F1
A keyboard shortcut key that usually provides help.
F2
A keyboard shortcut key that usually allows editing.
F7
A keyboard shortcut key that usually starts printing.
FAQs
Fast Ethernet
Like Ethernet but since it is at 100 Mb/s instead of 10 Mb/s; it requires special care.
FAT
File Allocation Table. The data that the OS uses to point to and find all the parts of all the files on your hard drive. The big three Microsoft FATs are FAT, NTFS, and FAT 32. See also my article on Hard Drives
FAT 32
See FAT.
fault tolerance

The ability to recover from hardware failure or mistakes with little or no interruption. This usually consists of the following:

• Electrical disaster prevention equipment (surge protectors, UPSs, etc.)
• Data protection and recovery (backup data, RAID, roll back transactions, etc.)
• Components that are redundant, parallel, and replaceable.

FCC
Federal Communications Commission. Organizes radiation emission and other issues in telecommunications.
FDD
Floppy Disk Drive.
FDDI

Fiber Distributed Data Interface. A scheme for forming a network that is for high speed transmission over great distances. FDDI uses a ring topology and fiber optic cable as media. See also my article on LANs.
feather
In desktop publishing this would mean to modify the spacing between lines of text to create vertical justification.
Federal Communications Commission
See FCC.
feed
In one sentence, a modern "feed" is an URL/link for syndicated content that can be consumed by a feed reader.

The syndicated content might be blog posts, newspaper articles, lists of events, etc., but is usually a stream of fresh content. How you discover or choose feeds is a matter of poking around. The format of the feed is usually XML like RSS or ATOM.

You probably already visit feed reading sites/apps that display their own XML feeds (most blogs), or provide you with links that headlines from XML feeds from other people (e.g. Google News), or let you choose what feeds to display (My Yahoo or personalized Google). There are also generic feed reading sites (e.g. Google Reader). Modern browsers have feed reading capabilities (IE7 makes it more prominent).
fiber
See process.
Fiber Distributed Data Interface
See FDDI.
fiber optic cable
field
FIF
.fif. Fractal Image Format. A graphic image file format by Iterated Systems, Inc. (www.iterated.com) which uses fractals to compress images down by as much as 1/100th.
FIFO
First-In, First-Out. See queue.
file:///
The beginning of an URL which locates a file on the same computer as the client's browser.
File Transfer Protocol
See FTP.
finger
A TCP/IP utility that returns system info from a remote host that supports finger.
firewall

Security for a network and its connections to the Internet. It is usually hardware (eg a screening router), software (eg a proxy server), or both. Most firewall systems use one or more of the following methods:

• Packet filtering: A hardware method that utilizes a SR (screening router) to check incoming and outgoing packets and then either allows or rejects the packet based on security parameters such as whether the IP address is preauthorized, or based upon the TCP and UDP port numbers, thus enabling certain types of connections such as telnet or FTP. This method if effective, but is difficult to configure and may still be surpassed by IP spoofing. Packet filtering operates at the Network layer of the OSI Reference Model.
• Proxy server: A software version of a router. It also intercepts messages to and from the network. It hides the true network address (thus making it spoof proof) and can perform function beyond just security. A proxy server may be an application specific proxy. EG: A server may proxy HTTP for Web pages, FTP, RealAudio/Video, SMTP/POP for e-mail, NNTP for newsgroups, nearly any MIME type etc. Proxy servers work at the Application layer of the OSI Reference Model.
• Application gateway: A software method that only allows applications like FTP or telnet servers to connect. This method is effective but has connection limitations.
• Circuit level gateway: A hardware methods that only allows certain circuits to connect.

In addition to a firewall, other security methods are commonly used such data encryption or, the most common method, requiring users to provide usernames and passwords. See also my article on Security.

