address portion of the bus, activates the “read memory” line, and waits a specified length of time. The memory places the contents of that loca- tion onto the data portion of the bus so that the CPU can read it. To put data into memory, the CPU puts both the address and the data onto the bus and activates the “write memory” line. Some computers also include “read port” and “write port” lines, which are like the lines used for accessing memory except that addresses are understood as applying to input and output devices (printer ports, etc.) rather than memory. Most computers use a VON NEUMANN ARCHITECTURE, which means that programs and data are stored in the same kind of memory. Some micro- controllers use a HARVARD ARCHITECTURE, with separate memories for program and data (mainly because programs are kept permanently recorded in ROM, but data must be changeable). Programmers normally do not write CPU instructions. Instead, they write programs in a high-level language such as BASIC, C, or Pascal, and use a COMPILER to translate the programs into machine language. It is also possible to write programs in ASSEMBLY LANGUAGE, which trans- lates into machine language more directly. computer ethics the responsible use of computers and computer networks. Malicious misuse of computers is rare, but serious misjudgments by well-meaning people are unfortunately common. Some important points to remember are the following: 1. People have the same legal and ethical responsibilities when using a computer as at any other time. Slander, deception, harassment, and the like are just as wrong when done via computer as when done any other way, and they incur the same legal penalties. Using a computer without the owner’s permission is prose- cutable as theft of services (just like using any other machine with- out the owner’s permission). Damaging property or data by releasing a computer virus is also prosecutable as a crime. 2. Computers will not necessarily prevent all improper acts; users are responsible for what they do. For example, if a computer is set up incorrectly so that it lets unauthorized people use it without a password, that does not justify the unauthorized usage, just as a defective door lock does not justify burglary. 3. Some of the information stored in computers is private and confiden- tial and should not be abused. This applies particularly to credit records, educational records, and the like. Such information may also be incomplete or inaccurate because people did not correct errors that they considered inconsequential. If the information is later used for a completely different purpose, the errors can be damaging. 4. Electronic communications are not guaranteed to be private. You do not know what path your electronic mail follows or who may see it en route. Do not send credit card numbers or other confi- dential information through e-mail unless you have confirmed that it is traveling by a secure path. 107 computer ethics 7_4105_DO_CompInternetTerms_C 12/29/08 10:21 AM Page 107 Also, be aware that e-mail can be faked; there is no guarantee that a piece of mail actually came from the person or site shown on the header. 5. Users must respect software copyrights and licenses. The price of a piece of software is more than just the cost of the disk and manual; it’s also your share of the cost of developing the product. If people don’t pay for software, there will be no software. 6. Manufacturers, programmers, and independent consultants have responsibilities to their customers. It’s wrong to claim to be more of an expert than you really are; it’s also wrong to sell a shoddy product while concealing defects in it. Admittedly, no one can ensure that any complex piece of software is 100% reliable, but common decency requires programmers and vendors to act in good faith—when there’s a problem, do your best to correct it or at least warn the user about it. In the past, many manufacturers have tried to disclaim all responsibility for the performance of their products, but there are encouraging signs that the user com- munity will no longer tolerate this dubious practice. 7. On the Internet, you are everyone else’s guest. The cost of running the Internet is paid by the sites that receive messages, not just the sites that send them. Accordingly, you must be careful what you send out, and to whom. For more about ethical aspects of computer communications see ACCEPTABLE-USE POLICY; COMPUTER LAW; DOMAIN NAME POACHING; HACKER ETHIC; INTERNET; MAIL BOMBING; NETIQUETTE; OBSCENITY; PORNOGRAPHY; SPAM; SPOOFING; USENET. computer law laws pertaining to computers. An important principle is that computers are not exempt from the pre-existing laws. For instance, com- puter users must obey laws against fraud, misrepresentation, harassment, eavesdropping, theft of services, and tampering with other people’s property, even if the laws do not specifically mention computers. Further, many jurisdictions have specific laws against COMPUTER TRES- PASS and similar acts. See also ACCEPTABLE-USE POLICY; COMMUNICATIONS DECENCY ACT; COPYRIGHT; DMCA; ECPA; GAMBLING; LICENSE; MICROSOFT ANTITRUST CHARGES; PATENT; PORNOGRAPHY; PUBLIC DOMAIN; PYRAMID SCHEME; TRADE SECRET; VIRUS. computer priesthood (1970s slang, still used) computer specialists; the experts on whom ordinary people rely for their access to the