Barrons Publishing Dictionary of Computer and Internet Terms 10th
.pdfdusty deck |
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dusty deck (slang) an ancient, poorly understood computer program that goes back to the days of punched cards; something that is obsolete but has to be kept usable because someone needs it. Compare LEGACY.
Dutch auction
1.an auction in which several items, all alike, are being sold at once to the highest bidders. Dutch auctions are popular on eBay and similar online auction services. See EBAY.
2.an auction in which, instead of asking for bids, the would-be seller gradually lowers the asking price until someone accepts it. This is rarely done online.
duty cycle the percentage of the time that a piece of equipment is in use or powered on. For example, if the lights in a room are on 8 hours out of every 24, they have a 33.3% duty cycle.
DVD (Digital Versatile Disc, originally Digital Video Disc) an optical disc similar to CD-ROM but with much greater capacity (4.7 GB singlelayer, 8.5 GB double-layer). Normally, DVD drives also read CDs. In 2006, an even higher-capacity disc of the same general type, the Blu-Ray disc (BD), was introduced. See BLU-RAY DISC.
DVD was introduced in order to store a complete, digitized featurelength movie on a single disc. However, despite “video” in the name, DVD can store any kind of computer data. See also CD-ROM.
DVDs can be 8 or 12 cm in diameter (the same as the two sizes of CDs), singleor double-sided, and singleor double-layered. Data DVDs store sets of computer files, which can contain any type of data. Video DVDs, playable in consumer DVD players, are the same types of disc but with a different filesystem designed specifically for video playback.
Video DVD technology includes some controversial measures to protect the copyrights of movies and music. Because movie copyrights have different owners in different countries, some discs include region codes to control where the disc can be played. Region codes are also built into the firmware of DVD drives, and regardless of software, most drives will not play a disc from a different region. With some drives, the region code can be changed a few times (in case the drive is sold or used in a country other than the original market), but repeated changes are not possible. Region codes are not encrypted or secret.
More controversial is the Content Scrambling System (CSS), an encryption-based security system. The effect of CSS is to make illegally copied discs unusable, because although the data can be copied, the keys needed to decrypt it do not survive the copying process. This prevents people from making backup copies of their own discs.
An unusual provision of the Digital Millennium Copyright Act makes it illegal to circumvent the CSS algorithm or provide others with tools or information to do so (see DMCA). Despite this, the algorithm has been cracked and posted on the Internet (see DECSS).
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DVD-R a type of DVD designed to be recorded with studio equipment and played in ordinary DVD drives, whether or not they are compatible with home-recorded discs. DVD-R discs are not erasable or rewritable.
Compare CD-R.
DVD-RAM an older type of recordable, erasable, rewritable DVD. DVDRAM drives can read ordinary DVD discs, but not vice versa. Contrast
DVD+RW; DVD-RW.
DVD-ROM a non-erasable DVD, typically one containing computer files rather than audio or video programs. See DVD.
DVD+R, DVD-R two types of user-recordable DVDs with similar capacity and performance but different technical specifications, designed to be readable in ordinary DVD drives. Many DVD drives record and play both. DVD+R and DVD-R discs cannot be erased or rewritten. Compare CD-R.
DVD+RW, DVD-RW two types of user-recordable and erasable DVDs with similar capacity and performance but different technical specifications. Like DVD+R and DVD-R discs, they are designed to be readable in ordinary DVD drives. Like CD-RW discs, DVD+RW and DVD-RW discs can be erased and rewritten. Compare CD-RW.
DVI
1.(Digital Visual Interface) the newer type of connector for linking computers to monitors and projectors. It carries digital signals as well as the same analog signals as a VGA connector. The connector is roughly rectangular and has room for up to 29 pins, one of which is wide and flat (Fig. 89). Contrast VGA CONNECTOR.
2.device-independent output from TEX or LATEX, which can be printed on any printer using the appropriate DVI program.
3.(Digital Video Interface) Intel’s file format for storing video on disk.
FIGURE 89. DVI video connector.
DVR digital video recorder, a device that records video on digital media, usually DVDs.
dweeb (slang) an unsophisticated, untidy, obnoxious person.
dxdiag (directx diagnostics) a utility program for testing DirectX under Windows. To run it, go to the Start Menu, choose “Run...” and type dxdiag. See DIRECTX.
dyadic operation |
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dyadic operation an operation on two numbers (operands). For example, addition, multiplication, subtraction, and division are all dyadic operations because each of them operates on two numbers. Negation is not a dyadic operation because it operates on only one number.
dye-sublimation printer a type of color printer that gives excellent color images. Dye-sub printouts appear to be continuous-tone images like photographs. Actually they are composed of tiny dots (like laser or ther- mal-wax printouts), but the dots of dye have spread together. The intense colors, glossy finish, and lack of apparent halftone dots make these printouts especially suitable for fine art prints or presentations.
dynamic HTML enhancements to HTML that allow the display of a page to change in response to user actions, such as mouse movements, without having to reload the page from the server. A page is viewed as a set of objects (see DOM) whose appearance can be changed by scripts (see JAVASCRIPT) in response to user actions such as mouse clicks. For example, a page can contain headings that are supported by detailed text that will only be visible when the user clicks on the headings.
