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DB-25 => This is the name for the connector used for parallel ports on PCs.
DCOM => (Distributed COM (Component Object Model)) This is yet another Microsoft technology. It is a version of the COM that is designed to work across networks and, specifically, the Internet.
Desktop Case => A computer case designed to sit on your desktop. It's wider than it is tall.
Device Bay Interface Specification => This is a new specification designed to provide a simple and generic way of interfacing computers and their components. Device Bay devices will be about the size of a VCR tape and will interface via the USB or Fi...
Diamondtron => This is Mitsubishi's answer to Sony's Trinitron. Instead of rectangular pixels, Diamondtron used diamond-shaped ones which supposedly offer crisper text.
DIB => (Dual Independent Bus) This is the bus architecture between Intel's Pentium II processor, memory, and L2 cache. One bus connects the processor to L2 cache and a second connects the processor to main memory. Having two buses instead of one incr...
Die size => Simply put, this is the two dimensional (length by width) measurement of a microprocessor. The thickness of the processor is not considered. For example, a die size may be 384 square millimeters.
Digital => Digital implies a value represented by a group of discrete steps. Some claim that digital representations of images and sound are more accurate; others that the translation of analog sounds and pictures into digital representations causes ...
Digital Control => This is a control that doesn't directly cause a physical change in something, but rather sends a signal that a processor interprets. The processor then makes the change. An example of a digital control would be a television set wit...
DIMM => (Dual In-Line Memory Module) Very much like a SIMM except that they are larger and you need only one in place of two SIMMs. DIMMs are 64-bit memory devices, so you just need a single DIMM for a processer with a 64-bit memory path to work prop...
DirectDraw => A set of APIs for Windows 95 and NT that allow programmers to directly access the video controller, allowing for faster graphics response.
DirectPC => TCP/IP over satellite. This is a system for going on the Internet by satellite at about 800 Kbps. Unfortunately, you also need a modem to be able to send anything to the Internet because the satellite is one way only.
DirectX => A Microsoft technology that works under Windows 95 and Windows NT 4.x. Basically, it's a set of APIs that allow programmers to access more directly sound and graphics capabilities of the computer allowing for, among other things, great gam...
Disk Duplexing => See RAID 1
Disk Mirroring => See RAID 1
Disk Striping => See RAID 0
Disk Striping with Parity => See RAID 5
DLL => (Dynamic Link Library) This is a library of procedures that programs can call with input. The DLL produces output related to that input.
DLT => (Digital Linear Tape) A technology designed by DEC and sold to Quantum used for backing up huge amounts of data (up to 35 GB per tape without compression, 70 GB with compression). The drives are very expensive and so is the media, but they are...
DMA => (Direct Memory Access) PCs have DMA channels that allow certain devices to directly access memory in order to speed up the process.
DMI => (Desktop Management Interface) This interface standard is designed to allow PCs to intelligently broadcast information on their system configurations and support remote management so that they can be managed more easily.
DMTF => (Desktop Management Task Force) This motley crew was assembled to create the DMI standard.
DNS => (Domain Name Service) This service maps TCP/IP numbers such as 123.12.4.245 to a more easily remembered name, such as www.ugeek.com. Thus, when you type www.ugeek.com into your browser, it goes out to the DNS server you specified when you inst...
DNS Entry => The DNS routing tables are filled with DNS entries that map TCP/IP addresses to more easily recognized names. If your browser says it can't find a particular DNS entry, here are some possible reasons: => You may not be able to communicat...
Domain name => Domain names are used to represent more complex TCP/IP addresses. For example, we purchased the UGeek.com domain name so we could use it to represent our server's address. You purchase domain names through the InterNIC. They can be rea...
Domain Name Service => See DNS.
DOS => (Disk Operating System) This OS is what got it all started for PCs.
Dot Matrix Printer => This type of printer prints out little dots that can form graphics or characters. This type of printer was popular a while back because the only other choice was a daisy-wheel printer that didn't print any graphics. These printe...
Dot Pitch => The smaller the better, as it relates to monitors. The dot pitch is a measure of distance between phosphor dots of the same color on a CRT monitor. A high dot pitch generally produces a blurred and unclear picture. Smaller dot pitches pr...
Double Buffering => This shows you that the graphics engine uses two layers, or buffers, to produce an image: one for display and one for rendering. Since the viewer only sees the finished image, this allows for smooth-motion animation. (Again, play ...
DPMA => (Dynamic Power Management Architecture) This architecture allows computers to have a variety of advanced power management features.
DRAM => (Dynamic Random Access Memory) The standard and cheapest memory available. The fastest DRAM is about 60 nanoseconds. This is the most common form of computer memory. It needs to be continually refreshed in order to properly hold data, thus th...
