DAC: Digital/Analog Converter. The chip that converts a
digital signal into an appropriate analog signal. Higher bits--i.e. 18, 20,
24--give you theoretical better resolution.
daisy-chained: Devices connected in a series, with each
device serving as a data conduit for the next device in the chain. This precludes
the need to connect each individual device to a central computer or hub.
DAT: Digital Audio Tape. A magnetic storage device. The
first implementation of consumer and semi-professional stereo digital recordable
audio. Still a popular format among musicians.
data degradation: What happens when the video signal loses
digital picture information.
data packet: A piece of a message transmitted over a packet-switching
network. A packet contains the destination address in addition to the data.
Data packets are often called datagrams in IP networks.
data rate: The amount of raw data transferred over the
pipeline. Generally, data rates in hard drives are referred to in MB/sec.
The higher the transfer rate the better. Because data is stored in a buffer
on the drive, it is important to know both the data rate the recording head
is capable of as well as the "burst transfer rate" at which data is sent from
the drive to the outside world.
data striping: Interleaving data by bytes or sectors across
multiple hard drives to improve performance.
data visualization: The translation of numeric data into
a visual picture that helps the human eye pick out patterns in the numbers
that are not as easy to pick out when looking at the raw data. Graphing spreadsheet
data in Excel is a simple form of data visualization.
database integration: When a web site uses a database back-end
to store information, database integration refers to how a web interface can
access that information.
daughtercard: A circuit board that plugs into a larger
circuit board. The main circuit board inside a PC is known as the "motherboard"
or "mainboard"; an example of a daughtercard is a Pentium II or Celeron cartridge.
(The daughtercard is inside the cartridge housing.) PCI cards generally aren't
called daughtercards, though.
deathmatch: A term used to describe any multiplayer gaming
scenario where the object of the game is to kill as many of your opponents
as possible. Made popular in id's first-person shooters Doom and Quake.
decompressors: A routine or program that restores compressed
data back to its original size.
dedicated frame buffer: Video processors need a specific
chunk of memory dedicated for frame-buffer/z-buffer data storage. Often used
when describing a split-memory architecture, where the 3D architecture needs
two independent chunks of memory-one for the frame-buffer, the other for texture
storage. 3Dfx's Voodoo/Voodoo2 and Intel's i740 are examples of cards requiring
a dedicated frame buffer. All other cards use a unified memory architecture.
deformable: Able to be bent, twisted, etc.
deformation lattice modeling: Altering the shape of a 3D
object using an imaginary lattice of points surrounding the object to be modeled.
By moving the lattice, a force is exerted on the object itself causing it
to deform.
depth of field: The range of distance that a camera can
acquire objects in sharp focus--objects outside of this range will be blurred.
An important cue and method for improving realism in computer generated scenes.
development tool: A program that programmers use to write
programs. Dev tools come in many forms, but often include a text editor (for
entering source code), a compiler (for converting source code into object
code), and a debugger (for finding and fixing bugs).
DHCP: Dynamic Host Control Protocol. DHCP is used to dynamically
assign IP addresses to machines. Utilizing a DHCP server
greatly decreases the workload of Windows NT administrators, since it automatically
assigns all the TCP/IP information required by a machine. It also allows them
to manage their entire collection of IP addresses in one place. You may be
familiar with the infamous Windows message that asks "Obtain an IP address
from a DHCP server?"
dial-up connection: A connection to a remote network (such
as the Internet) through an analog modem over an ordinary telephone line.
It's a slower and less convenient connection than a direct digital hookup,
such as an ISDN, ADSL, or cable modem.
die: The actual square piece of silicon that contains integrated
circuits.
diffuse tail: As the echoes of reverberation build up on
each other, the reverberation quickly reaches a crescendo, then dies away.
The trailing end of the reverberation of a sound (particularly a sharp sound
like a single hand-clap) becomes composed of so many echoes it sounds noise-like
and "diffuse" as it decays to zero. Acousticians refer to this as the "diffuse
tail" of the reverberation response.
digital audio: Digital or Redbook audio is the audio standard
used to notch the tracks of commercial CDs.
Digital Video Disc-Read Only Memory: The next-generation
CD-ROM standard. A single-sided DVD-ROM media can hold up to 4.7GB, with double-sided
media holding twice that.
digital zoom: Method of magnifying a digital image that
does not employ optical magnification via lens differential. Instead, image
data is interpolated up from existing data.
digital zoomed video: A standard for sending high-bandwidth video directly
to the display adapter and bypassing the CPU and system bus.
