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D
Database
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DDR
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Default
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Defragment
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Degauss |
DHCP
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DIMM
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DLL |
DNS
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Domain Name
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Dongle
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Dot Pitch
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Download
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Driver
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DSL
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DVD
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DVI
Database
This is a data structure
used to store organized information. A database is typically
made up of many linked tables of rows and columns. For
example, a company might use a database to store information
about their products, their employees, and financial
information. Databases are now also used in nearly all
e-commerce sites to store product inventory and customer
information. Database software, such as Microsoft Access,
FileMaker Pro, and MySQL is designed to help companies and
individuals organize large amounts of information in a way
where the data can be easily searched, sorted, and updated.
While the first databases were relatively "flat" (limited to
simple rows and columns), today's relational databases allow
users to access, update, and search information based on the
relationship of data in one database to another. Certain
databases even let users store data such as sound clips,
pictures, and videos.
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DDR
Stands for "Double Data Rate." It is an advanced version of
SDRAM, a type of computer memory. DDR-SDRAM, sometimes called
"SDRAM II," can transfer data twice as fast as regular SDRAM
chips. This is because DDR memory can send and receive signals
twice per clock cycle. The efficient operation of DDR-SDRAM
makes the memory great for notebook computers since it uses up
less power.
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Default
This term is used to
describe a preset value for some option in a computer program.
It is the value used when a setting has not been specified by
the user. For example, the default font setting in Netscape
Communicator is "Times." If you don't go to the Netscape
preferences and change it to something else, the "Times" font
will be used -- by default. Typically, default settings are
set to what most people would choose anyway, so there's often
no reason to change them. However, if you're one of those
people who has to customize everything that you possibly can,
then you can go ahead and change all the default settings you
want.
"Default" can also be used as a verb. If a custom setting
won't work for some reason, the program will "default" to the
default setting. For example, say you're working on computer
that is on a network and you print something when there is no
printer specified. If you're lucky and don't get some nasty
error message, the print job will default to the default
printer and your work will be printed.
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Defragment
Defragmenting your hard
drive is a great way to boost the performance of your
computer. Though the term "defragment" sounds a little
abrasive, it is actually a simple and helpful process. After
all, a defragmented hard drive is a happy hard drive.
Adding and deleting files from your hard drive is a common
task. Unfortunately, this process is not always done very
efficiently. For example, when you delete a bunch of little
files and add a new large file, the file may get broken up
into multiple sections on the hard drive. The computer will
still read the newly added file as a single valid file, but it
will have to scan multiple parts of the drive to read it.
Because hard disk seek time is one of the biggest bottlenecks
in a computer's performance, this can drag down your
computer's speed quite a bit. If you have a ton of
"fragmented" files on your hard disk, you might hear extra
grinding, sputtering, and other weird noises coming from your
computer.
You computer doesn't like having fragmented files any more
than you do. This is why defragmenting your hard drive is such
a good idea. When you start to hear extra grinding sounds, or
your computer doesn't open files as quickly as it did before,
it's time to defragment. With Windows, you can use the
pre-installed Intel defragment program to defragment your hard
drive. You can also use a commercial software program like
Norton Utilities to defragment your hard drive more
efficiently and with more options. For Mac users, Norton
Utilities or another hard drive utility is the only way to do
it. If you use your computer daily, defragmenting your hard
drive once a month should keep the fragment-fiends away.
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Degauss
Ever wonder what that
"degauss" button on your monitor does besides make a buzzing
noise and cause the screen to go crazy for a second? Though
that's its main purpose, the degauss button has another useful
feature. To understand it, you'll first need to know that the
earth has natural magnetic fields. The magnetic charges from
these fields can build up inside your monitor, causing a loss
of color accuracy. Degaussing scares the bad magnetism out of
the monitor and fills it with good karma. If your monitor
doesn't have a degauss button, fear not -- many new monitors
automatically degauss themselves. If you have a flat-panel
display, there is no degauss button because magnetism doesn't
build up in flat screen displays.