Drive Bay => Usually a 5.25"-wide 1"-tall hole in a computer case, suitable for the installation of some sort of drive. Some are exposed so that a removable drive (e.g., floppy, CD-ROM) can fit. Some are not exposed and are meant for hard drives, tap...
Driver => A driver is software that works to communicate between an operating system and a peripheral. Think of it as a translator. If you use a crappy driver, your OS won't understand your video card and may become unstable and crash. Hardware manuf...
DS-0 => (Digital Signal level 0) This is the signal used to carry a standard analog or digital phone line connection. 24 DS-0 connections can be carried on a T1 line. The speed of the signal is either 64 Kbps, or 56 Kbps if the eighth bit is used for...
DS-1 => (Digital Signal level 1) Synonym for T1.
DS-3 => (Digital Signal level 3) Synonym for T3.
DS-4 => (Digital Signal level 4) Synonym for T4.
DSP => (Digital Signal Processor) A DSP is a microprocessor designed to work with analog signals such as video or audio that have been digitally encoded. The DSP then takes these digital representations and performs operations on them. DSPs are used ...
DSTN => (Double-layer Supertwist Nematic) This is a form of passive matrix LCD screen. It is an improved version of the standard supertwist nematic passive matrix LCD screen where the display is divided into two sections and addressed separately to d...
Dual boot => This describes a system that can boot to two different operating systems. Some OSs, such as Windows NT and OS/2, allow for dual booting when installed. Of course, you can also use other methods such as commercial programs that install a ...
Dualscan => Refers to a passive matrix LCD screen that uses a better method of displaying graphics, producing a sharper, more vivid image than normal passive matrix screens.
Dumb Terminal => These are hooked up to mainframes, and are little more than a monitor attatched to a keyboard. All they are good for is running programs using the mainframe's hard drive and memory.
DVD => (Digital Variable/Versatile/Video Disc) Much like a CD-ROM except that it stores up to 12 times as much and is re-writeable. Although the industry claims that DVD really stands for NOTHING, I think otherwise. DVD is the successor to CD-ROM tec...
EBCDIC => see Extended Binary Coded Decimal Interchange Code.
EBIOS => (Enhanced BIOS) The EBIOS translates between the partition table limitations of a standard computer BIOS and the IDE limitations to provide up to 8 GB of storage space using the IDE interface. Your computer's BIOS has maximums of 1024 cylind...
ECC => (Error Checking and Correcting) Generally refers to memory chips, or motherboards that support this type of behavior in full-parity memory chips. ECC memory uses some extra memory on the memory chips for parity information and checks to see wh...
EDO RAM => (Extended Data Out RAM) This refers to the successor of DRAM. Most systems today support EDO RAM. It's a conceptually faster RAM chip that has small bits of SRAM cache built into it. It still runs at slow DRAM speeds ( <= 50 MHz), however.
EIDE => (Enhanced IDE) Allows for two IDE channels that can each support two devices in peaceful coexistence. It also allows for hard drives up to 8 GB in size and CD-ROM devices.
EISA => (Extended Industry Standard Architecture) 16-bit ISA was extended to 32-bits and they called it EISA. Pretty creative. But, really, it's generally used only in server machines, and it never caught on because of VL-Bus and PCI. It beats out VL...
Enhanced Small Device Interface => (ESDI) This was a popular form of hard drive and controller before IDE took over the PC market.
Environment => Normally, this is your surroundings. In your computer, the environment is what a group of variables are set to. Think of it as your computer's surroundings.
EPIC => see Explicitly Parallel Instruction Computing.
ESCD => (Extended System Configuration Data) This is setup data that is stored in a Plug-and-Play-compatible system BIOS. It consists of the system resource requirements of legacy (non PNP) devices, and the last working configuration of Plug-and-Play...
ESDI => see Enhanced Small Device Interface.
Expansion Slot => Refers to any type of slot in a computer that you can plug an expansion card into. Generally, it's limited to ISA, EISA, PCI, and PCMCIA, but there are other types and there will be more in the future.
Explicitly Parallel Instruction Computing => (EPIC) This is Intel and Hewlett-Packard's invention, designed to be used on Intel's forthcoming Merced processor. It is a method for arranging instructions so that they are ordered to be explicitly parall...
Extended Binary Coded Decimal Interchange Code => (EBCDIC) This is a way of encoding 256 characters in binary, much like ASCII, but used mainly on mainframes. Most of the time, EBCDIC is only mentioned in translations between EBCDIC and ASCII.
Extended partition => This is a type of partition that is an extension of a primary partition. It's possible to have many extended partitions on a hard drive.
Extranet => An Extranet is an intranet that extends onto the Internet. Confusing? Yes. Extranets are external extensions of a company's intranet that allow certain people to interact from the Internet. Not all intranets are Extranets. 
