Backbone: A network through which other, smaller networks are connected.

Backup: A duplicate copy of files or an entire hard drive. A backup of your important files should be done regularly.

Bandwidth: The amount of data that can be transmitted along a communications channel in a fixed amount of time. Usually expressed in bits per second (bps).

Baud Rate: A measurement of how quickly a modem transfers data. Although, strictly speaking, this is not the same as bits per second, the two terms are often used interchangeably.

BBS (Bulletin Board System): A service accessible via modem or other connection through which users may exchange messages privately or post messages to a publicly accessible forum; may or may not have Internet access.

Benchmarks: A set of conditions or criteria against which a product or system is measured.

Beta: Beta versions of commercial software are work-in-progress test copies released prior to the full version. They're used to put the product through real-world tests and to ferret out bugs before the finished software hits the shelves. Betas often expire after a period of time, usually when the full version or the next beta is released.

BGA: Ball Grid Array - the method chipsets are attached to motherboards, using solder balls.

Bios: Basic Input/Output System. Software that determines what a computer can do without accessing programs. Your BIOS has the information to control the keyboard, screen, drives, serial communications, and other functions. BIOS is typically built into a ROM chip installed on the motherboard.

Bit: Short for binary digit; either a 1 or a 0; the smallest unit into which digital information may be broken.

Boot Sequence: The order of drives that a system's BIOS follows when looking for the operating system to boot after the computer has performed POST. This can be defined by you in your computers BIOS.

Boot up: The process of turning on the computer, which includes a number of functions that are performed automatically every time the power switch is turned on.

BPS (Bits per Second): A measure of the speed of data transmission; the number of bits of data that can be transmitted each second. Modems are generally measured by their BPS rate (14.4K - 14400 BPS, 28.8K - 28800 BPS)

Broadband: High speed internet access via cable lines or ADSL phone lines.

Browser: A client software program used to search networks, retrieve copies of files and display them in an easy-to-read, often graphical, format. Browsers such as SPRY Mosaic, Netscape Navigator, and Microsoft Internet Explorer are used to access information on the World Wide Web.

BSOD: Blue Screen of Death - when the Windows OS continually shows a blue screen and a reboot is required.

BTW or IMHO: Abbreviation for "By the way" or "in my humble opinion", respectively. Abbreviations such as these are commonly used in email, newsgroups, or listservs.

Bulletin Board System (BBS): A computer system to which other computers can connect so their users can read and leave messages, or retrieve and leave files.

Burn: To record information onto a writable optical medium such as a CD-R or CD-RW.

Burn in: A given period of time in which a new computer is fully stressed to make sure there are no faults.

Bus Mastering: Allows for peripherals to directly communicate to each other without the help of the CPU. This often results in higher performance as well as less CPU utilization.

Byte: A collection of eight BITS.

Capacitor: A small electric element that is used to temporarily store electrical charge.

Card Bus: 32-bit industry standard used for devices that fit into a laptop PC slot.

CAT5: Referring to Category 5 Ethernet cabling, the CAT5 standard allows for data transfers up to 100 Mbps.

CAT7: Category 7 quality cabling is needed for Gigabit (Gbps) Ethernet transmissions.

CD-R: Recordable CD technology for data and music storage using a low-cost disc that can be written only once.

CD-ROM: Compact Disc Read Only Memory - A compact disc format used to hold text, graphics and hi-fi stereo sound. The audio CD player cannot play CD-ROMs, but CD-ROM players can play audio discs.

CD-RW: CD ReWritable - A rewritable CD technology. CD-RW drives can also be used to write CD-R discs, and they can read CD-ROMs. A CD-RW disc can be rewritten over a thousand times and read on MultiRead CD-ROM drives or CD-RW compatible Audio CD players.

Chat: A program that connects computers on a network for instantaneous, multi-way communication. People who use chat can type messages for delivery to a server, which displays the messages instantly so that users who are logged on to the chat service can respond immediately. On the Internet, chat is sometimes referred to as Internet Relay Chat (IRC).

CIX: An acronym for Commercial Information Exchange.

Client: A software program that provides access to network resources by working with information stored on a server.

CMOS: Complementary Metal Oxide Semiconductor - a chip that packs many components into a very small semiconductor. A CMOS computer circuit consumes very little power and is used in computers to keep track of the system setup information, data, time, type of disk and hard drives, etc. that a computer has installed. The CMOS information is powered by the computer's on-board battery. So if the on-board battery fails, the information in CMOS is lost.

CNR: Communications Network Riser - Small slot next to the PCI slots which a modem or sound riser card plugs into.

Coax: Referring to coaxial cable, Coax is similar to TV cabling. Used for older 10Base2 Ethernet networks.

