F

F

F n. See farad.

F2F adv. Short for face-to-faceIn person, rather than over the Internet. The term is used in e-mail. .

face n. 1. In geometry and computer graphics, one side of a solid object, such as a cube. 2. In printing and typography, short for typeface.

face time n. Time spent dealing face-to-face with another person, rather than communicating electronically.

facsimile n. See fax.

factor n. In mathematics, an item that is multiplied in a multiplication problem; for example, 2 and 3 are factors in the problem 2 x 3. The prime factors of a number are a set of prime numbers that, when multiplied together, produce the number.

factorial n. Expressed as n! (n factorial), the result of multiplying the successive integers from 1 through n; n! equals n x (n 1) x (n 2) x ... x 1.

failback n. In a cluster network system (one with two or more interconnected servers), the process of restoring resources and services to their primary server after they have been temporarily relocated to a backup system while repairs were implemented on the original host. See also cluster, failover.

failover vb. In a cluster network system (one with two or more interconnected servers), to relocate an overloaded or failed resource, such as a server, a disk drive, or a network, to its redundant, or backup, component. For example, when one server in a two-server system stops processing because of a power outage or other malfunction, the system automatically fails over to the second server, with little or no disruption to the users. See also cluster, failback.

fail-safe system n. A computer system designed to continue operating without loss of or damage to programs and data when part of the system breaks down or seriously malfunctions. Compare fail-soft system.

fail-soft system n. A computer system designed to fail gracefully over a period of time when an element of hardware or software malfunctions. A fail-soft system terminates nonessential functions and remains operating at a diminished capacity until the problem has been corrected. Compare fail-safe system.

failure n. The inability of a computer system or related device to operate reliably or to operate at all. A common cause of system failure is loss of power, which can be minimized with a battery-powered backup source until all devices can be shut down. Within a system, electronic failures generally occur early in the life of a system or component and can often be produced by burning in the equipment (leaving it turned on constantly) for a few hours or days. Mechanical failures are difficult to predict but are most likely to affect devices, such as disk drives, that have moving parts.

failure rate n. The number of failures in a specified time period. Failure rate is a means of measuring the reliability of a device, such as a hard disk. See also MTBF.

fair queuing n. A technique used to improve quality of service that gives each session flow passing through a network device a fair share of network resources. With fair queuing, no prioritization occurs. Acronym: FQ. See also quality of service, queuing. Compare weighted fair queuing.

fair use n. A legal doctrine describing the boundaries of legitimate use of copyrighted software or other published material.

fallout n. Any failure of components that occurs while equipment is being burned in, especially when the test is done at the factory. See also burn in (definition 1).

family n. A series of hardware or software products that have some properties in common, such as a series of personal computers from the same company, a series of CPU chips from the same manufacturer that all use the same instruction set, a set of 32-bit operating systems based on the same API (for example, Windows 95 and Windows 98), or a set of fonts that are intended to be used together, such as Times New Roman. See also central processing unit, font, instruction set, operating system.

fan¹ n. The cooling mechanism built into computer cabinets, laser printers, and other such devices to prevent malfunction due to heat buildup. Fans are the main source of the continuous humming associated with computers and other hardware.

fan² vb. To flip through a stack of printer paper to ensure that the pages are loose and will not stick together or jam the printer.

fanfold paper n. Paper with pin-feed holes on both margins designed to be fed into the tractor-feed mechanism of a printer, page by page, in a continuous, unbroken stream. Also called: z-fold paper.

fan-in n. The maximum number of signals that can be fed to a given electronic device, such as a logic gate, at one time without risking signal corruption. The fan-in rating of a device depends on its type and method of construction. Compare fan-out.

fan-out n. The maximum number of electronic devices that can be fed by a given electronic device, such as a logic gate, at one time without the signal becoming too weak. The fan-out rating of a device depends on its type and method of construction. Compare fan-in.

fanzine n. A magazine, distributed on line or by mail, that is produced by and devoted to fans of a particular group, person, or activity. See also ezine.

FAQ n. Acronym for frequently asked questions. A document listing common questions and answers on a particular subject. FAQs are often posted on Internet newsgroups where new participants tend to ask the same questions that regular readers have answered many times.

farad n. The unit of capacitance (the ability to hold a charge). A 1-farad capacitor holds a charge of 1 coulomb with a potential difference of 1 volt between its plates. In practical use, a farad is an extremely large amount of capacitance; capacitance is usually expressed in terms of microfarads (10 ⁶ ) or picofarads (10 ¹² ). Abbreviation: F.

FARNET n. See Federation of American Research Networks.

Fast Ethernet n. See 100BaseX.

fast Fourier transform n. A set of algorithms used to compute the discrete Fourier transform of a function, which in turn is used for solving series of equations, performing spectral analysis, and carrying out other signal-processing and signal-generation tasks. Acronym: FFT. See also Fourier transform.

fast infrared port n. See FIR port.

fast packet n. A standard for high-speed network technology that utilizes fast switching of fixed-length cells or packets for real-time transmission of data. Also called: Asynchronous Transfer Mode, ATM. See also packet (definition 2), packet switching.

fast packet switching adj. Of, describing, or pertaining to high-speed packet-switching networks that perform little or no error checking. The term is often, however, restricted to high-speed networking technologies, such as ATM, that transmit fixed-length cells rather than including those, such as frame relay, that transmit variable-length packets.

fast page-mode RAM n. See page mode RAM.

Fast SCSI n. A form of the SCSI-2 interface that can transfer data 8 bits at a time at up to 10 megabytes per second. The Fast SCSI connector has 50 pins. Also called: Fast SCSI-2. See also SCSI, SCSI-2. Compare Fast/Wide SCSI, Wide SCSI.

Fast/Wide SCSI n. A form of the SCSI-2 interface that can transfer data 16 bits at a time at up to 20 megabytes per second. The Fast/Wide SCSI connector has 68 pins. Also called: Fast/Wide SCSI-2. See also SCSI, SCSI-2. Compare Fast SCSI, Wide SCSI.

FAT n. See file allocation table.

fatal error n. An error that causes the system or application program to crash that is, to fail abruptly with no hope of recovery.

fatal exception error n. A Windows message signaling that an unrecoverable error, one that causes the system to halt, has occurred. Data being processed when the error occurs is usually lost, and the computer must be rebooted. See also error handling.

fat application n. An application that can be used on both PowerPC processor based Macintosh computers and 68K-based Macintosh computers.

fat binary n. An application format that supports both PowerPC processor based Macintosh computers and 68K-based Macintosh computers.

fatbits n. 1. Originally (as FatBits), a feature of the Apple MacPaint program in which a small portion of a drawing can be enlarged and modified one pixel (FatBit) at a time. 2. A similar feature in any program that allows pixel-by-pixel modification through a zoom feature.

fat client n. In a client/server architecture, a client machine that performs most or all of the processing, with little or none performed by the server. The client handles presentation and functions, and the server manages data and access to it. See also client (definition 3), client/server architecture, server (definition 2), thin server. Compare fat server, thin client.

FAT file system n. The system used by MS-DOS to organize and manage files. The FAT (file allocation table) is a data structure that MS-DOS creates on the disk when the disk is formatted. When MS-DOS stores a file on a formatted disk, the operating system places information about the stored file in the FAT so that MS-DOS can retrieve the file later when requested. The FAT is the only file system MS-DOS can use; OS/2, Windows NT, and Windows 9x operating systems can use the FAT file system in addition to their own file systems (HPFS, NTFS, and VFAT, respectively). See also file allocation table, HPFS, NTFS, OS/2, VFAT, Windows.

father n. See generation (definition 1).

father file n. A file that is the last previously valid set of a changing set of data. The father file is immediately preceded by a grandfather file and immediately succeeded by its son. The pairs father and son, parent and child (or descendant), and independent and dependent are synonymous. See also generation (definition 1).

fat server n. In a client/server architecture, a server machine that performs most of the processing, with little or none performed by the client. Applications logic and data reside on the server, and presentation services are handled by the client. See also client (definition 3), client/server architecture, server (definition 2), thin client. Compare fat client, thin server.

fatware n. Software that monopolizes hard disk space and power due to an overabundance of features or inefficient design. Also called: bloatware.

fault n. 1. A physical defect, such as a loose connection, that prevents a system or device from operating as it should. 2. A programming error that can cause the software to fail. 3. As page fault, an attempt to access a page of virtual memory that is not mapped to a physical address. See also page fault.

fault resilience n. See high availability.

fault tolerance n. The ability of a computer or an operating system to respond to a catastrophic event or fault, such as a power outage or a hardware failure, in a way that ensures that no data is lost and any work in progress is not corrupted. This can be accomplished with a battery-backed power supply, backup hardware, provisions in the operating system, or any combination of these. In a fault-tolerant network, the system has the ability either to continue the system s operation without loss of data or to shut the system down and restart it, recovering all processing that was in progress when the fault occurred.

favorite n. In Microsoft Internet Explorer, a user-defined shortcut to a page on the World Wide Web, analogous to a bookmark in Netscape Navigator. See also Favorites folder, hotlist. Compare bookmark (definition 2).

Favorites folder n. In Microsoft Internet Explorer, a collection of shortcuts to Web sites that a user has selected for future reference. Other Web browsers refer to this collection by other names, such as bookmarks or hotlists. See also bookmark file (definition 1), Internet Explorer, URL. Compare bookmark (definition 2), hotlist.

fax n. Short for facsimile. The transmission of text or graphics over telephone lines in digitized form. Conventional fax machines scan an original document, transmit an image of the document as a bit map, and reproduce the received image on a printer. Resolution and encoding are standardized in the CCITT Groups 1 4 recommendations. Fax images can also be sent and received by microcomputers equipped with fax hardware and software. See also CCITT Groups 1 4.

fax machine n. Short for facsimile machine. A device that scans pages, converts the images of those pages to a digital format consistent with the international facsimile standard, and transmits the image through a telephone line. A fax machine also receives such images and prints them on paper. See also scan (definition 2).

fax modem n. A modem that sends (and possibly receives) data encoded in a fax format (typically CCITT fax format), which a fax machine or another modem decodes and converts to an image. The image must already have been encoded on the host computer. Text and graphic documents can be converted into fax format by special software usually provided with the modem; paper documents must first be scanned in. Fax modems may be internal or external and may combine fax and conventional modem capabilities. See also fax, modem.

fax on demand n. An automated system that makes information available for request by telephone. When a request is made, the system faxes the information to the telephone number given in the request. Acronym: FOD.

fax program n. A computer application that allows the user to send, receive, and print fax transmissions. See also fax.

fax server n. A computer on a network capable of sending and receiving fax transmissions to and from other computers on the network. See also fax, server (definition 1).

