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`© Copyright 2009, 2006, 2003, 2000, 1998, 1996, 1995, 1992, 1989, and 1986 by Barron’s Educational
`All rights reserved.
`No part of this book may be reproduced or distributed in any form or by any means without the written permission
`
`All inquiries should be addressed to:
`Barron’s Educational Series, Inc.
`250 Wireless Boulevard
`Hauppauge, NY 11788
`www.barronseduc.com
`
`ISBN-13: 978-978-0-764-18175-7 ISBN-10: 978-0-764-18175-7
`
`Library of Congress Catalog Card No. 2008044365
`
`Library of Congress Cataloging­in­Publication Data
`Downing, Douglas.
`Dictionary of computer and Internet terms / Douglas A. Downing, Michael A. Covington, Melody Mauldin
`p. cm.
`ISBN 978-978-0-764-18175-7
`1. Computers—Dictionaries. 2. Internet—Dictionaries. I. Covington, Michael A., 1957- II. Covington, Melody
`
`QA76.15.D667 2009
`004.03—dc22 2008044365
`
`PRINTED IN CHINA
`9 8 7 6 5 4 3 2 1
`TO THE READER
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`Computers are no longer just for specialists. Today, computing is not just a profession and
`virtually all human activities.
`That’s why we’ve compiled this book of background knowledge. Its purpose is to tell you
`already know.
`We design this book to have a convenient size so it can be easily carried around. In compiling
`had to be selective. The quickest way to identify a word that you can’t find in a book is probably
`SEARCH ENGINE). Also, some terms are almost always abbreviated, and in that case you
`rather than the full term.
`Much has changed since the first edition of this book was published more than twenty years
`invented every day. We regularly update the book, and this edition contains new entries on
`Windows Vista and Mac OS X. We’ve also cut out material that was showing its age.
`Terms are marked slang or humorous if they are seldom used in serious writing. They are
`estimation, they are somewhat pretentious new names for old concepts and are not likely to
`Usage notes to explain grammar, spelling, and proper use of words, such as the exact difference
`Throughout, we use SMALL CAPITALS to mark important words that are defined elsewhere
`cross-references, you can quickly find many entries that pertain to whatever interests you.
`wish to start with to learn about particular topics:
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`downstream (describing data transmission) in a direction from the server to the client, or
`peripheral. Compare DOWNLOAD. Contrast UPSTREAM.
`downward compatibility the ability to work with older equipment and/or software than
`program or accessory was designed. Contrast UPWARD COMPATIBILITY.
`dpi (dots per inch) the number of pixels or printer dots per linear inch. The first generation
`with a resolution of 300 dots per inch. 600- and 1200-dpi laser printers are now available.
`details.
`draft quality a printout in low resolution, unsuitable for CAMERA-READY COPY, but adequate
`checking the placement and alignment of graphics.
`drag to move an object by using a mouse. To do this, move the mouse pointer to the object,
`button (usually the leftmost button if there is more than one), and move the mouse. The selected
`mouse pointer, as if the pointer were dragging the object. When you are finished, drop the
`
` 
`drag and drop
`
`FIGURE 85. Drag
`
`1. the ability to move text or graphics by dragging it to a new location with the mouse.
`2. a method of opening an application program. Simply pick up a file icon and drag it
`application program that can open the file.
`
`drain one of the three regions in a field-effect transistor.
`DRAM (Dynamic Random-Access Memory, pronounced “D-ram”) a computer memory that
`sent to it periodically. Almost all computers use DRAM chips for memory. See EDO; MEMORY;
`Contrast SRAM.
`draw program a graphics program that operates in terms of lines and shapes. Unlike a paint
`treats the picture as a collection of objects, each of which will be printed as sharply as the printer
`sharpness of the picture is not limited by the resolution of the screen. Also, individual circles,
`shapes can be moved around without affecting other objects they overlap. However, individual
`Draw programs are sometimes called vector graphics or object­oriented graphics programs.
`Draw programs are preferred for drawing diagrams, while paint programs are superior for
`photographs. Some popular draw programs include Adobe Illustrator, CorelDraw, and Macromedia
`PAINT PROGRAM.
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`server a computer that provides services to another computer (called the client). On multitasking
`provides services to another process is sometimes called a server. For specific examples, see
`X SERVER.
`server­side application a computer program that runs on a network server rather than
`Java servlets are server-side applications; when you view a web page that contains a servlet,
`server rather than on your PC. Contrast CLIENT-SIDE APPLICATION.
