Daisy Chain- A hardware configuration in which devices are connected one to another in a series. The SCSI interface , for example, supports a daisy chain of up to 7 devices.
Data- Anything that is recorded or used for processing. The stuff that transfers between computers needed a name -- data seemed good.
Data Bus- A group of parallel conductors (circuit traces) found on the motherboard that is used by the CPU to send and receive data from all the devices in the computer. Also called the external data bus.
Data Conversion- The translation of data from one format to another. Often when data are moved from one system to another, some form of data conversion is required to convert the data to a format the receiving system can interpret. Sometimes it is necessary to have an intermediate format.
Database- Anything that accepts data is a database. A pile of newspapers is a database. A computer database has the ability to manipulate that data. It is possible to attach applications to that database to search the contents.
Data mining- Sorting through data to identify patterns and establish relationships. Data mining parameters include:
- Association - looking for patterns where one event is connected to another event.
- Sequence or path analysis - looking for patterns where one event leads to another later event.
- Classification - looking for new patterns (May result in a change in the way the data is organized but that's ok).
- Clustering - finding and visually documenting groups of facts not previously known.
- Forecasting - discovering patterns in data that can lead to reasonable predictions about the future.
Data Rate- Speed that information moves from one item to another. This is usually in the form of bits.
Daughter Card- A printed circuit board that plugs into another circuit board (usually the motherboard). A daughter card is similar to an expansion board, but it accesses the motherboard components (memory and CPU) directly instead of sending data through the slower expansion bus.
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.
DDS- Stands for Direct Digital Signal. A network whose infrastructure equipment is completely digital. All signals on such a network are transmitted digitally and there is no need for analog-to-digital converters.
Decoder- A circuit or device that restores a coded signal to its original form based on knowledge of the process used to code the signal.
Decryption- Decryption is the process of converting encrypted data back into its original form, so it can be understood.
Dedicated Line- This is a phone line meant specifically for one thing, like being attached to a computer.
Degauss- To remove magnetism from a device. The term is usually used in reference to color monitors and other display devices that use a Cathode Ray Tube (CRT). These devices aim electrons onto the display screen by creating magnetic fields inside the CRT. External magnetic forces -- such as the earth's natural magnetism or a magnet placed close to the monitor -- can magnetize the shadow mask, causing distorted images and colors. To remove this external magnetic forces, most monitors automatically degauss the CRT whenever you turn on the monitor. In addition, many monitors have a manual degauss button that performs a more thorough degaussing of the CRT. You can also use an external degausser that degausses the monitor from the outside. Since it may be impossible to remove the external magnetic force, degaussing works by re-aligning the magnetic fields inside the CRT to compensate for the external magnetism.
Delimiter- A text character that marks the beginning and/or end of a unit of data or separates different data components. For example, periods are used as delimiters in domain names, hyphens and parentheses are used in phone numbers and social security numbers, and blank spaces and commas are used in written text. In HTML the opening delimiter of an element or tag is the less than symbol, <, and the closing delimiter is greater than symbol, >.
Demodulation- This is the process of converting analog information (like over phone lines) into digital information (like in a computer). See "Modem" for more.
DHCP- Dynamic Host Configuration Protocol. This protocol provides a mechanism for allocating IP addresses dynamically so that addresses can be reused. Often used for managing the IP addresses of all the cable modems in a cable plant and the PC's connected to the cable modems.
DHTML- Stands for Dynamic HTML.
Dial-Up Line- This is a telephone line that is connected to a server. When it is called, tones are exchanged between the server and the devise calling in order to attach.
Dial-Up Networking- A component in Windows 95 that enables you to connect your computer to a network via a modem. If your computer is not connected to a LAN and you want to connect to the Internet, you need to configure Dial-Up Networking (DUN) to dial a Point of Presence (POP) and log into your Internet Service Provider (ISP). Your ISP will need to provide certain information, such as the gateway address and your computer's IP address. You access DUN through the My Computer icon. You can configure a different profile (called a connectoid) for each different online service you use. Once configured, you can copy a connectoid shortcut to your desktop so that all you need to do to make a connection is double-click the connectoid icon.
Digital- A system that defines data in a discrete, non-fluctuating (i.e., non-analogue), numerical method. Similar to a binary system.
DIMM- Short for dual in-line memory module, a small circuit board that holds memory chips. A single in-line memory module (SIMM) has a 32-bit path to the memory chips whereas a DIMM has 64-bit path. Because the Pentium processor requires a 64-bit path to memory, you need to install SIMMs two at a time. With DIMMs, you can install memory one DIMM at a time.
