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Barrons Publishing Dictionary of Computer and Internet Terms 10th

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copy protection

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copy protection any of numerous techniques to keep a diskette, CD, or DVD from being copied with ordinary equipment. Copy-protected diskettes were common in the 1970s and 1980s but fell into disfavor because they were incompatible with newer disk drives. A number of types of copy-pro- tected CDs have appeared recently, and similar problems may befall them. DVD technology has copy protection built in, backed up by a rather unusual copyright law (see DVD; DMCA). See also DRM.

copyleft (humorous) a copyright whose owner gives permission for the product to be distributed free subject to certain conditions. See GNU.

copyright (the right to copy) a legal restriction on the copying of books, magazines, recordings, computer programs, and other materials, in order to protect the original author’s right to ownership of, and compensations for reproduction of, an original work. Most computer programs are protected not only by copyright but also by a software license (see SOFTWARE LICENSE; FREE SOFTWARE).

Since 1989, literary works and computer programs have been protected under U.S. copyright law from the moment they are created. It is not necessary to include a copyright notice or register the copyright with the government.

However, it is still prudent to include a notice of the form Copyright 1996 John Doe or © 1996 John Doe in any work to which you claim copyright. If you think the copyright is likely to be infringed, you should also register it at the time of publication, since this increases the penalties you can collect from the infringer. In general, copies of copyrighted published works must be sent to the Library of Congress whether or not the copyright is registered. For up-to-date information see www.copyright.gov.

U.S. copyright law allows limited copying of books and magazines for private study or classroom use. However, this does not apply to computer programs, which can only be copied with the permission of the copyright owner, or in order to make backup copies that will not be used as long as the original copy is intact.

Do not reproduce copyrighted material on web pages or anywhere on the INTERNET without the owner’s permission. Placing something on a web page constitutes republication just as if you were making printed copies. Remember that copyrights apply to sounds and pictures as well as texts. Distributing a sound bite from a movie or a picture of a cartoon character can be a copyright violation.

Copyright protects expressions of ideas, not the ideas themselves. Copyrights do not cover algorithms, mathematical methods, techniques, or the design of machines (which, however, can be patented).

The purpose of copyright is to encourage communication. It is therefore paradoxical that the Digital Millennium Copyright Act prohibits the publication of certain information about copy protection schemes. See

DMCA. See also COMPUTER LAW; PATENT; TRADE SECRET.

CORBA (Common Object Request Broker Architecture) a standard set of definitions for objects to interact with each other. CORBA was created

BLEND; DRAW PRO-

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country codes

by the Object Management Group (see OMG). CORBA defines a standard for a layer of middleware called the ORB (Object Request Broker). The way that components interact with other components is specified by IDL (Interface Definition Language). This allows client-server computing where the clients don’t need to have any knowledge of the specific operation of the component they are interacting with. For example, the client doesn’t need to know the language in which the component was written; it only needs to know the IDL specification of how the component interacts. For an alternative standard, see DCOM.

core

1.the central part of a CPU, containing the circuitry needed to execute a single series of instructions. A CPU with more than one core can run more than one series of instructions at the same time without switching back and forth between them.

2.the essential design of a CPU, in detail; thus, two different models of CPU might be described as being built on the same core.

3.an old term for RAM, especially magnetic RAM consisting of dough- nut-shaped ferrite “cores” strung on a lattice of wires.

Core Duo one of several models of Intel Pentium microprocessors that have two cores. See CORE (definition 1).

