Operating instructions

and a common security policy. On the Internet, a domain is a group of computers
that share a common element in their hierarchical name. Other types of domains
exist—e.g., collision domain.
domain controller A Microsoft Windows NT machine that stores the user
and server account information for its domain in a database called a SAM (secu
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rity accounts manager) database.
DOS (Disk Operating System) The first popular operating system available
for PCs. It was a text-based, single-tasking operating system that was not com
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pletely replaced until the introduction of Windows 95.
DOS prompt A symbol, usually a letter representing the disk drive followed by
the greater-than sign (>), which tells you that the operating system is ready to
receive a command. Windows systems use the term command prompt rather
than DOS prompt.
DOSKEY A DOS utility that enables you to type more than one command on
a line, store and retrieve previously used command-line commands, create
stored macros, and customize all commands. DOSKEY is still supported in
Windows XP.
dot pitch A value relating to CRTs, showing the diagonal distance between
phosphors measured in millimeters.
dot-matrix printer A printer that creates each character from an array of dots.
Pins striking a ribbon against the paper, one pin for each dot position, form the
dots. The printer may be a serial printer (printing one character at a time) or a
line printer.
double word A unit of 32 binary digits; four bytes.
double-side high density A type of floppy disk that is capable of holding 1.2
MB on a 5.25-inch disk and 1.44 MB on a 3.5-inch disk. This format can be read
in all modern floppy disk drives.
double-sided RAM A RAM stick with RAM chips soldered to both sides of
the stick. May only be used with motherboards designed to accept double-sided
RAM. Very common.
downstream A term used to define the part of a USB connection that plugs
into a USB device.
GLOSSARY 23
Passport / Mike Meyers‘ A+ Certification Passport / Meyers / 226308-3 / Glossary
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