Barrons Publishing Dictionary of Computer and Internet Terms 10th

identifier a symbolic name used in a program and defined by the programmer. Most identifiers stand for variables (see VARIABLE); however, some languages allow the use of identifiers to represent constants, so that the value of a particular constant, wherever it occurs in the program, can be changed by changing the statement that defines the identifier. See

CONSTANT.

identity in Outlook Express or similar mail-reading programs, a setting that determines which of several individuals is using the computer. This enables several people to share a computer and keep their e-mail separate even though the operating system is not set up for multiple users.

identity theft the crime of impersonation (i.e., pretending to be someone else), using forged documents of various kinds. Crucially, identity theft goes beyond the theft of a single credit card number or the forgery of a single document. It is an attempt to assume a person’s entire identity, including name and credit rating, in order to create new accounts under the victim’s name.

Identity theft often involves electronic communications media by taking advantage of the fact that online and mail-order merchants are often not very thorough in checking credit card users. See also COMPUTER ETHICS; EVIL TWIN; PHISHING.

ideogram, ideograph a written symbol that represents an idea rather than the pronunciation of a word. Symbols such as &, $, numerals, and computer icons are ideograms.

IDL (Interface Definition Language) see CORBA.

IE abbreviation for INTERNET EXPLORER.

IEC (International Electrotechnical Commission) an organization that sets numerous standards for the electronics industry. Web address: www.iec.ch.

IEC power connector the type of connector commonly used to attach a PC’s power cord to the computer, using three prongs oriented in the same direction.

FIGURE 137. IEC power connector

IEEE (Institute of Electrical and Electronics Engineers) the leading professional society for electrical and computer engineers in the United States. It publishes journals, holds conferences, and publishes many standards applicable to computer equipment. The IEEE is headquartered

247 if

in Piscataway, New Jersey, and can be reached on the Web at www.ieee.org.

IEEE 1284 an IEEE standard for PC parallel ports, compatible with the designs used previously, but including provision for high-performance bidirectional communication with tape drives, disk drives, and other devices, not just printers. It is fully compatible with earlier EPP and ECP standards.

The IEEE 1284 standard defines three connectors: the traditional 25pin socket on the PC (IEEE 1284A), the 36-pin Centronics connector on the printer (IEEE 1284B), and a new miniature connector (IEEE 1284C).

Parallel ports are IEEE 1284 compliant if they implement the whole IEEE 1284 standard; they are IEEE 1284 compatible if they implement one or more of the older standards of which IEEE 1284 is a superset.

See CENTRONICS INTERFACE; PARALLEL PORT.

IEEE 1394, 1394a, 1394b see FIREWIRE.

IEEE 802.11 see 802.11.

IETF (Internet Engineering Task Force) an international group of network professionals who work on advances in Internet architecture and work to ensure smooth operation of the Internet. The IETF is organized into several working groups on specific topics. Their web address is www.ietf.org.

if a keyword in many programming languages that specifies that different actions are to be performed depending on the result of some test. Here is a simple example of an if statement in Java:

if (price == 0)

{

System.out.println

(”Price can’t be equal to zero!”);

}

Here is a more practical example:

if (hours<=40)

{

pay=hours*wage;

System.out.println(”No overtime hours”);

}

else

{

overtime = hours-40;

pay= wage*40 + 1.5*wage*overtime; System.out.println(”Overtime paid”);

}

In C, C++, Java, and C#, a very common error is to write if (x=5) when you mean if (x==5) or the like. Here x=5 is a command to assign the value 5 to the variable x. Some compilers will object when you embed

the command in an if statement, but in C, doing so is legal (and always comes out true if the value assigned is nonzero).

ignore list a list of users you have blocked in a chat or instant messaging program. When another user is on your ignore list, your software will ignore messages from them. Synonyms: BLACKLIST; KILL FILE.

IIOP (Internet Inter-ORB Protocol) a protocol that extends TCP/IP by adding CORBA defined messages for objects to connect to each other over the network. See CORBA; PROTOCOL.

IIRC online abbreviation for “if I remember correctly.”