Fabless => This term refers to a company that produces chips but doesn't own a fabrication plant, or fab. These companies are starting to become more and more successful at creating chips and renting out other companies' excess fabs to produce their ...
Fabrication Plant => A fab is a factory that takes raw silicon wafers and creates chips with them. Often, fabs are categorized by what micron process they use. For example, the Intel Pentium chip with MMX is produced in a fab with a 0.35 micron proce...
FAQ => (Frequently Asked Questions) This is a document that lists the most common questions about something (with the answers, of course).
Fast SCSI 2 => This version of SCSI transfers data at 10 Mbps. The connections all contain 50 pins. See also Fast-Wide SCSI 2.
Fast-SCSI => Plain vanilla fast-SCSI never really existed. See Fast-SCSI 2
Fast-Wide SCSI 2 => This version of SCSI upped the pin count to 68, effectively doubling the signal speed of Fast-SCSI 2 to 20 Mbps.
Fat Client => Today's fast PCs are fat clients. They've got lots of memory and big hard drives. They store information and run programs locally off of their hard drives. Fat clients usually work in client/server environments, where they leave the ser...
FCC => (Federal Communications Commission) These are the people in the government who decide what's legal and illegal to broadcast, including what frequencies are allowed to be used by whom.
FDDI => (Fiber Distributed Data Interface) This is a fiber optic interface that allows data to travel extreme distances (many miles/kilometers) without signal loss. It is far superior to copper wire for data integrity as well. FDDI is often used to c...
Feature => A feature is something that a piece of hardware or software is designed to do. Many things that appear to be bugs are actually features. Often, a hardware or software developer will have to make a tradeoff in functionality that causes some...
Fiber Optic => A method of transmission alternative to copper. The way it works is by pulsing light down a strand of glass. These pulses represent binary code. So far, that's no better than copper. The advantage is that a single strand of fiber optic...
FIFO Buffer (First In First Out Buffer) => An area of memory that holds information in the order in which it was received until the computer has time to use it.
Firewall => This is a form of Internet security that stands between a private network and the Internet. It is like a wall in that it can prevent unwanted traffic from passing either way. Some firewalls have proxy functions built in. In fact, the dist...
Firewire => An up and coming serial technology that promises to speed data at 200 => 400 Mbps. This standard may eventually replace your serial ports, parallel ports, game ports, USB and maybe even SCSI.
FishNet => This is a type of stocking material that Joel likes to wear under his pants.
Flash BIOS => This BIOS contains a flash ROM chip that can be updated under certain conditions, but is otherwise static.
Flash ROM => A rewriteable ROM that doesn't lose its info when the power turns off.
Flat Screen => A CRT that is made more flat than a standard tube by using more than one electron gun. It is most useful to professionals who rely on the precision of their monitors. It is also better for the standard user because a straight light acr...
Flat Shading => This is the most basic shading technique. The entire triangle is only one color. This causes the image to appear blocky.
FM synthesis => This is a method of creating music using frequencies to represent instruments.
Fortran => This is a high-level programming language, a bit more advanced than BASIC, but not quite as complex as C. This language refuses to die because it is so huge in the scientific research community. It's not a tough language to learn and it's ...
Fractional T1 => This term refers to using a theoretical "piece" of a T1 line, such as 128 Kbps, 256 Kbps or 512 Kbps worth of the 1.5 Mbps T1 line. Many ISPs offer fractional T1 as a lower-cost alternative to a full T1, and a higher-cost alternative...
Frame Relay => A method of communication that can go from the speed of an ISDN to the speed of a T1 in increments. It has a flat rate billing instead of a per time usage. It connects by using the telephone company's network.
Free text search => This type of search allows you to give a fragment of a word and have it found in any part of that word. For example, doing a free text search for "the" could return "Thesis", "Blithe", and "Diphtheria."
FTP => (File Transfer Protocol) This is the method of moving files from system to system using TCP/IP.
Full parity => This refers to the ability to send and receive a signal at the same time. It can effectively double bandwidth, assuming that you can benefit from sending and receiving data at the same time. Most of the time, this doesn't happen, since...
Gate => A gate is a tiny electronic switch. These switches, when linked together, can perform logical functions.
Gateway => The computer or device onto which the first hop needs to go to get out of your network. As you know a TCP/IP route uses many hops to get from here to there.
GDI => (see Graphics Device Interface) see Graphics Device Interface
GIF => (Graphical Interface Format) Invented by CompuServe for efficient transmission of graphics. The format can only support 256 colors, or 8 bits. The newer revision, 89a, allows for multiple images in one file to simulate animation.
Gigabyte => (1 billion bytes) There are a few different ways of getting to this number. No one uses the same exact number, but they are all around 1 billion. One way of deriving the number is by multiplying 1 byte by 1024 for 1 KB then again by 1024 ...
