Dell Latitude D820 Technical Manual page 115

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.