fa from FOLDOC

FAC

Functional Array Calculator. An APL-like language, but purely functional and lazy. It allows infinite arrays.

["FAC: A Functional APL Language", H.-C. Tu and A.J. Perlis, IEEE Trans Soft Eng 3(1):36-45 (Jan 1986)].

facebook.com

<web>

One of the most popular social networking websites.

FaceBook home.

Last updated: 2007-11-16

face time

<jargon>

Time spent interacting with somebody face-to-face (as opposed to via electronic links). "Oh, yeah, I spent some face time with him at the last Usenix."

[Jargon File]

face-to-face

<jargon, chat>

(F2F, IRL) Used to describe personal interaction in real life as opposed to via some digital or electronic communications medium.

Last updated: 1997-01-31

Facile

<language>

A concurrent extension of ML from ECRC.

http://ecrc.de/facile/facile_home.html.

["Facile: A Symmetric Integration of Concurrent and Functional Programming", A. Giacalone et al, Intl J Parallel Prog 18(2):121-160, Apr 1989].

Last updated: 1994-12-01

facsimile

<communications>

("fax") A process by which fixed graphic material including pictures, text, or images is scanned and the information converted into electrical signals which are transmitted via telephone to produce a paper copy of the graphics on the receiving fax machine.

Some modems can be used to send and receive fax data. V.27 ter and V.29 protocols are used.

[Details? Standards?]

Last updated: 2004-07-26

FACT

Fully Automated Compiling Technique

fact

<artificial intelligence, programming>

The kind of clause used in logic programming which has no subgoals and so is always true (always succeeds). E.g.

 wet(water).
 male(denis).

This is in contrast to a rule which only succeeds if all its subgoals do. Rules usually contain logic variables, facts rarely do, except for oddities like "equal(X,X).".

Last updated: 1996-10-20

factor

A quantity which is multiplied by another quantity.

factorial

<mathematics>

The mathematical function that takes a natural number, N, and returns the product of N and all smaller positive integers. This is written

 N! = N * (N-1) * (N-2) * ... * 1.

The factorial of zero is one because it is an empty product.

Factorial can be defined recursively as

 0! = 1
 N! = N * (N-1)!	 , N > 0

The gamma function is the equivalent for real numbers.

For example, the number of ways of shuffling 52 playing cards is 52! or nearly 10^68. 52 Factorial.

Last updated: 2012-11-23

FAD

["FAD, A Simple and Powerful Database Language", F. Bancilon et al, Proc 13th Intl Conf on VLDB, Brighton, England, Sep 1987].

failback

failover

<systems>

Automatically switching to a different, redundant system upon failure or abnormal termination of the currently active system. Failover can be applied to a cluster of servers, to network or storage components or any other set of redundant devices that must provide high availability because down-time would be expensive or inconvenient. It may be implemented in hardware, software or a combination.

A "hot standby" is continuously active at the same time as the failed system, using some kind of load balancing to share the work, whereas a "warm standby" is ready to become active at short notice.

When the failed system is operational again it may "failback", i.e. become (one of) the active system(s) or it may become a warm standby.

Last updated: 2008-01-15

failure

The inability of a system or system component to perform a required function within specified limits. A failure may be produced when a fault is encountered.

Last updated: 1996-05-13

failure-directed testing

<programming>

(Or "heuristics testing") Software testing based on the knowledge of the types of errors made in the past that are likely for the system under test.

Last updated: 1996-05-16

FAIR

<language>

An early system on the IBM 705.

[Listed in CACM 2(5):1959-05-16].

Last updated: 1996-05-13

Fairchild F8

<processor>

An 8-bit microprocessor. The processor itself had no address bus - program and data memory access were contained in separate units, which reduced the number of pins and the associated cost. It also featured 64 registers, accessed by the ISAR register in cells (register windows) of eight, which meant external RAM wasn't always needed for small applications. In addition, the 2-chip processor didn't need support chips, unlike others which needed seven or more.