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DHCP
Stands for "Dynamic Host Configuration Protocol." A network
server uses this protocol to dynamically assign IP addresses
to networked computers. The DHCP server waits for a computer
to connect to it, then assigns it an IP address from a master
list stored on the server. DHCP helps in setting up large
networks, since IP addresses don't have to be manually
assigned to each computer on the network. Because of the slick
automation involved with DHCP, it is the most commonly used
networking protocol.
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DIMM
Stands for "Dual In-Line Memory Module." It is a type of
computer memory. A DIMM is a small circuit board that holds
memory chips. It uses a 64-bit bus to the memory, whereas a
single in-line memory module (SIMM) only has a 32-bit path.
This allows DIMMs to transfer more data at once. Because DIMMs
have faster data transfer capabilities than SIMMs, they have
pretty much replaced SIMMs.
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DLL
Stands
for "Dynamic Link Library." A DLL (.dll) file contains a
library of functions and other information that can be
accessed by a Windows program. When a program is launched,
links to the necessary .dll files are created. If a static
link is created, the .dll files will be in use as long as the
program is active. If a dynamic link is created, the .dll
files will only be used when needed. Dynamic links help
programs use resources, such as memory and hard drive space,
more efficiently.
DLL files can also be used by more than one program. In fact,
they can even be used by multiple programs at the same time.
Some DLLs come with the Windows operating system while others
are added when new programs are installed. You typically don't
want to open a .dll file directly, since the program that uses
it will automatically load it if needed. Though DLL filenames
usually end in ".dll," they can also end in .exe, .drv, and .fon,
just to make things more confusing.
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DNS
Stands for "Domain Name System." The primary purpose of DNS is
to keep Web surfers sane. Without DNS, we would have to
remember the IP address of every site we wanted to visit,
instead of just the domain name. Can you imagine having to
remember "17.254.3.183" instead of just "apple.com"? While I
have some Computer Science friends who might prefer this, most
people have an easier time remembering simple names.
The reason the Domain Name System is used is because Web sites
are actually located by their IP addresses. For example, when
you type in "http://www.adobe.com," the computer doesn't
immediately know that it should look for Adobe's Web site.
Instead, it sends a request to the nearest DNS server, which
finds the correct IP address for "adobe.com." Your computer
then attempts to connect to the server with that IP number.
DNS is just another one of the many features of the Internet
that we take for granted.
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Domain
Name
This is the name that identifies an Web site. For example,
"microsoft.com" is the domain name of Microsoft's Web site. A
single Web server can serve Web sites for multiple domain
names, but a single domain name can point to only one machine.
For example, Apple Computer has Web sites at www.apple.com,
www.info.apple.com, and store.apple.com. Each of these sites
could be served on different machines.
Then there are domain names that have been registered, but are
not connected to a Web server. The most common reason for this
is to have e-mail addresses at a certain domain name without
having to maintain a Web site. In these cases, the domain name
must be connected to a machine that is running a mail server.
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Dongle
This funny-sounding computer term has two different meanings:
1. A
security key.
This is a little hardware device that plugs into the serial or
USB port of a computer. Its purpose is to ensure that only
authorized users can use certain software applications. If you
have never seen a dongle, don't be surprised. They are only
used with expensive, high-end software programs that most
people have never heard of, much less use. When a program that
comes with a dongle runs, it checks the dongle for
verification as it is loading. If it doesn't find the dongle,
the computer explodes. Well, not really -- usually the program
just quits. If more than one application requires a dongle,
multiple dongles using the same port can be daisy-chained
together. Basically, if you ever find yourself daisy-chaining
multiple dongles together, you must be doing pretty well in
life.
2. A
laptop Ethernet card adapter.
This is a little connector that attaches to a PC card in a
laptop on one end, and to an Ethernet cable on the other end.
Since most PC (or PCMCIA) network interface cards are too
small to connect directly to a standard RJ-45 Ethernet cable,
they need this little adapter that connects the card to the
cable. (3Com cards that use an "X-Jack" connector do not need
a dongle.) As far as why the name dongle is used, I have no
idea.
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Dot Pitch
This is the measurement used to determine how sharp the
display of a CRT (Cathode Ray Tube) monitor is. It is measured
in millimeters and the smaller the number, the finer the
picture. Most CRT monitors will have a dot pitch between .25
and .28. However, some large presentation monitors have dot
pitches from .30 to .50 (which would make for really fuzzy
images on a standard 17" desktop monitor). The difference
between a "dot" (as in dot pitch) and a pixel is that a pixel
is mapped onto the dots on the screen. When the monitor is set
to lower resolutions, one pixel encompasses multiple dots. So
pixels are typically larger than the "dots" on the actual
screen.