DIP- Acronym for dual in-line package, a type of chip housed in a rectangular casing with two rows of connecting pins on either side.
Direct X- A set of APIs developed by Microsoft that enables programmers to write programs that access hardware features of a computer without knowing exactly what hardware will be installed on the machine where the program eventually runs. DirectX achieves this by creating an intermediate layer that translates generic hardware commands into specific commands for particular pieces of hardware. In particular, DirectX lets multimedia applications take advantage of hardware acceleration features supported by graphics accelerators. DirectX 2, released in 1996, supports the Direct3D architecture. DirectX 5, released in 1998, adds new layers to the DirectX API. In addition to the low-level layer that communicates directly with multimedia hardware, DirectX 5 also includes a Media layer that enables programmers to manipulate multimedia objects and streams. DirectX 5 also supports USB and IEEE 1394 buses, AGP, and MMX.
DLL- Dynamic Link Library. A file of functions, compiled, linked, and saved separately from the processes that use them. Functions in DLLs can be used by more than one running process. The operating system maps the DLLs into the process's address space when the process is started up or while it is running. Dynamic link libraries are stored in files with the .DLL file extension.
DMA- Hardware devices attached to PCs (ranging from keyboards to sound cards) can be designed to send their instructions to and from main memory in one of two ways. The default is to ask the CPU to do the work. The more efficient way is to allocate one of the PC's DMA channels to send instructions directly to memory. This leaves the CPU free to do more important things. Like IRQs, DMA channels are limited in number, and you can't allocate one channel to more than one device (unless you want to grind your system to a halt). Most users come in contact with DMA when they install a sound card that--if they're lucky--picks the right channel during setup.
DNS- Domain Name Service, is the system used on the Internet for mapping names (called domain names) to the actual numerical addresses of machines on the Internet (IP addresses). Every computer on the Internet has its own number. Since humans can remember names more easily, DNS maps the numbers, such as 906.87.42.119, to names, such as www.5starsupport.com. When you type a Web page address into your browser, your computer consults a DNS server to find the actual numerical address for the machine that goes by that name.
DOCSIS- Data Over Cable Service Interface Specification. The dominating cable modem standard. Defines technical specifications for both cable modem and CMTS.
Dongle- A device that attaches to a computer to control access to a particular application. Dongles provide the most effective means of copy protection. Typically, the dongle attaches to a PC's parallel port. On Macintoshes, the dongle sometimes attaches to the ADB port. The dongle passes through all data coming through the port so it does not prevent the port from being used for other purposes. In fact, it's possible to attach several dongles to the same port.
DOS- Stands for Disc Operating System. It is a generic term for the many programs that accept commands to trip applications to run. The most popular is MS-DOS (MS stands for Microsoft).
Downstream- The data flowing from the Cable Modem Termination System to the cable modem.
Downstream frequency- The frequency used for transmitting data from the Cable Modem Termination System to the cable modem. Normally in the 42/65-850 MHz range depending on the actual cable plant capabilities.
Domain- PA group of computers and devices on a network that are administered as a unit with common rules and procedures. Within the Internet, domains are defined by the IP address. All devices sharing a common part of the IP address are said to be in the same domain.
Domain Name- A name that identifies one or more IP addresses. Every domain name has a suffix that indicates which top-level (TLD) domain it belongs to. There are only a limited number of such domains.
For example:
gov - Government agencies
edu - Educational institutions
org - Organizations (nonprofit)
mil - Military
com - commercial business
net - Network organizations
ca - Canada
th - Thailand
Because the Internet is based on IP addresses, not domain names, every Web server requires a Domain Name System (DNS) server to translate domain names into IP addresses.
Dot Pitch- A measurement that indicates the diagonal distance between like-colored phosphor dots on a display screen. Measured in millimeters, the dot pitch is one of the principal characteristics that determines the quality of display monitors. The lower the number, the crisper the image. The dot pitch of color monitors for personal computers ranges from about 0.15 mm to 0.30 mm. Another term for dot pitch is phosphor pitch.
DPI- Stands for Dots Per Inch.
DRAM- DRAM (dynamic random access memory) is most commonly used type of memory in computers. A bank of DRAM memory usually forms the computer's main memory. It is called Dynamic because it needs to be refreshed.