Firewire
Apple's implementation of the IEEE 1394 standard. A Plug-and-Play technology designed to replace SCSI connections. It consists of a PCI card that supports data transfer that is good enough for video and hard drives. Firewire 400 is 400 Mb/s. Firewire 800 is 800 Mb/s. See also iLink.
firmware
Software written into ROM. ROMs, PROMs and EPROMs with data or programs recorded onto them are firmware.
first-class function
A function that is treated like first class object. A programming language is said to support first-class functions if a function can be made, used, and passed around like a class/object. A first-class function can be constructed, passed as an argument, returned as a value, etc. Here is an example in JavaScript:
function Bark() {
return "Ruff!";
}
Bark(); //The function can be run. Note the parentheses.

function Dog(name, says) {
this.Name = name;
this.Speak = says;
}
myDog = new Dog("Spot", Bark); //The function passed. Note no parentheses.
myDog.Speak();

flash memory
Aka flash EEPROM. An EEPROM chip that writes or erases entire blocks of memory at a time instead of one byte at a time. Flash memory is therefore much faster and is commonly found in digital cameras.
A memory address that starts with zero and increments to the maximum address. In contrast, a memory address space is logically divided into segments. To access a space, a program must specify the segment number and the offset within the argument. Conversion between the two is called thunking.

Intel's 16-bit microprocessors (8086s to the80286s) and Win 3.X used 16-bit flat address spaces. Intel's 32-bit microprocessors (80386s to the Pentium III)  and Win 95+ use 32 bit segmented memory address spaces. The Mac OS has always used flat addressing.
flat database
A file of records without any particular organization. It is a collection of one-to-one relationships.
floating-point number
A number expressed as manitssa (basic number), an exponent, and a radix (number base). EG: 256 = 2.56 x 10^2, where 2.56 is the mantissa, 2 is the exponent, and 10 is the radix. Floating-point numbers with a radix of 10 are so common that they it is often assumed. EG: 256 may also be expressed as 2.56E2 or 2.56D2. See also Database Datatypes.
floating point unit
See FPU.
flip flop
(1) Aka bi-stable multi-vibrator. An electronic circuit that can be in one of two stable conditions. A flip flop is typically used to store a one bit of information.

The most common types of flip flops include: T (toggle), S-R (set/reset), J-K (a pair of S-R), and D (data).

At minimum such a circuit consists of two transistors or vacuum tubes. The first electronic flip-flop was invented in 1919 by W. H. Eccles and F. W. Jordan. It was called the Eccles-Jordan trigger circuit.

(2) To turn something on while simultaneously turning something off. Variations include closing and opening.
FLOPS
FLoating-point Operations Per Second. A unit of measure for the processing power of a computer to perform operations involving floating-point numbers. Since floating-point computations are extensively used in graphics, scientific, or real-time processing applications, it is a good measure of a computers power. EG: On 2000/06/29 IBM publicly introduced its ASCI super computer which can perform 12 TFLOPS, i.e. 12,000,000,000,000 FLOPS. See also MHz and MIPS.
floppy disk
A medium used for storage of computer data. This is long term or permanent memory as opposed to the transient working memory of RAM since the latter must be supplied with power to retain its contents whereas the former does not. Like audio tape, a floppy disk is typically a material embedded with metal particles such as iron oxide. To avoid friction and gouging, the disk is slower than a hard disk, i.e. 300 rpm versus 3,600 rpm.

The current popular size is 3.5 in High Density (HD) holding 1.44 MB. Older sizes include 3.5 in Double Density (DD) holding 800 MB, and 5.25 in holding even less. See also removable storage.
flow chart

A diagram used to show the rough flow of a computer system. Here are what the common shapes usually represent:

• Ovals are start/stop points.
• Rectangles are math operations.
• Diamonds are decision points.
• Parallelograms are output.
flow control
Syntax which decides when and which statements are executed. Here are the three most common flow control devices (written in a fake programming language syntax):
IF condition1 THEN
statementA
ELSEIF condition2 THEN
statement
ELSE
statement
The "If...Then" flow control in English: IF  condition1 is true, THEN execute statementA. ELSE, IF condition1 is false and condition 2 is true, THEN execute the statementB. ELSE in all other cases ( i.e. conditions 1 and 2 are false) execute statementC. Note that the case when both condition1 and condition2 are true is already handled by the first line.
FOR (ItemSetup; testcondition; change)
statement
The "For" flow control loop in English: Step 1: FOR an item, set up its initial condition. Step 2: If the testcondition is true then execute the statement. If the condition is false, then skip the statement and end the loop. Step 3: Change the item. Go back to Step 2.
DO
statement
LOOP WHILE condition
The "Do" flow control loop in English: Step 1: DO (execute) the statement. Step 2: Check to see if the condition is true. WHILE it is true, LOOP back and re-DO the statement. Eventually the statement should make the condition false and end the loop.