Digital/Analog Converter: A device that converts a digital
signal into an appropriate analog signal. It is often used by videocards in
the last stage of the pipeline, when the digital content must be converted
into an analog signal so the device downstream (your monitor) can display
it properly. A higher DAC/ADC, such as 18-bit or 20-bit, means better resolution
when converting digital signals to analog.
DIMM: Dual Inline Memory Module. A DIMM is a RAM module
configuration that allows dual channels to be used in a single interface.
On a motherboard's, that would be dual 32-bit memory paths forming a single
64-bit path. Before DIMMs, RAM modules came in SIMMs (Single Inline Memory
Modules), which provided a single 32-bit path. With most SIMM motherboards,
memory modules needed to be installed in pairs. DIMMs can be installed individually.
DIMMs tend to be faster and hold more memory than their SIMM counterparts.
DIP switch: Dual Inline Package switch. A tiny switch that
manually controls some function of a computer device. DIP switches are often
found on disk drives, printers, and motherboards.
Direct Memory Execution: A term specific to AGP, this describes
a videocard 3D chipset's ability to store textures in a computer's system
memory and directly perform texture processing from this storage place. Under
all other conditions, textures are first stored in your computer's system
memory--when it's needed, the card grabs the texture, stores it in the videocard's
local memory, then processes it. Direct memory execution bypasses the second,
local-video texture-memory storage step. In effect, the videocard will treat
your system memory as more local video memory, thus opening the way for massive
texture storage. How much system memory is allocated for AGP textures is determined
by BIOS settings.
Direct RAMBUS: Short for Direct Rambus DRAM (developed
by Rambus, Inc), RAMBUS is a new high-speed memory technology that can transfer
data at 600MHz. Both Intel and AMD would like to use this memory with their
CPUs, but manufacturing problems are slowing the memory type's introduction.
Direct RDRAM: See RDRAM.
DirectInput: Falls under the umbrella of Microsoft's DirectX, an API used
by developers to create great games. DirectInput in particular allows for
better mouse and joystick interactivity.
DirectSound: A Microsoft API that is part of the DirectX
package and eases the burden on game developers. Games send their audio output
to the DirectSound "port," where a Windows 95Ðcompatible soundcard is listening
and plays the appropriate sound. This helps with compatibility because developers
no longer need to be concerned with what soundcard an end user has, as was
typical in the DOS days. They can be assured that any properly configured
card will work with their game.
DirectSound3D: Microsoft's API for handling 3D positional
sound. Plagued by problems when originally introduced, it has improved greatly
and is beginning to generate more developer support.
Direct3D: A subset of Microsoft's DirectX Application Program
Interface. This interface allows developers to use hardware acceleration for
3D graphics, which helps games run faster by offloading the 3D processing
onto a dedicated piece of hardware.
DirectX: A collection of Application Programming Interfaces
(APIs) developed by Microsoft. This driver model helps create a unified multimedia
platform on PCs. Parts include Direct3D, DirectSound, DirectInput, DirectDraw,
and DirectPlay. Multimedia developers can theoretically write to the standard
DirectX API and know hardware that supports it will work instead of writing
to individual hardware APIs. It also allows graphics applications to take
advantage of hardware acceleration supported by graphics accelerators.
Disc-at-Once: A method of writing CDs where one or more
tracks are written in a single operation without turning off the laser.
disk cache: Memory located internally on a hard drive that's
used to bridge data between the drive and the interface. This cache memory
is much faster than the mechanical drive and is used to store data that has
been previously read. So when data is requested, the cache is checked first
before checking the actual drive.
displacement map: In the context of bump-mapping, a black-and-white
map that describes how bumpiness will be simulated via shadowing.
distortion: A change in an audio signal from input to output.
Typically a change in level, or a fixed delay, is not considered a distortion,
but any change that introduces new frequencies of sound is considered distortion.
dithered textures: When an image's color depth is lowered
from a higher count to a lower count, it is said to be dithered down. When
this happens, any lost color data may be seen by the naked eye as dotted patterns
or extraneous artifacts.
dithering: When an image's color depth is lowered from
a higher count to a lower count, it is said to be dithered down. When this
happens, any lost color data may be seen by the naked eye as dotted patterns
or extraneous artifacts.
DLL: Dynamic Link Library. An indispensable little nugget
of software that gets deposited surreptitiously on your hard drive and makes
everything melt down when it's unintentionally uninstalled.
DLS: Downloadable Sample. Although not fully supported
by Microsoft yet, DLS will offer more consistent music and sounds. Because
different soundcard manufacturers use different MIDI patches, developers can
never be sure how music will sound. With Microsoft's forthcoming DirectMusic
standard, game developers will be able to create their own patches and issue
them with software for better uniformity.