Driver- A program that controls a device. Every device, whether it be a printer, disk drive, or keyboard, must have a driver program. Many drivers, such as the keyboard driver, come with the operating system. For other devices, you may need to load a new driver when you connect the device to your computer. In DOS systems, drivers are files with a .SYS extension. In Windows environments, drivers often have a .DRV extension. A driver acts like a translator between the device and programs that use the device. Each device has its own set of specialized commands that only its driver knows. In contrast, most programs access devices by using generic commands. The driver, therefore, accepts generic commands from a program and then translates them into specialized commands for the device.
DSP: (Digital Signal Processor)- DSP chips are widely used in sound cards, fax machines, modems, cellular phones, high-capacity hard disks and digital TVs. The first DSP chip used in a commercial product was believed to be from Texas Instruments, which was used in its very popular Speak & Spell game in the late 1970s. DSP chips are used in sound cards for recording and playback and speech synthesis. Other audio uses are amplifiers that simulate concert halls and surround-sound effects for music and home theater.
DTP- Desk Top Publisher(ing) - A PC Term that describes a program that enables you to design, create and print a variety of projects such as letterheads, birthday cards, calendars, business cards, invitations etc. that would have previously only been possible by using the services of an outside printers business.
Dumb Terminal- This a video screen that is seeing manipulation in another computer. Example: If you log in to AOL, your computer is not doing the work -- AOL's computer is. You are just being offered a window into that world. That window is your screen. It's a terminal, but it's just watching -- thus a dumb terminal.
DVD- Short for digital versatile disc or digital video disc, a new type of CD-ROM that holds a minimum of 4.7GB (gigabytes), enough for a full-length movie. Many experts believe that DVD disks, called DVD-ROMs, will eventually replace CD-ROMs, as well as VHS video cassettes and laser discs. The DVD specification supports disks with capacities of from 4.7GB to 17GB and access rates of 600 KBps to 1.3 MBps. One of the best features of DVD drives is that they are backward-compatible with CD-ROMs. This means that DVD players can play old CD-ROMs, CD-I disks, and video CDs, as well as new DVD-ROMs. Newer DVD players, called second-generation or DVD-2 drives, can also read CD-R and CD-RW disks. DVD uses MPEG-2 to compress video data.
Dynamic URL- A URL that results from the search of a database-driven Web site or the URL of a Web site that runs a script. In contrast to static URLs, in which the contents of the Web page do not change unless the changes are coded into the HTML, dynamic URLs are generated from specific queries to a site's database. The page is merely a template to display the results of the query. Most of the content comes from the database that is associated with the site. Instead of changing information in the HTML code, the data is changed in the database.
EBCDIC- Extended Binary Coded Decimal Interchange Code. It is also called the Extended ASCII Code, as it adds an eighth digit to the normal seven-digit code
ECC Memory- Error Checking and Correction. A method of detecting and correcting system memory errors by adding additional bits and using a special algorithm.
EDO Memory- Short for Extended Data Output Dynamic Random Access Memory, a type of DRAM that is faster than conventional DRAM. Unlike conventional DRAM which can only access one block of data at a time, EDO RAM can start fetching the next block of memory at the same time that it sends the previous block to the CPU.
EEPROM- Acronym for electrically erasable programmable read-only memory. Pronounced double-ee-prom or e-e-prom, an EEPROM is a special type of PROM that can be erased by exposing it to an electrical charge. Like other types of PROM, EEPROM retains its contents even when the power is turned off. Also like other types of ROM, EEPROM is not as fast as RAM. EEPROM is similar to flash memory (sometimes called flash EEPROM). The principal difference is that EEPROM requires data to be written or erased one byte at a time whereas flash memory allows data to be written or erased in blocks. This makes flash memory faster.
EIDE- (Enhanced Integrated Development Environment), also called EIDE, is a term that Western Digital coined in 1994 to represent a particular set of extensions it devised to the original AT Attachment standard. At that time, the official ATA standard was rather limiting, and work was progressing towards the new ATA-2 standard. Western Digital decided that it did not want to wait for the new standard, and also that it could better position itself as a market leader by creating a new feature set for (then) future drives. The name "Enhanced IDE" was presumably selected to build upon the common name for ATA then in popular use: IDE.
E-Mail- Stands for Electronic Mail. This is a system of relaying messages across the Internet, from one Internet user to another.