A variation on the Do loop is to check the condition before executing the statement. Another variation is to execute the statements UNTIL the condition is true instead of WHILE the condition is true.

"If...Then" is used for making decisions as to which statements to execute. The "For" is for repeating statements a set number of times. "Do" is for repeating statements a number of times dependent upon certain conditions.
folding
Collapsing and expanding parts of an application for convenience. A folding text editor may fold chunks of code such as functions. A section of text on an application may be minimized to an icon.
font
The computer data that transforms text to a specific typeface. Fonts are either bitmapped or outlined. Common kinds of outlined fonts are PostScript, TrueType, and QuickDraw GX. See also typeface. See also my article on Typography.
foobar
A common variable name used for in explanations or as a temporary file. The origin of foobar is unclear. Some say it is tied to the emergency room slang "fubar" which stands for "f---ed up beyond all recognition."
fora
A plural form of "forum". See message board.
foreign key
In databases, it is a column of a table that contains primary key values of another table.
form factor
The size and shape of something, usu. a circuit board. This includes the Socket 7 used in X86 chips. Pentium Pros use Socket 8. Pentium IIs use Slot 1.
forum
See message board.
FPO
For Position Only. Usually written on position images.
fps
frames per second. When a series of still images are shown in rapid sequence they give the illusion of motion. The more fps that a video or animation posses, the better the quality.
FPU
Floating Point Unit. A part of a CPU designed specifically for handling floating point operations. An ALU (Arithmetic and Logical Unit) usually handles math for the CPU but offhands integer division and floating point calculations to a FPU. Since the mid 1990s, FPUs have been incorporated as part of the main processor.
fractal
A geometric construct composed of simple curves or shapes that repeat themselves according to simple rules and will look the same regardless of the scale at which the construct is examined. Since it is composed of repeating geometric shapes, an infinitely complex object can be described with a finite number of equations. The word fractal was coined by mathematician Benoit Mandelbrot in 1975. Fractals or Mandelbrot sets are not integer-dimensioned, eg it would have 1.47 dimensions instead of 2 or 3.
Fractal Image Format
See FIF.
frame
(1) In HTML, it is dividing a web page into sections each of which is another web page.

(2) In video and animation, it is one still image in the series of stills, which, when shown in rapid sequence, give the illusion of motion. See fps.

(3) In communications, it is a packet of information in frame relay protocol.

(4) In graphics and DTP programs, it is an area in which particular types of objects can be place, eg text, vector images, or rasterized images.
frame relay
A packet switching protocol used in WANs. In the US, it supports rates from 56 kb/s to T3 (45 Mb/s). In Europe, it supports rates from 64 kb/s to 2 Mb/s. Frame relay is relatively inexpensive to use over leased lines but some are choosing faster protocols such as ATM.
Free Standard Game Server
See FSGS.
freeware
Proprietary (closed source) software that is available free of charge (gratis). Usually gratis but if used commercially then there is a charge.
free software
Aka FLOSS or F/LOSS (Free/Libre Open Source Software); GLOSS or G/LOSS (Gratis/Libre OSS); or some other combination. Libre (open source) software that is available free of charge (gratis). Note that just plain "OSS" can be commercial instead of gratis.
free variable
(1) A free variable is a notation that specifies places in an expression where substitution may take place. In contrast, a bound variable has limited range of substitution.
Here is an example in plain English: In "Sue hurt her arm", the pronoun her is a free variable because it may refer to Sue or any other female. In "Sue hurt herself", the reflexive pronoun herself is a bound variable becuase it is limited to Su.
Here is an example in a C-like language: i is a bound variable, while y is a free variable.
for (i = 0; i < 9; i++) { a += i * y; }

(2) In programming, a free variable is a variable in a function that is not local to the function or an argument of the function. EG:
function myFun (par) { var loc = 3; return par * loc * free; }

If a free variable is an in an enclosure (has its scope limited), then it is called an upscaled variable.
frontend
(1) The hardware for input and output. These peripheral devices are for communication between the user and the computer system. This includes the keyboard, the monitor, and the printer.