FCB n. See file control block.

FCC n. Acronym for Federal Communications Commission. The U.S. agency created by the Communications Act of 1934, which regulates interstate and international wire, radio, and other broadcast transmissions, including telephone, telegraph, and telecommunications.

F connector n. A coaxial connector, used primarily in video applications, that requires a screw-on attachment. See the illustration.

F connector.

FDDI n. Acronym for Fiber Distributed Data Interface. A standard developed by the American National Standards Institute (ANSI) for high-speed fiber-optic LANs (local area networks). FDDI provides specifications for transmission rates of 100 megabits (100 million bits) per second on networks based on the token ring standard. See also token ring network.

FDDI II n. Acronym for Fiber Distributed Data Interface. An extension of the FDDI standard, FDDI II contains additional specifications for the real-time transmission of analog data in digitized form for high-speed fiber-optic LANs (local area networks). See also FDDI.

FDHP n. Acronym for Full Duplex Handshaking Protocol. A protocol used by duplex modems to determine the source type of the transmission and match it. See also duplex¹, handshake.

FDM n. Acronym for Frequency Division Multiplexing. A means of loading multiple transmission signals onto separate bands of a single communications channel so that all signals can be carried simultaneously. FDM is used in analog transmissions, as on a baseband network or in communications over a telephone line. In FDM the frequency range of the channel is divided into narrower bands, each of which can carry a different transmission signal. For example, FDM might divide a voice channel with a frequency range of 1400 hertz (Hz) into four subchannels 820 990 Hz, 1230 1400 Hz, 1640 1810 Hz, and 2050 2220 Hz with adjacent subchannels separated by a 240-Hz guard band to minimize interference.

FDMA n. Acronym for Frequency Division Multiple Access. A method of multiplexing in which the set of frequencies assigned to cellular phone service is divided into 30 separate channels, each of which can be used by a different caller. FDMA is the technology used in the AMPS phone service, which is widespread in North America and in other countries around the world. See also AMPS. Compare TDMA.

fear, uncertainty, and doubt n. See FUD.

feasibility study n. An evaluation of a prospective project for the purpose of determining whether or not the project should be undertaken. Feasibility studies normally consider the time, budget, and technology required for completion and are generally used in computing departments in large organizations.

feature n. A unique, attractive, or desirable property of a program or of a computer or other hardware.

feature extraction n. The selection of significant aspects of a computer image for use as guidelines in computerized pattern matching and image recognition. See also image processing.

featuritis n. Jargon for a tendency to add new features to a program at the expense of its original compact size or elegance. Creeping featuritis describes the accretion of feature upon feature over time, eventually resulting in a large, unwieldy, generally inelegant program that is, or appears to be, a collection of ad-hoc additions. The result of featuritis is a program condition known as software bloat. Also called: creeping featuritis, creeping featurism, feeping creaturism. See also bloatware.

February 30 n. See double leap year.

Federal Communications Commission n. See FCC.

Federal Information Processing Standards n. A system of standards, guidelines, and technical methods for information processing within the U.S. federal government. Acronym: FIPS.

Federal Internet Exchange n. See FIX.

federated database n. A database to which scientists contribute their findings and knowledge regarding a particular field or problem. A federated database is designed for scientific collaboration on problems of such scope that they are difficult or impossible for an individual to solve. See also database.

Federation of American Research Networks n. A nonprofit association of internetworking technology companies in the United States that serves as a national advocate for internetworking, with a primary focus on the education, research, and related communities. Acronym: FARNET. See also internetwork.

Federation on Computing in the United States n. The U.S. representative of the International Federation of Information Processing (IFIP). Acronym: FOCUS. See also IFIP.

feed¹ n. See news feed.

feed² vb. 1. To advance paper through a printer. 2. To supply media to a recording device, as by inserting disks into a disk drive.

feedback n. The return of a portion of system output as input to the same system. Often feedback is deliberately designed into a system, but sometimes it is unwanted. In electronics, feedback is used in monitoring, controlling, and amplifying circuitry.

feedback circuit n. Any circuit or system that returns (feeds back) a portion of its output to its input. A common example of a feedback system, although it is not completely electronic, is a thermostatically controlled household heating system. This self-limiting or self-correcting process is an example of negative feedback, in which changes in output are fed back to the source so that the change in the output is reversed. In positive feedback, an increase in output is fed back to the source, increasing the output further, which creates a snowballing effect. An example of unwanted positive feedback is the screech that occurs when the microphone of a public address system is brought too close to its loudspeaker.

feed scanner n. See sheet-fed scanner.

feeping creaturism n. See featuritis.

female connector n. A connector that has one or more receptacles for the insertion of pins. Female connector part numbers often include an F (female), an S (socket), a J (jack), or an R (receptacle). For example, a female DB-25 connector might be labeled DB-25S or DB-25F. (Note that although the letter F can denote a female connector, it does not have that meaning in F connector, which is a type of coaxial cable connector.) See the illustration. Compare male connector.

Female connector.

femto- prefix Metric prefix meaning 10 ¹⁵ (one quadrillionth).

femtosecond n. One quadrillionth (10 ¹⁵ ) of a second. Abbreviation: fs.

FEP n. See front-end processor.

ferric oxide n. The chemical substance Fe₂O₃, an oxide of iron used with a binding agent in the magnetic coating applied to disks and tapes for data storage.

ferric RAM n. See FRAM.

ferromagnetic domain n. See magnetic domain.

ferromagnetic material n. A substance that can become highly magnetized. Ferrite and powdered iron are ferromagnetic materials commonly used in electronics, for example, as cores for inductors to increase their inductance, and as part of the coating on floppy and hard disks and magnetic tape.

FET n. Acronym for field-effect transistor. A type of transistor in which the flow of current between the source and the drain is modulated by the electric field around the gate electrode. FETs are used as amplifiers, oscillators, and switches and are characterized by an extremely high input impedance (resistance) that makes them particularly suitable for amplification of very small signals. Types of FETs include the junction FET and the metal-oxide semiconductor FET (MOSFET). See the illustration. See also MOSFET.

FET. An N-channel junction field-effect transistor.

fetch vb. To retrieve an instruction or an item of data from memory and store it in a register. Fetching is part of the execution cycle of a microprocessor; first an instruction or item of data must be fetched from memory and loaded into a register, after which it can be executed (if it is an instruction) or acted upon (if it is data).

fetch time n. See instruction time.

FF n. See form feed.

FFT n. See fast Fourier transform.

FFTDCA n. See Final-Form-Text DCA.

Fiber Distributed Data Interface n. See FDDI.

fiberoptic cable or fiber-optic cable n. A form of cable used in networks that transmits signals optically, rather than electrically as do coaxial and twisted-pair cable. The light-conducting heart of a fiberoptic cable is a fine glass or plastic fiber called the core. This core is surrounded by a refractive layer called the cladding that effectively traps the light and keeps it bouncing along the central fiber. Outside both the core and the cladding is a final layer of plastic or plastic-like material called the coat, or jacket. Fiberoptic cable can transmit clean signals at speeds as high as 2 Gbps. Because it transmits light, not electricity, it is also immune to eavesdropping.

fiber optics n. A technology for the transmission of light beams along optical fibers. A light beam, such as that produced in a laser, can be modulated to carry information. Because light has a higher frequency on the electromagnetic spectrum than other types of radiation, such as radio waves, a single fiber-optic channel can carry significantly more information than most other means of information transmission. Optical fibers are thin strands of glass or other transparent material, with dozens or hundreds of strands housed in a single cable. Optical fibers are essentially immune to electromagnetic interference. See also optical fiber.

fiber to the curb n. See FTTC.

fiber to the home n. See FTTH.

Fibonacci numbers n. In mathematics, an infinite series in which each successive integer is the sum of the two integers that precede it for example, 1, 1, 2, 3, 5, 8, 13, 21, 34, . . . . Fibonacci numbers are named for the thirteenth-century mathematician Leonardo Fibonacci of Pisa. In computing, Fibonacci numbers are used to speed binary searches by repeatedly dividing a set of data into groups in accordance with successively smaller pairs of numbers in the Fibonacci sequence. For example, a data set of 34 items would be divided into one group of 21 and another of 13. If the item being sought is in the group of 13, the group of 21 is discarded, and the group of 13 is divided into groups of 5 and 8; the search would continue until the item was located. The ratio of two successive terms in the Fibonacci sequence converges on the Golden Ratio, a magic number that seems to represent the proportions of an ideal rectangle. The number describes many things, from the curve of a nautilus shell to the proportions of playing cards or, intentionally, the Parthenon, in Athens, Greece. See also binary search.

fiche n. See microfiche.

Fidonet n. 1. A protocol for sending e-mail, newsgroup postings, and files over telephone lines. The protocol originated on the Fido BBS, initiated in 1984 by Tom Jennings, and maintaining low costs has been a factor in its subsequent development. Fidonet can exchange e-mail with the Internet. 2. The network of BBSs, private companies, NGOs (nongovernment organizations), and individuals that use the Fidonet protocol.

field n. 1. A location in a record in which a particular type of data is stored. For example, EMPLOYEE-RECORD might contain fields to store Last-Name, First-Name, Address, City, State, Zip-Code, Hire-Date, Current-Salary, Title, Department, and so on. Individual fields are characterized by their maximum length and the type of data (for example, alphabetic, numeric, or financial) that can be placed in them. The facility for creating these specifications usually is contained in the data definition language (DDL). In relational database management systems, fields are called columns. 2. A space in an on-screen form where the user can enter a specific item of information.

field-effect transistor n. See FET.

field expansion n. See date expansion.

Field Programmable Gate Array n. See FPGA.

field-programmable logic array n. An integrated circuit containing an array of logic circuits in which the connections between the individual circuits, and thus the logic functions of the array, can be programmed after manufacture, typically at the time of installation in the field. Programming can be performed only once, typically by passing high current through fusible links on the chip. Acronym: FPLA. Also called: PLA, programmable logic array.

field separator n. Any character that separates one field of data from another. See also delimiter, field (definition 1).