Corel a corporation headquartered in Ottawa, Ontario, that introduced one of the first successful DRAW PROGRAMs, CorelDraw, in 1989. In 1996, Corel acquired the WordPerfect Office business applications. Other Corel products include a variety of computer programs and utilities such as Corel Painter, DVD MovieFactory, and WinDVD. Their web address is www.corel.com.

corona wire a wire, in a laser printer, that emits a strong electric charge (a corona discharge) into the air and onto the adjacent drum. See DRUM.

correspondence points points in two objects (or images) that are associated with each other for blending or morphing. See

GRAM; MORPH.

cos, cosine the cosine trigonometric function. If A is an angle in a right triangle, then the cosine of A (written as cos A) is defined as:

cos A = length of adjacent side length of hypotenuse

The function cos(A) in many programming languages calculates the value of cos A, expressed in radians. For an illustration, see TRIGONOMETRIC FUNCTIONS.

coulomb a unit of electric charge equivalent to the charge of 6.25 × 1018 electrons. See AMPERE.

country codes See CCTLD.

Courier

118

Courier a typewriter-like typeface often used on laser printers. Unlike other typefaces, Courier has fixed pitch; that is, all characters are the same width. It was designed for IBM typewriters in the 1960s, but on modern laser printers, it is often unpleasantly light (thin).

FIGURE 69. Courier, a fixed-pitch font

CP/M (Control Program for Microcomputers) an operating system developed by Digital Research, Inc., and used on microcomputers in the 1980s. (See OPERATING SYSTEM.) The original CP/M (now called CP/M- 80) was widely employed on computers that used the 8-bit Z80 processor. CP/M greatly influenced the early development of DOS. See MS-DOS.

CPU (Central Processing Unit) the part of a computer where arithmetic and logical operations are performed and instructions are decoded and executed. The CPU controls the operation of the computer. A microprocessor is an integrated circuit that contains a complete CPU on a single chip.

CR (carriage return) the character code that tells a printer or terminal to return to the beginning of the line; ASCII code 13. On the Macintosh, CR indicates the end of a line in a text file; UNIX uses LF, and Windows uses CRLF. See CRLF; LF.

cracker a person who “breaks into” computers via the Internet and uses them without authorization, either with malicious intent or simply to show that it can be done. Compare HACKER. See also 2600; COMPUTER TRESPASS; ETHICAL HACKING; HONEYPOT.

crash the sudden, complete failure of a computer because of a hardware failure or program error. A well-designed operating system contains protection against inappropriate instructions so that a user’s program will not be able to cause a system crash.

crawler a computer program that automatically explores the WORLD WIDE WEB and collects information; also called a spider.

Cray Research, Inc. a company founded by Seymour Cray, a manufacturer of supercomputers (see SUPERCOMPUTER). Cray’s first major product was the Cray-1, introduced in 1977, a vector processor designed for repetitious numeric calculations. See VECTOR PROCESSOR. Web address: www.cray.com.

BELLS AND WHISTLES.

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crunch mode

CRC see CYCLICAL REDUNDANCY CHECK.

creeping featurism (slang) the practice of trying to improve software by adding features in an unsystematic way, ultimately making it less reliable and harder to use. Compare

crippleware (slang) software that is distributed free as an incomplete or time-limited version in the hope that the user will purchase the fully functional version. See FREE SOFTWARE.

CRLF (carriage return, line feed) a pair of ASCII codes, 13 and 10, that tell a terminal or printer to return to the beginning of the line and advance to the next line. Under Windows, CRLF indicates the end of a line in a text file; the Macintosh uses CR alone and UNIX uses LF alone. See CR; LF.

CRM (customer relationship management) software for keeping track of past customers, sales prospects, and the like.

crop factor the factor by which the image sensor of a DSLR camera is smaller than the film for which the camera’s lenses were designed. For example, on 35-mm film, each picture is 24 × 36 mm. If a DSLR has an image sensor half as big, 12 × 18 mm, it will have a crop factor of 2. Popular DSLRs actually have a crop factor of about 1.5.

The crop factor effectively multiplies the focal length of the lens. A 100-mm lens on a DSLR with a crop factor of 1.5 will cover the same field of view as a 150-mm lens on a 35-mm film SLR. That is, it has a “35-mm equivalent” of 150 mm.

cross-platform applicable to more than one kind of computer (e.g., PC and Macintosh).

cross-post to place a single copy of a message into two or more newsgroups at once. This is less expensive than posting separate copies of it in different newsgroups. It also ensures that all replies made in any of the newsgroups will be cross-posted to all of them. See NEWSGROUP.