GIS => (Geographic Information System) This is a system for capturing and manipulating data relating to the Earth.
GlidePad => A touch-sensitive pad about 2" x 2" that will track the touch of a finger. It is not a pressure sensor so there is no need to press down, only to touch. This device acts like a mouse for pointing.
Gouraud Shading => This method analyzes the color at each corner of the triangle and takes an average of the colors where the corners meet. This causes the triangles to "bleed" together, making for a smoother, clearer, more colorful image.
Graphics => The pictures that computers display. Not text, but just about everything else.
Graphics card => The graphics card is generally an add-in board that plugs into the motherboard. It sends signals out to the monitor to represent what should be shown on the screen. A graphics card can send only simple text, or it can be designed to ...
Graphics Device Interface => (GDI) This is a standard set of programming functions provided by Microsoft for the production of graphic output in Windows. Microsoft provides these functions in its Software Development Kits. The functions are device in...
GroupWare => This term is used to describe any form of software designed to allow a group of people to easily share ideas and data. Examples include Lotus Notes, Novell GroupWise, and Microsoft Exchange.
GUI => (Graphical User Interface) Any system that uses graphics to represent the functions of a program. All Windows operating systems are GUI.
HAL => (Hardware Abstraction Layer) This is the portion of the operating system that lets programs deal with hardware directly. This allows programs needing more speed from the computer to bypass the standard OS calls to hardware. So instead of calli...
Hard Drive => A device that physically stores data in your computer. Much like a floppy disk, but the system is closed and the disks are hard (usually metal, although some glass versions have been developed). The closed system gives the possibility o...
Hash table => A table that contains "hash values," generally used for speeding up searching algorithms on sorted data. For example, a hash table for a dictionary might contain all the letters of the alphabet and the page numbers where each letter sta...
HEL => (Hardware Emulation Layer) This provides software-based emulation of features that are not directly available in hardware.
Help Desk => If you've ever worked in an office environment, you've probably done some help desk work, or at least called them. The help desk is the support organization designed to take care of your computer and phone problems. They work long hours,...
Hertz => A rental company, formerly represented by O.J. Simpson. Also a measure of speed. One Hertz means one time per second, so one megahertz (MHz) means 1 million times per second. This is the common measure of speed for processors and electronic ...
Heterogeneous Data sources => This is a data-warehousing term that describes the idea of drawing data from several different (heterogeneous) data sources on different platforms and computers.
Hidden Surface Removal => See Z-buffering.
Hierarchical relationship => This relationship is one where elements at lower levels are submissive to elements at higher levels. Just think of a hierarchy, where the King is above the Duke, who is above a peasant.
High Color => The name given to 16-bit or 65,536 colors.
Hit => When a user requests an HTML document on the World Wide Web, the server records that request as a "hit." The problem with measuring "hits" is that some Web servers also count each graphic on that page as a hit. For example, if you look at a pa...
Hop => A small jump. In reference to the Internet, the route that a computer needs to take in order to get its information from here to there. Think of all the main computers in the world that are physically connected (by T1 and T3 and M1 and such) a...
Hot Spare => This refers to a drive in a RAID configuration that sits idle until one of the RAIDed drives fails. The hot spare then assumes the role of the dead drive. When the dead drive is replaced, you can make it the hot spare. (The old hot spare...
Hot-pluggable => Same as hot-swappable, but also connotes a simple plug-in mechanism for easy swapping.
Hot-swappable => This type of mechanism implies that you can remove or add things while the system is running. For example, hard drives and power supplies are often candidates for this term. Normally, they come in special proprietary form factors in ...
HTML => (Hyper Text Markup Language) A standard language made for typesetting, currently up to Version 3.2. It is mainly used for creating documents on the World Wide Web. Included in the language are provisions for including pictures and links to ot...
HTTP => (Hyper Text Transfer Protocol) The way the data in an HTML document is transferred. What it really is is what tells the program looking at the data what to use it as. So, a document coming in HTTP is read as an HTML document.
Hub => A central connection point. Standard terminology for a device that connects multiple computers in a network. 
I/O => (Input/Output) This abbreviation refers to any operation in a computer where data is transferred in or out of the computer. I/O may seem like a vague concept, but it refers to the basic throughput power of a computer.
I2O => The I2O standard is designed to simplify and speed up I/O operations on servers. It will eliminate the need for different drivers for each OS, and for each SCSI card and network card. The speedup is achieved by using an Intel 960 chip on the s...
IA-32 => (Intel Architecture-32 bit) This is Intel's 32-bit instruction architecture that runs on their 386, 486, Pentium, Pentium Pro, and Pentium II chips.
IA-64 => (Intel Architecture-64 bit) Intel's 64-bit instruction architecture that will feature EPIC and run on the Merced processor when it is released.