FIFO n. See first in, first out.

fifth-generation computer n. See computer.

fifth normal form n. See normal form (definition 1).

file n. A complete, named collection of information, such as a program, a set of data used by a program, or a user-created document. A file is the basic unit of storage that enables a computer to distinguish one set of information from another. A file is the glue that binds a conglomeration of instructions, numbers, words, or images into a coherent unit that a user can retrieve, change, delete, save, or send to an output device.

file allocation table n. A table or list maintained by some operating systems to manage disk space used for file storage. Files on a disk are stored, as space allows, in fixed-size groups of bytes (characters) rather than from beginning to end as contiguous strings of text or numbers. A single file can thus be scattered in pieces over many separate storage areas. A file allocation table maps available disk storage space so that it can mark flawed segments that should not be used and can find and link the pieces of a file. In MS-DOS, the file allocation table is commonly known as the FAT. See also FAT file system.

file attribute n. A restrictive label attached to a file that describes and regulates its use for example, hidden, system, read-only, archive, and so forth. In MS-DOS, this information is stored as part of the file s directory entry.

file backup n. See backup.

file compression n. The process of reducing the size of a file for transmission or storage. See also data compression.

file control block n. A small block of memory temporarily assigned by a computer s operating system to hold information about an opened file. A file control block typically contains such information as the file s identification, its location on a disk, and a pointer that marks the user s current (or last) position in the file. Acronym: FCB.

file conversion n. The process of transforming the data in a file from one format to another without altering the data for example, converting a file from a word processor s format to its ASCII equivalent. In some cases, information about the data, such as formatting, may be lost. Another, more detailed, type of file conversion involves changing character coding from one standard to another, as in converting EBCDIC characters (which are used primarily with mainframe computers) to ASCII characters. See also ASCII, EBCDIC.

file extension n. See extension (definition 1).

file extent n. See extent.

file format n. The structure of a file that defines the way it is stored and laid out on the screen or in print. The format can be fairly simple and common, as are files stored as plain ASCII text, or it can be quite complex and include various types of control instructions and codes used by programs, printers, and other devices. Examples include RTF (Rich Text Format), DCA (Document Content Architecture), PICT, DIF (Data Interchange Format), DXF (Data Exchange File), TIFF (Tagged Image File Format), and EPSF (Encapsulated PostScript Format).

file fragmentation n. 1. The breaking apart of files as they are stored by the operating system into small, separate segments on disk. The condition is a natural consequence of enlarging files and saving them on a crowded disk that no longer contains contiguous blocks of free space large enough to hold them. File fragmentation is not an integrity problem, although it can eventually slow read and write access times if the disk is very full and storage is badly fragmented. Software products are available for redistributing (optimizing) file storage to reduce fragmentation. 2. In a database, a situation in which records are not stored in their optimal access sequence because of accumulated additions and deletions of records. Most database systems offer or contain utility programs that resequence records to improve efficiency of access and to aggregate free space occupied by deleted records.

file gap n. See block gap.

file handle n. In MS-DOS, OS/2, and Windows, a token (number) that the system uses to identify or refer to an open file or, sometimes, to a device.

file-handling routine n. Any routine designed to assist in creating, opening, accessing, and closing files. Most high-level languages have built-in file-handling routines, although more sophisticated or complex file-handling routines in an application are often created by the programmer.

file header n. See header (definition 2).

file layout n. In data storage, the organization of records within a file. Frequently, descriptions of the record structure are also included within the file layout.

file librarian n. A person or process responsible for maintaining, archiving, copying, and providing access to a collection of data.

file maintenance n. Broadly, the process of changing information in a file, altering a file s control information or structure, or copying and archiving files. A person using a terminal to enter data, the program accepting the data from the terminal and writing it to a data file, and a database administrator using a utility to alter the format of a database file are all forms of file maintenance.

file management system n. The organizational structure that an operating system or program uses to order and track files. For example, a hierarchical file system uses directories in a so-called tree structure. All operating systems have built-in file management systems. Commercially available products implement additional features that provide more sophisticated means of navigating, finding, and organizing files. See also file system, hierarchical file system.

file manager n. A module of an operating system or environment that controls the physical placement of and access to a group of program files.

file name n. The set of letters, numbers, and allowable symbols assigned to a file to distinguish it from all other files in a particular directory on a disk. A file name is the label under which a computer user saves and requests a block of information. Both programs and data have file names and often extensions that further identify the type or purpose of the file. Naming conventions, such as maximum length and allowable characters of a file name, vary from one operating system to another. See also directory, path (definition 5).

file name extension n. See extension (definition 1).

filename globbing n. A Linux command-line feature, available on most FTP servers, which allows a user to refer to sets of files without individually listing each file name. Filename globbing can be used to select or delete all files in a working directory with a single command. At the discretion of the user, globbing can match all files, or only those with filenames containing a specific character or range of characters. See also wildcard character.

file property n. A detail about a file that helps identify it, such as a descriptive title, the author name, the subject, or a keyword that identifies topics or other important information in the file.

file protection n. A process or device by which the existence and integrity of a file are maintained. Methods of file protection range from allowing read-only access and assigning passwords to covering the write-protect notch on a disk and locking away floppy disks holding sensitive files.

file recovery n. The process of reconstructing lost or unreadable files on disk. Files are lost when they are inadvertently deleted, when on-disk information about their storage is damaged, or when the disk is damaged. File recovery involves the use of utility programs that attempt to rebuild on-disk information about the storage locations of deleted files. Because deletion makes the file s disk space available but does not remove the data, data that has not yet been overwritten can be recovered. In the case of damaged files or disks, recovery programs read whatever raw data they can find, and save the data to a new disk or file in ASCII or numeric (binary or hexadecimal) form. In some instances, however, such reconstructed files contain so much extraneous or mixed information that they are unreadable. The best way to recover a file is to restore it from a backup copy.

file retrieval n. The act of accessing a data file and transferring it from a storage location to the machine where it is to be used.

file server n. A file-storage device on a local area network that is accessible to all users on the network. Unlike a disk server, which appears to the user as a remote disk drive, a file server is a sophisticated device that not only stores files but manages them and maintains order as network users request files and make changes to them. To deal with the tasks of handling multiple sometimes simultaneous requests for files, a file server contains a processor and controlling software as well as a disk drive for storage. On local area networks, a file server is often a computer with a large hard disk that is dedicated only to the task of managing shared files. Compare disk server.

File Server for Macintosh n. An AppleTalk network integration service that allows Macintosh clients and personal computers clients to share files. Also called: MacFile. See also Print Server for Macintosh, Services for Macintosh.

file sharing n. The use of computer files on networks, wherein files are stored on a central computer or a server and are requested, reviewed, and modified by more than one individual. When a file is used with different programs or different computers, file sharing can require conversion to a mutually acceptable format. When a single file is shared by many people, access can be regulated through such means as password protection, security clearances, or file locking to prohibit changes to a file by more than one person at a time.

file size n. The length of a file, typically given in bytes. A computer file stored on disk actually has two file sizes, logical size and physical size. The logical file size corresponds to the file s actual size the number of bytes it contains. The physical size refers to the amount of storage space allotted to the file on disk. Because space is set aside for a file in blocks of bytes, the last characters in the file might not completely fill the block (allocation unit) reserved for them. When this happens, the physical size is larger than the logical size of the file.

filespec n. See file specification (definition 1).

file specification n. 1. The path to a file, from a disk drive through a chain of directory files to the file name that serves to locate a particular file. Abbreviated filespec. 2. A file name containing wildcard characters that indicate which files among a group of similarly named files are requested. 3. A document that describes the organization of data within a file.

file structure n. A description of a file or group of files that are to be treated together for some purpose. Such a description includes file layout and location for each file under consideration.

file system n. In an operating system, the overall structure in which files are named, stored, and organized. A file system consists of files, directories, or folders, and the information needed to locate and access these items. The term can also refer to the portion of an operating system that translates requests for file operations from an application program into low-level, sector-oriented tasks that can be understood by the drivers controlling the disk drives. See also driver.

file transfer n. The process of moving or transmitting a file from one location to another, as between two programs or over a network.

File Transfer Protocol n. See FTP¹ (definition 1).

file type n. A designation of the operational or structural characteristics of a file. A file s type is often identified in the file name, usually in the file name extension. See also file format.

fill¹ n. In computer graphics, the colored or patterned paint inside an enclosed figure, such as a circle. The portion of the shape that can be colored or patterned is the fill area. Drawing programs commonly offer tools for creating filled or nonfilled shapes; the user can specify color or pattern.

fill² vb. To add color or a pattern to the enclosed portion of a circle or other shape.

fill handle n. The small black square in the lower-right corner of a cell selection. When you point to the fill handle, the pointer changes to a black cross.

film at 11 n. A phrase sometimes seen in newsgroups. An allusion to a brief newsbreak on TV that refers to a top news story that will be covered in full on the 11 o clock news, it is used sarcastically to ridicule a previous article s lack of timeliness or newsworthiness. See also newsgroup.

film recorder n. A device for capturing on 35-mm film the images displayed on a computer screen.

film ribbon n. See carbon ribbon.

filter n. 1. A program or set of features within a program that reads its standard or designated input, transforms the input in some desired way, and then writes the output to its standard or designated output destination. A database filter, for example, might flag information of a certain age. 2. In communications and electronics, hardware or software that selectively passes certain elements of a signal and eliminates or minimizes others. A filter on a communications network, for example, must be designed to transmit a certain frequency but attenuate (dampen) frequencies above it (a lowpass filter), those below it (a highpass filter), or those above and below it (a bandpass filter). 3. A pattern or mask through which data is passed to weed out specified items. For instance, a filter used in e-mail or in retrieving newsgroup messages can allow users to filter out messages from other users. See also e-mail filter, mask. 4. In computer graphics, a special effect or production effect that is applied to bitmapped images; for example, shifting pixels within an image, making elements of the image transparent, or distorting the image. Some filters are built into a graphics program, such as a paint program or an image editor. Others are separate software packages that plug into the graphics program. See also bitmapped graphics, image editor, paint program.

filtering program n. A program that filters information and presents only results that match the qualifications defined in the program.

FilterKeys n. A Windows 9x accessibility control panel feature that enables users with physical disabilities to use the keyboard. With FilterKeys, the system ignores brief and repeated keystrokes that result from slow or inaccurate finger movements. See also accessibility. Compare MouseKeys, ShowSounds, SoundSentry, StickyKeys, ToggleKeys.

Final-Form-Text DCA n. A standard in Document Content Architecture (DCA) for storing documents in ready-to-print form for interchange between dissimilar programs. A related standard is Revisable-Form-Text DCA (RFTDCA). Acronym: FFTDCA. See also DCA (definition 1). Compare Revisable-Form-Text DCA.

finally n. A keyword used in the Java programming language that executes a block of statements regardless of whether a Java exception, or run-time error, occurred in a previous block defined by the try keyword. See also block, exception, keyword, try.

find vb. See search².

