sectors of the floppy disk expecting to find the
operating system. If the computer is infected, the boot
virus may replicate itself onto all the floppy disks that are
read or written in that computer until the virus is
eradicated.
V — volt — The measurement of electric potential or
electromotive force. One V appears across a resistance of
1 ohm when a current of 1 ampere flows through that
resistance.
W
W — watt — The measurement of electrical power.
One W is 1 ampere of current flowing at 1 volt.
WHr — watt-hour — A unit of measure commonly used
to indicate the approximate capacity of a battery. For
example, a 66-WHr battery can supply 66 W of power for
1 hour or 33 W for 2 hours.
wallpaper — The background pattern or picture on the
Windows desktop. Change your wallpaper through the
Windows Control Panel. You can also scan in your favorite
picture and make it wallpaper.
write-protected — Files or media that cannot be changed.
Use write-protection when you want to protect data from
being changed or destroyed. To write-protect a 3.5-inch
floppy disk, slide its write-protect tab to the open
position.
WXGA — wide-aspect extended graphics array — A video
standard for video cards and controllers that supports
resolutions up to 1280 x 800.