Compact Flash: A very small removable mass storage device that relies on flash memory technology, a storage technology that does not require a battery to retain data indefinitely. Compact Flash cards can support 3.3V and 5V operation and can switch between the two, in contrast to other small-form factor flash memory cards that can only operate at one voltage. There are two types of Compact Flash cards to accommodate different capacities: Type I cards are 3.3mm thick while Type II cards are 5.5mm thick. The card was designed based on the PCMCIA PC Card standard and can fit into a PCMCIA slot with an adapter.

Compressed File: Computer files that have been reduced in size by a compression program. Such programs are available for all computer systems.

Cookie: A small file placed on your hard drive by a website to identify you when you visit again. For example, these can store user information such as your username and password to the website or keep track of ads you have been shown. While many cookies can be good, some now track where you go and report this information back to the tracking website. See spyware for more on this.

Corona: Another AMD DDR Athlon board reference name. Also a great beer, even better with lime.

Corrupted: When data gets damaged and can no longer be used.

CPU: Central Processing Unit - Your processors, for example, Pentium IV, AMD Athlon. It is your computer's brain, taking requests from applications and then processing, or executing, actions or operations. The faster your processor, the more operations it can execute per second. The more operations you have per second, the faster things happen in your applications. Often people refer to a computers tower as the "CPU" but as explained above, the CPU is simply one of many parts in that tower.

Crash: An unexpected shutdown either of a program or the whole system.; sometimes traumatic, always frustrating ; often fixable by turning off the computer and turning it back on; results in losing any unsaved work. Can also be used in instances of a hard disk physically being damaged.

Crossover cable: Cat 5 cable in which the internal wiring crosses over; used to connect computer-to-computer or when no uplink ports are available on a hub.

Cruise: Navigating the Internet by following hyperlinks from one Web site or page to another.

CRT: Cathode Ray Tube - the glass portion of any traditional monitor. Operates by shooting electrons through a screen which enables images to be projected on the back of a phosphorescent coating on the screen.

CSCW: This is an acronym for Computer Supported Co-operative Work, more commonly called groupware. See also Lotus Notes.

Cyberspace: A term coined by author William Gibson. It describes the imaginary space in which computer users travel when "surfing" the Internet.

Daemon: In UNIX, a program running all the time in the "background" (that is, unseen by users), providing special services when required. An example of a daemon is biff, which lets you know when mail arrives.

Daisy-chain: Connecting devices together in a string. Most often associated with SCSI devices.

DARPA: US Defence Advanced Research Projects Agency (now ARPA). One of the bodies which `created' the concept of the Internet and funded the development of Internet facilities for many years.

DDR: Double Data Rate - a type of Synchronous DRAM, or SDRAM. DDR SDRAM enables data transfers to occur on both edges of the clock cycle, thus doubling the memory throughput of the chip.

DDR RAM: An extension of SDRAM technology, DDR effectively doubles the bandwidth available by sending data on the falling edge of the clock cycle as well as on the rising edge.

Desktop: No, not the thing your keyboard and mouse are sitting on, but rather the main screen on your monitor where you find your icons, background wallpaper and maybe your screensaver.

DHCP: Dynamic Host Configuration Protocol - Method of assigning temporary IP addresses to computers to ensure network security.

Dedicated Line: A telephone line that is leased from the telephone company and used for one purpose only. In the early days of the Internet, it was a line dedicated to a server.

Dial-in Direct Connection: An Internet connection that is accessed by dialling in to a computer through a telephone line. Once connected, your computer acts as if it were an Internet host. This type of service is often called SLIP, CSLIP or PPP.

Dial-up Service: A common Internet term for a dial-on terminal connection.

Digi board: Hardware to build a ras server.

Digital: Terms used to describe any information that has been translated into a corresponding series of 1s and 0s; any information - text, sound, image, colour, may be digitized.

Dimm: DIMM RAM is characterized by its 168 pins.

DIMM Slots: DIMM memory fits into special 168 pin slots which are located on the motherboard, usually adjacent from the processor.

Discussion Board: A forum on a Web site for the discussion of a specific topic or set of related topics.

DOCSIS: Data Over Cable Service Interface Specification - A standard for transferring internet data over cable lines.

Dot Pitch: Used to describe the horizontal size of pixels on CRT and LCD displays. The smaller the dot pitch (for example 0.25 mm) the better the resolution of the display.

Domain Names: A name given to a host computer on the Internet. E-mail names are good examples of domain names (i.e., anyname@netcom.com).

Dot: Short for the "period" usually heard in a reference to a url -- "www.pchelp4free.com"

Double Click: 2 clicks of the mouse at the same time. If the program detects a double click it often will open the selected application.

Download: The process of transferring information from one computer to another, usually from a server to a client. You download a file from another computer to yours.

DSL: Digital Subscriber Line - High-speed internet connection offered by telephone companies over existing phone lines.

DVD: Digital Versatile Disc - Introduced in 1996, the optical discs share the same overall dimensions of a CD, but have significantly higher capacities - holding from 4 to 28 times as much data.