Finder n. The standard interface to the Macintosh operating system. The Finder allows the user to view the contents of directories (folders); to move, copy, and delete files; and to launch applications. Items in the system are often represented as icons, and a mouse or similar pointing device is used to manipulate these items. The Finder was the first commercially successful graphical user interface, and it helped launch a wave of interest in icon-based systems. See also MultiFinder.

finger¹ n. An Internet utility, originally limited to UNIX but now available on many other platforms, that enables a user to obtain information on other users who may be at other sites (if those sites permit access by finger). Given an e-mail address, finger returns the user s full name, an indication of whether or not the user is currently logged on, and any other information the user has chosen to supply as a profile. Given a first or last name, finger returns the logon names of users whose first or last names match.

finger² vb. To obtain information on a user by means of the finger program.

fingerprint¹ vb. To scan a computer system to discover what operating system (OS) the computer is running. By detecting a computer s OS through fingerprinting, a hacker is better able to specify attacks on system vulnerabilities and therefore better able to plan an attack on that system. A hacker may use several different fingerprinting schemes separately and in tandem to pinpoint the OS of a target computer.

fingerprint² n. Information embedded or attached to a file or image to uniquely identify it. Compare digital watermark.

fingerprint reader n. A scanner that reads human fingerprints for comparison to a database of stored fingerprint images.

fingerprint recognition n. A technology used to control access to a computer, network, or other device or to a secure area through a user s fingerprints. The patterns of an individual s fingers are scanned by a fingerprint reader or similar device and matched with stored images of fingerprints before access is granted. See also biometric.

FIPS n. See Federal Information Processing Standards.

FIPS 140-1 n. Acronym for Federal Information Processing Standard 140-1. A U.S. Government standard, issued by the National Institute of Standards and Technology (NIST), entitled Security Requirements for Cryptographic Modules. FIPS 140-1 defines four levels of security requirements related to cryptographic hardware and software modules within computer and telecommunications systems used for sensitive but unclassified data. The four security levels range from basic module design through increasingly stringent levels of physical security. The standard covers such security-related features as hardware and software security, cryptographic algorithms, and management of encryption keys. FIPS 140-1products can be validated for federal use in both the United States and Canada after independent testing under the Cryptographic Module Validation (CMV) Program, developed and jointly adopted by NIST and the Canadian Communication Security Establishment. See also cryptography.

firewall n. A security system intended to protect an organization s network against external threats, such as hackers, coming from another network, such as the Internet. Usually a combination of hardware and software, a firewall prevents computers in the organization s network from communicating directly with computers external to the network and vice versa. Instead, all communication is routed through a proxy server outside of the organization s network, and the proxy server decides whether it is safe to let a particular message or file pass through to the organization s network. See also proxy server.

firewall sandwich n. The use of load-balancing appliances on both sides of Internetworked firewalls to distribute both inbound and outbound traffic among the firewalls. The firewall sandwich architecture helps to prevent firewalls from degrading network performance and creating a single point of network failure. See also firewall, load balancing.

FireWire n. A high-speed serial bus from Apple that implements the IEEE 1394 standard. See also IEEE 1394.

firmware n. Software routines stored in read-only memory (ROM). Unlike random access memory (RAM), read-only memory stays intact even in the absence of electrical power. Startup routines and low-level input/output instructions are stored in firmware. It falls between software and hardware in terms of ease of modification. See also RAM, ROM.

FIR port n. Short for fast infrared port. A wireless I/O port, most common on a portable computer, that exchanges data with an external device using infrared light. See also infrared, input/output port.

FIRST n. Acronym for Forum of Incident Response and Security Teams. An organization within the Internet Society (ISOC) that coordinates with CERT in order to encourage information sharing and a unified response to security threats. See also CERT, Internet Society.

first-generation computer n. See computer.

first in, first out n. A method of processing a queue, in which items are removed in the same order in which they were added the first in is the first out. Such an order is typical of a list of documents waiting to be printed. Acronym: FIFO. See also queue. Compare last in, first out.

first normal n. See normal form (definition 1).

fishbowl n. A secure area within a computer system in which intruders can be contained and monitored. A fishbowl is typically set up by a security administrator to impersonate important applications or information so that the system administrator can learn more about hackers who have broken into the network without the hacker learning more about or damaging the system. See also honeypot.

fitting n. The calculation of a curve or other line that most closely approximates a set of data points or measurements. See also regression analysis.

five-nines availability n. The availability of a system 99.999 percent of the time. See also high availability.

FIX n. Acronym for Federal Internet Exchange. A connection point between the U.S. government s various internets and the Internet. There are two Federal Internet Exchanges: FIX West, in Mountain View, California; and FIX East, in College Park, Maryland. Together, they link the backbones of MILNET, ESnet (the TCP/IP network of the Department of Energy), and NSInet (NASA Sciences Internet) with NSFnet. See also backbone (definition 1), MILNET, NSFnet, TCP/IP.

fixed disk n. See hard disk.

fixed-length field n. In a record or in data storage, a field whose size in bytes is predetermined and constant. A fixed-length field always takes up the same amount of space on a disk, even when the amount of data stored in the field is small. Compare variable-length field.

fixed-pitch spacing n. See monospacing.

fixed-point arithmetic n. Arithmetic performed on fixed-point numbers. See also fixed-point notation.

fixed-point notation n. A numeric format in which the decimal point has a specified position. Fixed-point numbers are a compromise between integral formats, which are compact and efficient, and floating-point numeric formats, which have a great range of values. Like floating-point numbers, fixed-point numbers can have a fractional part, but operations on fixed-point numbers usually take less time than floating-point operations. See also floating-point notation, integer.

fixed space n. A set amount of horizontal space used to separate characters in text often, the width of a numeral in a given font. See also em space, en space, thin space.

fixed spacing n. See monospacing.

fixed storage n. Any nonremovable storage, such as a large disk that is sealed permanently in its drive.

fixed-width font n. See monospace font.

fixed-width spacing n. See monospacing.

fixed-word-length computer n. A description that applies to almost all computers and refers to the uniform size of the data units, or words, that are processed by the microprocessor and shuttled through the system over the hardware lines composing the main data bus. Fixed-word-length computers, including IBM and Macintosh personal computers, commonly work with 2 or 4 bytes at a time.

F keys n. See function key.

flag n. 1. Broadly, a marker of some type used by a computer in processing or interpreting information; a signal indicating the existence or status of a particular condition. Flags are used in such areas as communications, programming, and information processing. Depending on its use, a flag can be a code, embedded in data, that identifies some condition, or it can be one or more bits set internally by hardware or software to indicate an event of some type, such as an error or the result of comparing two values. 2. In the HDLC communications protocol, a flag is the unique series of bits 01111110, used to start and end a transmission frame (message unit). See also HDLC.

flame¹ n. An abusive or personally insulting e-mail message or newsgroup posting.

flame² vb. 1. To send an abusive or personally insulting e-mail message or newsgroup posting. 2. To criticize personally by means of e-mail messages or newsgroup postings.

flame bait n. A posting to a mailing list, newsgroup, or other online conference that is likely to provoke flames, often because it expresses a controversial opinion on a highly emotional topic. See also flame¹, flame war. Compare troll.

flamefest n. A series of inflammatory messages or articles in a newsgroup or other online conference.

flamer n. A person who sends or posts abusive messages via e-mail, in newsgroups and other online forums, and in online chats. See also chat¹ (definition 1), newsgroup.

flame war n. A discussion in a mailing list, newsgroup, or other online conference that has turned into a protracted exchange of flames. See also flame¹.

Flash n. A vector graphics file format (extension .swf) developed by Macromedia to enable designers to add animation and interactivity to multimedia Web pages. Flash files can be played back with a downloadable Shockwave plug-in or a Java program. The file format has been released by Macromedia as an open standard for the Internet.

flash vb. See burn.

flash memory n. A type of nonvolatile memory. Flash memory is similar to EEPROM memory in function but it must be erased in blocks, whereas EEPROM can be erased one byte at a time. Because of its block-oriented nature, flash memory is commonly used as a supplement to or replacement for hard disks in portable computers. In this context, flash memory either is built into the unit or, more commonly, is available as a PC Card that can be plugged into a PCMCIA slot. A disadvantage of the block-oriented nature of flash memory is that it cannot be practically used as main memory (RAM) because a computer needs to be able to write to memory in single-byte increments. See also EEPROM, nonvolatile memory, PC Card, PCMCIA slot.

flash ROM n. See flash memory.

flat address space n. An address space in which each location in memory is specified by a unique number. (Memory addresses start at 0 and increase sequentially by 1.) The Macintosh operating system, OS/2, and Windows NT use a flat address space. MS-DOS uses a segmented address space, in which a location must be accessed with a segment number and an offset number. See also segmentation. Compare segmented address space.

flatbed plotter n. A plotter in which paper is held on a flat platform and a pen moves along both axes, traveling across the paper to draw an image. This method is slightly more accurate than that used by drum plotters, which move the paper under the pen, but requires more space. Flatbed plotters can also accept a wider variety of media, such as vellum and acetate, because the material does not need to be flexible. See also plotter. Compare drum plotter, pinch-roller plotter.

flatbed scanner n. A scanner with a flat, transparent surface that holds the image to be scanned, generally a book or other paper document. A scan head below the surface moves across the image. Some flatbed scanners can also reproduce transparent media, such as slides. See the illustration. Compare drum scanner, handheld scanner, sheet-fed scanner.