Emulation- Refers to the ability of a program or device to imitate another program or device. Many printers, for example, are designed to emulate Hewlett-Packard LaserJet printers because so much software is written for HP printers. By emulating an HP printer, a printer can work with any software written for a real HP printer. Emulation tricks the software into believing that a device is really some other device. Communications software packages often include terminal emulation drivers. This enables your PC to emulate a particular type of terminal so that you can log on to a mainframe. It is also possible for a computer to emulate another type of computer. For example, there are programs that enable an Apple Macintosh to emulate a PC.
Encryption- Encryption is the process of converting data into "unreadable code" is so that unauthorized people cannot understand the content. Encryption may be used to make stored data private (e.g., data that is stored on a potentially vulnerable hard disk), or to allow a nonsecure communications channel to serve as a private communications channel. Encryption is sometimes described as the process of converting plaintext into ciphertext. To decipher the message, the receiver of the encrypted data must have the proper decryption key.
Engine: (as in "Search Engine"): - This is the working part of a database or application.
EPROM- (Acronym for erasable programmable read-only memory, and pronounced ee-prom, EPROM is a special type of memory that retains its contents until it is exposed to ultraviolet light. The ultraviolet light clears its contents, making it possible to reprogram the memory. To write to and erase an EPROM, you need a special device called a PROM programmer or PROM burner. An EPROM differs from a PROM in that a PROM can be written to only once and cannot be erased. EPROMs are used widely in personal computers because they enable the manufacturer to change the contents of the PROM before the computer is actually shipped. This means that bugs can be removed and new versions installed shortly before delivery.
Error Rate- In many cases, it may be acceptable if an input device generates a certain number of errors. This is often referred to as the error rate and the acceptable level will vary according to the input device being used and the business application. Optical character recognition, for example, is generally considered a comparatively unreliable means of entering data. At present, a typical OCR software package will have an error rate of between five and ten per cent.
ESD- Stands for Electro Static Discharge and is defined as a sudden flow of electricity between two objects at different electrical potentials. ESD is a primary cause of integrated circuit damage or failure.
ESD Testing- One kind of test that hardware usually has to pass to prove it is suitable for sale and use. The hardware must still work after is has been subjected to some level of electrostatic discharge. Some organizations have their own ESD requirements which hardware must meet before it will be considered for purchase.
Different countries have different legal regulations about levels of ESD.
How to help prevent ESD- The best way to help prevent ESD is either to use a wrist strap, or a grounding mat. However most users do not have access to such items therefore you can follow the below guidelines to help prevent ESD as much as possible.
- Clothes - Insure what you are not wearing an item that conducts a lot of Electrical Charge, such as a wool sweater. Also it is generally a good idea to remove all jewelry as well.
- Weather - When working on your computer insure there is not an electrical storm outside which increases the potential of ESD.
- Cords - Insure everything is removed from the back of the computer (power cord, mouse, keyboard, etc).
- Zero Potential - Insure you and the computer are at Zero Potential by continuously touching the un-painted metal chassis (computer frame) or the Power supply.
- Standing - When working inside the computer it is highly recommended that you stand at ALL times.
- Surface - It is always best to stand on a wooden surface. Avoid working on a computer in carpeted areas.
Ethernet- A networking system that enables high speed data communication over coaxial cables. The Ethernet network system supports TCP/IP, AppleTalk, Novell Netware, and other network protocols. An Ethernet (LAN) connection is 10 Mbit/s or 100 Mbit/s, and is used to connect many computers that can all "talk" directly to each other. Normally they will all talk with a few servers and printers, but the network is all-to-all. The distance is normally limited to below 1 km.
Executable File- A file in a format that the computer can directly execute. Unlike source files, executable files cannot be read by humans. To transform a source file into an executable file, you need to pass it through a compiler or assembler. In DOS systems, executable files have either a .COM or .EXE extension and are called COM files and EXE files, respectively.
Expanded Memory- Also known as EMS (Expanded Memory Specification), expanded memory is a technique for utilizing more than 1MB (megabyte) of main memory in DOS -based computers. The limit of 1MB is built into the DOS operating system. The upper 384K is reserved for special purposes, leaving just 640K of conventional memory for programs.
Expansion Bus- A group of control lines that provide a buffered interface to devices located either on the system board or on cards that are plugged into expansion connectors. Common expansion buses included on the system board are USB, PC Card, and PCI.
Extended Memory- Memory above and beyond the standard 1MB (megabyte) of main memory that DOS supports. Extended memory is only available in PCs with an Intel 80286 or later microprocessor. Two types of memory can be added to a PC to increase memory beyond 1MB: expanded memory and extended memory. Expanded memory conforms to a published standard called EMS that enables DOS programs to take advantage of it. Extended memory, on the other hand, is not configured in any special manner and is therefore unavailable to most DOS programs. However, MS-Windows and OS/2 can use extended memory.
