Specifications

Glossary
25
and time of creation, and a pointer to the location
of the file. Each entry in a directory is 32 bytes
long. Windows refers to subdirectories (directories
beneath the root directory) as folders.
DirectX A set of graphics-related drivers and
APIs that translates generic hardware commands
into specific commands for particular pieces of
hardware. Developed by Microsoft, DirectX lets
graphical or multimedia applications take advan-
tage of specific features supported by various
graphics accelerators.
disc Flat, circular, rotating medium that can store
various types of information, both analog and digi-
tal. Disc is often used in reference to optical storage
media, whereas disk refers to magnetic storage
media. Disc also is often used as a short form for
videodisc or compact audio disc (CD).
Disk At Once (DAO) A method of burning CDs
and DVDs where the entire disc is burned in a
single session.
disk Alternative spelling for disc that generally
refers to magnetic storage medium on which infor-
mation can be accessed at random. Floppy disks
and hard disks are examples.
disk access time See access time.
disk cache A portion of memory on the PC
motherboard or on a drive interface card or con-
troller used to store frequently accessed informa-
tion from the drive (such as the file allocation table
[FAT] or directory structure) to speed up disk access.
With a larger disk cache, additional data from the
data portion of a drive can be cached as well. See
also cache, L1 cache, and L2 cache.
disk partition See partition.
display A device used for viewing information
generated by a computer.
display adapter The interface between the
computer and the monitor that transmits the sig-
nals which appear as images on the display. This
can take the form of an expansion card or a chip
built into the motherboard.
dithering The process of creating more colors
and shades from a given color palette. In mono-
chrome displays or printers, dithering varies the
black-and-white dot patterns to simulate shades of
gray. Grayscale dithering is used to produce differ-
ent shades of gray when the device can produce
only limited levels of black or white outputs. Color
screens or printers use dithering to create addi-
tional colors by mixing and varying the dot sizing
and spacing. For example, when converting from
24-bit color to 8-bit color (an 8-bit palette has only
256 colors compared to the 24-bit palette’s mil-
lions), dithering adds pixels of different colors to
simulate the original color. Error diffusion is a type
of dithering best suited for photographs.
DLC (Data Link Control) Refers to the Data
Link Layer in the OSI model. Every network inter-
face card (NIC) has a unique DLC address or DLC
identifier (DLCI) that identifies the node on the
network. For Ethernet networks, the DLC address is
usually called the Media Access Control (MAC)
address.
DLL (Dynamic Link Library) An executable
driver program module for Microsoft Windows that
can be loaded on demand, linked in at runtime,
and subsequently unloaded when the driver is no
longer needed.
DLT (digital linear tape) A tape drive technol-
ogy that writes data in multiple linear tracks as tape
is wound forward and backward. Supports native/
2:1 compressed capacities of up to 80/160GB. See
also Super DLT (SDLT).
DMA See direct memory access.
DMI (Desktop Management Interface) DMI
is an operating-system– and protocol-independent
standard developed by the Desktop Management
Task Force (DMTF) for managing desktop systems
and servers. DMI provides a bidirectional path to
interrogate all the hardware and software compo-
nents within a PC, enabling hardware and software
configurations to be monitored from a central sta-
tion in a network.
DNS (domain name system or service) An
Internet service that translates domain names into
numeric IP addresses. Every time you use a domain
name, a DNS server must translate the name into
the corresponding IP address.
docking station Equipment that enables a lap-
top or notebook computer to use peripherals and
accessories normally associated with desktop
systems.
Appendix A
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