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F. Fahrenheit.

facilities. See optional facilities.

facilities extension. In the X.25 API, an extension to the optional facilities field in a packet that allows further, non-CCITT-specified, optional facility information to be added.

factorization. An arithmetic transformation in which common factors are removed from subexpressions within an expression, and then multiplied by the resulting expression.

factory method. See class method.

fake target name. A control name used in a makefile file that looks like a target name, but actually tells the make command to perform some operation differently.

family. An Ada-language library unit together with its body and subunits (if any). Not all potential family members need be present; a library unit may have a missing optional body, and a main program procedure may have only an implicit specification. The family of a secondary unit is that unit together with any subunits.

fast select. In X.25 communications, an optional facility that allows inclusion of data in call-request and clear-request packets. See also optional facilities.

FCC. Federal Communications Commission.

FCFS. See first-come-first-served.

FD. Full duplex. See duplex.

FDDI. Fiber-optic Distributed Data Interface. A 100-Mbit/sec optical LAN interface. An ANSI standard for a high-speed, 100-Mbit/sec, general-purpose network for the interconnection of computers, networks, and peripheral equipment using optical fiber cable in a dual-ring configuration. FDDI can connect as many as 500 stations with a maximum link-to-link distance of 2 kilometers and a total LAN circumference of 100 kilometers.

FDX. Full duplex. See duplex.

feature. A programming or hardware option, usually available at an extra cost.

fiber optics. The branch of optical technology concerned with the transmission of radiant power through fibers made of transparent materials such as glass, fused silica, and plastic.

field. (1.) An area in a record or panel used to contain a particular category of data. (2.) The smallest identifiable component of a record. An individually addressable subdivision of a record containing a specific portion of the data in the record. For example, a record of data about an employee might be subdivided into fields containing the employee's name, identification number, and salary. (3.) An area in a presentation space into which the program accepts input. (4.) In the INed editor, an area in a structured file defined in the form used to enter and display data. Fields are defined using either text data paths or tree data paths. (5.) In video, a field is one-half of a frame. Fields are drawn 60 times per second. See also structured field.

field of view. In GL, the extent of the area which is under view. The field of view is defined by the viewing matrix in use.

field return. The action that moves a data cursor from field to field in a reverse direction, as determined by the panel layout.

FIFO. See first-in-first-out.

file. (1.) A collection of related data that is stored and retrieved by an assigned name. Contrast with special file. (2.) A sequence of records. If the file is located in internal storage, it is an internal file; if it is on an input/output device, it is an external file. (3.) A collection of related information stored in a single location for organizational purposes and processed as a unit. See also filename.

file descriptor. A small positive integer that the system uses instead of the file name to identify an open file. See also shared memory ID (shmid).

file format. A description of the entries to be made in an ASCII file, such as a configuration or customization profile.

file index. 64 bytes of information describing a file. The file index contains the type and size of the file and the location of the file data on the physical device. This index is the same as the operating system i-node. Synonym for i-node.

file manager. A program that manipulates files or directories.

file memory. Virtual-memory pages that are currently in real memory that are not part of computational memory. Normally these are pages of nonexecutable files.

file mode creation mask. See mask.

file name. (1.) A name assigned or declared for a file. (2.) The name used by a program to identify a file. See also label.

file name substitution. The process in which the shell recognizing a word (character string) that contains any of the *, ?, [, or { characters, or begins with the ~ character, and replaces it with an alphabetically sorted list of file names that match the pattern of the word. Synonymous with globbing.

file owner. The user who has the highest level of access authority to a file, as defined by the file.

file pointer. An identifier that indicates a structure containing the file name.

file scope. A C++ name declared outside all blocks and classes has file scope and can be used after the point of declaration in a source file.

file server. In CDE, a host computer that stores data files used by applications.

file spec. See file specification.

file specification (filespec). The name and location of a file. A file specification consists of a drive specifier, a path name, and a file name.

file suffix. In CDE, a suffix added to the end of a file name, often used in file typing or to categorize files for the user.

file system. The collection of files and file management structures on a physical or logical mass storage device, such as a diskette or minidisk.

file transfer. In remote communications, the transfer of a file or files from one system to another over a communications link.