Flatbed scanner.

flat file n. A file consisting of records of a single record type in which there is no embedded structure information that governs relationships between records.

flat-file database n. A database that takes the form of a table, where only one table can be used for each database. A flat-file database can only work with one file at a time. Compare relational database.

flat file directory n. A directory that cannot contain subdirectories but simply contains a list of file names. Compare hierarchical file system.

flat file format n. An image file format in which individual objects cannot be edited. Files stored in JPEG, GIF, and BMP formats, for example, are all flat files.

flat file system n. A filing system with no hierarchical order in which no two files on a disk may have the same name, even if they exist in different directories. Compare hierarchical file system.

flat memory n. Memory that appears to a program as one large addressable space, whether consisting of RAM or virtual memory. The 68000 and VAX processors have flat memory; by contrast, 80x86 processors operating in real mode have segmented memory, although when these processors operate in protected mode, OS/2 and 32-bit versions of Windows access memory using a flat memory model. Also called: linear memory.

flat pack n. An integrated circuit housed in a flat rectangular package with connecting leads along the edges of the package. The flat pack was a precursor of surface-mounted chip packaging. See also surface-mount technology. Compare DIP (definition 1).

flat-panel display n. A video display with a shallow physical depth, based on technology other than the CRT (cathode-ray tube). Such displays are typically used in laptop computers. Common types of flat-panel displays are the electroluminescent display, the gas discharge display, and the LCD display.

flat panel monitor n. A desktop computer monitor that uses a liquid crystal display (LCD) rather than a cathode ray tube (CRT) to display data. Flat panel monitors are not as deep as CRT monitors and so occupy much less physical space.

flat screen n. See flat-panel display.

flatten vb. In digital graphic creation and manipulation programs, to combine all layers of text, images, and other graphic elements into a single layer. Elements cannot be edited after the graphic is flattened, so a graphic is not usually flattened until the final step when all adjustments have been made to the individual layers. Flattening an image significantly reduces its file size and allows it to be saved in a wider range of formats. Flattening is similar to grouping in that both actions combine a set of objects. However, flattening is a permanent action, whereas a group of objects can be ungrouped. See also layering.

flavor n. One of several varieties of a system, having its own details of operation. UNIX in particular is found in distinct flavors, such as BSD UNIX or AT&T UNIX System V.

flex circuit n. A circuit printed on a thin sheet of flexible polymer film that can be used in applications requiring circuits to curve and bend. Flex circuits offer space and weight savings over traditional circuits, and are used extensively for medical, industrial, and telecommunications applications.

flexible disk n. See floppy disk.

flexible transistor n. See plastic transistor.

flicker n. Rapid, visible fluctuation in a screen image, as on a television or computer monitor. Flicker occurs when the image is refreshed (updated) too infrequently or too slowly for the eye to perceive a steady level of brightness. In television and raster-scan displays, flicker is not noticeable when the refresh rate is 50 to 60 times per second. Interlaced displays, in which the odd-numbered scan lines are refreshed on one sweep and even-numbered lines on the other, achieve a flicker-free effective refresh rate of 50 to 60 times per second because the lines appear to merge, even though each line is actually updated only 25 to 30 times per second.

flies n. In Web development and marketing, individuals who spend significant time on the Web and who are the targets of specific Web content or advertising.

flight simulator n. A computer-generated recreation of the experience of flying. Sophisticated flight simulators costing hundreds of thousands of dollars can provide pilot training, simulating emergency situations without putting human crews and planes at risk. Flight simulator software running on personal computers simulates flight in a less realistic fashion; it provides entertainment and practice in navigation and instrument reading.

flip-flop n. A circuit that alternates between two possible states when a pulse is received at the input. For example, if the output of a flip-flop is high and a pulse is received at the input, the output flips to low; a second input pulse flops the output back to high, and so on. Also called: bistable multivibrator.

flippy-floppy n. An outmoded 5.25-inch floppy disk that uses both sides for storage but is used in an older drive that can read only one side at a time. Thus, to access the opposite side, the disk must be physically removed from the drive and flipped over. See also double-sided disk.

float n. The data type name used in some programming languages, notably C, to declare variables that can store floating-point numbers. See also data type, floating-point number, variable.

floating-point arithmetic n. Arithmetic performed on floating-point numbers. See also floating-point notation, floating-point number.

floating-point constant n. A constant representing a real, or floating-point, value. See also constant, floating-point notation.

floating-point notation n. A numeric format that can be used to represent very large real numbers and very small real numbers. Floating-point numbers are stored in two parts, a mantissa and an exponent. The mantissa specifies the digits in the number, and the exponent specifies the magnitude of the number (the position of the decimal point). For example, the numbers 314,600,000 and 0.0000451 are expressed respectively as 3146E5 and 451E-7 in floating-point notation. Most microprocessors do not directly support floating-point arithmetic; consequently, floating-point calculations are performed either by using software or with a special floating-point processor. Also called: exponential notation. See also fixed-point notation, floating-point processor, integer.

floating-point number n. A number represented by a mantissa and an exponent according to a given base. The mantissa is usually a value between 0 and 1. To find the value of a floating-point number, the base is raised to the power of the exponent, and the mantissa is multiplied by the result. Ordinary scientific notation uses floating-point numbers with 10 as the base. In a computer, the base for floating-point numbers is usually 2.

floating-point operation n. An arithmetic operation performed on data stored in floating-point notation. Floating-point operations are used wherever numbers may have either fractional or irrational parts, as in spreadsheets and computer-aided design (CAD). Therefore, one measure of a computer s power is how many millions of floating-point operations per second (MFLOPS or megaflops) it can perform. Acronym: FLOP. Also called: floating-point operation. See also floating-point notation, MFLOPS.

floating-point processor n. A coprocessor for performing arithmetic on floating-point numbers. Adding a floating-point processor to a system can speed up the processing of math and graphics dramatically if the software is designed to recognize and use it. The i486DX and 68040 and higher microprocessors have built-in floating-point processors. Also called: math coprocessor, numeric coprocessor. See also floating-point notation, floating-point number.

floating-point register n. A register designed to store floating-point values. See also floating-point number, register.

flooding n. The networking technique of forwarding a frame onto all ports of a switch except the port on which it arrived. Flooding can be used for robust data distribution and route establishment. Also called: flood routing.

FLOP n. See floating-point operation.

floppy disk n. A round piece of flexible plastic film coated with ferric oxide particles that can hold a magnetic field. When placed inside a disk drive, the floppy disk rotates to bring different areas, or sectors, of the disk surface under the drive s read/write head, which can detect and alter the orientation of the particles magnetic fields to represent binary 1s and 0s. A floppy disk 5.25 inches in diameter is encased in a flexible plastic jacket and has a large hole in the center, which fits around a spindle in the disk drive; such a disk can hold from a few hundred thousand to over one million bytes of data. A 3.5-inch disk encased in rigid plastic is also called a floppy disk or a microfloppy disk. In addition, 8-inch floppy disks were common in DEC and other minicomputer systems. See also microfloppy disk.

floppy disk controller n. See disk controller.

floppy disk drive n. An electromechanical device that reads data from and writes data to floppy or microfloppy disks. See the illustration. See also floppy disk.

Floppy disk drive.

FLOPS n. Acronym for floating-point operations per second. A measure of the speed at which a computer can perform floating-point operations. See also floating-point operation, MFLOPS. Compare MIPS.

floptical adj. Using a combination of magnetic and optical technology to achieve a very high data density on special 3.5-inch disks. Data is written to and read from the disk magnetically, but the read/write head is positioned optically by means of a laser and grooves on the disk.

flow analysis n. A method of tracing the movement of different types of information through a computer system, especially with regard to security and the controls applied to ensure the integrity of the information. See also flowchart.

flowchart n. A graphic map of the path of control or data through the operations in a program or an information-handling system. Symbols such as squares, diamonds, and ovals represent various operations. These symbols are connected by lines and arrows to indicate the flow of data or control from one point to another. Flowcharts are used both as aids in showing the way a proposed program will work and as a means of understanding the operations of an existing program. See the illustration.

Flowchart.

flow control n. The management of data flow in a network to ensure that the receiver can handle all the incoming data. Flow-control mechanisms, implemented in both hardware and software, prevent a sender of traffic from sending it faster than the receiver can receive it.

flush¹ adj. Aligned in a certain way on the screen or on paper. Flush left, for example, means aligned on the left side; flush right means aligned on the right side. See also align (definition 1).

flush² vb. To clear a portion of memory. For example, to flush a disk file buffer is to save its contents on disk and then clear the buffer for filling again.

flux n. 1. The total strength of a magnetic, electric, or radiation field over a given area. 2. A chemical used to aid the binding of solder to electrical conductors.

flux reversal n. The change in orientation of the minute magnetic particles on the surface of a disk or tape toward one of two magnetic poles. The two different alignments are used to represent binary 1 and binary 0 for data storage: a flux reversal typically represents a binary 1, and no reversal represents a binary 0.

fly swapping n. See swap-on-the-fly.

FM n. See frequency modulation.

FM encoding n. See frequency modulation encoding.

focus vb. In television and raster-scan displays, to make an electron beam converge at a single point on the inner surface of the screen.

FOCUS n. See Federation on Computing in the United States.

FOD n. See fax on demand.

folder n. In the Mac OS, 32-bit versions of Windows, and other operating systems, a container for programs and files in graphical user interfaces, symbolized on the screen by a graphical image (icon) of a file folder. This container is called a directory in other systems, such as MS-DOS and UNIX. A folder is a means of organizing programs and documents on a disk and can hold both files and additional folders. It first appeared commercially in Apple Computer s Lisa in 1983 and in the Apple Macintosh in 1984. See also directory.

folio n. A printed page number.

follow-up n. A post to a newsgroup that replies to an article. The follow-up has the same subject line as the original article, with the prefix Re: attached. An article and all of its follow-ups, in the order they were received, constitute a thread, which a user can read together using a newsreader.

font n. A set of characters of the same typeface (such as Garamond), style (such as italic), and weight (such as bold). A font consists of all the characters available in a particular style and weight for a particular design; a typeface consists of the design itself. Fonts are used by computers for on-screen displays and by printers for hard-copy output. In both cases, the fonts are stored either as bit maps (patterns of dots) or as outlines (defined by a set of mathematical formulas). Even if the system cannot simulate different typefaces on the screen, application programs may be able to send information about typeface and style to a printer, which can then reproduce the font if a font description is available. See also bit map, font generator.

font card n. See font cartridge, ROM card.

font cartridge n. A plug-in unit available for some printers that contains fonts in several different styles and sizes. Font cartridges, like downloadable fonts, enable a printer to produce characters in sizes and styles other than those created by the fonts built into it. Also called: font card. See also ROM cartridge.