DVD Video: Popular format for high quality MPEG2 video and digital surround sound. Enables multi-language, multi-subtitling and other advanced user features.

DVD+RW: DVD ReWritable - It is the only rewritable format that provides full, non-cartridge, compatibility with existing DVD-Video players and DVD-ROM drives for both real-time video recording and random data recording across PC and entertainment applications.

DVD-Audio: This audio-only storage format similar to CD-Audio, however offers 16, 20 and 24-bit samples at a variety of sampling rates from 44.1 to 192KHz, compared to 16 bits and 44.1KHz for CDs. DVD-Audio discs can also contain music videos, graphics and other information.

DVD-RAM: DVD Random Access Memory - A rewritable DVD disc endorsed by Panasonic, Hitachi and Toshiba. It is a cartridge-based, and more recently, bare disc technology for data recording and playback. DVD-RAM bare discs are fragile and do not guarantee data integrity. The first DVD-RAM drives had a capacity of 2.6GB (single sided) or 5.2GB (double sided). DVD-RAM Version 2 discs have double-sided 9.4GB discs. DVD-RAM drives typically read DVD-Video, DVD-ROM and CD media. The current installed base of DVD-ROM drives and DVD-Video players cannot read DVD-RAM media.

DVD-ROM: Read Only Memory - This read-only DVD disc is used for storing data and interactive sequences as well as audio and video. DVD-ROMs run in DVD-ROM or DVD-RAM drives, not DVD-Video players connected to TVs and home theatres. However, most DVD-ROM drives will play DVD-Video movies.

DVD-RW: DVD ReWritable - A rewritable DVD format that is similar to DVD+RW, but its capability to work as a random access device is not as good as +RW. It has a read-write capacity of 4.7 GB.

E1: A four-wire European telephone company standard that carries data at 2.048 Mbit/s. The European-equivalent of a US T1 line.

EAROM: Electrically Alterable Read-Only Memory.

EAX: Environmental Audio Extensions: a hardware and software audio standard developed by Creative Labs. And used originally in the company's SoundBlaster cards. EAX has subsequently become a widely supported standard offering 3D positional audio and allowing the manipulation of sounds so that they can appear to be heard in different listening environments.

ECC: Error Correcting Code - A method of generating redundant information which can be used to detect and correct errors in stored or transmitted data.

ECC optimised: On a SIMM or DIMM, the use of a module addressing architecture that facilitates the use of the memory module by systems with ECC. ECC optimised memory modules do not have byte-write capability.

EDAP: Extended Data Availability and Protection: Created by the RAID Advisory Board in 1997, EDAP introduces a classification system for the resilience of the entire storage system and that is not confined to disk-based storage alone. Availability of an EDAP-certified system is sustainable even in the event of failure, the degree of resiliency provided being reflected in the level of EDAP capability attributed to the system.

EDC: Error Detection Code: 32 bits in each sector which are used to detect errors in the sector data.

EDGE: Enhanced Data for GSM Evolution: a technology that gives GSM and TDMA similar capacity to handle services for 3G. EDGE was developed to enable the transmission of large amounts of data at rates of 384 Kbit/s.

EDO: Extended Data Output - a type of random access memory (RAM) chip designed to improve the time to read from memory on faster microprocessors such as the Intel Pentium.

EDP: Enhanced Dot Pitch: Hitachi's tube technology in which the phosphor triads are spaced closer together horizontally than they are vertically.

EDRAM: Enhanced Dynamic Random Access Memory: a form of DRAM that boosts performance by placing a small complement of static RAM (SRAM) in each DRAM chip and using the SRAM as a cache. Also known as cached DRAM, or CDRAM.

EDI: An acronym for Electronic Data Interchange. Also referred to as electronic commerce.

EDVAC: Electronic Discrete Variable Automatic Computer: the first computer to incorporate von Neumann's "stored program" concept, in which the programme executed by the computer was stored as data, rather than existing as wire connections. Designed in 1946, when EDVAC became fully operational in 1952 it comprised contained approximately 4,000 vacuum tubes and 10,000 crystal diodes.

EEPROM: Electronically Erasable Programmable Read Only Memory - like ROM cannot be erased unless it receives proper erasing signals from the mother device. Commonly used for BIOS's of motherboards.

EFM: Eight to Fourteen Modulation: used on every CD for modulation and error correction.

EGA: Enhanced Graphics Adapter: the IBM standard for colour displays prior to the VGA standard. It specified a resolution of 640x350 with up to 256 colours and a 9-pin (DB-9) connector.

EIA: Electronic Industries Association: a trade association representing the U.S. high technology community which began life in 1924 as the Radio Manufacturers Association. It has been responsible for developing some important standards, such as the RS-232, RS-422 and RS-423 standards for connecting serial devices. In 1988, it spun off its Information & Telecommunications Technology Group into a separate organisation known as the TIA.