External Modem- A modem that resides in a self-contained box outside the computer system. Contrast with an internal modem, which resides on a printed circuit board inserted into the computer. External modems tend to be slightly more expensive than internal modems. Many experts consider them superior because they contain lights that indicate how the modem is functioning. In addition, they can easily be moved from one computer to another. However, they do use up one COM port.
Extranet- An extranet is a private network that uses the Internet protocols and the public tele-communication system to share a business's information , data or operations with external suppliers, vendors or customers. An extranet can be viewed as the external part of a company's Intranet. See Also: Intranet
FAT- Stands for File Allocation Table. Basically this is a table of contents in a directory that tells the computer what all is in there. Look at your Netscape cache, you'll see a FAT. It'll be the first file.
FAT 32- A new version of the file allocation table (FAT) available in Windows 95 OSR 2 and Windows 98. FAT32 increases the number of bits used to address clusters and also reduces the size of each cluster. The result is that it can support larger disks (up to 2 terabytes) and better storage efficiency (less slack space).
Fault Tolerance- The ability of a system to respond gracefully to an unexpected hardware or software failure. There are many levels of fault tolerance, the lowest being the ability to continue operation in the event of a power failure. Many fault-tolerant computer systems mirror all operations -- that is, every operation is performed on two or more duplicate systems, so if one fails the other can take over.
FAQ- Stands for Frequently Asked Questions. An FAQ is a file or document where a moderator or administrator will post commonly asked questions and their answers.
Fax Modem- A device you can attach to a personal computer that enables you to transmit and receive electronic documents as faxes. A fax modem is like a regular modem except that it is designed to transmit documents to a fax machine or to another fax modem. Some, but not all, fax modems do double duty as regular modems. As with regular modems, fax modems can be either internal or external. Internal fax modems are often called fax boards.
FDDI- Fiber Distributed Data Interface -- A standard for transmitting data on optical fiber cables at a rate of around 100,000,000 bits-per-second (10 times as fast as Ethernet, about twice as fast as T-3).
FDISK- A program found in all Aptiva software loads that allows modification of the partitions and/or logical drives on the hard drive. It can Display, Delete and Create partitions and logical drives, defining them for DOS, OS/2 or Windows, depending on which version of FDISK is used and how it is used. Type FDISK and hit Enter to start the program. This is a DESTRUCTIVE command and incorrect use will result in data loss!
Fiber Optic- An alternative to copper wire for transmitting information. In fiber optics, pulses of light representing binary data are flashed along a flexible glass fiber. The advantage over copper wiring is that a single strand of optical fiber can carry thousands and thousands of different frequencies at once without data loss.
File Sharing- This is the most important feature of the Internet. This is a method of allowing one server to give the same file to many different end users.
Firmware- Software (programs or data) that has been written onto read-only memory (ROM). Firmware is a combination of software and hardware. ROMs, PROMs and EPROMs that have data or programs recorded on them are firmware.
FORTRAN- FORmula TRANslator. Developed in 1954 by IBM, it is a high-level programming language, most widely used for scientific and engineering applications because it has excellent mathematical functions. Many programmers consider it to sacrifice "elegance" for speed of numerical manipulations.
Freeware- This is a shortened version of Free Software. Programmers offer their work without wanting pay in return.
FSB- Stands for Front Side Bus, which denotes the speed at which your processor interacts with the components on the motherboard. Typically the FSB is 100Mhz or 133Mhz, but overclockers often manipulate this value to increase the speed at which their processor runs. i.e. 100Mhz FSB X 5.0 clock multiplier = 500Mhz processor.
FTP- Stands for File Transfer Protocol
Full Duplex- Refers to the transmission of data in two directions simultaneously. For example, a telephone is a full-duplex device because both parties can talk at once. In contrast, a walkie-talkie is a half-duplex device because only one party can transmit at a time.
Most modems have a switch that lets you choose between full-duplex and half-duplex modes. The choice depends on which communications program you are running.
In full-duplex mode, data you transmit does not appear on your screen until it has been received and sent back by the other party. This enables you to validate that the data has been accurately transmitted. If your display screen shows two of each character, it probably means that your modem is set to half-duplex mode when it should be in full-duplex mode.
Source: "The Free On-line Dictionary of Computing, http://www.foldoc.org/, Editor Denis Howe"
|
Network Technologies