Glossary of Computer Terms—D

Glossary of Computer Terms—D

D

DAISY-WHEEL PRINTER: An impact printer that uses a print element shaped like a flat disk or large thimble to form the alphanumeric and punctuation marks that are part of its print element. Unlike dot-matrix, ink-jet, and laser printers, daisy-wheel printers can not print graphics. See LETTER-QUALITY PRINTER.

DATABASE: A collection of similar information stored in a file, such as a database of addresses. This information may be created and stored in a database management system (DBMS).

DATA: Anything that is recorded or used for processing. The stuff that transfers between computers needed a name — data seemed good.

DATA RATE: Speed that information moves from one item to another. This is usually in the form of bits.

DATA-BASE MANAGEMENT SYSTEM (DBMS): A software program that controls and supervises the updating, editing, and execution of items from multiple files in a data base environment.

DDR: Stands for “Double Data Rate.” A type of advanced SDRAM designed to deliver data at a double rate of speed for a given clock frequency.

DEBUG: The process of detecting, locating, and correcting a problem in a software program or hardware.

DECODER: A software, hardware or circuit that is designed to translate a coded or scrambled signal in to a readable form. A common use for this is by cable companies that scramble a signal until a subscriber becomes authorized to view the signal. The cable company then decodes the signal in to a viewable form.

DECRYPTION:This is a process of converting information in to a readable form that has been encrypted by the use of an encryption algorithm. A common use could be that a person would like to protect sensitive data that resides on their computer system, so they would use an encryption software to scramble the information. The same software that scrambles the information would be the only authorized entity to decrypt the information. This software could be made available to any authorized person for decryption purposes at other locations.

DECREMENT: The reduction of the numerical contents of a counter. A decrement of 1 is usually assumed, unless otherwise specified. It is the complementary operation of INCREMENT.

DEFAULT: The pre-defined configuration of a system or an application. In most programs, the defaults can be changed to reflect personal preferences.

DESKTOP: The main directory of the user interface. Desktops usually contain icons that represent links to the hard drive, a network (if there is one), and a trash or recycling can for files to be deleted. It can also display icons of frequently used applications, as requested by the user.

DESKTOP PUBLISHING: The production of publication-quality documents using a personal computer in combination with text, graphics, and page layout programs.

DEVICE: In a computer system, this term refers to a unit of processing equipment external to the CPU. It is sometimes synonymous with the term PERIPHERAL.

DEDICATED LINE: This is a phone line meant specifically for one thing, like being attached to a computer.

DEMODULATION: This is the process of converting analog information (like over phone lines) into digital information (like in a computer). See “Modem” for more.

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-IN: An Internet account that can connect any stand-alone computer directly to the Internet. The account is used by having a computer-based software application dial-in to an Internet service provider (ISP). The software connects with the ISP and establishes a TCP/IP link to the Internet that enables your software to access Internet information. The computer that accesses a dial-in connection needs either a modem to connect via a regular phone line or a terminal adapter (TA) to connect via an ISDN phone line.

DIGITAL: Your CD player is digital. It is a series of small samples of data playing together very quickly (30,000 times a second). Digital recording of information means representing the bits of data through ones and zeros. Playing the bits back to again create what was recorded is called digital processing.

DIODE-TRANSISTOR LOGIC (DTL): One of the first bipolar monolithic IC families of logic gates. A diode in an IC logic gate performs the required logic with a transistor amplifying and inverting the output. The DTL family has been made obsolete by the Transistor-Transistor Logic (TTL) family.

DIRECTORY: A list of files stored in the computer.

DISK: Two distinct types. The names refer to the media inside the container:

      A hard disc stores vast amounts of data. It is usually inside the computer but can be a separate peripheral on the outside. Hard discs are made up of several rigid coated metal discs. Currently, hard discs can store 15 to 30 Gb (gigabytes)

      A floppy disc, 3.5" square, usually inserted into the computer and can store about 1.4 megabytes of data. This has become obsolete now.

DIRECT ADDRESS: A memory accessing mode in which the contents of the accessed location is called the OPERAND.

DIRECT MEMORY ACCESS (DMA): A method of transferring blocks of data directly between an external device and the computer system memory without the need for intervention by the CPU. This method significantly speeds up the data transfer rate, improving system efficiency.