File Transfer Protocol (FTP). In TCP/IP, the protocol that makes it possible to transfer data among hosts and to use foreign hosts indirectly.

file tree. The complete directory and file structure of a particular node, starting at the root directory. A file tree contains all local and remote mounts performed on directories and files.

file type. In the operating system, one of the five possible types of files: ordinary file, directory, block device, character device, and first-in-first-out(FIFO or named pipe).

filename. In DOS, that portion of the file name that precedes the extension. See also file.

fileset. (1.) An individually installable option or update. Options provide specific function and updates correct an error in, or enhance, a previously installed option. (2.) One or more separately installable, logically grouped units in an installation package.

filetab. A kernel parameter establishing the maximum number of files that can be open simultaneously.

fill characters. (1.) Characters used to fill fields in storage. (2.) Visual representations of enterable character positions on the display (for example, dots in each position or vertical bars between positions).

filter. (1.) A command that reads standard input data, modifies the data, and sends it to the display screen. (2.) A device or program that separates data, signals, or materials in accordance with specified criteria.

filter primitive. A program that separates data in accordance with specified criteria.

fine clipping. In GL, fine clipping masks all drawing commands to a rectangular region of the screen. It would be unnecessary except for the case of character strings. The origin of a character string after transformation may be clipped out by gross, or 3-D, clipping, and the string would not be drawn. By doing gross clipping with the viewport and fine clipping with the screen masks, strings can be moved smoothly off the screen to the left or bottom. See also clipping and gross clipping.

FINGER. Name/Finger Protocol. An application-level Internet protocol that provides an interface between finger command and the fingered daemon.

firewall. A system or machine that controls the access between outside networks and private networks.

first-come-first-served (FCFS). In general, a queuing technique in which the next item to be retrieved is the item that has been in the queue for the longest time. Synonym for first-in-first-out. Contrast with shortest-job-next. See also discipline.

first-in-first-out (FIFO). In the operating system, a named permanent pipe. A FIFO allows two unrelated processes to exchange information through a pipe connection. Synonym for first-come-first-served.

first-level interrupt handler (FLIH). A routine that receives control of the system as a result of a hardware interrupt. One FLIH is assigned to each of the six interrupt levels.

fix number. The fix level of a program, which is an indicator of small updates that are to be built into a regular modification or release at a later time. The version, release, modification, and fix levels together comprise the program level or version of a program. See also program level, modification number, release number, version, and version number.

fixed box. (1.) A geometry management technique. (2.) A type of bounding box that has a fixed number of children created by the parent. These managed children do not make geometry manager requests.

fixed disk. (1.) A flat, circular, nonremovable plate with a magnetizable surface layer on which data can be stored by magnetic recording. A rigid magnetic disk used in a fixed-disk drive.(2.) The term fixed disk is also used loosely in the industry for boards and cartridges containing microchips or bubble memory that simulate the operations of a fixed-disk drive.

fixed-disk drive. The mechanism used to read and write information on a fixed disk.

fixed icon. An icon that is fixed on the desktop. Fixed icons are ordinarily used for files that are necessary to use Common Desktop Environment and therefore always appear on the desktop, such as the Home directory.

fixed part (of a record). In Pascal, the part of a record that is common to all instances of a particular record type.

fixed point type. See real type.

fixed storage space. Any storage device defined during system configuration to be an integral part of system DASD. If a fixed storage device is not available at some time during normal operation, the operating system detects an error.

flag. (1.) A modifier that appears on a command line with the command name that defines the action of the command. A dash usually precedes a flag. (2.) An indicator or parameter that shows the setting of a switch. (3.) A character that signals the occurrence of some condition, such as the end of a word. (4.) An internal indicator that describes a condition to the processing unit. In the processing unit of the PC AT, flags indicate if the result of an operation is zero, if interrupts are enabled, and other conditions. Synonymous with condition code.

flat file. (1.) A file that has no hierarchical structure. (2.) A one-dimensional or two-dimensional array. A list or table of items.

flat network. A network in which all hosts are administered by one central authority.

flattened character. An ASCII character created by translating an extended character to the ASCII character most like it. The code point information is lost and the character cannot be retranslated to an extended character. For example, a cedilla character would be flattened to a plain "c."