EIRP: The Effective Isotropic Radiated Power of a transmitter (uplink) is the power that the transmitter appears to have if the transmitter was an isotropic radiator, i.e., if it radiated equally in all directions. By virtue of the gain of a radio antenna, dish, radio telescope or optical telescope, a beam is formed that preferentially transmits the energy in one direction. The EIRP is given by the product of the gain and the transmitter power.

EIDE: Enhanced Integrated Device Electronics or Enhanced Intelligent Drive Electronics: an enhanced version of the IDE drive interface that expands the maximum disk size from 504Mb to 8.4Gb, more than doubles the maximum data transfer rate, and supports up to four drives per PC (as opposed to two in IDE systems). EIDE's primary competitor is SCSI-2, which also supports large hard disks and high transfer rates.

EISA: Extended Industry Standard Architecture: an open 32-bit extension to the ISA 16-bit bus standard designed by Compaq, AST and other clone makers in response to IBM's proprietary MCA (Micro Channel Architecture) 32-bit bus design. Unlike the Micro Channel, an EISA bus is backward-compatible with 8-bit and 16-bit expansion cards designed for the ISA bus.

Electron Beam: The invisible stream of electrons that flow from a CRT monitor's cathode to its screen.

Electronic Commerce: The transacting of business electronically rather than via paper.

E-mail (Electronic Mail): A means of sending typed messages from one computer to another, over a network or the Internet.

Embedded Servo: The method most disks use to help the head locate tracks accurately; servo fields are interspersed with the real data, acting like runway lights for the head to line up on.

Emoticon: Emoticons, or smileys :-) , are used to convey emotion. The expressions and inflections of voice we use to convey emotion, irony, sarcasm, etc. when talking are lost when communicating over the Internet. To make up for that, a system of symbols has developed which uses common keyboard marks.

EMI: Electromagnetic Interference - A form of electronic radiation which can potentially corrupt data transfer.

Encoding: A method whereby a group of data bits is translated into a group of recording bits.

Energy Star: Launched in 1993, this is a program established by the Environmental Protection Agency (EPA) as a partnership with the computer industry to promote the introduction of energy-efficient personal computers which help reduce air pollution caused by power generation. To comply with the Energy Star guidelines, a computer system or monitor must consume less than 30 watts of power in its lowest power state.

EPP: Enhanced Parallel Port: a parallel port that conforms to the EPP standard developed by the IEEE 1284 standards committee. The EPP specification transforms a parallel port into an expansion bus that can handle up to 64 disk drives, tape drives, CD-ROM drives, and other mass-storage devices.

EPROM: Erasable Programmable Read Only Memory: an integrated circuit memory chip that can store programs and data in a non-volatile state. These devices can be erased by high-intensity ultraviolet (UV) light and then rewritten, or "reprogrammed", in a manner similar to common DRAM. EPROM chips normally contain UV-permeable quartz windows exposing the chips' internals.

Error Control: The encoding of text or data so that a receiving modem can detect and sometimes correct errors in data transmissions. LAPM and MNP classes 1 through 4 are two different error control protocols.

Escape Sequence: A sequence of three characters (normally "+++") that switches the modem from the on-line mode to the command mode without breaking the telephone connection.

ESCD: Region of non-volatile memory used by BIOS and ICU (Intel Configuration Utility) or PnP operating system to record information about the current configuration of the system.

ESD Strap: A device that plugs into a standard outlet which discharges static electricity from a person.

ESDI: Enhanced Small Device Interface: an interface standard developed by a consortium of the leading PC manufacturers for connecting disk drives to PCs. Introduced in the early 1980s, ESDI was two to three times faster than the older ST-506 standard. It has long since been superseded by the IDE, EIDE and SCSI interfaces.

Etch: A process using a chemical bath (wet etch) or a plasma (dry etch) that removes unwanted substances from the wafer surface.

Ethernet: The most widely-installed local area network technology. An Ethernet LAN typically uses coaxial cable or special grades of twisted pair wires.

ETSI: European Telecommunications Standards Institute: a non-profit membership organisation founded in 1988, dedicated to standardising telecommunications throughout Europe. It promotes worldwide standards, and its efforts are co-ordinated with the ITU.

Expansion Bus: An input/output bus typically comprised of a series of slots on the motherboard. Expansion boards are plugged into the bus. ISA, EISA, PCI and VL-Bus are examples of expansion buses used in a PC.

Expansion Card: A circuit board that fits into a computer expansion slot to add a certain function (like a modem, sound card, or SCSI interface).

External Drive: A drive mounted in an enclosure, separate from the computer system enclosure, with its own power supply and fan, and connected to the system by a cable.

Extrusion: Taking a flat, 2-D object and adding a z plane to expand it into 3-D space.

Fan Header: A place where you can plug a Fan with RPM monitoring straight into the board.