IIS (Internet Information Services) the component of Microsoft Windows (professional and server editions only) that enables the computer to work as a web, FTP, and e-mail server.

i.LINK see FIREWIRE.

illegal operation an operation that a program is not permitted to perform, such as writing on a read-only disk or using memory allocated to some other program. Illegal operations are almost invariably the result of errors in programming.

IM Instant Message or Messenger; see AIM; LIVE MESSENGER.

iMac a line of Apple Macintosh computers with a distinctive streamlined design introduced in 1998. The current iMac computer is built entirely within its flat-screen monitor. See also APPLE; MACINTOSH.

image

1.a picture, represented in a computer’s memory. See GRAPHICS.

2.a copy, on a disk, of the contents of a computer’s memory. A BOOT DISK may contain an image in this sense, i.e., a large block of data that can be copied directly into memory.

image map a web page graphic to which multiple links have been assigned. It is possible to click on different parts of the picture and activate different links. For example, you might create a map of your community that appears on the web page; if the user clicks on the part of the map representing one neighborhood, then the browser will jump to a link providing information about that neighborhood. This gives the links a visual meaning that would not be there in a list of text-only links. Image maps can be created with some web-creation software programs, or they can be defined directly by hand-coding the proper HTML.

image processing the use of a computer to modify pictures (usually bitmap images). Applications of image processing include computer vision, enhancement of photographs, and creation of works of art. Many image processing functions are built into PAINT PROGRAMs as FILTERs (definition

1). For examples, see ADD NOISE; BLEND; BLUR; BRIGHTNESS; COLOR/GRAY MAP; EDGE DETECT; EQUALIZE; HISTOGRAM; MOTION BLUR; PIXELATE, PIXELIZE; REMOVE SPOTS; SHARPEN; UNSHARP MASKING. See also COLOR; COMPUTER; CONVOLUTION; DEBLURRING; RETOUCHING; VISION.

imagesetter a high-quality output device. Imagesetters can deliver up to 2400 DPI (dots per inch) instead of the 300 to 1200 DPI of ordinary laser printers.

IMAP (Internet Mail Access Protocol) a protocol for viewing e-mail on a personal computer while leaving it in place on the host system. Contrast POP, which delivers the mail and deletes it from the server. See PROTOCOL.

IMG tag used in HTML to indicate an image file. For example, see HTML.

IMHO online abbreviation for “in my humble opinion.”

IMO online abbreviation for “in my opinion.”

impact printer a printer that prints on paper by impacting a cloth ribbon coated with ink, thus transferring ink to the paper. Dot-matrix printers are the most common type of impact printer. Today, impact printers are used mainly for business forms that involve carbon paper or carbonless copy paper. See DOT-MATRIX PRINTER; LINE PRINTER; PICKUP ROLLER.

impedance a measure of how easily an alternating current can pass through an electrical circuit. The impedance of a resistor is the same as its resistance. Capacitors and inductors also affect impedance, depending on the frequency of the current. The impedance of a capacitor decreases as the frequency increases; the impedance of an inductor increases as the frequency increases. The characteristic impedance of coaxial cable results from the interaction of its inductance and capacitance. It is not a resistance and cannot be measured with an ohmmeter. See COAXIAL CABLE.

import to load a file from a format other than the application program’s native format. Many word processing and graphics programs have the ability to import text and graphics from several different file formats. Because importing is a type of file conversion, formatting and image detail may be lost in the process. See CONVERSION PROGRAM.

in the loop (jargon) involved in decision-making or control, like an automatic control system that uses feedback. See LOOP (definition 2).

incremental backup a backup operation that only copies files that have changed since the last backup. See BACKUP COPY.

incremental compiler a compiler that compiles the lines of a program as they are typed into the computer, rather than compiling the whole program at once. The purpose is to keep the programmer from having to wait a long time for the complete program to be compiled when it is finished. See COMPILER.

indecency material that offends ordinary people but does not meet the legal criterion of obscenity. In the United States, indecent material is protected by the First Amendment (freedom of speech) and is legal in printed publications, cable TV, and the Internet, but not on radio and TV broadcasts that use publicly available channels. See also ICRA; OBSCEN-

ITY; PORNOGRAPHY.

indent to leave a space at the beginning of the first line of a paragraph. Indented margins are also used to set off long quotations. See also HANG-

ING INDENT.

index

1.an alphabetical listing of important words and concepts found in a book and the pages on which these terms may be found. Many page layout and word processing programs have the ability to automatically generate indexes from properly tagged terms (see DESKTOP PUBLISHING; TAG). Note that the process is not wholly automatic; the human still has to specify which words should be indexed.