(2) The client's programs which access the server.
FSGS
Free Standard Game Server. Originally created as an alternative to Battle.net, FSGSs support games by Blizzard and other makers, including Age of Empires and Tiberian Sun.
FTP
File Transfer Protocol. Internet protocol that allows FTP clients to download files from an FTP server. Archie is a popular search engine for FTPs. The specs for FTP, RFC 454, were proposed in 1973. Unlike HTTP, which is used on the Web to download files, FTP can be used to both download and upload files.

An FTP client/user must start an FTP session by making a connection to an FTP socket. The FTP socket has tow parts: the IP address of an FTP server and the FTP port at that address, (usually 21).

FTP transmissions are very reliable since the computer sending data expects an acknowledgement for each packet sent. In addition, all packets include a checksum to insure data integrity.

Most operating systems come with FTP client software built in that uses a CLI (Command Level Interface).

FTP client CLIs can be accessed at a command prompt by entering "ftp " and then (optionally) an IP address. To test FTP on your computer, you can use an IP address of 127.0.0.1. The FTP server will then ask for a user name (typically "anonymous"). The FTP server will then ask for a password (typically your e-mail address). Following are some of the commands that may be used at the prompt:
Command		Purpose
---------------------------------------------------------
bye		Ends the FTP session.
delete <file>	Deletes the file.
dir		Lists directories.
help		Provides help on FTP commands.
open <IP>	Connects to that FTP server.
mkdir <path>	Makes a directory remotely.
!		Temporarily returns to system prompt.
!<command>	Executes a system command locally.

Here are common FTP server return codes:

Code	Meaning
-----------------------------------
119	Terminal not available, will try mailbox
120	Service ready in n minutes
125	Data connection already open, transfer starting
150	File status OK, about to open data connection
151	User not local, will forward to <user>@<host>
152	User unknown, mail will be forwarded by the operator
200	Command OK.
211	System status or system help reply
212	Directory status
213	File status
214	Help message
220	Service ready for new user
221	Service closing telnet connection
225	Data connection open, no transfer in progress
226	Closing data connection; requested file action successful
227	Entering passive mode
230	User logged in, proceed
331	User name OK, need password
350	Requested file action pending further info
421	Service not available, try closing telnet connection
425	Cannot open data connection
426	Connection closed, transfer aborted
450	Requested file action not taken: file unavailable
530	Not logged in
532	Need account for storing files
550	Requested action not taken

An alternative to FTP client applications that use CLI, are friendlier applications that use GUI (Graphic User Interface). A web browser can be an FTP client.

Full Duplex Ethernet
A rarer version of Ethernet which is full duplex instead of half duplex.
function
A useful block of programming code performs meaningful work and returns the result. Functions can be named and then summoned forth by name when needed instead of being retyped. Functions are usually in this format: functionname(arguments), eg sum(3,6,11). Many API's have common and proprietary functions available for use. Common functions usually deal with math, date, time, or financial functions.

In OOP, functions are objects often appended with a name that refers to code to create a function, eg document.print. Such a function is called a method.
fuzzy logic

Logic based on multiple degrees of truth. Contrast this with Boolean logic which has two degrees of truth: true or false, i.e. 1 or 0. Fuzzy logic was introduced by Lotfi Zadeh of the University of California at Berkeley in the 1960s.

Fuzzy logic includes 0 and 1 but also includes states of truth in between. EG: An apple might be red (1) or not red (0), but it might also have a degree of red (0.4).

Fuzzy logic was originally applied to natural languages and their seeming non-compliance with Boolean logic. Fuzzy logic has also had application is the development of AI (Artificial Intelligence) and neural networks. EG:

• Data is collected
• Partial truths are formed
• These truths are aggregated to form higher truths
• More complex behavior and thinking can ensue

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