DMA: Direct Memory Access. A method used to speed up data
transfers between peripherals (such as hard drives) and RAM. DMA avoids the
delays imposed by the CPU's data-flow regulation, accessing RAM directly.
DME: see Direct Memory Execution
Document Type Definition: A file associated with an XML
document that defines the format of the document's tags. XML is an extensible
metalanguage that allows anyone to define new tags, so a DTD declares how
those tags should work. An XML document can refer to a public DTD at any URL
on the Internet.
Dolby Digital 5.1: A digital surround-sound audio specification
that provides for six discrete channels, including two rear-placement effects
channels and a low-frequency effects channel.
Dolby Surround Sound: A digital audio spec defined by four
discrete sound channels: independent left, middle, and right channels positioned
in front of the listener, and a single rear effects channel emanating from
two rear speakers positioned on the left and right behind the listener.
D1: Otherwise known as Serial Digital. It is an uncompressed
video form.
dongle: A security or copy protection device that must be
connected to an I/O port of the computer while the application is run.
doppler: shift In the sound realm, a doppler shift is the
apparent frequency shift you hear as an object approaches and passes, such
as a train passing by and diminishing as it moves past you.
DOS partition: A special section of the hard drive that
uses the traditional Disk Operating System instead of a Windows-based operating
system. Disk drives can have multiple partitions, each of which are assigned
a separate drive letter (C:\, D:\, E:\).
double data rate: SDRAM Also know as DDR SDRAM. A type
of memory that can transfer data on both edges of the clock cycle--for, you
guessed it, double the performance.
double-precision floating point: A floating-point number
represented in a computer by 64 binary digits (bits). Commonly used in financial,
scientific, and technical applications.
downsample: Process of taking a file with more resolution
and eliminating unnecessary data to achieve a smaller file.
drive: head see heads
drive cache: A small amount of memory installed in a hard
drive or CD-ROM drive that stores recently accessed data. When a program looks
to a drive for fodder to chew on, it first turns to the cache. Retrieving
data from solid-state cache is much faster than retrieving data from a mechanical
drive.
driver: The closest layer of software between an operating
system and a piece of hardware. It's often what makes or breaks your OS.
DSL: Digital Subscriber Line. A broadband Internet technology
that wrings fast-speed access from regular, old telephone lines.
DSP: Digital Signal Processor. A special type of microprocessor
chip that's optimized for performing repetitive operations on large sets of
data. DSPs are often used for communications, networking, multimedia, and
other specialized tasks.
D3D: See Direct3D
DTMF: Dual Tone Multi-Frequency. The system used by touch-tone
telephones. DTMF assigns a specific frequency, or tone, to each key so that
a microprocessor can easily identify it.
dual-pipeline: Refers to the number of processors in a
graphics engine. See single cycle for more information.
dual-Scan Line Interleave: see Scan Line Interleave
dual 32-bit graphics pipeline: Refers to the number of
processors, and the data bit width, of a graphics processor. See single-rendering
cycle for more information.
dual-TMU: Refers to the Dual Texture Management Units that
handle the multitexturing duties in the Voodoo architecture.
dual voice coil: Used to describe a speaker design where
the manufacturer winds two sets of wires (the voice coil) in a speaker. Normally,
a speaker uses only one voice coil, but in bass/subwoofer situations, a dual-voice-coil
scenario helps with power handling.
DualBus: Specifically refers to the two independent 128-bit
processing pipelines working inside the Matrox G400 graphics processor.
DVD: Digital Versatile Disc. It's the next-generation CD-ROM,
storing more data per disc, and also a possible replacement for videotapes,
especially in the rental business. By using multiple layers and both sides
of a disc, DVD can store 4.7GB to 17GB of data, while CDs are limited to a
maximum 682MB.
DVD +RW: A DVD rewritable format based on CD patents from
Sony and Philips that uses CD-RW phase-change technology. It is formerly known
as +RW and is not a DVD Forum-approved specification. It has a capacity of
3GB for a single-sided discs and 6GB for a dual-sided discs. It should be
available in early 1999.
DVD Hardware Decoder: A physical card inserted into a PCI
slot whose sole purpose is to decode MPEG-2 video streamed to it via a DVD
drive, taking the pressure off the CPU.
DVD-ROM: see Digital Video Disc-Read Only Memory.
dynamic attachment: Attaching a skin (or object) to another object. Wrapping
a soft skin around the skeleton avoids the problem of showing joints (holes
where the pieces meet).
Dynamic HTML: HTML for 4.0 and later browsers that allows web pages to become more "interactive" via animations and other effects. These browser-specific behaviors are based on the following standards: Document Object Model (DOM), HTML, Cascading Style Sheets (CSS), and EcmaScript (standardized JavaScript).