2.a pictograph of a pointing hand. Sometimes called a fist.

3.the number that picks out an element of an array. For example, in A[2], 2 is the index. See ARRAY.

FIGURE 138. Index (definition 2)

indexed file a file in which the order of the items is recorded in a separate file called the index. For example, if the computer is looking for John Smith’s billing records, it first looks up “Smith, John” in the index, and then the index tells it where to look in the billing record file.

index.htm, index.html on many web servers, the file name that is used for a WEB PAGE when no file name is specified in the URL. Thus, index.html is usually the main page of a web site (hence its name). Compare

DEFAULT.ASP.

Industry Standard Architecture see ISA.

INF file a type of file, with extension .inf, that tells the Windows Setup program how to install a particular piece of hardware or software.

inference engine the part of an EXPERT SYSTEM that draws conclusions by reasoning logically from information. See also

GENCE; PROLOG.

inferior character a subscript; small letters and numbers set on or below the baseline like this. Used mainly in mathematical typesetting. See SUBSCRIPT. Contrast SUPERIOR CHARACTER; SUPERSCRIPT.

.info a suffix for a web or e-mail address. Unlike .biz, etc., .info domain names can be assigned to any individual or organization, in any country.

Contrast .BIZ, .COM. See also ICANN; TLD.

Infobahn German for INFORMATION SUPERHIGHWAY.

informatics the study of information and computation; a European name for computer science. See COMPUTER SCIENCE.

information extraction the act of extracting, by computer, recognizable information from documents written in a human language; an example would be reading weather reports in English and constructing a table of dates and temperatures. Compare INFORMATION RETRIEVAL.

information hiding see STRUCTURED PROGRAMMING.

information retrieval the act of identifying, by computer, documents written in a human language that are relevant to some specific question. This goes beyond simply searching for words and phrases and often includes statistical analysis of vocabulary (to determine subject matter) and a considerable amount of NATURAL LANGUAGE PROCESSING.

Information Superhighway a network of electronic and digital communication equipment that is quietly revolutionizing businesses and our private lives (see INTERNET).

Not only is information being disseminated faster than ever, but worldwide electronic communication is creating a unique community— one that does not have a physical location, but rather exists in what is called CYBERSPACE. Some portions of cyberspace are rather lawless right now; an ill-considered message may bring down an avalanche of angry messages (called FLAMEs) upon your e-mail account. However, some standards of ethics and personal behavior are being worked out. See

COMPUTER ETHICS.

The term information superhighway is also used to refer to a system of fiber-optic cables that may one day link every home to the Internet, replacing the current television and telephone cables.

infrared a kind of radiation similar to visible light but at a slightly longer wavelength, used to transmit data through the air in TV remote controls, wireless mice, wireless keyboards, and the like, and occasionally for short-distance computer-to-computer links. Like light, infrared signals require a clear line of sight and cannot go through walls.

Infrared radiation is abundant in ordinary sunlight and, at the levels used for communication, is not hazardous.

inheritance the process by which one object is defined to be just like another except for some specified differences. The second type of object then “inherits” the properties of the first. See OBJECT-ORIENTED PROGRAMMING.

INI file a file (with the extension .ini) that stores initialization information for Microsoft Windows or a specific piece of software. Windows INI files consist of editable text.

instance variables the variables (fields) that contain data unique to each object in OBJECT-ORIENTED PROGRAMMING.

instant messaging the sending of brief text messages instantly to other users of a network through software such as AOL Instant Messenger, Microsoft MSN messaging, ICQ, or (originally) the talk command in UNIX. Besides computers, instant messages can be sent to and from pagers and cellular telephones.

instantiated created or initialized. Once a new instance of a particular object type is created, it is said to be instantiated. In Prolog, a variable is said to be instantiated when it is given a value. See INSTANCE VARIABLES;

OBJECT-ORIENTED PROGRAMMING; PROLOG.