Unfortunately, some of the advanced features have not yet been standardized, so different browsers will not always display the same result.
See also
dynamic IP address an IP address that is assigned to a computer when it actually connects to a network and is not necessarily the same from one session to the next. Contrast STATIC IP ADDRESS.
dynamic link library see DLL.
dynamic RAM see DRAM.
dynamic range the ratio between the smallest and largest signals that a system can handle. For instance, if an analog-to-digital converter can digitize signals from 2 millivolts to 200 millivolts, it has a dynamic range of 100:1.
The dynamic range of an audio system or piece of music is often given in DECIBELs. Dynamic ranges that involve brightness are often given in terms of F-RATIOs or as logarithms to base 10. For instance, if a film scanner can handle a slide or negative whose dark areas transmit only 1/1000 as much light as the bright areas, then its dynamic range of 1000:1 can be described as the logarithmic value 3.0, because log10 1000 = 3.
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ear |
E
e (in mathematics) an important number whose value is approximately 2.71828. The reason e is important is that the function ex is its own derivative. In many programming languages, the function exp(x) computes ex. If y = ex, then x is the natural logarithm of y.
E see
e- prefix meaning electronic, especially when applied to terms in the context of the Internet or World Wide Web. See E-MAIL; E-ZINE; and E-COMMERCE for examples.
Usage note: Spelling of e-words is not yet standardized, and the new words are often spelled without hyphenation (e.g., email, ezine).
e-commerce see
E format see
e-mail (noun) electronic mail; (verb) to send a message or file by electronic mail. See ELECTRONIC MAIL.
Usage note: The spelling e-mail, with the hyphen, is now widely preferred. The older spelling is email. Either way, the noun and verb are spelled alike.
e-mail broadcasting the sending of the same e-mail message sent to many people from one source. Newsletters and SPAM advertisements are both e-mail broadcasts. See also MAILING LIST. Compare FAX BROADCASTING.
e-tail retail sales conducted on the Internet. For an example, see
AMAZON.COM.
e-zine, ezine (slang) electronically published magazine (i.e., a magazine published on a web page or the like). See WORLD WIDE WEB.
ear
1.the small stroke on the right side of the letter g.
2.a small box of information on either side of a headline or masthead. In newspapers, an ear is commonly used for the weather forecast.
FIGURE 90. (A) Ear, definition 1 (B) Ears, definition 2
Easter egg |
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Easter egg (slang) a hidden part of a computer program. Easter eggs are usually activated only by a bizarre series of actions—then the user is treated to an amusing presentation that usually includes the names of the development team. The actions necessary to see an egg are very complex and would never be performed by a casual user of the program; one has to be looking for the Easter egg. Information about Easter eggs is often spread on the World Wide Web.
eBay (www.ebay.com) an online auction house established in 1995 and headquartered in San Jose, California. By acting as an auctioneer, eBay enables individuals to buy and sell almost anything through the World Wide Web.
An online auction has several advantages over a conventional one. Bids on an item can be collected for several days, typically a week, rather than having to be delivered all at once. Perhaps more importantly, the actual bidding can be done by computer. Would-be buyers specify their maximum bids, but the computer places actual bids that are just high enough to outbid the other bidders. Finally, the computer can search quickly through thousands of item descriptions. See also BID; DUTCH AUCTION; RESERVE PRICE.
EBCDIC (pronounced ”ebb-see-dik”) (Extended Binary Coded Decimal
Information Code) the numeric representation of characters on IBM mainframe computers. (Contrast ASCII and UNICODE, which are used on most other computers.)
ebook, e-book
1.a book distributed electronically (online or on CD-ROM or similar electronic media) rather than on paper. See PDF.
2.a special-purpose handheld computer for reading texts of books.
EC
1.abbreviation for ELECTRONIC COMMERCE.
2.abbreviation for European Community.
ECC see ERROR-CORRECTING CODE.
ECC RAM random-access memory (RAM) that uses an ERROR-CORRECT- ING CODE to recover automatically from single errors in data storage, and to detect and report more serious errors.
echo to send information back to where it came from. With computers, this refers to two things:
1.When communicating by modem, a computer echoes typed characters if it sends them to its own screen as well as to the other computer. If you can’t see what you’re typing, turn echoing on; if what you type appears twice, turn echoing off.