FAQ: Frequently Asked Questions - A place where common questions are answered already, saving users time so they don't have to ask the same thing.

Fast Multiword DMA: An alternative protocol to PIO modes for a controller to send and receive data to and from a drive.

Fast Ethernet: A local area network transmission standard that provides a data rate of 100 megabits per second.

FAT: File Allocation Table: the file system used by DOS and Windows to manage files stored on hard disks, floppy disks, and other disk media. The file system takes its name from an on-disk data structure known as the file allocation table, which records where individual portions of each file are located on the disk. Earlier versions of Windows used the 16-bit version known as FAT16. Windows 98 has the option of using FAT32, which supports larger partition sizes and smaller cluster sizes, thereby improving disk performance and increasing available disk space. See also VFAT.

FAT32: File Allocation Table - Maintained by an operating system on a hard disk that provides a map of the clusters that a file has been stored in. FAT 32 supports 32-bit processors.

FCBGA: Flip Chip Ball Grid Array: a micro CPU package for surface mount boards consisting of a die placed face-down on an organic substrate. Instead of using pins, the package uses small balls, which acts as contacts for the processor. The advantage of using balls instead of pins is that there are no leads that bend. The package uses 479 balls, which are .78 mm in diameter.

FCC: Federal Communications Commission: the U.S. Government agency that supervises, licenses, and regulates electronic and electromagnetic transmission standards.

FCI: Flux Changes per Inch. See also BPI.

FC-PGA: CPU's with the die on the top instead of the bottom uses the Flip Chip Pin Grid Array. This is done to improve thermal heat transfer to the heatsink.

FC-PGA2: Because FC-PGA CPU's often got damaged when the heatsink is installed, Intel came up with the idea of putting a heat spreader on top of the CPU to protect it from damage.

FDD: Floppy Disk Drive - Traditionally refers to the A: drive or 1.44 MB (3.5") High Density Floppy format, but can also refer to older 720K (5.25") Floppy drives.

FDDI: Fibre Distributed Data Interface: an ANSI standard token passing network that uses optical fibre cabling and transmits at 100 Mbit/s up to two kilometres. Typically used as backbones for wide area networks (WANs).

FDM: Frequency Division Multiplexing: a technique that uses different frequencies to combine multiple streams of data for transmission over a communications medium. Each signal travels within its own unique frequency range (carrier), which is modulated by the data (text, voice, video, etc.). Many carrier frequencies are then combined for transmission.

FDMA: Frequency Division Multiple Access: a mobile communications technique in which radio spectrum is divided into frequency bands.

Feathering: A term used when describing printed text quality. Feathering occurs when deposited ink follows the contours of the paper. Depending on the viscosity of the ink, the rougher the grain of the paper the more pronounced the feathering will be.

FED: Field Emission Display: a display technology which use vacuum tubes (one for each pixel) with conventional RGB phosphors.

Ferrite: A ferromagnetic compound of ferric oxide used in the construction of magnetic recording heads and media.

FHSS: Frequency Hopping Spread Spectrum: a radio transmission method that continuously changes the center frequency of a conventional carrier several times per second according to a pseudo-random set of channels, thereby making illegal monitoring extremely difficult, if not impossible. See also DSSS.

Fibre Channel: A technology for transmitting data between computer devices at a data rate of up to 1 Gbps, especially suited for connecting computer servers to shared storage devices and for interconnecting storage controllers and drives. Devices can be as far as ten kilometres apart. The longer distance requires optical fibre as the physical medium. Fibre Channel also works using coaxial cable and ordinary telephone twisted pair.

Field: One-half of a complete video frame, consisting of every other analogue scan line.

FIFO: First In-First Out: a storage method that retrieves the item stored for the longest time. See also LIFO.

File Server: A computer that provides network stations with controlled access to shareable resources. The network operating system is loaded on the file server, and most shareable devices (disk subsystems, printers) are attached to it. The file server controls system security and monitors station-to-station communications. A dedicated file server can be used only as a file server while it is on the network. A non-dedicated file server can be used simultaneously as a file server and a workstation.

File Transport Protocol (FTP): A service for moving an electronic file of any type from one computer to another over the Internet.

Fill Factor: Used in connection with digital display technologies (such as LCD and DLP) to convey how much of the area of a single pixel is used for the image as opposed to the grid surrounding the pixel. The higher the "fill factor" the better. See also Screen Door Effect.

Filtering: A process used in both analogue and digital image processing to reduce bandwidth. Filters can be designed to remove information content such as high or low frequencies, for example, or to average adjacent pixels, creating a new value from two or more pixels.

Finalisation: When a disc is "finalised" the absolute lead-in and lead-out for the entire disc is written, along with information which tells the reader not to look for subsequent sessions. This final table of contents (TOC) conforms to the ISO 9660 file standard.

Firewall: Firewalls are used to create a protective barrier for the internal network (LAN) against the external one (WAN, Internet) which monitors packets travelling in and out of the network. Usually located at the network's gateway.