Crossfire technology allowing the use of multiple graphics cards to enhance the computer’s ability to display graphics, developed by ATI (now part of AMD). Contrast NVIDIA.

crossover cable a cable with RJ-45 connectors that swap the input and output lines. A crossover cable can be used to connect two computers with 10base-T networking without a hub. See RJ-45 (wiring table).

CRT (cathode ray tube) a glass tube with a screen that glows when struck by electrons. An image is formed by constantly scanning the screen with an electron beam. Examples of CRTs include television screens and computer monitors. See also EYEGLASSES, COMPUTER.

crunch mode (slang) a work situation in which a deadline is near and everyone is working hard, keeping extended hours. Crunch mode is usually the result of a mistaken estimate made by management, not a genuine emergency. See SOFTWARE ENGINEERING.

cryptography

120

cryptography the technology of encoding information so that it cannot be read by an unauthorized person. See ENCRYPTION and its cross-references.

C/SC text typeset in capitals and small capitals (LIKE THIS). Sometimes written “C + SC.” See also CAPS; SMALL CAPS; U/LC. Contrast EVEN SMALLS.

CSMA/CD see ETHERNET.

CSS

1.See CASCADING STYLE SHEET.

2.(Content Scrambling System) an encryption-based software system developed by movie studios to prevent the copying of DVDs. See DVD;

DECSS; DMCA.

CSV file a text file of comma-separated values, usually with character strings in quotes, thus:

Covington, Michael A.,Valdosta,4633,2.98

Downing, Douglas,Seattle,1234,4.23

Spaces after the commas are permitted but have no effect. This is a popular way of saving the contents of a SPREADSHEET as a text file that can be read back in without losing the arrangement of the data. Compare

TAB-DELIMITED.

Ctrl see CONTROL KEY.

Ctrl-Alt-Del a combination of keys with a special function on PC-compat- ible computers, typed by holding down Ctrl and Alt while pressing Del (Delete). Under Windows, it brings up a menu that makes it possible to kill (terminate) a malfunctioning program. (To do so, in current versions, choose Task Manager.)

In Windows NT and its successors, users must also press Ctrl-Alt-Del in order to log in. For hardware reasons, only the operating system is able to respond to Ctrl-Alt-Del, so this provides assurance that when logging in, the user is seeing a real login prompt, not a fake screen put there by a prankster wanting to collect passwords.

cubic spline a curve that connects a set of points smoothly by solving a system of cubic equations. Unlike a Bézier spline, a cubic spline is defined only by the points that the curve must pass through; it has no control points that are not on the curve.

Cubic splines are the natural shapes of bent objects that are secured at particular points and are free to bend in between. The spline goes through each point smoothly, without sharp bends.

Each segment of the spline (from one point to the next) is modeled by a third-degree (cubic) polynomial of the form y = ax3 + bx2 + cx + d, where a, b, c, and d depend on the endpoints of the segment and the slope that the segment should have at each end.

If (x1,y1) and (x2,y2) are the endpoints and y 1 and y 2 are the slopes, then a, b, c, and d can be found by solving the four-equation system:

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current loop

y1 = ax13 + bx12 + cx1 + d y2 = ax23 + bx22 + cx2 + d y 1 = 3ax12 +2bx1 + c

y 2 = 3ax22 +2bx2 + c

More commonly, the slopes are not known, but the slope at the end of each segment is set equal to the slope at the beginning of the next segment. The slopes and coefficients are then found by solving a system of simultaneous linear equations (linear because x, x2, and x3 are known and can be treated as constants). Compare B-SPLINE; BÉZIER SPLINE.