.int a suffix indicating that a web or e-mail address belongs to an international organization such as the United Nations. Along with .com, .edu,

.gov, .net, .org, and .mil, this is one of the original set of Internet toplevel domains. Contrast .COM. See also ICANN; TLD.

int data type representing an integer in Java and other languages.

Occupying 32 bits of memory, a Java variable of type int can hold values from –231 = –2, 147, 483, 648 to 231 – 1 = 2, 147, 483, 647.

integers whole numbers and negated whole numbers, such as 1, 2, 3, 0,

–10, –26, 157, 567, and –2397. An integer does not contain a fractional part. Thus, 3.4 and 22⁄3 are not integers.

integrated circuit (IC) an electronic device consisting of many miniature transistors and other circuit elements on a single silicon chip. The first integrated circuits were developed in the late 1950s, and since then there has been continued improvement. The number of components that can be placed on a single chip has been steadily rising. See Figure 79, page 141.

The advantages of integrated circuits over discrete components include the facts that they are very small (most are less than 14 inch [6

mm] square), their internal connections are more reliable, they consume much less power, they generate much less heat, and they cost less than similar circuits made with separate components.

Integrated circuits are classified by their level of complexity. Smallscale integration describes circuits containing fewer than 10 logic gates; medium-scale integration, circuits containing 10 to 100 gates; and largescale integration, circuits with more than 100 gates.

An integrated circuit is made by adding impurities to a silicon crystal in specific places to create P-type and N-type regions, and adding metal conductive paths to serve as wires. (See SEMICONDUCTOR.) The whole process uses light-sensitive chemicals whose action is controlled by a tiny image projected through a device that is like a microscope working backward; thus, tiny regions on the IC can be created from a much larger picture of the desired layout.

Integrated circuits are mass produced by making many identical circuits at the same time from a single wafer of silicon. Each circuit must be individually tested, because a single defect in the crystal can completely ruin the circuit.

The ultimate integrated circuit is the microprocessor, which is a single chip that contains the complete arithmetic and logic unit of a computer, and sometimes other parts of the computer as well. See MICROPROCESSOR.

Intel the manufacturer of the microprocessors used in PC-compatible computers, although other companies also make compatible equivalents. Intel products include the 8088, 80286, 386, 486, Pentium and its descendents, and Celeron. See MICROPROCESSOR. Earlier, Intel developed the first microprocessors (4004, 8008) and the microprocessor for which CP/M was developed (the 8080, soon superseded by Zilog’s Z80). Intel Corporation is headquartered in Santa Clara, California. Its web address is www.intel.com.

interactive system a computer system in which the user communicates with the computer through a keyboard and screen. The computer presents the results almost immediately after an instruction has been entered, and the user can type in new instructions after seeing the results of the previous ones. Nowadays, almost all computing is interactive.

Contrast BATCH PROCESSING.

intercaps capitalized letters in the middle of a word. The word PostScript contains an example. See also CAMEL NOTATION; PASCAL NOTATION. The companies that have coined such trademarks contend that the unusual capitalization is part of the correct spelling.

Not everybody accepts these unusual spellings. At one time there was a company that claimed the only correct spelling of its name was “en•vos.” Almost everyone printed it as Envos. The moral of the story is that names need not reproduce trademarks and logos. In fact, a company can be at a real disadvantage if it makes its name too hard to print—jour- nalists may simply ignore it.

intercharacter spacing the spacing in between characters within words. Also called LETTERSPACING. See KERNING; TRACKING.

interface the connection between two systems through which information is exchanged. For example, in computer hardware, an interface is an electrical connection of the proper type. In software, it is a standard format for exchanging data. The USER INTERFACE of a piece of software is the way it interacts with the human being who is using it. See also DATA COMMUNICATION; USER INTERFACE.

interlaced GIF a BITMAP file that has been optimized for downloading to a remote site. An interlaced GIF displays faster because it can be displayed in rough form before all the information has been received. The picture initially appears in coarse blocks, which refine themselves into finer detail as the complete file is downloaded. See GIF.