2.In Windows and UNIX, the echo command sends a message to the screen; for example,
echo Hello there!
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writes “Hello there!” on the screen. In a .BAT file, the command echo off tells Windows not to print commands on the screen as they are executed. You can prevent the echo off command itself from being displayed by prefixing it with @, like this:
@echo off
In fact the @ prevents display of any command, not just echo.
Eclipse a free, open-source interactive development environment (editor, compiler, and debugger) for Java and other programming languages. For further information, see www.eclipse.org.
ECPA (Electronic Communications Privacy Act) the main U.S. law against wiretapping and other interception of private electronic communications, whether they are transmitted by wire, radio (including wireless network), or other means. It was passed in 1986 and superseded a number of earlier laws (18 USC 2510).
Critics point out that the ECPA does not require the sender of a message to encrypt (scramble) it to make it private. Thus, private messages can still be intercepted deliberately or even by accident. For example, first-generation analog cellular telephones were assigned to frequencies formerly occupied by UHF TV channels, and they used the same kind of modulation as TV sound. Thus, telephone calls could be picked up on old television sets. Similarly, radio technicians tracking down sources of interference could find themselves hearing things that are illegal to listen to.
On the whole, however, the ECPA is an essential part of the laws protecting computer networks and communication systems from tampering and eavesdropping. It is one of the laws most commonly violated by crackers. See COMPUTER LAW; CRACKER; WIRELESS NETWORK.
edge detect a paint program filter or image processing technique that outlines the edges of objects. See Figure 91.
FIGURE 91. Edge detect
EDI see ELECTRONIC DATA INTERCHANGE.
edit to examine a file and make changes in it, usually with the aid of an
EDITOR.
editor a computer program that enables the user to create, view, and modify text files.
EDO |
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EDO (extended data out) a type of dynamic random-access memory (DRAM) that holds its output on the BUS until the beginning of the next bus cycle. This enables the computer to retrieve data from memory in one bus cycle instead of two. (To further gain speed, memory is attached to a fast bus that connects directly to the CPU, rather than the slower bus that connects to expansion cards.) EDO DRAM is often used with Pentium processors. Contrast SDRAM.
.edu a suffix indicating that a web or e-mail address belongs to a universitylevel educational institution (in any country, but mostly the United States). Along with .com, .gov, .int, .net, .org, and .mil, this is one of the original set of Internet top-level domains. Contrast .COM. See also TLD; ICANN.
EEPROM (Electrically Erasable Programmable Read-Only Memory) a type of memory chip whose contents can be both recorded and erased by electrical signals, but do not go blank when power is removed. (It is called “read-only” because the recording process is too slow to be used more than occasionally.) EEPROM contrasts with permanently recorded ROM chips and with EPROMs that can be programmed electrically but cannot be erased electrically. See EPROM; ROM.
effective megapixels the number of megapixels actually used for the image in a digital camera. Contrast GROSS MEGAPIXELS.
efficiency the conservation of scarce resources. In order to measure efficiency, you have to decide which resource you want to conserve. For example, one program might be more “efficient” than another if it uses less memory, and another program might be more “efficient” in terms of speed; the question is whether you would rather conserve memory or time.
With computers, some of the most important resources are:
1.computer execution time;
2.computer memory capacity;
3.auxiliary storage capacity (i.e., disk space);
4.programmer’s time.
The general rule is: it is more important to work to conserve a resource if it is more scarce. With early computers, which were very slow and had limited memory (compared to computers available now), it was more important to write programs that would not require much memory and would not require as many steps for the computer to execute. Now that computers are faster and have more memory, it is often the case that the programmer’s labor is the most scarce resource. This means that it is more efficient to write software in a way that simplifies the programmer’s job, even if it uses more computer time and memory. An added benefit is that if the programmer’s job is simplified, errors (bugs) are less likely.
egosurfing the practice of entering one’s own name into a SEARCH ENGINE to see how many times it turns up. By doing this, one of the authors discovered that there is a professional boxer named Michael Covington.
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electronic data interchange |
EIA (Electronic Industries Alliance) an American organization that promotes industrial standards. On older computer equipment, “EIA” often marks an RS-232 or EIA-232D serial port. The EIA web site is at www.eia.org.
EIA-232D the new official designation for the RS-232 standard for data communication. See RS-232.
EICC (Electronic Industry Citizenship Coalition) a coalition of companies promoting socially responsible practices (web address: www.eicc.info).