The F8 inspired other similar CPUs, such as the Intel 8048. The use of the ISAR register allowed a subroutine to be entered without saving a bunch of registers, speeding execution - the ISAR would just be changed. Special purpose registers were stored in the second cell (regs 9-15), and the first eight registers were accessed directly. The windowing concept was useful, but only the register pointed to by the ISAR could be accessed - to access other registers the ISAR was incremented or decremented through the window.

Last updated: 1994-11-16

fall back

<communications>

A feature of a modem protocol where two modems which experience data corruption, e.g. due to line noise, can renegotiate to use a lower speed connection, possibly applying fall forward if the channel improves.

Last updated: 2004-07-30

fall forward

<communications>

A feature of a modem protocol where two modems which fall back to a lower speed because of data corruption can later return to the higher speed if the connection improves.

Last updated: 2004-07-30

fall over

<programming>

An IBM synonym for crash.

"Fall over hard" equates to crash and burn.

[Jargon File]

Last updated: 2018-09-05

fall through

<programming>

(The American misspelling "fall thru" is also common)

1. To exit a loop by exhaustion, i.e. by having fulfilled its exit condition rather than via a break or exception condition that exits from the middle of it. This usage appears to be *really* old, dating from the 1940s and 1950s.

2. To fail a test that would have passed control to a subroutine or some other distant portion of code.

3. In C, "fall-through" occurs when the flow of execution in a switch statement reaches a "case" label other than by jumping there from the switch header, passing a point where one would normally expect to find a "break". A trivial example:

 switch (colour)
 {
 case GREEN:
   do_green();
   break;
 case PINK:
   do_pink();
   /* FALL THROUGH */
 case RED:
   do_red();
   break;
 default:
   do_blue();
   break;
 }

The effect of the above code is to "do_green()" when colour is "GREEN", "do_red()" when colour is "RED", "do_blue()" on any other colour other than "PINK", and (and this is the important part) "do_pink()" and then "do_red()" when colour is "PINK". Fall-through is considered harmful by some, though there are contexts (such as the coding of state machines) in which it is natural; it is generally considered good practice to include a comment highlighting the fall-through where one would normally expect a break. See also Duff's Device.

fall thru

fall through

FALSE

A small, compiled extensible language with lambda abstractions by W. van Oortmerssen.

For Amiga.

FancyIndexing

<web>

An option supported by the Apache web server mod_autoindex that, if enabled, sorts the output in various ways according to query string parameters.

For example,

 https://foldoc.org/pub/misc/?C=M;O=D

sorts the output by column "Last modified" (C=M) in descending order (O=D).

Last updated: 2020-04-05

fandango on core

<jargon, programming>

(Unix/C, from the Mexican dance) In C, a wild pointer that runs out of bounds, causing a core dump, or corrupts the malloc arena in such a way as to cause mysterious failures later on, is sometimes said to have "done a fandango on core". On low-end personal machines without an MMU, this can corrupt the operating system itself, causing massive lossage. Other frenetic dances such as the rhumba, cha-cha, or watusi, may be substituted.

See aliasing bug, precedence lossage, smash the stack, memory leak, memory smash, overrun screw, core.

[Jargon File]

Last updated: 1994-12-16

fan-out

<electronics>

The number of logic gate inputs that can be driven from a single gate output of the same type. Circuit designers need to add extra buffers if a signal goes to more inputs than the fan-out of the gate that produces it allows.

Last updated: 2007-05-16

FAP

<language>

The assembly language for Sperry-Rand 1103 and 1103A.

[Listed in CACM 2(5):16 (May 1959)].

Last updated: 1994-12-16

FAQ

frequently asked question

FAQL

frequently asked question

FAQ list

frequently asked question

faradise

/far'*-di:z/ [US Geological Survey] To start any hyper-addictive process or trend, or to continue adding current to such a trend. Telling one user about a new octo-tetris game you compiled would be a faradising act - in two weeks you might find your entire department playing the faradic game.

farkled

<jargon>

/far'kld/ (From DeVry Institute of Technology, Atlanta) A synonym for hosed. Possibly related to Yiddish "farblondjet" and/or the "Farkle Family" skits on Rowan & Martin's Laugh-In.