computers, as if they were priests with access to a secret part of the temple. computer science the mathematical and scientific study of the possible uses of computers. Computer science is a wide-ranging field including pure mathematics (see COMPLEXITY THEORY; HALTING PROBLEM), engi- neering (see COMPUTER ARCHITECTURE), management (see SOFTWARE ENGINEERING), and even the study of the human mind (see ARTIFICIAL INTELLIGENCE). Indeed, computer scientists often work on problems in almost any field to which computers can be applied. Computer science computer law 108 7_4105_DO_CompInternetTerms_C 12/29/08 10:21 AM Page 108 is more than just training in the use of today’s computers and software; it includes preparation to understand the technology of the future and its theoretical underpinnings. computer security the protection of computers from tampering, physical danger, and unwanted disclosure of data. The advent of personal com- puters has made it easy for important business records or confidential data to be lost, sabotaged, or misused. Computers need protection from the following kinds of hazards: 1. Machine failure. Make backups of important files frequently. Every disk drive in the world will one day fail, losing all data. 2. Physical hazards. Protect the computer from fire, flood, and sim- ilar hazards, and store backups at a remote location. Remember, too, that the machine can be stolen. An increasing number of computer thieves are after data, not just equipment. When traveling with a laptop computer, never let it out of your possession. Many thefts occur at airport check-in counters: while you are preoccupied making your arrangements, someone can quietly steal the laptop computer you placed on the floor. Keep the computer in your hand. Stay close to the computer as it goes through the airport security check. Always bring your laptop on board as carry-on luggage. Checked baggage is treated far too roughly. 3. Operator error. It is easy to delete information accidentally. This hazard can be minimized with software that retains original files while altered copies are being made. 4. Computer tampering. Can someone come in and alter your records without your knowing it? Bear in mind that large numbers of people know how to use popular business software packages. If possible, use software that keeps records of changes—recording who made them and when—and requires validation (such as a password) to make unusual changes. 5. Malicious programming. Some computer crimes have been per- petrated by programmers who did such things as collect all the money that was lost by rounding interest payments to the nearest penny. A clever bookkeeping system run by a dishonest pro- grammer can easily conceal abuse. More recently, some people have gotten their kicks by distrib- uting destructive computer programs over the Internet. See TRO- JAN HORSE. Even more have gotten their kicks by circulating false warnings (see HOAX). 6. Malicious programs arriving in e-mail, often falsely described as other things. Never open a file that arrives unexpectedly, even if it’s from someone you know, unless you have confirmed what the file is. See WORM. 7. Break-ins by modem or network. Make sure you know all the pos- sibilities for connecting to your computer from elsewhere, and that you’ve blocked all access that you don’t want to allow. The 109 computer security 7_4105_DO_CompInternetTerms_C 12/29/08 10:21 AM Page 109 UNIX operating system, designed originally for use in laborato- ries where no security was needed, is generally thought to be par- ticularly vulnerable. See DICTIONARY ATTACK; WAR DIALING. 8. Be especially careful with wireless networks, and make sure all communications are encrypted. A cracker with a special antenna can access your wireless network from ten times the normal dis- tance. See WAR DRIVING; WIRELESS NETWORK. 9. Easily guessed passwords. A computer password must never be a person’s initials, nickname, child’s name, birthdate, etc., nor should it be a correctly spelled word in any language. A common way to crack accounts is to try all the words in a large dictionary, as well as all names and abbreviations that are associated with a person. Also, if a user signs onto a computer and then leaves the terminal unattended, others can tamper with it without typing the password. 10. Viruses and known software defects. Always run antivirus soft- ware, and make sure your software and operating system are kept up to date. 11. Excessive security measures. Excessive attempts to build security into a computer can easily make the computer so hard to use that productivity is crippled. In the final analysis, all computer security depends on human trustworthiness. Concentrate on securing the people, not the machine. That is, ensure that employees are trust- worthy and that strangers have no access to the machine; then give authorized users all the access they need to do their jobs effectively. See also 2600; DDOS; DENIAL-OF-SERVICE ATTACK; ENCRYPTION; ETHICAL HACKING; FINE-GRAINED SECURITY; HONEYPOT; MAIL BOMBING; PING FLOOD- ING; VIRUS. computer trespass the crime of using a computer without the owner’s per- mission (see CRACKER). Even in jurisdictions that have no specific law against it, computer trespass is illegal under pre-existing laws that pro- hibit unauthorized use of other people’s