DISK DRIVE: The mechanical/electronic section that can accept and operate a compatible floppy or hard disk. It may include several motors (for disk rotation and reading/writing head positioning), position sensors, and control circuits.

DISK MIRRORING: simultaneously storing a copy of information on another disc so that the information can be recovered if the main disc crashes.

DISK STRIPING: storing a bit of information across several discs (instead of storing it all on one disc and hoping that the disc doesn’t crash).

DISK OPERATING SYSTEM (DOS): A software program on a disk which coordinates the operation, transfer of data, supervision, and control of a computer. This software program must first be booted into the working memory of the computer from the disk before it can operate.

DISK STORAGE: A method of storing software programs and data on a rotating circular disk (either a floppy or hard disk) coated with magnetic material, such as iron oxide. Data is written (stored) and read (retrieved) by movable read/write heads positioned over data tracks on the surface of the disk. Addressable portions of the disk can be selected for read or write operations.

DISPLAY: A peripheral device serving as a computer readout, such as a cathode-ray tube (CRT), flat-panel (generally for laptop computers), or other readout devices. The screen can be amber, green, or full-color display. Also called a MONITOR.

DNS: This stands for Domain Name System. The Internet runs by assigning different sites “Names.” They are actually 4-part strains of numbers associated with names, but names nonetheless. Getting a DNS error means that the address you are attempting to reach is not recognized by the Internet community.

DOCUMENTATION: Information that explains how to use computer hardware or software. It is usually provided as a manual or stored on a disk.

DOMAIN: A domain is a computer, web site or network that is connected to the Internet. A typical domain name looks like this: www.5starsupport.com. The “www” prefix signifies that it is connected to the world wide web. The “5starsupport” or body usually indicates the company name and the suffix “com” is the indicates that it is a commercial site.

DONGLE: A device that attaches to a computer to control access to a particular application. Dongles provide the most effective means of copy protection. 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.

DOT-MATRIX PRINTER: An impact printer with a computer-driven, multipin print element (print-head). It create images by imprinting a series of tiny dots on a paper to print a wide variety of character styles and/or finely detailed graphics. Generally, these printers are extremely fast and are used for draft-quality documents and precise graphics.

DOTS PER INCH (DPI): The measurement of density on dot-matrix printers or other dot-matrix devices. As the DPI increases, image clarity increases.

DOWNLOAD: The process of transferring information from a web site (or other remote location on a network) to the computer. It is possible to “download a file” or “view a download.”

      v. To transfer information from a web site (or other remote location on a network) to the computer.

DOWNSTREAM: This refers data that is received from an ISP. Upstream in the data you send back. Some new technology allows for tremendous downstream data transfer rates (100 kilobytes per second or more), but with very slow upstream rates (33.6 kilobits per second or less).

DOWN TIME: A period of time during which a computer is not functioning. It is inoperable because of temporary or permanent failure of hardware or software, or when routine hardware or software maintenance procedures are indicated.

DPI: Stands for Dots Per Inch.

DRIVERS: A driver is a software program that is the driving force behind a device. Each computer device needs a driver. Many drivers are included with a computers operating system when you purchase it.

DROP-DOWN MENU: A menu window that opens vertically on-screen to display context-related options. Also called pop-up menu or pull-down menu.

DSL: Digital Subscriber Line. A method of connecting to the Internet via a phone line. A DSL connection uses copper telephone lines but is able to relay data at much higher speeds than modems and does not interfere with telephone use.

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.

DUAL CORE: This refers to a new Central Processing Unit (CPU) structure. The difference between a single core and dual core is that a dual core system has two CPU’s that are electronically wired together. These two CPU’s wired together in parallel gives twice the performance than that of its single core counterpart.

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: Digital Video Disc—Similar to a CD-ROM, it stores and plays both audio and video. 
DYNAMIC RANDOM ACCESS MEMORY (DRAM): A type of semiconductor memory in which the presence or absence of a capacitive charge in each element of the memory represents the state of the bit (1 or 0). This charge must be periodically recharged (refreshed) to maintain the desired binary state of the element. See RANDOM ACCESS MEMORY.