Firmware: Permanent instructions and data programmed directly into the circuitry of read-only memory for controlling the operation of the computer or peripheral devices. Distinct from software, which is stored in read/write memory and can be altered.

Fixation: The process of writing the lead-in and lead-out information to the disc. This process finishes a writing session and creates a table of contents. Fixation is required for a CD-ROM or CD-Audio player to play the disc. Discs which are "fixated for append" can have additional sessions recorded, with their own session lead-in and lead-out, creating a multi-session disc.

Flame Mail: An excessively angry or rancorous message, generally containing personal insults, sent through e-mail.

Flamer: Someone who writes flame mail. Flamee should be obvious.

Flash Memory: Flash memory is a non-volatile memory device that retains its data when the power is removed. The device is similar to EPROM with the exception that it can be electrically erased, whereas an EPROM must be exposed to ultra-violet light to erase. Commonly used in digital cameras.

Flash ROM: A type of memory used for firmware in modems and other digital devices. Unlike conventional ROM (read-only memory), flash ROM can be erased and reprogrammed, making it possible to update a product's firmware without re-placing memory chips.

Flat Panel Display: A thin display screen that uses any of a number of technologies, such as LCD, plasma and FED. Traditionally used in laptops, flat panel displays are slowly beginning to replace desktop CRTs for specialised applications.

Flat Shading: The simplest form of 3D shading which fills polygons with one colour. Processor overheads are negligible and 3D games will allow the graphics to be stripped down to flat shading to improve the frame rate.

Floppy Disk: A removable storage medium that is used in conjunction with a floppy drive, usually 5.25-inch or 3.5-inch in size.

Floppy Drive: Practically all PCs come with a floppy disk drive. 3.5in high density 1.44MB floppy disks are now the standard. They come in hard plastic cases and have replaced the older, literally floppy, 5.25in disks.

Flow Control: The mechanism that regulates the flow of data between two devices. Modems typically have two methods of flow control software flow control (XON/XOFF) and hardware flow control (CTS/RTS).

Flux Density: The number of magnetic field patterns that can be stored on a given area of disk surface, used as a measure of data density. The number is usually stated as flux changes per inch (FCI), with typical values in the tens of thousands.

Fly Height: The distance between the read/write head and the disk surface, made up of a cushion of air that keeps the head from contacting the media. Smaller flying heights permit denser data storage but require more precise mechanical designs.

FM Synthesis: Frequency Modulation Synthesis: an outdated technique for synthesising music reproduction but still widely supported to provide compatibility with older games software.

Fogging: The alteration of the visibility or clarity of an object, depending on how far the object is from the camera. Usually implemented by adding a fixed colour (fog colour) to each pixel. Also known as Haze.

Folder: A folder is space on your hard drive holding files. Similar to a filing cabinet, you can store many files in your folders and create as many folders as you need.

Foot-lambert: fL: a unit of luminance equal to 3.463 candelas per square metre.

Foot Print: The amount of physical space or memory a component will take up.

Format: A preparatory process that is necessary before data can be recorded to some storage devices. Formatting erases any previously stored data.

Formatted Capacity: The amount of room left to store data on a disk after writing the sector headers, boundary definitions, and timing information during a format operation. The size of a Quantum drive always is expressed in formatted capacity, accurately reflecting the usable space available.

Form Factor: The physical size and shape of a device. It is often used to describe the size of circuit boards. The physical size of a device as measured by outside dimensions. With regard to a disk drive, the form factor is the overall diameter of the platters and case, such as 3.5in or 5.25in, not the size in terms of storage capacity. If the drive is a 5.25in form factor it means that the drive is the same size as a 5.25in diskette drive and uses the same fixing points.

Forum: The dedicated area where people come together to discuss issues, hobbies, or news. Also called newsgroups.

FPM DRAM: Fast Page Mode RAM: a timing option that permits several bits of data in a single row on a DRAM to be accessed at an accelerated rate. Fast Page Mode involves selecting multiple column addresses in rapid succession once the row address has been selected.

FPS: Frames Per Second: an expression of frame rate.

FPU: Floating Point Unit: a formal term for the math co-processors (also called numeric data processors, or NDPS) found in many personal computers. FPUs perform certain calculations faster than CPUs because they specialise in floating-point math, whereas CPUs are geared for integer math. Today, most FPUs are integrated with the CPU rather than packaged and sold separately.

FPX: FlashPIX: an emerging WWW standard for images. The FPX file format is a single, interoperable digital imaging format which supports other file formats like JPEG, PCX, PICT and TIFF. It has multi-resolutions because it stores images in multiple sizes.

Fractals: Along with raster and vector graphics, a way of defining graphics in a computer. Fractal graphics translate the natural curves of an object into mathematical formulas, from which the image can later be constructed.