[Jargon File]

Last updated: 1998-09-07

farm

processor farm

farming

<jargon>

(From Adelaide University, Australia) What the heads of a disk drive are said to do when they plow little furrows in the magnetic media during a head crash. Typically used as follows: "Oh no, the machine has just crashed; I hope the hard drive hasn't gone farming again."

[Jargon File]

Last updated: 2001-03-26

FARNET

A non-profit corporation, established in 1987, whose mission is to advance the use of computer networks to improve research and education.

fas

1. Frankenstein Cross Assemblers. A reconfigurable assembler package, especially suited for 8-bit processors, consisting of a base assembler module and a yacc parser, for each microprocessor, to handle mnemonics and addressing. Second party parser modules available from many sites.

Base assembler and yacc parser modules by Mark Zenier. FTP: ftp.njit.edu/pub/msdos/frankasm/frankasm.zoo.

2. FAS. A general purpose language sponsored by the Finnish government in the 70's and 80's.

FASBOL

["FASBOL. A SNOBOL4 Compiler", P.J. Santos, Memo ERL-M134, UC Berkeley 1971].

fascist

<jargon>

Said of a computer system with excessive or annoying security barriers, usage limits, or access policies. The implication is that said policies are preventing hackers from getting interesting work done. The variant "fascistic" seems to have been preferred at MIT.

In the design of languages and other software tools, "the fascist alternative" is the most restrictive and structured way of capturing a particular function; the implication is that this may be desirable in order to simplify the implementation or provide tighter error checking. Compare bondage-and-discipline language, although that term is global rather than local.

[Jargon File]

Last updated: 2003-07-29

FASE

Fundamentally Analyzable Simplified English.

L.E. McMahon, Bell Labs.

[Sammet 1969, p.720].

Last updated: 1994-11-09

FAST

<body>

1. Federation Against Software Theft.

<language>

2. Fortran Automatic Symbol Translator.

Last updated: 1996-05-19

Fast ATA

Advanced Technology Attachment Interface with Extensions

Fast ATA-2

Advanced Technology Attachment Interface with Extensions

Faster LEX

<language>

(FLEX) A reimplementation of the Lex scanner generator, by Vern Paxson <[email protected]>.

Flex++ produces C++ and aflex produces Ada.

FTP flex-2.3.8.tar.Z from a GNU archive site or ftp://ftp.ee.lbl.gov/pub/flex-2.4.3.tar.Z.

["The FLEX Scanner Generator", Vern Paxson <[email protected]>, Systems Engineering, LBL, CA].

[Home? Current version?]

Last updated: 2003-12-16

Fast Ethernet

<networking>

A version of Ethernet developed in the 1990s(?) which can carry 100 Mbps compared with standard Ethernet's 10 Mbps. It requires upgraded network cards and hubs.

The relevant standards are 100BaseT, 100BaseFX and 100BaseVG.

Last updated: 1998-03-23

Fast Fourier Transform

<algorithm>

(FFT) An algorithm for computing the Fourier transform of a set of discrete data values. Given a finite set of data points, for example a periodic sampling taken from a real-world signal, the FFT expresses the data in terms of its component frequencies. It also solves the essentially identical inverse problem of reconstructing a signal from the frequency data.

The FFT is a mainstay of numerical analysis. Gilbert Strang described it as "the most important algorithm of our generation". The FFT also provides the asymptotically fastest known algorithm for multiplying two polynomials.

Versions of the algorithm (in C and Fortran) can be found on-line from the GAMS server here.

["Numerical Methods and Analysis", Buchanan and Turner].

Last updated: 1994-11-09

Fast Packet

Asynchronous Transfer Mode

Fast Page Mode Dynamic Random Access Memory

<hardware, storage>

Is this the same as Page Mode Dynamic Random Access Memory?

Last updated: 1996-10-06

Fast SCSI

<hardware>

A variant on the SCSI-2 bus. It uses the same 8-bit bus as the original SCSI-1 but runs at up to 10MB/s - double the speed of SCSI-1.

Last updated: 1994-11-24

FAT

File Allocation Table

FAT32

File Allocation Table

fatal

<programming>

Resulting in termination of the program.

