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Glossary 313
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.