property. computer virus see VIRUS. computer vision see VISION, COMPUTER. computers, history of a story spanning many centuries. The abacus, on which information is stored by moving beads along rods, was one of the earliest calculating devices. Blaise Pascal developed an adding machine in 1642 that used toothed wheels to handle carries from one digit to the next. Charles Babbage developed the concept of a stored program com- puter when he designed the “Analytical Engine” in 1833. Unfortunately, the mechanical devices of his day could not be made to work reliably, so the “Analytical Engine” was never completed. An important data processing device, the punched card, was devel- oped by Herman Hollerith to help the U.S. Census Bureau tabulate the census of 1890. (See PUNCHED CARD.) The first electronic digital com- computer trespass 110 7_4105_DO_CompInternetTerms_C 12/29/08 10:21 AM Page 110 puter was the ENIAC (Electronic Numerical Integrator and Calculator), which was built for the U.S. Army in 1946, largely because of the need to calculate ballistics tables. The ENIAC was programmed by plugging in cables to connect different units. In 1945 John von Neumann intro- duced the modern concept of a stored-program computer, in which the computer memory could store both programs and data. Once the concept was established, major improvements were made by developing smaller and more reliable electronic components. The ENIAC was a huge machine made with vacuum tubes. The invention of the transistor in the late 1940s made it possible to build much smaller computers that needed less cooling. Continued improvements in inte- grated circuits, which were first developed in the late 1950s, made it pos- sible to continue the miniaturization of computers. An important advance occurred in the mid-1970s when the first microcomputers were built. Previously, all computers had been large and expensive. Microcomputers are small enough and cheap enough that they can be purchased by small businesses and individuals. A micro- computer is built around a microprocessor chip, such as the 486 or Pentium, that contains the entire central processing unit on a single crys- tal of silicon. The advent of powerful, low-cost microcomputers has made the computer a common household appliance. concatenation the operation of joining two or more character strings together, end to end. For example, ”ABC” concatenated with ”DEF” equals ”ABCDEF”. See STRING OPERATIONS. concurrent processing the apparently simultaneous execution of two pro- grams, where a single CPU is actually switching its attention back and forth between them very rapidly. See also MULTITASKING; PARALLEL PRO- CESSING; TIMESHARING. conferencing the use of computer networks to enable workers to commu- nicate in real time (without delay) while working together. See IRC; MUD. confidence factor (certainty factor) a truth value between 0 and 1, used to describe the reliability of a piece of information whose truth is unclear or uncertain. There are several systems of reasoning that use confidence factors; for one example, see FUZZY LOGIC. Contrast DEFAULT LOGIC, which deals with exceptions without using confidence factors. CONFIG.SYS in DOS and early versions of Windows, a file that contains information about the machine configuration, including device drivers to be loaded as the machine boots up. It is processed before AUTOEXEC.BAT. In Windows NT, 2000, XP, and their successors, the function of CONFIG.SYS has been taken over by the Registry. A separate file, CONFIG.NT, if present, is processed at the beginning of every DOS-mode program. configure to set up a computer or program to be used in a particular way. Many commercial software packages have to be configured, or installed; 111 configure 7_4105_DO_CompInternetTerms_C 12/29/08 10:21 AM Page 111 this involves setting them up for a particular machine (including video card and printer) and for a particular user’s preferences. console 1. the main keyboard and screen of a multi-user computer. 2. a keyboard and (non-graphical) screen, or a window serving the pur- pose of such a screen. console application a Windows program that runs in CONSOLE MODE. console mode the way in which Windows runs programs that do not use win- dowing (Figure 66), including but not limited to DOS programs. A win- dow is used as a substitute for the whole screen in text mode. By pressing Alt-Enter, the user can give the program control of the whole screen. FIGURE 66. Console mode constant a value that remains unchanged during the execution of a pro- gram. Literal expressions, such as 3.5 and ”DOLLY MADISON”, are con- stants because they always stand for the same value. constrain (in drawing programs) to restrict or limit the available move- ments or shapes. For example, when drawing a circle with a circle tool, you must hold down the Control key to constrain the rounded shape to a circle. If you let go of the constraining key too soon, you may get a fat oval rather than a perfect circle. The constrain command is also used with the rectangle drawing tool (constrains to a square) and the line drawing tool (constrains to preset angles). constructor in OBJECT-ORIENTED PROGRAMMING, a method called when a new object is created. content provider a company or organization that provides information (content) online. For example, www.cnn.com (Cable News