FLIH. See first-level interrupt handler.

float constant. A number containing a decimal point, an exponent, or both a decimal point and an exponent. The exponent contains an "e" or "E," an optional sign (+ or -), and one or more digits (0 through 9).

floating display. In text formatting, a block of text that the nroff command keeps on one page. However, if there is no room for a floating display on the current page, the nroff command sets aside the display and finishes filling the page with the text from the input file that follows the display. When the page is full, the nroff command places the display at the top of the next page and then continues with the text from the previous page. See also static display.

floating keep. A keep ensures that bracketed text is not broken across a page boundary, by comparing the size of the text block against the space remaining on the page. If it does not fit, the block is printed at the first possible opportunity on the following page. A fixed keep leaves the remainder of the page blank and a floating keep moves subsequent text onto that page.

floating license. See concurrent-use license.

floating point. A way of representing real numbers (that is, values with fractions or decimals) in 32 bits or 64 bits. Floating-point representation is useful to describe very small or very large numbers.

floating-point constant. A constant representation of a floating-point number expressed as an optional sign followed by one or more digits and including a decimal point. See also floating-point number.

floating-point exception. See exception.

floating-point number. A real number represented by a pair of distinct numerals. The real number is the product of the fractional part, one of the numerals, and a value obtained by raising the implicit floating-point base to a power indicated by the second numeral. See also floating-point constant.

floating point type. See real type.

flow control. In X.25 communications, the procedure for controlling the data transfer rate.

flow diagram. Deprecated term for flow chart.

flyback. A movement similar to a reversing line feed.

FM. See frequency modulation.

FM Header. Function Management Header.

focus window. Synonym for input focus.

fold. (1.) To compact data by combining parts of the data; for example, to transform a two-word numeric key by adding the numeric equivalents of the letters. (2.) To translate the lowercase characters of a character string into uppercase. See also constant folding. (3.) To place on the next line a portion of a line that does not fit on the line. Contrast with truncate.

folder. (1.) In Message Handler, a directory of messages. (2.) In CDE, an icon that represents a directory.

folio. A page numbering format that places the page number at the outside of the running head at the top of the page. See also blind folio, dropped folio, and expressed folio.

font. (1.) A set of characters in a particular style. See also raster font and primitive font. (2.) In Enhanced X-Windows, a set of glyphs, usually characters. The protocol does not translate or interpret character sets. The client indicates values used to access the glyph arrays. A font contains additional metric information to determine inter-glyph and inter-line spacing. (3.) A complete set of graphic characters of the same size, style, and typeface. For example, a Times 12 point font is different in size from a Times 24 point font, different in style from a Helvetica 12 point font, and different in typeface from a Times 12 point boldface font.

font ascent. Height of a character in a specified font.

font list. In AIXwindows, a list of available fonts specified by the fontlist parameter. Also, the list of fonts to be used in formatting a source document. See also font table.

font structure. A data structure that contains all the information necessary to create a font set.

font table. A list of all fonts that have been loaded into the system. See also font list.

font unit. Any group of characters regarded as a whole, especially for the determination of values, variables, and other data pertaining to font characteristics.

footer. Text that appears at the bottom of every page of a document, for example, a page number.

footnote. A note of reference, explanation, or comment placed below the text of a column or page, but within the body of the page above the footer.

footnote text. The text within the footnote.

for statement. In programming languages, a statement that executes one or more statements for each of a set of values assigned to one or more variables.

foreground. (1.) A mode of running a program in which the shell waits for the program specified on the command line to complete before responding to user input. (2.) In multiprogramming, the environment in which high-priority programs are run. Contrast with background.

foreground color. A single color assigned to all of the graphic elements that appear in front of all the background graphic elements within a displayed image. Contrast with background color.