EIDE (Extended Integrated Device Electronics) a newer type of IDE disk drive and controller that allows a larger number of sectors per track and thereby overcomes the original limit of 528 megabytes per drive.
EISA (Enhanced Industry-Standard Architecture) a standard 32-bit bus for IBM PC-compatible computers using the 386, 486, or Pentium microprocessor. EISA was developed by a group of competitors as an alternative to IBM’s Micro Channel, retaining more compatibility with the original (ISA) bus. It has been largely superseded by PCI.
In general, EISA computers can use ISA as well as EISA cards. The extra contacts on the EISA card edge connector are in a second row above the contacts that correspond to those on ISA cards.
See ISA; BUS; PCI.
eject
1.to remove a diskette or similar storage device from a computer.
2.to tell a computer that a diskette, CompactFlash card, or other storage device is about to be removed. The Eject operation tells the computer to finish writing data to the device immediately. The drive may or may not physically eject the storage device.
electronic circuit diagram symbols graphical symbols used in schematic diagrams of electronic circuits. Examples are shown in Figure 92 on page 164. See also AND GATE; LOGIC CIRCUITS; NAND GATE; NOT GATE;
OHM’S LAW; OR GATE; PARALLEL; SERIAL; TRANSISTOR.
electronic commerce (EC) the carrying out of business transactions by computers. For example, computers at a store can monitor inventory levels and automatically order more merchandise when it is needed. Electronic commerce also includes transactions where there is a human participant, but the process is highly computerized, such as making purchases over the Internet. See also ELECTRONIC DATA INTERCHANGE; E-TAIL.
Electronic Communications Privacy Act see ECPA.
electronic data interchange (EDI) the transfer of information between organizations in machine-readable form in order to carry out business transactions. Electronic data interchange is becoming popular because it minimizes the errors that can occur if the same information has to be typed into computers several times. See OASIS.
electronic document |
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FIGURE 92. Electronic circuit diagram symbols
electronic document a document intended to be read as it is displayed on a monitor. An electronic document can use HYPERTEXT to create an interactive environment for the reader. It can also use special effects such as animation, sounds, and music. Unlike with traditional printed documents, there is no extra cost for full color. WEB PAGEs are a type of electronic document; so are catalogs, documentation, and MULTIMEDIA presentations distributed on CD-ROM.
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ELIZA |
electronic mail (e-mail) the transmission of messages by computer from one person to another. Messages are saved until the recipient chooses to read them. E-mail is much more convenient than ordinary mail or telephone calls because it arrives immediately but does not require the recipient to be present, nor does it interrupt anything else the recipient may be doing. Messages are easily printed out, saved on disk, or forwarded to other people.
All users of e-mail should be aware that backup copies of the messages can be saved and forwarded to others and that perfect privacy cannot be guaranteed. Contrast CHAT ROOM; INSTANT MESSAGING; NEWSGROUP. See also SPAM.
For abbreviations commonly used in electronic mail, see
FWIW; IANAL; IMHO; IRL; RYFM; TIA; YMMV.
See also ELECTRONIC DATA INTERCHANGE; EMOTICON; FLAME; LOCALAREA NETWORK; WIDE-AREA NETWORK.
electronic paper a display screen that has similar characteristics to ordinary paper.
electronic publishing
1.the creation, manufacturing, and distribution of paperless documents. Examples of electronic documents are CD-ROM encyclopedias and web pages. Each of these new formats brings new challenges and technical problems, but all need the skill of someone who knows how to work with type and how to produce a pleasing combination of graphics and text.
2.the use of specialized computer-controlled equipment in the publishing and printing industries. Desktop publishing may be considered part of this trend, but electronic publishing encompasses the use of equipment not readily available to the mass market (powerful workstation class computers and digital presses, for example). Electronic publishing is superseding traditional methods of PREPRESS production.
electrostatic printer a printer that operates by using an electric charge to deposit toner on paper. Laser printers are electrostatic printers.
element one of the items in an ARRAY or LIST.
elephant’s ear (slang) the symbol @; see AT SIGN.
ELIZA a computer program developed by Joseph Weizenbaum of M.I.T. in 1966 to demonstrate that it is easy to make computers seem intelligent. ELIZA carries on a conversation with the user in the style of a psychotherapist, but it actually responds only to certain patterns of words in the input, ignoring the rest. For example, if the user mentions “mother,” ELIZA might reply, “Tell me more about your mother.”
A version of ELIZA is built into the Emacs editor (Figure 93). To run it, press Esc X and type doctor and then press Enter. See EMACS.
ELIZA passes the TURING TEST in a crude way, thereby demonstrating that human-like intelligence is easily faked. See also ARTIFICIAL INTELLIGENCE.