`service in Windows, a program that runs continuously, unseen by the user, such as a Web
`a more mundane function such as updating the system clock; the equivalent of a UNIX DAEMON.
`service bureau a business that provides services to computer users, such as high-quality
`conversions, or the like.
`service pack a set of updates to a software package, delivered together or even delivered with
`Usage note: The phrase Windows XP Service Pack 2 can mean either “Service Pack 2 for
`with Service Pack 2 included.”
`service provider a company that provides computer or networking services to customers.
`INTERNET.
`servlet a Java program that runs on a web server. By contrast, an applet is a Java program
`client.
`session
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`1. a period of time during which a person is using a particular computer service, such
`Internet.
`2. an occasion upon which data is written to a recordable CD-ROM. Multisession CDs
`them more than once.
`
`set
`
`1. the input of a flip-flop that places it into state 1, as opposed to the reset input. See FLIP-FLOP.
`2. the command in Windows and UNIX, that stores information in the operating system’s
`ENVIRONMENT).
`3. in mathematics, a collection of objects of any kind. For example, {2, 4, -425} is a set
`{4, 5}} is a set of sets. See INTERSECTION; SET DIFFERENCE; UNION.
`4. a data type in Pascal that consists of a group of values of a specified type.
`
`set difference the set of elements that belong to one set and not to another. For example,
`and {b, c} is {a}.
`SETI@home a distributed computer system where users sign up to have their computers
`from radio telescopes, in a search for extra-terrestrial intelligence (SETI). See setiathome.ssl.berekely.edu
`seven layers see DATA COMMUNICATION.
`SGML (Standard Generalized Markup Language) a standard set of codes for marking boldface,
`files, which became the basis for HTML. See HTML; XML.
`shadow
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`1. (or shadows) the darkest area in a digitized photograph. Contrast HIGHLIGHT (definition
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`upstream (describing data transmission) in a direction from the client to the server, or from
`computer. Compare UPLOAD. Contrast DOWNSTREAM.
`upward compatibility the situation in which a computer program or accessory works not
`it was designed but also on newer models. For instance, programs written for the IBM PC in
`faster) on present-day Pentium machines. Thus we say that the Pentium is upward compatible
`Contrast DOWNWARD COMPATIBILITY.
`urban legend a story that is told by highly educated people as if it were true, but cannot be
`happened to a “friend of a friend” (i.e., a person who is almost, but not quite, identifiable),
`but highly amusing misadventure. The term was coined by Jan Harold Brunvand, who has
`subject. The Internet is one of many means by which urban legends circulate. See also HOAX.
`URL (Uniform Resource Locator, Universal Resource Locator) a way of specifying the location
`information on the Internet, in the form
`
`protocol://machine:port number/filename
`
`Often the port number and/or the filename is unnecessary. For example,
`
`means connect to port 80 of csam.uga.edu using Hypertext Transfer Protocol, and
`ftp://ai.uga.edu/pub/natural.language/Contents means to download a particular file
`Transfer Protocol. A user name and password can be included thus:
`
`This is a handy way to access your web site on its server from your browser. See also
`The URL for a World Wide Web site often includes www, as in http://www.spu.edu
`include gopher and telnet. See ABSOLUTE URL; BROWSER; GOPHER; HTML; HTTP;
`PROTOCOL; RELATIVE URL; TELNET; TILDE; TLD; WORLD WIDE WEB.
`
`.us suffix indicating that an e-mail or web address is registered in the United States. Although
`organizations, .us addresses are used mostly by local governments. See TLD.
`U.S. legal the size of paper used for legal documents in the United States, 8½ × 14 inches.
`U.S. LETTER. See also PAPER SIZES; illustration at Figure 151 on page 281.
`U.S. letter the size of paper used for business letters in the United States, 8½ × 11 inches.
`nearest equivalent. Contrast EXECUTIVE SIZE; U.S. LEGAL. See also PAPER SIZES; illustration
`USB (Universal Serial Bus) a standard way of connecting peripherals to computers, designed
`SCSI, and other kinds of ports. USB 1.0 provides a data rate of 12 million bits per second (Mbps),
`Firewire (IEEE 1394), but cheaper to implement. USB 2.0 (“Hi-Speed USB”) achieves 480
`with the previous version. The maximum cable length is 5 meters (16 feet). Any USB port can
`by using a USB hub, and long cable runs can be achieved by inserting a hub every 5 meters
`Page 505
`Unlike parallel, serial, and SCSI ports, USB ports allow devices to be plugged in and unplugged
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