Frame: A single, complete picture in video or film recording. A video frame consists of two interlaced fields of either 525 lines (NTSC) or 625 lines (PAL/SECAM), running at 30 frames per second (NTSC) or 25 frames per second (PAL/SECAM).

Frame Buffer: Display memory that temporarily stores (buffers) a full frame of picture data at one time. Frame buffers are composed of arrays of bit values that correspond to the display's pixels. The number of bits per pixel in the frame buffer determines the complexity of images that can be displayed.

Frame Grabber: A device that "captures" and potentially stores one complete video frame. Also known as frame storer.

Frame Rate: How fast the source repaints the screen with a new frame. NTSC repaints the screen every 1/30th of a second for a frame rate for 30 frames per second. PAL is 25 frames per second. "Full-motion" playback of compressed MPEG files is at 30 frames per second.

Freeware: Software provided free by its originator. See shareware.

Frequently Asked Questions (FAQ): An area or document dedicated to answering common questions.

Frontside Bus: The bus within a microprocessor that connects the CPU with main memory. See also Backside Bus.

Front Projection: Front projection is when a projection unit is positioned in front of the screen. See also Rear Projection.

FSAA: Full Screen Anti Aliasing - What is done by video card to remove the jagged edges in lines. The resulting image is much smoother on the eyes, though performance may suffer.

FSB: Front Side Bus - Which denotes the speed at which your processor interacts with the components on the motherboard. Typically the FSB is 100Mhz or 133Mhz, but overclockers often manipulate this value to increase the speed at which their processor runs. i.e. 100Mhz FSB X 5.0 clock multiplier = 500Mhz processor.

FSK: Frequency Shift Keying: a data transmission technique that blends a data signal into a carrier by varying (modulating) the frequency of the carrier.

FST: Flat Square Tube: describes the viewing surface of a cathode ray tube that is nearly flat. Flatter screens give the appearance of straighter lines, and they can aid in the reduction of glare, compared to conventional tubes.

FTP: File Transfer Protocol: a set of rules that allows two computers to communicate with each other as a file transfer is carried out.

Full Duplex: Data transfer that allows a switch to send and receive data to a node at the same time. Also known as bidirectional communication.

Full-Motion Video: FMV: video reproduction at 30 frames per second (NTSC-original signals), 25 frames per second (PAL-original signals) and 30 frames per second (compressed MPEG).

Gain: The increase in signalling power as an audio signal is boosted by an electronic device. It is measured in decibels.

Gamma: A mathematical curve representing both the contrast and brightness of an image. Moving the curve in one direction will make the image both darker and decrease the contrast. Moving the curve the other direction will make the image both lighter and increase the contrast.

Gamma Correction: A form of tone mapping in which the shape of the tone map is a gamma.

Gamma Curve: A mathematical function that describes the non-linear tonal response of many printers and monitors. A tone map that has the shape of this its compensating function cancels the nonlinearities in printers and monitors.

Gamut: The range of colours that can be captured or represented by a device. When a colour is outside a device's gamut, the device represents that colour as some other colour.

Gateway: Hybrid device that translates data into different protocols, serves as network security and distributes high-speed internet connections.

GB: Giga Byte - Or 1 billion bytes of information.

Gbps: Giga Bits Per Second - Refers to bits of information travelling at 1 billion bits per second. Gbps is usually associated with Gigabit Ethernet.

Gflops: Gigaflops: 1 thousand million floating-point instructions per second.

GDI: Graphical Device Interface: a component of Windows that permits applications to draw on screens, printers, and other output devices. A GDI-compliant printer will print exactly what is displayed on a Windows screen without having to transpose it into a printer language. Since all the processing happens on the PC, the printer doesn't require since image processing circuitry, reducing its price.

General MIDI: A table of 128 standard sounds or instruments for MIDI cards and synthesisers.

Geometry: The computation of the base properties for each point (vertex) of the triangles forming the objects in the 3D world. These properties include x-y-z co-ordinates, RGB values, alpha translucency, reflectivity and others. The geometry calculations involve transformation from 3D world co-ordinates into corresponding 2-D screen co-ordinates, clipping off any parts not visible on screen and lighting.

GFD: Golden finger device - This is the device that you attach to the Slot A Athlon to manipulate the clock multiplier and voltage.

Ghosting: A visual effect in which an area of 'on' pixels causes a shadow on 'off' pixels in the same rows and columns. A particular problem with passive matrix LCDs.

GiB: Gibibyte: a unit of measure consisting of 1024MiB.

Gigabit: 1,000,000,000 (10 9 ) bits

Gigabit Ethernet: 1000Mbps Ethernet connection. 10 times faster than fast Ethernet.

Gigabyte: 1, 000,000,000 (10 9 ) bytes.

GIF: (Graphic Interchange Format): One of two popular systems used to compress the size of image files so they require less bandwidth to transfer on the Web.

