Barrons Publishing Dictionary of Computer and Internet Terms 10th

address portion of the bus, activates the “read memory” line, and waits a specified length of time. The memory places the contents of that location 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 microcontrollers 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 translates 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 prosecutable as theft of services (just like using any other machine without 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 confidential 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 confidential information through e-mail unless you have confirmed that it is traveling by a secure path.

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 community 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, computer 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

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), engineering (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

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 computers 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 similar 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 perpetrated 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 programmer can easily conceal abuse.

More recently, some people have gotten their kicks by distributing destructive computer programs over the Internet. See TROJAN 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 possibilities for connecting to your computer from elsewhere, and that you’ve blocked all access that you don’t want to allow. The

UNIX operating system, designed originally for use in laboratories where no security was needed, is generally thought to be particularly 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 distance. 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 software, 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 trustworthy 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 FLOODING; VIRUS.

computer trespass the crime of using a computer without the owner’s permission (see CRACKER). Even in jurisdictions that have no specific law against it, computer trespass is illegal under pre-existing laws that prohibit 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 computer 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 developed by Herman Hollerith to help the U.S. Census Bureau tabulate the census of 1890. (See PUNCHED CARD.) The first electronic digital com-

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 introduced 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 integrated circuits, which were first developed in the late 1950s, made it possible 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 microcomputer is built around a microprocessor chip, such as the 486 or Pentium, that contains the entire central processing unit on a single crystal 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 programs, where a single CPU is actually switching its attention back and forth between them very rapidly. See also MULTITASKING; PARALLEL PROCESSING; TIMESHARING.

conferencing the use of computer networks to enable workers to communicate 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;

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 purpose 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 windowing (Figure 66), including but not limited to DOS programs. A window 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 program. Literal expressions, such as 3.5 and ”DOLLY MADISON”, are constants because they always stand for the same value.

constrain (in drawing programs) to restrict or limit the available movements 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.

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 noncontiguous sectors. (See DISK.) Access is slowed if the sectors are not contiguous, 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 similar 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

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 settings that affect the computer’s operation. These range from desktop color, mouse tracking, and the like, to network communication parameters 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 brightnesses, you can use the following convolution matrix: