Operating instructions

virtual memory A section of a system’s hard drive that is set aside to be used
when physical memory is unavailable or completely in use.
virus A program that can make a copy of itself without you necessarily being
aware of it; some viruses can destroy or damage files, and generally the best
protection is always to maintain backups of your files.
virus definition or data file These files are also called signature files depend
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ing on the virus protection software in use. These files enable the virus protec
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tion software to recognize the viruses on your system and clean them. These files
should be updated often.
VIS (viewable image size) A measurement of the viewable image that is dis
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played by a CRT rather than a measurement of the CRT itself.
voice coil motor A type of motor used to spin hard drive platters.
volatile Memory that must have constant electricity in order to retain data.
Alternatively, any programmer six hours before deadline after a non-stop,
48-hour coding session, running on nothing but caffeine and sugar.
volts (V) The pressure of the electrons passing through a wire is called voltage
and is measured in units called volts (V).
volume A physical unit of a storage medium, such as tape reel or disk pack,
that is capable of having data recorded on it and subsequently read. Also refers
to a contiguous collection of cylinders or blocks on a disk that are treated as a
separate unit.
volume boot sector The first sector of the first cylinder of each partition has a
boot sector called the volume boot sector, which stores information important
to its partition, such as the location of the operating system boot files.
VRAM (video RAM) A type of memory in a video display adapter that’s used
to create the image appearing on the CRT screen. VRAM uses dual-ported
memory, which enables simultaneous reads and writes, making it much quicker
than DRAM.
VRM (voltage regulator module) A small card supplied with some CPUs to
ensure that the CPU gets correct voltage. This type of card, which must be used
with a motherboard specially designed to accept it, is not commonly seen today.
GLOSSARY 71
Passport / Mike Meyers‘ A+ Certification Passport / Meyers / 226308-3 / Glossary
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