Network) is a content provider for world news and related information. Contrast ASP (definition 2); INTERNET SERVICE PROVIDER. console 112 7_4105_DO_CompInternetTerms_C 12/29/08 10:21 AM Page 112 contention see DEVICE CONTENTION. context-sensitive help information provided by a computer program when you ask for help, chosen to match what you are doing at the time. For example, a context-sensitive help key will give you information about how to edit if you press it while editing, or how to print if you press it while preparing to print. contiguous adjacent, next to each other. For instance, the states of North Dakota and South Dakota are contiguous, but Texas and Maine are not. Most computers can store a disk file in either contiguous or noncon- tiguous sectors. (See DISK.) Access is slowed if the sectors are not con- tiguous, since to get from one part of the file to another, the read/write head must jump from one part of the disk to another. See FRAGMENTATION. continuous speech speech that is spoken without pauses between words. See SPEECH RECOGNITION. Contrast DISCRETE SPEECH. contrast the range of light and dark values in a grayscale (continuous tone) image. A high-contrast image is mostly white and black with very few intermediate gray shades. A low-contrast image has little difference between the darkest darks and lightest lights. See Figure 67. Contrast is best adjusted at the time of scanning the image. If that is not possible, contrast can be adjusted in a PAINT PROGRAM. See SCANNER; HISTOGRAM. FIGURE 67. Contrast: low, normal, and high contrast ratio the luminosity of the brightest white that can be produced by a monitor divided by the luminosity of the darkest black. control a reusable software component in Visual Basic, ActiveX, or a sim- ilar system. Many of the first controls were user interface components— check boxes, sliding bars, and the like—hence the name. control box (Windows) a small box at the left of the title bar of a window. Clicking the control box pops up a menu for controlling the size of the 113 control box 7_4105_DO_CompInternetTerms_C 12/29/08 10:21 AM Page 113 window. Double-clicking on the control box closes the window and the application running in it. Control key (Ctrl or Cntl key) a special key on many computer keyboards. When it is pressed in conjunction with another key, it gives the other key a new meaning that depends on the program in use. See ASCII to see how the Control key can be used to type nonprintable control characters. control menu (Windows) a menu that appears when the user clicks on the CONTROL BOX (the box at the left of the title bar). The control menu for each window allows you to maximize, minimize, restore, resize, or close the window. See Figure 68 for illustration. See also WINDOW. FIGURE 68. Control menu Control Panel (in Windows) a group of utility programs for making set- tings that affect the computer’s operation. These range from desktop color, mouse tracking, and the like, to network communication parame- ters and printer drivers. control point see NODE. CONUS abbreviation for continental United States, usually meaning the 48 contiguous states. (Alaska is part of the North American continent but is commonly overlooked.) conversion program a program that is capable of changing a file from one format to another. For example, to use a TIFF (Tagged Image File Format) file in a web page design, the image must be converted to .JPEG or .GIF format. This can be done with a separate conversion program or by using the “Save as . . . ” command in the appropriate image-editing program. (See IMPORT; EXPORT; FILE FORMAT.) Note that simply changing the name of the file from myfile.tif to myfile.jpg does not convert the file type. The data contained in the file has to be reorganized by the conversion program. convolution an image processing computation described by a matrix. Suppose, for example, that you want to bring out fine detail in an image. One way to do this is to increase the difference between each pixel and its neighbors. Treating the pixels as numbers representing their bright- nesses, you can use the following convolution matrix: Control key 114 7_4105_DO_CompInternetTerms_C 12/29/08 10:21 AM Page 114 –1 –1 –1 –19–1 –1 –1 –1 That means: Work through the whole image, one pixel at a time. Whenever you get to a pixel, multiply it by 9, multiply each of the sur- rounding pixels by –1, and add them together. Then replace the original pixel with that value. If all of the pixels are the same brightness, nothing changes, but if a pixel is brighter or fainter than its neighbors, the difference is exagger- ated by a factor of 9. Other convolutions can perform other special effects, such as smoothing, eliminating details smaller or larger than a certain size, and even eliminating streaks in a particular direction. When performing a convolution, the input is always from the origi- nal, unprocessed image. That is, the next pixel will not be affected by any changes made by the processing of the previous pixel. convolve to perform a convolution. See CONVOLUTION. cookie information stored on a user’s computer by a WEB BROWSER at the request of software at a web site. Web sites use cookies to recognize users who have previously visited them. The next time the user accesses that site, the information in the cookie is sent back