Font/DA Mover n. An application for older Apple Macintosh systems that allows the user to install screen fonts and desk accessories.

font editor n. A utility program that enables the user to modify existing fonts or to create and save new ones. Such an application commonly works with a screen representation of the font, with a representation that can be downloaded to a PostScript or other printer, or with both. See also PostScript font, screen font.

font family n. The set of available fonts representing variations of a single typeface. For example, Times Roman and Times Roman Italic are members of the same font family. When the user indicates italic, the system selects the correct italic font for the font family, with its characteristic appearance. If there is no italic font in the family, the system simply slants, or obliques, the corresponding roman character. See also italic, roman.

font generator n. A program that transforms built-in character outlines into bit maps (patterns of dots) of the style and size required for a printed document. Font generators work by scaling a character outline to size; often they can also expand or compress the characters they generate. Some font generators store the resultant characters on disk; others send them directly to the printer.

font number n. The number by which an application or operating system internally identifies a given font. On the Apple Macintosh, for example, fonts can be identified by their exact names as well as their font numbers, and a font number can be changed if the font is installed in a system already having a font with that number. See also font.

font page n. A portion of video memory reserved for holding programmer-specified character definition tables (sets of character patterns) used for displaying text on the screen on IBM Multi-Color Graphics Array video systems.

font size n. The point size of a set of characters in a particular typeface. See also point¹ (definition 1).

font suitcase n. A file on Macintosh computers that contains one or more fonts or desk accessories. Such files are indicated in early versions of the operating system with the icon of a suitcase marked with a capital A. From System 7.0 onward, this icon is used to denote individual fonts.

foo n. A string used by programmers in place of more specific information. Variables or functions in code examples intended to demonstrate syntax, as well as temporary scratch files, may all appear with the name foo. Likewise, a programmer may type foo to test a string input handler. If a second placeholder string is needed, it will often be bar, suggesting that the origin of both is the U.S. Army phrase FUBAR (an acronym which, in discreet language, represents Fouled Up Beyond All Recognition/Repair). However, other origins have been claimed. Compare fred (definition 2).

footer n. One or more identifying lines printed at the bottom of a page. A footer may contain a folio (page number), a date, the author s name, and the document title. Also called: running foot. Compare header (definition 1).

footprint n. The surface area occupied by a personal computer or other device.

force vb. In programming, to perform a particular action that would normally not occur. The term is most often used in the context of forcing data to be within a particular range of values for example, forcing a divisor to be nonzero. See also cast.

force feedback n. A technology that generates push or resistance in an input/output device. Force feedback enables an input/output device, such as a joystick or a steering wheel, to react to the user s action in appropriate response to events displayed on the screen. For example, force feedback can be used with a computer game to react to a plane rising in a steep ascent or a race car turning a tight corner. See also input/output device.

foreground¹ adj. Currently having control of the system and responding to commands issued by the user. See also multitasking. Compare background¹.

foreground² n. 1. The color of displayed characters and graphics. Compare background² (definition 1). 2. The condition of the program or document currently in control and affected by commands and data entry in a windowing environment. Compare background² (definition 4).

forest n. A collection of one or more domains in Microsoft Windows that share a common schema, configuration, and global catalog and are linked with two-way transitive trusts. See also domain, global catalog, schema, transitive trust, two-way trust.

fork¹ n. One of the two parts of a file recognized by the Mac OS. A Macintosh file has a data fork and a resource fork. Most or all of a typical user-produced document is in the data fork; the resource fork usually contains application-oriented information, such as fonts, dialog boxes, and menus. See also data fork, resource fork.

fork² vb. To initiate a child process in a multitasking system after a parent process has been started. See also multitasking.

fork bomb n. In UNIX-based systems, a program or shell script that locks up the system by recursively spawning copies of itself using the Unix system call fork(2) until they occupy all the process table entries. Also called: logic bomb.

FOR loop n. A control statement that executes a section of code a specified number of times. Actual syntax and usage vary from language to language. In most cases, the value of an index variable moves through a range of values, being assigned a different (and usually consecutive) value each time the program moves through the section of code. See also iterative statement, loop¹ (definition 1). Compare DO loop.

form n. 1. A structured document with spaces reserved for entering information and often containing special coding as well. 2. In some applications (especially databases), a structured window, box, or other self-contained presentation element with predefined areas for entering or changing information. A form is a visual filter for the underlying data it is presenting, generally offering the advantages of better data organization and greater ease of viewing. 3. In optical media, a data storage format used in compact disc technology. 4. In programming, a metalanguage (such as Backus-Naur form) used to describe the syntax of a language. See also Backus-Naur form.

formal language n. A combination of syntax and semantics that completely defines a computer language. See also Backus-Naur form, semantics (definition 1), syntax.

formal logic n. A study of the logical expressions, sequences, and overall construction of a valid argument, without regard to the truth of the argument. Formal logic is used in proving program correctness.

format¹ n. 1. In general, the structure or appearance of a unit of data. 2. The arrangement of data within a document file that typically permits the document to be read or written by a certain application. Many applications can store a file in a more generic format, such as plain ASCII text. 3. The layout of data storage areas (tracks and sectors) on a disk. 4. The order and types of fields in a database. 5. The attributes of a cell in a spreadsheet, such as its being alphabetic or numeric, the number of digits, the use of commas, and the use of currency signs. 6. The specifications for the placement of text on a page or in a paragraph.

format² vb. 1. To change the appearance of selected text or the contents of a selected cell in a spreadsheet. 2. To prepare a disk for use by organizing its storage space into a collection of data compartments, each of which can be located by the operating system so that data can be sorted and retrieved. When a previously used disk is formatted, any preexisting information on it is lost.

format bar n. A toolbar within an application used for modifying the format of the document being displayed, such as changing font size or type.

formatting n. 1. The elements of style and presentation that are added to documents through the use of margins, indents, and different sizes, weights, and styles of type. 2. The process of initializing a disk so that it can be used to store information. See also initialize.

form control n. On a Web site, an individual box or button with which you enter information on an electronic form.

form factor n. 1. The size, shape, and configuration of a piece of computer hardware. The term is often applied to subcomponents such as disk drives, circuit boards, and small devices, such as handheld PCs. It can also be used more broadly to include the arrangement and positioning of external switches, plugs, and other components of the device, or it can refer to the footprint of an entire computer. 2. A term used in computer graphics, specifically with reference to a method of rendering known as radiosity, which divides an image into small patches for calculating illumination. The form factor is a calculated value that represents the amount of energy radiated by one surface and received by another, taking into account such conditions as the distance between the surfaces, their orientation with respect to one another, and the presence of obstructions between them. 3. When used to describe software, refers to the amount of memory required, the size of the program, and so on.

form feed n. A printer command that tells a printer to move to the top of the next page. In the ASCII character set, the form-feed character has the decimal value 12 (hexadecimal 0C). Because its purpose is to begin printing on a new page, form feed is also known as the page-eject character. Acronym: FF.

form letter n. A letter created for printing and distribution to a group of people whose names and addresses are taken from a database and inserted by a mail-merge program into a single basic document. See also mail merge.

formula n. A mathematical statement that describes the actions to be performed on numeric values. A formula sets up a calculation without regard to the actual values it is to act upon, such as A + B, with A and B representing whatever values the user designates. Thus, a formula is unlike an arithmetic problem, such as 1 + 2, which includes values and must be restated if any value is changed. Through formulas, users of applications such as spreadsheets gain the power to perform what-if calculations simply by changing selected values and having the program recalculate the results. Sophisticated programs include many built-in formulas for performing standard business and mathematical calculations.

Forte n. Sun Microsystems integrated development environment (IDE) for Java developers. See also integrated development environment.

Fortezza n. A cryptographic technology developed by the United States National Security Agency (NSA) for enabling secure communication of sensitive information. Fortezza is based on encryption, authentication, and other technologies built into a personalized card known as the Fortezza Crypto Card that can be inserted into a PCMCIA slot on a computer. This card works with Fortezza-enabled hardware and software to secure applications such as e-mail, Web browsing, e-commerce, and file encryption. An RS-232 token can also be used with legacy systems that do not have card-reading capability. The technology is supported by a number of commercial vendors.

Forth n. A programming language originated by Charles Moore in the late 1960s. Moore chose the language s name, a shortened version of the word fourth, because he believed it was a fourth-generation language and his operating system would allow him to use only five letters for a program name. Forth is an interpreted, structured language that uses threading, which lets programmers easily extend the language and enables Forth to fit a great deal of functionality into limited space. Unlike most other programming languages, Forth uses postfix notation for its mathematical expressions and requires the programmer to work with the program stack directly. See also 4GL, interpreted language, postfix notation, stack, threading.

FORTRAN or Fortran n. Short for formula translation. The first high-level computer language (developed over the period 1954 58 by John Backus) and the progenitor of many key high-level concepts, such as variables, expressions, statements, iterative and conditional statements, separately compiled subroutines, and formatted input/output. FORTRAN is a compiled, structured language. The name indicates its roots in science and engineering, where it is still used heavily, although the language itself has been expanded and improved vastly over the last 35 years to become a language that is useful in any field. See also compiled language, structured programming.

fortune cookie n. A proverb, prediction, joke, or other phrase chosen at random from a collection of such items and output to the screen by a program. Fortune cookies are sometimes displayed at logon and logoff times by UNIX systems.

forum n. A medium provided by an online service or BBS for users to carry on written discussions of a particular topic by posting messages and replying to them. On the Internet, the most widespread forums are the newsgroups in Usenet.

Forum of Incident Response and Security Teams n. See FIRST.

forward vb. In e-mail, to send a received message, either modified or in its entirety, to a new recipient.

forward chaining n. In expert systems, a form of problem solving that starts with a set of rules and a database of facts and works to a conclusion based on facts that match all the premises set forth in the rules. See also expert system. Compare backward chaining.

forward error correction n. In communications, a means of controlling errors by inserting extra (redundant) bits into a stream of data transmitted to another device. The redundant bits are used by the receiving device in detecting and, where possible, correcting errors in the data. See also error-correction coding.

forward pointer n. A pointer in a linked list that contains the address (location) of the next element in the list.

FOSDIC n. Acronym for film optical sensing device for input to computers. A device used by the U.S. government to read documents on microfilm and store them digitally on magnetic tape or on a disk that can be accessed by a computer.

Fourier transform n. A mathematical method, developed by the French mathematician Jean-Baptiste-Joseph Fourier (1768 1830), for signal processing and signal generation tasks such as spectral analysis and image processing. The Fourier transform converts a signal value that is a function of time, space, or both into a function of frequency. The inverse Fourier transform converts a function of frequencies into a function of time, space, or both. See also fast Fourier transform.

four-nines availability n. The availability of a system 99.99 percent of the time. See high availability.

fourth-generation computer n. See computer.

fourth-generation language n. See 4GL.

fourth normal form n. See normal form (definition 1).

FPD n. See full-page display.

FPGA n. Acronym for Field Programmable Gate Array. A type of programmable logic chip that can be configured for a wide range of specialized applications after manufacture and delivery. FPGAs can be reprogrammed to incorporate innovations and upgrades. Because of their flexibility and adaptability, FPGAs are used in devices from microwave ovens to supercomputers.

FPLA n. See field-programmable logic array.

FPM RAM n. See page mode RAM.

FPU n. Acronym for floating-point unit. A circuit that performs floating-point calculations. See also circuit, floating-point operation.

FQ n. See fair queuing.

fractal n. A word coined by mathematician Benoit Mandelbrot in 1975 to describe a class of shapes characterized by irregularity, but in a way that evokes a pattern. Computer graphics technicians often use fractals to generate naturelike images such as landscapes, clouds, and forests. The distinguishing characteristic of fractals is that they are self-similar ; any piece of a fractal, when magnified, has the same character as the whole. The standard analogy is that of a coastline, which has a similar structure whether viewed on a local or continental scale. Interestingly, it is often difficult to measure the length of the perimeter of such a shape exactly because the total distance measured depends on the size of the smallest element measured. For example, one could measure on a given coastline the perimeter of every peninsula and inlet, or at a higher magnification the perimeter of every small promontory and jetty, and so on. In fact, a given fractal may have a finite area but an infinite perimeter; such shapes are considered to have a fractional dimension for example, between 1 (a line) and 2 (a plane) hence the name fractal. See the illustration. See also cellular automata, graftal.