Last updated: 1997-08-03

fatal error

<programming, operating system>

Any error which causes abrupt termination of the program. The program may be terminated either by itself or by the operating system (a "fatal exception"). In the former instance, the program contains code which catches the error and, as a result, returns to the operating system or calls an operating system service to terminate the program.

Last updated: 1997-08-03

fatal exception

<programming, operating system>

A program execution error which is trapped by the operating system and which results in abrupt termination of the program.

It may be possible for the program to catch some such errors, e.g. a floating point underflow; others, such as an invalid memory access (an attempt to write to read-only memory or an attempt to read memory outside of the program's address space), may always cause control to pass to the operating system without allowing the program an opportunity to handle the error. The details depend on the language's run-time system and the operating system.

fat binary

<operating system>

An executable file containing code for more than one CPU. The correct code is selected automatically at run time. This is convenient for distributing software and sharing it between multiple platforms.

NEXTSTEP supports fat binaries, e.g. for Motorola 68000, Intel 80486 and SPARC ("triple fat"). Mac OS supports fat binaries for both 680x0 and PowerPC native code.

[Other OSes?]

Last updated: 1995-09-23

fat client

<networking>

Opposite of "thin client".

Last updated: 1996-12-08

fat electrons

<electronics, humour>

Old-time hacker David Cargill's theory on the cause of computer glitches. Your typical electricity company draws its line current out of the big generators with a pair of coil taps located near the top of the dynamo. When the normal tap brushes get dirty, they take them off line to clean them up, and use special auxiliary taps on the *bottom* of the coil. Now, this is a problem, because when they do that they get not ordinary or "thin" electrons, but the fat sloppy electrons that are heavier and so settle to the bottom of the generator. These flow down ordinary wires just fine, but when they have to turn a sharp corner (as in an integrated-circuit via), they're apt to get stuck. This is what causes computer glitches.

[Obviously, fat electrons must gain mass by bogon absorption - ESR]

Compare bogon, magic smoke.

[Jargon File]

Last updated: 1996-12-08

fault

<programming>

1. A manifestation of an error in software. A fault, if encountered, may cause a failure.

<architecture>

2. page fault.

Last updated: 1996-05-14

fault-based testing

<testing>

Software testing using test data designed to demonstrate the absence of a set of pre-specified faults; typically, frequently occurring faults. For example, to demonstrate that the software handles or avoids divide by zero correctly, the test data would include zero.

Last updated: 1996-05-15

fault tolerance

<architecture>

1. The ability of a system or component to continue normal operation despite the presence of hardware or software faults. This often involves some degree of redundancy.

2. The number of faults a system or component can withstand before normal operation is impaired.

Last updated: 1995-04-06

fault tolerant

fault tolerance

Fault Tolerant Unix

<operating system>

(FTX) Stratus's own Unix System V Release 4 multiprocessor operating system. In 2016, FTX is supported but no longer developed.

FTX was one of three operating systems supplied by Stratus on their hardware, the other two, HP-UX and VOS, were the more common choices, FTX was only sold on an exceptional basis.

Early FTX 3.x releases used an in-house virtual disk layer (VDL) driver, but later releases switched to a version of Veritas VxVM.

FTX supported many of the proprietary communications boards (ISDN, serial, parallel, X.25, etc.).

http://www.openpa.net/systems/stratus_continuum.html

Last updated: 1998-07-06

fault tree analysis

<programming>

A form of safety analysis that assesses hardware safety to provide failure statistics and sensitivity analyses that indicate the possible effect of critical failures.

Last updated: 1996-05-15

favicon.ico

<web>

A special image file used to represent a web site in, e.g. the web browser tab header or a list of bookmarks. Orignally this file was always called "favicon.ico" and always appeared at the top level. Now there are many other schemes for finding such images.

Last updated: 2025-01-16

fax

facsimile

Fax over IP

<communications>

(FoIP) Transmission of a facsimile over an IP networking instead of PSTN, analogous to Voice over IP.

Last updated: 1999-04-26

Nearby terms:

f2c ♦ F2F ♦ F68K ♦ FAC ♦ facebook.com ♦ face time ♦ face-to-face ♦ Facile

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