foreground process. A process that must run to completion before another command is issued to the shell. The foreground process is in the foreground process group, which is the group that receives the signals generated by a terminal. Contrast with background process.

foreign cell.A cell other than the one to which the local machine belongs. See also local cell.

foreign host. Synonym for remote host.

fork. To create and start a child process. See also exec.

form. A predefined INed structured file with specially defined fields that allow you to view and edit special types of data.

formal parameter. A parameter declared in a routine heading. It specifies what can be passed to a routine as an actual parameter. See also conformant string and dummy argument. For Ada programming, see also parameter. Contrast with actual parameter.

format. (1.) A defined arrangement of such things as characters, fields, and lines, usually used for displays, printouts, or files. (2.) The pattern that determines how data is recorded. (3.) To arrange such things as characters, fields, and lines. (4.) In programming languages, a language construct that specifies the representation, in character form, of data objects in a file. See also formatted data.

formatted data. Data that is transferred between main storage and an input/output device according to a specified format. See also list-directed data and format.

formatted diskette. A diskette on which track and control information for a particular computer system has been written but that may or may not contain any data.

formatter. (1.) A computer program that prepares a source document for printing. (2.) The part of a text processor that formats input lines for printing or display on a particular type of device.

FORTRAN (FORmula TRANslation). A high-level programming language used primarily for scientific, engineering, and mathematical applications.

forward difference matrix. In GL, 4x4matrix that is iterated by adding each row to the next and the bottom row is output as the next point. Points so generated generally fall on a rational cubic curve.

FP. See FPU.

FPU (FP). Floating-point unit.

fragment. A unit of disk storage that is smaller that a (4KB) page.

frame. (1.) In a high-level data link control (HDLC), the sequence of contiguous bits bracketed by and including opening and closing flag (01111110) sequences. (2.) A set of consecutive digit time slots in which the position of each digit time slot can be identified by reference to a frame alignment signal. (3.) In an interlaced video monitor, a frame consists of two fields, called "even" and "odd", each of which is one sixtieth of a second in duration. (4.) In block-multiplexer-channel-adapter and ESCON transmissions, the block of data that is transferred between the S/370 and the workstation in one CCW. (5.) A block of information corresponding to the FDDI protocol which is transmitted between two or more stations on a ring. An FDDI frame is similar to a packet.

frame buffer. A quantity of video RAM (VRAM) that is used to store the image displayed on the monitor. The frame buffer is the electronic canvas on which every drawing primitive is drawn. It is one of the last stops in the graphics pipeline, where the final image resides in the form of digitally coded intensities and brightnesses. These are converted into analog voltage signals 60 times a second and sent to the electron guns of the monitor. The dimensions of the frame buffer can be changed with GL. Typically, the main frame buffer might be 1024 pixels vertical by 1280 pixels horizontal by 8 color bits. The overlay planes might by 1024x1280x2. The z-buffer is considered a frame buffer, although it is not directly visible from the monitor. (There is no direct means of displaying the contents of the z-buffer, although this can be done indirectly.) The size of the z-buffer is typically 1024x1280x24. The cursor is a very specialized form of a frame buffer; one which can move around. The typical cursor is 32x32x2 in size. See also raster.

frame burst. A group of transmitter receive frames that are contiguous on the media.

frame level. In X.25 communications, the level between the physical level and the packet level, which works according to the high-level data link control procedure (HDLC). Synonymous with data-link level and level 2. See also level, packet level, and physical level.

frame-level interface. In X.25 communications, the level of the DTE/DCE interface in packet mode operation relating to the exchange of packets with local error control, where packets are contained in frames. See also packet-level interface.

frame window. In X.25 communications, the number of frames that can be outstanding without acknowledgment. See also packet window and window.

framing error. An asynchronous transmission error usually caused by the number of bits per character not being set the same on the sending and receiving workstations.

free list. A list of available blocks on each file system.

free-block list. See free list.

free space. Space reserved within the control intervals of a key-sequenced data set or file, used for inserting new records into the data set or file in key sequence; also, whole control intervals reserved in a control area for the same purpose. Synonym for distributed free space.

