Computer Glossary D
DDR RAM double data rate RAM. A kind of memory that can
handle data at twice the speed of SDRAM (static dynamic RAM).
Device Driver A program that controls a device which is attached
to a PC, such as a printer, modem, monitor, graphics card or
CD-ROM drive, and enables your PC to interact with it. Windows
comes with many popular device drivers already included.
Dimm dual inline memory module. A memory board that is
effectively a double Simm (the preceding standard of memory
board, that had to be installed in pairs). It uses a 168-pin
connector, and its 64bit-wide bus allows single modules to be
installed in Pentium systems.
Dithering A printing process that involves simulating additional
colours or shades by mixing available colours and varying dot
sizes and spacing.
DLL dynamic link library. A program module that contains
instructions common to different applications. Instead of
including all these instructions in each program, the DLL can be
called as required, loaded into memory and run. As the link is
dynamic, the majority of DLLs can be unloaded when no longer
needed, saving memory resources.
DMA direct memory access. A process for data retrieval from
a device such as a hard disk that writes information into main
memory without involving the processor, thus freeing it up for
other tasks.
Dot Pitch A measurement, usually in millimetres, that indicates
the diagonal distance between like-coloured phosphor dots on
a monitor. The lower the number the higher the image intensity.
DPI dots per inch. A measurement of image intensity.
Higher-intensity graphics and images will be smoother and
better defined.
DPOF digital print order format. A format used for recording
information from a digital camera to storage media. It allows
the user to specify what shots they want and in what order.
DRAM The most common and cheapest form of computer
memory, which uses one capacitor and transistor to store one
bit of information. It is ‘volatile’ memory, so if you turn off the
power you will lose any stored data.
Dualhead A graphics card capability that allows you to
connect two monitors to the same PC and double the amount
of workspace.
DVI digital visual interface. A kind of interface between
PCs and flat-panel monitors. Digital means that the monitor
and PC communicate in digital signals, rather than having
to translate between analogue and digital, providing
steadier images.
DVD digital versatile disc. A high-capacity CD-ROM disc that
can store up to 17GB of data. The latest discs have two layers
and DVD drives use a laser with two focal points to read each
one. Each layer holds 4.7GB, so a dual-layer, dual-sided disc
will store 17GB of data.
DVD-RAM Commonly houses its discs in protective caddies like
a large floppy. Your PC treats DVD-RAM drives as both optical
and removable drives. It’s therefore possible for users running
Windows XP to drag files on and off a DVD-RAM in Windows
Explorer as if it were a huge Zip disk.
DVD-R Essentially a higher capacity version of CD-R, its blank
discs can store up to 4.7GB each. Like CD-R you can only use
one side and record on them once, but the big bonus is that
thanks to higher reflectivity, they appear to work in virtually all
DVD-ROM drives.
DVD-RW and DVD+RW The former is pronounced ‘minus RW’.
Both use bare discs that can store up to 4.7GB on one side
only, and require writing software – just like a higher-capacity
version of CD-RW.
|