to the site so the infor- mation displayed can vary depending on the user’s preferences. Cookies are not a security risk because they only store information that came from the web site or was sent to it by the user. The term cookie comes from a 1980s prank computer program called Cookie Monster that would interrupt users and demand that they type the word “cookie” before continuing. .coop a suffix indicating that a web or e-mail address belongs to a cooper- ative (i.e., a customer-owned business [in any country]). Contrast .COM. See also ICANN; TLD. COPPA (Children’s Online Privacy Protection Act) a law passed by Congress in 1998 (15 USC 6501-6502) making it illegal for an operator of a web site or online service to collect personal information from chil- dren without parental consent. See COMPUTER LAW. coprocessor a separate circuit inside a computer that adds additional func- tions to the CPU (central processing unit) or handles extra work while the CPU is doing something else. copy 1. to duplicate information in another place, leaving the original unchanged. In many spreadsheets, editors, and drawing programs, copy means either of two things: a. to copy material from one place to another; b. to copy material from the document being edited into a holding area, from which you can then “paste” it elsewhere. See CUT; PASTE; CLIPBOARD. 2. a command that makes a copy of a disk file. See also XCOPY. 115 copy 7_4105_DO_CompInternetTerms_C 12/29/08 10:21 AM Page 115 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 pro- tected not only by copyright but also by a software license (see SOFT- WARE LICENSE; FREE SOFTWARE). Since 1989, literary works and computer programs have been pro- tected 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 copy- right. 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 copy- right 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 com- puter 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 there- fore 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 copy protection 116 7_4105_DO_CompInternetTerms_C 12/29/08 10:21 AM Page 116 [...]... microcomputers, such as dBASE and Microsoft Access, and some data management capabilities are provided with spreadsheets such as Lotus 1-2 -3 and Excel Some examples of database applications include maintaining employee lists and preparing payrolls; maintaining parts order lists and keeping track of inventories; maintaining customer lists and preparing bills for credit customers; and keeping track of. .. character that marks the beginning or end of a special part of a computer program For instance, /* and */ are delimiters marking the beginning and end of a comment in C In many programming languages, quotation marks are used as delimiters to mark character strings 7_4105_DO_CompInternetTerms_D 12/29/08 10:22 AM 133 Page 133 deselect Delphi an object-oriented version of the programming language PASCAL for... uses computers as a means of self-expression, 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 computer- controlled society cyberspace the part of human society and culture that exists in networked computer systems rather than in any particular physical location For 7_4105_DO_CompInternetTerms_C... 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... 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) 7_4105_DO_CompInternetTerms_D data rate... basic ways of doing this are the following: 1 An array consists of many items of the same type, identified by number The examination scores of a college class might be represented as an array of numbers A picture can be represented as a large array of brightness readings, one for each of the thousands of cells into which the picture is divided 2 A record (in C, a struct) consists of items of different... 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: 7_4105_DO_CompInternetTerms_C... designations for the kind of connectors commonly used on serial ports, video cards, and parallel ports respectively, with 9, 15, or 25 pins For pictures see Figure 235 (page 432 ) and Figure 189 (page 35 2) The suffix P means “plug” and S means “socket;” thus a DB-25P has 25 pins and a DB-25S has 25 holes See VGA CONNECTOR DB2 popular database management software from IBM (see www -30 6.ibm.com/software/data/db2)... 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... OPTION BUTTONS; TEXT BOX FIGURE 76 Dialog box 7_4105_DO_CompInternetTerms_D 12/29/08 10:22 AM 137 Page 137 digital divide dictionary attack an attempt to guess a computer password by trying every word in a large dictionary and, often, every combination of letters that would make a pronounceable word die (plural dice or die) the individual piece of silicon containing a transistor or integrated circuit . Users must respect software copyrights and licenses. The price of a piece of software is more than just the cost of the disk and manual; it’s also your share of the cost of developing the product which computers can be applied. Computer science computer law 108 7_4105_DO_CompInternetTerms_C 12/29/08 10:21 AM Page 108 is more than just training in the use of today’s computers and software; it. access to the computers, as if they were priests with access to a secret part of the temple. computer science the mathematical and scientific study of the possible uses of computers. Computer science