Fractal.

fractional T1 n. A shared connection to a T1 line, in which only a fraction of the 24 T1 voice or data channels are used. Acronym: FT1. See also T1.

FRAD n. See frame relay assembler/disassembler.

fraggle attack n. See smurf attack.

fragmentation n. The scattering of parts of the same disk file over different areas of the disk. Fragmentation occurs as files on a disk are deleted and new files are added. Such fragmentation slows disk access and degrades the overall performance of disk operations, although usually not severely. Utility programs are available for rearranging file storage on fragmented disks.

FRAM n. Acronym for ferromagnetic random access memory. A form of data storage technology in which data is recorded semipermanently on small cards or strips of material coated with a ferric oxide (iron-based) magnetic film. As with tape or disk, the data persists without power; as with semiconductor RAM, a computer can access the data in any order.

frame n. 1. In asynchronous serial communications, a unit of transmission that is sometimes measured in elapsed time and begins with the start bit that precedes a character and ends with the last stop bit that follows the character. 2. In synchronous communications, a package of information transmitted as a single unit. Every frame follows the same basic organization and contains control information, such as synchronizing characters, station address, and an error-checking value, as well as a variable amount of data. For example, a frame used in the widely accepted HDLC and related SDLC protocols begins and ends with a unique flag (01111110). See the illustration. See also HDLC, SDLC. 3. A single screen-sized image that can be displayed in sequence with other, slightly different, images to create animated drawings. 4. The storage required to hold one screen-sized image of text, graphics, or both. 5. A rectangular space containing, and defining the proportions of, a graphic. 6. The part of an on-screen window (title bar and other elements) that is controlled by the operating system rather than by the application running in the window. 7. A rectangular section of the page displayed by a Web browser that is a separate HTML document from the rest of the page. Web pages can have multiple frames, each of which is a separate document. Associated with each frame are the same capabilities as for an unframed Web page, including scrolling and linking to another frame or Web site; these capabilities can be used independently of other frames on the page. Frames, which were introduced in Netscape Navigator 2.0, are often used as a table of contents for one or more HTML documents on a Web site. Most current Web browsers support frames, although older ones do not. See also HTML document, Web browser.

Frame. The fields in an HDLC-SDLC frame.

frame buffer n. A portion of a computer s display memory that holds the contents of a single screen image. See also video buffer.

frame grabber n. See video digitizer.

frame rate n. 1. The speed at which full, single-screen images are transmitted to and displayed by a raster-scan monitor. Frame rate is calculated as the number of times per second (hertz) the electron beam sweeps the screen. 2. In animation, the number of times per second an image is updated. When the frame rate exceeds about 14 frames per second, animation seems to blend into smooth motion. See also animation.

frame relay n. A packet-switching protocol for use on WANs (wide area networks). Frame relay transmits variable-length packets at up to 2 Mbps over predetermined, set paths known as PVCs (permanent virtual circuits). It is a variant of X.25 but dispenses with some of X.25 s error detection for the sake of speed. See also ATM (definition 1), X.25.

frame relay access device n. See frame relay assembler/disassembler.

frame relay assembler/disassembler n. A combination channel service unit/digital service unit (CSU/DSU) and router that connects an internal network to a frame relay connection. The device converts data (which may be in the form of IP packets or conform to some other network protocol) into packets for transmission over the frame relay network and converts such packets back to the original data. Since this type of connection is direct without a firewall other network protection is necessary. Acronym: FRAD. See also firewall, frame relay, IP.

frame source n. In the HTML frames environment, a contents document that will look for the source document to display within a frame drawn by the local browser. See also HTML.

frames page n. A Web page that divides a Web browser window into different scrollable areas that can independently display several Web pages. One window can remain unchanged, while the other windows change based on hyperlinks that the user selects.

frames per second n. See frame rate.

framework n. In object-oriented programming, a reusable basic design structure, consisting of abstract and concrete classes, that assists in building applications. See also abstract class, object-oriented programming.

FRC n. See functional redundancy checking.

fred n. 1. An interface utility for X.500. See also CCITT X series. 2. A placeholder string used by programmers in syntax examples to stand for a variable name. If a programmer has used fred, the next placeholder needed is likely to be barney. Compare foo.

free block n. A region (block) of memory that is not currently being used.

FreeBSD n. A freely distributed version of BSD UNIX (Berkeley Software Distribution UNIX) for IBM and IBM-compatible PCs. See also BSD UNIX.

free-form language n. A language whose syntax is not constrained by the position of characters on a line. C and Pascal are free-form languages; FORTRAN is not.

freenet or free-net n. A community-based computer BBS and Internet service provider, usually operated by volunteers and providing free access to subscribers in the community or access for a very small fee. Many freenets are operated by public libraries or universities. See also ISP.

free software n. Software, complete with source code, that is distributed freely to users who are in turn free to use, modify, and distribute it, provided that all alterations are clearly marked and that the name and copyright notice of the original author are not deleted or modified in any way. Unlike freeware, which a user might or might not have permission to modify, free software is protected by a license agreement. Free software is a concept pioneered by the Free Software Foundation in Cambridge, Massachusetts. Compare freeware, open source, public-domain software, shareware.

Free Software Foundation n. An advocacy organization founded by Richard Stallman, dedicated to eliminating restrictions on people s right to use, copy, modify, and redistribute computer programs for noncommercial purposes. The Free Software Foundation is the maintainer of GNU software, which is UNIX-like software that can be freely distributed. See also GNU.

free space n. Space on a floppy disk or a hard drive not currently occupied by data. See also floppy disk, hard disk.

freeware n. A computer program given away free of charge and often made available on the Internet or through user groups. An independent program developer might offer a product as freeware either for personal satisfaction or to assess its reception among interested users. Freeware developers often retain all rights to their software, and users are not necessarily free to copy or distribute it further. Compare free software, public-domain software, shareware.

freeze-frame video n. Video in which the image changes only once every few seconds. Compare full-motion video.

frequency n. The measure of how often a periodic event occurs, such as a signal going through a complete cycle. Frequency is usually measured in hertz (Hz), with 1 Hz equaling 1 occurrence (cycle) per second. In the United States, household electricity is alternating current with a frequency of 60 Hz. Frequency is also measured in kilohertz (kHz, or 1000 Hz), megahertz (MHz, or 1000 kHz), gigahertz (GHz, or 1000 MHz), or terahertz (THz, or 1000 GHz). See the illustration. Compare wavelength.

Frequency.

frequency counter n. 1. An item of engineering test equipment that measures and displays the frequencies of electronic signals. 2. An electronic circuit, often found embedded in process-control computers, that counts the frequency of occurrence of an activity.

Frequency Division Multiple Access n. See FDMA.

frequency-division multiplexing n. See FDM.

frequency hopping n. The switching of frequencies within a given bandwidth during a point-to-point transmission. Frequency hopping reduces the chance of unauthorized signal interception or the effects of single-frequency jamming.

frequency modulation n. A way of encoding information in an electrical signal by varying its frequency. The FM radio band uses frequency modulation, as does the audio portion of broadcast television. See the illustration. Acronym: FM. Compare amplitude modulation.

Frequency modulation.

frequency modulation encoding n. A method of storing information on a disk in which both data and additional synchronizing information, called clock pulses, are recorded on the surface. FM encoding is relatively inefficient because of the extra disk space required by the clock pulses. It has been generally superseded by a more efficient method called modified frequency modulation (MFM) encoding and by the complex but extremely efficient technique called run-length limited (RLL) encoding. Abbreviation: FM encoding. Compare modified frequency modulation encoding, run-length limited encoding.

frequency response n. The range of frequencies an audio device can reproduce from its input signals. See also frequency.

frequency-shift keying n. See FSK.

frequently asked questions n. See FAQ.

friction feed n. A means of moving paper through a printer in which the paper is pinched either between the printer s platen and pressure rollers or (in printers that do not have a platen) between two sets of rollers. Friction feed is available on most printers, for use with paper that does not have pin-feed holes. In printers that have tractor feed as well as friction feed, the friction-feed mechanism should be left disengaged when the tractor is being used, to avoid unnecessary stress on the tractor gears. See also platen. Compare pin feed, tractor feed.

friendly adj. Referring to features built into hardware or software that make a computer or computer program easy to learn and easy to use. Friendliness is emphasized by most developers and sought after by most users. See also user-friendly.

fringeware n. Freeware whose reliability and value are questionable. See also freeware.

front end n. 1. In a client/server application, the part of the program that runs on the client. See also client/server architecture. Compare back end (definition 1). 2. In applications, software or a feature of software that provides an interface to another application or tool. Front ends are often used to supply a common interface for a range of tools produced by a software manufacturer. A front end generally offers a more user-friendly interface than that of the application running behind it. 3. In networking, a client computer or the processing that takes place on it. Compare back end (definition 2).

front-end processor n. 1. Generally, a computer or processing unit that produces and manipulates data before another processor receives it. Compare back-end processor (definition 2). 2. In communications, a computer that is located between communications lines and a main (host) computer and is used to relieve the host of housekeeping chores related to communications; sometimes considered synonymous with communications controller. A front-end processor is dedicated entirely to handling transmitted information, including error detection and control; receipt, transmission, and possibly encoding of messages; and management of the lines running to and from other devices. See also communications controller.

front panel n. The faceplate of a computer cabinet through which the control knobs, switches, and lights are available to an operator. See also console.

fry vb. To destroy a circuit board or another component of a computer by applying excessive voltage. Even when applied voltage is not excessive, an electronic component can become fried when it breaks down, conducting more current than its design permits.

fs n. See femtosecond.

FSK n. Acronym for frequency-shift keying. A simple form of modulation in which the digital values 0 and 1 are represented by two different frequencies. FSK was used by early modems running at 300 bits per second.

FT1 n. See fractional T1.

FTAM n. Acronym for File-Transfer Access and Management. A communications standard for transferring files between different makes and models of computer.

FTP¹ n. 1. Acronym for File Transfer Protocol, a fast, application-level protocol widely used for copying files to and from remote computer systems on a network using TCP/IP, such as the Internet. This protocol also allows users to use FTP commands to work with files, such as listing files and directories on the remote system. See also TCP/IP. 2. A common logon ID for anonymous FTP.