Figure 70. Cubic spline

cue (in animation and presentation programs) an embedded code that specifies when an action is to occur.

Cuil (www.cuil.com) a search engine that was created to be a rival to Google. It delivers search results in tabs and menus that help the user to narrow the search.

curly brackets the characters { }, also called BRACES. Contrast SQUARE BRACKETS; PARENTHESES; ANGLE BRACKETS.

current the flow of electrical charge. Current is measured in amperes; 1 ampere = 6.25 × 1018 electrons per second = 1 coulomb per second.

current directory the directory in which the computer looks for files if no other directory is specified. The current directory can be changed by cd commands in Windows and UNIX. In Windows, there is a current directory on each drive, so that, for example, C:MYFILE means file MYFILE in the current directory of drive C (whereas C:\MYFILE would mean MYFILE in the root directory).

To see the current directory and current drive, type cd in Windows, or pwd in UNIX.

current drive in Windows and similar operating systems, the disk drive on which the computer looks for files if no other drive is specified. See CUR-

RENT DIRECTORY.

current loop a predecessor of RS-232 serial communication; it is occasionally still seen on older equipment. (See RS-232.) Do not connect current loop equipment directly to RS-232 equipment; the current loop system uses voltages as high as 100 volts and can cause damage.

cursor

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cursor

1.the symbol on a computer terminal that shows you where on the screen the next character you type will appear. Cursors often appear as blinking dashes or rectangles. Many computers have cursor movement (arrow) keys that allow you to move the cursor vertically or horizontally around the screen. This ability is essential for text-editing purposes such as word processing. You can use the mouse to move the cursor quickly around the screen. Compare INSERTION POINT.

2.the mouse pointer. See also HOURGLASS.

cusp node a type of NODE that marks a sudden change in the direction of the line. See Figure 71. Contrast SMOOTH NODE.

FIGURE 71. Cusp node

cut to remove material from the document you are editing and place it into a holding area. See COPY; PASTE; CLIPBOARD.

cyan a vivid greenish-blue color that is one of the standard printing ink colors. See CMYK.

cyber- (prefix) see CYBERNETICS.

cyber cafe an INTERNET CAFE.

Cyberabad nickname for the city of Hyderabad, India, a center of hightechnology industry.

cybernetics the study of the processing of information by machinery, especially computers and control systems; derived from Greek kybernetes meaning “helmsman”; first conceived in the 1940s. Cybernetics has evolved into computer science, operations research, and a number of other fields. The prefix cyber- on numerous computer terms is derived from this word.

cyberpunk

1.an antisocial person who uses computers as a means of self-expres- sion, often performing destructive acts.

2.a genre of science fiction dating from William Gibson’s 1982 novel Neuromancer, with themes of pessimism and rebellion against a com- puter-controlled society.

cyberspace the part of human society and culture that exists in networked computer systems rather than in any particular physical location. For

123

Cyrillic

example, cyberspace is where most bank accounts and electronic messages reside.

cybersquatting another name for DOMAIN NAME POACHING. See also UDRP.

cyburbia (cyber suburbia) the community of computer users that exists in cyberspace. See CYBERSPACE; NETIZEN.

cycle one oscillation of a computer’s CPU CLOCK; the shortest step into which computer actions can be divided. When two or more programs are running at once, they are said to be competing for cycles.

cyclical redundancy check an error-detecting code similar to a CHECKSUM but computed with a more elaborate algorithm. Each segment of the original message is combined with additional bits to make a binary number that is divisible by some previously chosen divisor.

Cyclical redundancy checks are used to ensure that data is read correctly from disks and other storage media. A defective CD or DVD often causes a cyclical redundancy check failure.

cylinder see DISK.

Cyrillic the Russian alphabet. Contrast LATIN.