frequency modulation (FM). Modifying the frequency of a fixed amplitude carrier signal in accordance with an informational signal so that it can carry data signals.

friend class. A C++ class in which all the member functions are granted access to the private and protected members of another class. It is named in the declaration of another class and uses the keyword friend as a prefix to the class. For example, class me { on one line followed by friend class you; on the next and then // ... and ending with }; makes all the functions in class you friends of class me.

friend function. A C++ function that is granted access to the private and protected parts of a class. It is named in the declaration of the class and uses the keyword friend as a prefix.

front and back buffers. In GL, in double buffer mode, the main frame buffer bit planes are separated into two sets--the front and back buffers. Bits in the front buffer planes are visible and those in the back buffer are not. Typically, an application draws into the back buffer and views the front buffer for dynamic graphics.

Front Panel. In CDE, a centrally located window containing controls for accessing applications and utilities, including the workspace switch. The Front Panel occupies all workspaces.

Front Panel control. In CDE, an object in the Front Panel used as an interface to basic system services and frequently performed tasks and operations. Controls in the default Front Panel are: Clock, Calendar, Mailer, Text Editor, Help Viewer, File Manager, Printer, Style Manager, Application Manager, and Trash Can. See also control.

Front Panel move handles. In CDE, an area on each end of the Front Panel used for moving the Front Panel and for bringing it to the front of the workspace.

frustum. In GL, a truncated, four-sided pyramid; that is, a pyramid with the point cut off. In a perspective projection, the shape of the clipping volume is a frustum. The bottom of the frustum is referred to the far clipping plane, the top of the frustum is the near clipping plane, and the sides are respectively the top, left, bottom, and right clipping planes. In an orthographic projection, the clipping volume is a parallelepiped. See also clipping panes.

FTP. File Transfer Program. See also File Transfer Protocol.

full backup. Backup copies of all the files on the system. Contrast with incremental backup.

full duplex (FDX). Synonym for duplex.

full high. Pertains to a storage device that has the original height (82.5 mm or 3.25 inches), width (146 mm or 5.75 inches), and length (203 mm or 8.0 inches). See also half high.

full path name. The name of any directory or file expressed as a string of directories and files beginning with the root directory. See also fully qualified name, path name, and relative path name.

full-screen editor. An editor that displays an entire screen at a time and that allows data to be accessed and modified only by moving the cursor and entering commands.

fullword. Synonym for word.

fully qualified host name. A complete qualified name. Includes all names in the hierarchical sequence above the structure member to which the name refers, as well as the member itself.

fully qualified name. A qualified name that includes all names in the hierarchical sequence above the structure member to which the name refers, as well as the name of the member itself. See also full path name.

function. (1.) A specific purpose of an entity, or its characteristic action. (2.) A machine action such as carriage return or line feed. (3.) A subroutine that returns the value of a single variable and that usually has a single exit, such as subroutines that compute mathematical functions. Synonymous with procedure. For Ada programming, see also subprogram.

function call. An expression that moves the path of execution from the current function to a specified function and evaluates to the return value provided by the called function. A function call contains the name of the function to which control moves and a parenthesized list of values.

function declarator. The part of a function definition that names the function, provides additional information about the return value of the function, and lists the function parameters.

function definition. The complete description of a function. A function definition contains an optional storage class specifier, an optional type specifier, a function declarator, optional parameter declarations, and a block statement (the function body).

function keys. Keys that request actions but do not display or print characters. This includes the keys that normally produce a printed character, but produce a function instead when used with the code key. See also character key.

function pointer. An identifier that gives the location of a function or procedure.

function reference. The appearance of an intrinsic function name or a user function name in an expression.

function scope. C++ labels that are declared in a function have function scope and can be used anywhere in that function.

function subprogram. See function.

function template. Provides a blueprint describing how a set of related individual C++ functions can be constructed.

functional equivalence. A situation in which different algorithms for a given problem domain yield identical results.

funnelling. Forcing device drivers and kernel extensions that are not known to be MP safe to run only on the master processor.

FX. See FXU.

FXU (FX). Fixed-point unit.

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