FTP² vb. To download files from or upload files to remote computer systems, via the Internet s File Transfer Protocol. The user needs an FTP client to transfer files to and from the remote system, which must have an FTP server. Generally, the user also needs to establish an account on the remote system to FTP files, although many FTP sites permit the use of anonymous FTP. See also FTP client, FTP server.

FTP client or ftp client n. A program that enables the user to upload and download files to and from an FTP site over a network, such as the Internet, using the File Transfer Protocol. See also FTP¹ (definition 1). Compare FTP server.

FTP commands n. Commands that are part of the File Transfer Protocol. See also FTP¹ (definition 1).

FTP program or ftp program n. See FTP client.

FTP server n. A file server that uses the File Transfer Protocol to permit users to upload or download files through the Internet or any other TCP/IP network. See also file server, FTP¹ (definition 1), TCP/IP. Compare FTP client.

FTP site n. The collection of files and programs residing on an FTP server. See also FTP¹ (definition 1), FTP server.

FTTC n. Acronym for fiber to the curb. The installation and use of fiber-optic cable from the central office (CO) to within a thousand feet of a user s home or office. With FTTC, coaxial cable or another medium carries the signals from the curb into the home or office. FTTC is a replacement for Plain Old Telephone Service (POTS) that enables the distribution of telephony, cable TV, Internet access, multimedia, and other communications over one line. Compare FTTH, POTS.

FTTH n. Acronym for fiber to the home. The installation and use of fiber-optic cable from the central office (CO) directly into a user s home or office. FTTH is a replacement for Plain Old Telephone Service (POTS) that enables the distribution of telephony, cable TV, Internet access, multimedia, and other communications over one line. Compare FTTC, POTS.

FUD n. Acronym for fear, uncertainty, and doubt. Derogatory slang used to express disagreement or displeasure with a vendor s public statements, particularly when the vendor is speaking of a competitor s products. If a vendor is perceived as implying that buying from a competitor is obviously the wrong choice, that vendor is said to be using FUD as a marketing technique.

fuel cell n. An electrochemical device, similar to a battery in function, in which the chemical energy of a fuel, such as hydrogen, and an oxidant, usually oxygen, are converted directly into electrical energy. Unlike batteries, however, fuel cells do not store energy, and they never run down or need recharging as long as the fuel and oxidant are supplied continuously. The principle of fuel cell technology was discovered more than 100 years ago, but until recently it had found use only in laboratories and in space travel (the Apollo missions and the space shuttle). Today, large and small fuel cells are being developed that will power portable devices such as laptop computers and cellular phones, generate electricity and heat, and replace automotive combustion engines.

fulfillment n. The process of delivering goods and services ordered by a consumer. Fulfillment involves establishing a reliable procedure for tracking orders and delivering products.

fulfillment service provider n. A company that provides fulfillment services for an e-commerce Web site by tracking, packing, and shipping goods ordered via the e-commerce site. A fulfillment service provider allows an e-business to save time, costs, and labor by outsourcing order processing.

full adder n. A logic circuit used in a computer to add binary digits. A full adder accepts three digital inputs (bits): 2 bits to be added and a carry bit from another digit position. It produces two outputs: a sum and a carry bit. Full adders are combined with two-input circuits called half adders to enable computers to add 4 or more bits at a time. See also carry bit, half adder.

full-duplex adj. See duplex¹.

full-duplex transmission n. See duplex(definition 1).

full justification n. In typesetting, word processing, and desktop publishing, the process of aligning text evenly along both the left and right margins of a column or page. See also justify (definition 2).

full mode n. The default operational state of Windows Media Player in which all of its features are displayed. The Player can also appear in skin mode. See also skin mode.

full-motion video n. Video reproduction at 30 frames per second (fps) for NTSC signals or 25 fps for PAL signals. Also called: continuous motion video. See also frame (definition 1). Compare freeze-frame video.

full-motion video adapter n. An expansion card for a computer that can convert motion video from devices such as a video cassette recorder to a digital format that a computer can use, such as AVI, MPEG, or Motion JPEG. See also AVI, Motion JPEG, MPEG.

full name n. A user s complete name, usually consisting of last name, first name, and middle initial. The full name is often maintained by the operating system as part of the information that identifies and defines a user account. See also user account.

full-page display n. A video display with sufficient size and resolution to show at least one 8¹/₂-by-11-inch image. Such displays are useful for desktop publishing applications. Acronym: FPD. See also portrait monitor.

full path n. In a hierarchical filing system, a pathname containing all the possible components of a pathname, including the network share or drive and root directory, as well as any subdirectories and the file or object name. For example, the MS-DOS full path c:\book\chapter \myfile.doc indicates that myfile.doc is located in a directory called chapter, which in turn is located in a directory called book in the root directory of the C: drive. Also called: full pathname. See also path (definition 2), root directory, subdirectory. Compare relative path.

full pathname n. See full path.

full-screen adj. Capable of using or being displayed on the full area of a display screen. Applications running in windowing environments, although they might use the entire area of the screen, commonly allocate different areas to different windows, any of which can be enlarged to fill the entire screen.

full-text search n. A search for one or more documents, records, or strings based on all of the actual text data rather than on an index containing a limited set of keywords. For example, a full-text search can locate a document containing the words albatrosses are clumsy on land by searching files for just those words without the need of an index containing the keyword albatross. See also index.

fully formed character n. A character formed by striking an inked ribbon with a molded or cast piece of type in the manner of a typewriter. Impact printers that produce fully formed characters use letters attached to wheels (daisy wheels), balls, thimbles, bands, or chains, rather than dot-matrix wires. See also daisy wheel, near-letter-quality, thimble.

fully populated board n. A printed circuit board whose integrated circuit (IC) sockets are all occupied. Memory boards in particular may have fewer than the maximum possible number of memory chips, leaving some IC sockets empty. Such a board is said to be partially populated.

function n. 1. The purpose of, or the action carried out by, a program or routine. 2. A general term for a subroutine. 3. In some languages, such as Pascal, a subroutine that returns a value. See also function call, procedure, routine, subroutine.

functional design n. The specification of the relationships between working parts of a computer system, including details of logical components and the way they work together. Functional design is shown graphically in a functional diagram, which uses special symbols to represent the elements of the system.

functional programming n. A style of programming in which all facilities are provided as functions (subroutines), usually without side effects. Pure functional programming languages lack a traditional assignment statement; assignment is usually implemented by copy and modify operations. Functional programming is thought to offer advantages for parallel-processing computers. See also side effect.

functional redundancy checking n. A method of preventing errors by having two processors execute the same instructions on the same data at the same time. If the results produced by the two processors do not agree, an error has occurred. The Intel Pentium and higher processors have built-in support for functional redundancy checking. Acronym: FRC.

functional specification n. A description of the scope, objectives, and types of operations that are to be considered in the development of an information-handling system.

function call n. A program s request for the services of a particular function. A function call is coded as the name of the function along with any parameters needed for the function to perform its task. The function itself can be a part of the program, be stored in another file and brought into the program when the program is compiled, or be a part of the operating system. See also function (definition 2).

function key n. Any of the 10 or more keys labeled F1, F2, F3, and so on, that are placed along the left side or across the top of a keyboard (or both) and are used for special tasks by different programs. The meaning of a function key is defined by a program or, in some instances, by the user. Function keys are used in application programs or the operating system to provide either a shortcut for a series of common instructions (such as calling up a program s on-screen help facility) or a feature that is not otherwise available. See also key (definition 1). Compare Command key, Control key, Escape key.

function library n. A collection of routines compiled together. See also function (definition 2), library (definition 1), toolbox.

function overloading n. The capability of having several routines in a program with the same name. The different functions are distinguished by their parameter types, return value types, or both; the compiler automatically selects the correct version, based on parameter types and return types. For example, a program might have one trigonometric sine function that uses a floating-point parameter to represent an angle in radians, and another that uses an integer parameter to represent an angle in degrees. In such a program, sin(3.14159/2.0) would return the value 1.0 (because the sine of p/2 radians is 1), but sin(30) would return the value 0.5 (because the sine of 30 degrees is 0.5). See also operator overloading.

Function procedure n. A procedure that returns a value and that can be used in an expression. You declare a function with the Function statement and end it with the End Function statement.

fuse n. A circuit element that burns out or breaks when the current passing through it exceeds a certain level. A fuse protects a circuit from damage caused by excess current. It performs the same function as a circuit breaker, but it cannot be reset, so it must be replaced if it breaks. A fuse consists of a short length of wire of a specific composition and thickness; the thicker the wire, the more current it can pass before the wire melts and breaks the circuit.

fusible link n. A circuit component, often part of an integrated circuit, that is designed to break, or burn like a fuse, when a relatively high current is applied. Rather than protecting against excessive current flow, fusible links allow intentional circuit modification in the field. Fusible links were used in PROM chips, and they form the foundation of a kind of integrated circuit known as a field-programmable logic array. One can customize such a circuit in the field, after it has been made in the factory, by selectively programming high current through certain fusible links and breaking them. See also field-programmable logic array, PROM.

fuzzy computing n. 1. A computing technique that deals with vague, incomplete, or ambiguous data in a precise mathematical way while providing solutions based on the human way of thinking. The term fuzzy relates to the type of data it processes, not to the technique itself, which is very exact. Fuzzy computing is also known as fuzzy set theory or fuzzy logic, and covers fuzzy control and fuzzy expert systems, for example. 2. A computing technology in which the computer interprets data by looking for patterns in problems while completing tasks. Using fuzzy computing, the computer is able to examine patterns in the data it receives and to make inferences based on that data, and act accordingly.

fuzzy logic n. A form of logic used in some expert systems and other artificial-intelligence applications in which variables can have degrees of truthfulness or falsehood represented by a range of values between 1 (true) and 0 (false). With fuzzy logic, the outcome of an operation can be expressed as a probability rather than as a certainty. For example, an outcome might be probably true, possibly true, possibly false, or probably false. See also expert system.

fuzzy set n. A set constructed using the principles of fuzzy logic. It is used in artificial intelligence to deal with vague or continuous data that cannot be expressed by conventional set theory. In a fuzzy set, the membership function for the set of objects is not binary but continuous, such that an object may be a member of the set to a specific degree or arbitrary value. In computer programming, a fuzzy set is usually effectively represented by an array. See also array, artificial intelligence, fuzzy logic.

FWIW adv. Acronym for for what it s worth. An expression used in e-mail and newsgroups.

FYI n. 1. Acronym for for your information. An expression used in e-mail and newsgroups to introduce information that is thought to be useful to the reader. 2. An electronic document distributed through InterNIC like a request for comments (RFC), but intended to explain an Internet standard or feature for users rather than to define it for developers, as the RFC does. See also InterNIC. Compare RFC.