In a CRT display with a shadow mask, the dot pitch is measured
as the distance between the holes of the shadow mask, again in
millimeters. "So what's a shadow mask?" you ask. It's
basically a metal screen full of holes where three electron
beams (red, green, and blue) pass through. These beams focus
to a single point on the tube's phosphor surface. Thousands of
these points make up the images on your screen. Neat, huh? In
a CRT display that uses an aperture grill (like a Sony
Trinitron monitor), the dot pitch is measured by the distance
between adjacent slots where electron beams of the same color
pass through.
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Download
This is the process in which data is sent to your computer.
Whenever you receive information from the Internet, you are
downloading it to your computer. For example, you might have
to download an upgrade for your computer's operating system in
order to play a new game (especially if you're using Windows).
Or you might download a demo version of a program you are
thinking about buying from the software company's Web site.
The opposite of this process, sending information to another
computer, is called uploading.
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Driver
This term usually refers to the person behind the wheel of a
moving car. In the computer world, however, a driver is a
small file that helps the computer communicates with a certain
hardware device. It contains information the computer needs to
recognize and control the device. In Windows-based PCs, a
driver is often packaged as a dynamic link library, or .dll
file. In Macs, most hardware devices don't need drivers, but
the ones that do usually come with a software driver in the
form of a system extension, or .kext file.
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DSL
Stands for "Digital Subscriber Line." It is another medium for
sending data over regular phone lines and connecting to the
Internet. However, like a cable modem, a DSL circuit is much
faster than a regular phone connection, even though the wires
it uses are copper like your typical phone line. An asymmetric
DSL (ADSL) connection allows download speeds of up to about
1.5 megabits (not megabytes) per second, and upload speeds of
128 kilobits per second. That is why it is called ADSL and not
just DSL (because of the asymmetric speeds). There is also a
"Symmetric Digital Subscriber Line" (SDSL) which is similar to
ADSL, but allows data transfer speeds of 384 Kilobits per
second in both directions. Theoretically, this type of
connection allows download speeds of up to 9 megabits per
second and upload speeds of up to 640 kilobits per second. The
difficult part in establishing an DSL circuit is that it must
be configured to connect two specific locations, unlike a
regular phone line or cable modem. DSL is often seen as the
new, better alternative to the older ISDN standard.
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DVD
Stands for "Digital Versatile Disc." It can also stand for
"Digital Video Disc," but with the mulitple uses of DVDs, the
term "Digital Versatile Disc" is more correct. Yep, the
technology naming people just love to confuse us. A DVD is a
high-capacity optical disc that looks like a CD, but can store
much more information. While a CD can store 650 to 700 MB of
data, a single-layer, single-sided DVD can store 4.7 GB of
data. This enables massive computer applications and
full-length movies to be stored on a single DVD.
The advanced DVD formats are even more amazing. There is a
two-layer standard that doubles the single-sided capacity to
8.5 GB. These disks can also be double-sided, ramping up the
maximum storage on a single disc to 17 GB. That's 26 times
more data than a CD can hold! To be able to read DVDs in your
computer you'll need a DVD-ROM drive. Fortunately, DVD players
can also read CDs. To play DVD movies on your computer, you'll
need to have a graphics card with a DVD-decoder, which most
computers now have.
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DVI
Stands for "Digital Video
Interface." It is a video connection standard created by the
Digital Display Working Group (DDWG). Most DVI ports support
both analog and digital displays. If the display is analog,
the DVI connection converts the digital signal to an analog
signal. If the display is digital, no conversion is necessary.
There are three types of DVI connections: 1) DVI-A (for
analog), 2) DVI-D (for digital), and 3) DVI-I (integrated, for
both analog and digital). The digital video interface supports
high bandwidth signals, over 160 MHz, which means it can be
used for high resolution displays such as UXGA and HDTV. You
may find DVI ports on video cards in computers as well as on
high-end televisions.
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