DAC, D/A converter

124

D

DAC, D/A converter see DIGITAL-TO-ANALOG CONVERTER.

daemon (under UNIX) a program that runs continuously in the background, or is activated by a particular event. The word daemon is Greek for “spirit” or “soul.”

dagger the character †, sometimes used to mark footnotes. See also FOOTNOTE. Also called an OBELISK or LONG CROSS.

daisy-chain to connect devices together in sequence with cables. For example, if four devices A, B, C, and D are daisy-chained, there will be a cable from A to B, a cable from B to C, and a cable from C to D.

daisywheel printer a printer that uses a rotating plastic wheel as a type element. Daisywheel printers were often used with microcomputers in the early 1980s. They printed high-quality text, but they were relatively slow and could not print graphics.

DAS see DIRECT(LY) ATTACHED STORAGE.

dash (—) a punctuation mark similar to a hyphen, but longer. On a typewriter, a dash is typed as two hyphens.

Proportional-pitch type often includes one or more kinds of dashes, such as an em dash (—), which is as wide as the height of the font, and an en dash (–), which is two-thirds as wide as the em dash. Normally, the em dash joins sentences and the en dash joins numbers (as in “1995–98”).

data information. The word was originally the plural of datum, which means “a single fact,” but it is now used as a collective singular.

data bits a parameter of RS-232 serial communication. Either 7 or 8 bits are used for each character, preceded by a start bit and followed by a parity bit (optional) and a stop bit. See also RS-232; KERMIT.

data communication the transfer of information from one computer to another. In order for communication to take place, several aspects of the communication process must be standardized. The international OSI (Open Systems Interconnection) standard (ISO Standard 7498) defines seven layers at which decisions have to be made:

1. Physical layer. What kind of electrical signals are sent from machine to machine? For examples of standards on this level, see

10BASE-T; RS-232; MODEM.

2.Link layer. How do the two machines coordinate the physical sending and receiving of signals? For examples, see HANDSHAKING;

PACKET.

3.Network layer. How does one machine establish a connection with the other? This covers such things as telephone dialing and the

ZIP FILE; STUFFIT;

125 Data Protection Act

routing of packets. For examples, see HAYES COMPATIBILITY (command chart); PACKET; COLLISION; X.25.

4.Transport layer. How do the computers identify each other and coordinate the sending of messages back and forth? This is the level at which most network protocols operate. For examples, see

TCP/IP; NETBEUI; IPX/SPX. See also PROTOCOL.

5.Session layer. How do users establish connections, log on, and identify themselves?

6.Presentation layer. What does the information look like when received on the user’s machine? The presentation layer includes file format and filename conversions and the like.

7.Application layer. How does software use the network—that is, how do application programs exchange data? The application layer does not consist of the programs themselves but, rather, the communication facilities that they use.

The OSI standard does not specify what any of these layers should look like; it merely defines a framework in terms of which future standards can be expressed. In a simple system, some of the layers are handled manually or are trivially simple.

data compression the storage of data in a way that makes it occupy less space than if it were stored in its original form. For example, long sequences of repeated characters can be replaced with short codes that mean “The following character is repeated 35 times,” or the like. A more thorough form of data compression involves using codes of different lengths for different character sequences so that the most common sequences take up less space.

Most text files can be compressed to about half their normal size. Digitized images can often be compressed to 10 percent of their original size (or even more if some loss of fine detail can be tolerated), but machine-language programs sometimes cannot be compressed at all because they contain no recurrent patterns. See also

JPEG; MPEG; MP3.

data mining the exploration of DATABASES to find patterns in the data. For instance, data mining of the sales records of a supermarket chain can reveal seasonal patterns and hidden relationships between products. The classic example is the discovery that an appreciable number of cus- tomers—presumably young fathers—are likely to buy both diapers and beer on Fridays.

data processing the processing of information by computers. This term dates back to the 1960s and often describes the part of a business organization that handles repetitive computerized tasks such as billing and payroll.

Data Protection Act a British law protecting people from misuse of their personal information, enforced by the Information Commissioner’s Office (web address: www.ico.gov.uk).

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