GMR: Giant Magneto resistive technology uses various thin film layers to produce a greater change in resistance and is even more sensitive than standard magneto resistive technology. See also Magneto resistive.

Gold Disc: The recordable disc used in recordable CD systems. The blank disc is made of a bottom layer of polycarbonate, with a preformed track spiral which the recording laser follows when inscribing information onto the disc. This type of disc is therefore also called pre-grooved. A translucent organic dye layer is laid on top of the polycarbonate, then a reflective layer of gold. On top there are thin layers of lacquer and label.

GOP: In an MPEG signal the GOP is a group of frames between successive I frames, the others being P and/or B frames. The GOP concept allows the temporal redundancy across frames (from frame to frame) for video content to be reduced.

GOPS: Giga Operations Per Second: in the case of multimedia processing, more GOPS translate to better video quality.

Gopher: An Internet service for locating and delivering electronic files. The Gopher interface includes a directory tree and a set of menus which can be used for exploring the Internet and downloading files.

Gouraud Shading: A method of hiding the boundaries between polygons by modulating the light intensity across each one in a polygon mesh.

GPF: General Protection Fault: the error code triggered when a Windows program causes a failure or lock-up.

GPRS: General Packet Radio Service: an enhancement for GSM and TDMA core networks that introduces packet data transmission. GPRS uses radio spectrum very efficiently and provides users with "always on" connectivity and greater bandwidth.

GPS: Global Positioning System: refers to satellite-based radio positioning systems that provide 24 hour three-dimensional position, velocity and time information to suitably equipped users anywhere on or near the surface of the Earth (and sometimes off the earth). GPS technology is used in a wide range of applications, including maritime, environmental, navigational, tracking and monitoring.

GPU: Graphics Processor Unit - A GPU takes on the task of working with Transform and Lighting (T&L) away from the CPU so it can focus on more important things such as AI.

Gradient: In graphics, having an area smoothly blend from one colour to another, or from black to white, or vice versa.

Graphics Card: An expansion card that interprets drawing instructions sent by the CPU, processes them via a dedicated graphics processor and writes the resulting frame data to the frame buffer. Also called video adapter (the term "graphics accelerator" is no longer in use).

Graphics Library: A tool set for application programmers, interfaced with an application programmer's interface, or API. The graphics library usually includes a defined set of primitives and function calls that enable the programmer to bypass many low-level programming tasks.

Graphics Processor: The specialised processor at the heart of the graphics card. Modern chipsets can also integrate video processing, 3D polygon setup and texturing routines, and, in some cases, the RAMDAC.

Greyscale: Shades of grey that represent light and dark portions of an image. Colour images can also be converted to greyscale where the colours are represented by various shades of grey.

GSM: Global System for Mobile Communications: first introduced in 1991, GSM is the largest digital mobile standard in use today. Implemented in 400MHz, 900MHz, 1800MHz and 1900MHz frequency bands.

Guard Time: A period of time during which the modem must not receive characters. The escape sequence has a guard time to ensure that data sent from a remote modem isn't interpreted as an escape sequence.

GUI: This is an acronym for Graphical User Interface. Examples are Windows and Apple's Macintosh operating system. The concept originated in the early 1970s at Xerox's PARC laboratory.

Guide Rails: Plastic or metal strips attached to the sides of a hard disk drive mounted in an IBM AT and compatible computers so that the drive easily slides into place.

H.261: A video compression standard developed for video teleconferencing systems. It is DCT-based and resembles MPEG to some degree. It is hoped that this will be the standard that allows a videophone from one manufacturer to "talk" to a videophone from another manufacturer, just as two different FAX machines can "talk" to each other.

Half Duplex: Data transfer that only sends or receives data to a node. Hubs commonly perform in half duplex mode.

Halftone: A method of expressing colour gradation in continuous-tone images. The image is resolved into dots, with dark colour being expressed by a large number of dots and diluted colour is by a smaller number of dots. The dot patterns used are called dithers. Halftone dots are not the same as printer dots.

Hard Disk: The rigid storage medium located within a hard drive; the relatively large storage area where a computer's operating system, applications, and data usually reside.

Hard Error: A data error that persists when the disk is reread, usually caused by defects in the physical surface.

HDA: Head Disk Assembly: The mechanical components of a disk drive (minus the electronics), which includes the actuators, access arms, read/write heads and platters. Typically housed in a sealed unit.

HDCP: High-bandwidth Digital Content Protection: an encoding method for distributing digital content via a DVI (Digital Visual Interface) port. Using hardware on both the graphics adapter card and the monitor, HDCP encrypts data on route to a display device, where it is then decrypted.

HDD: Hard Disk Drive - Also known as hard drive, it is a mechanical device used to store information on your computer. Information is stored on spinning discs magnetically. Usually your main hard drive is known as your "C" drive in Windows Explorer or My Computer.

HD-DVD: High Density DVD: the next generation optical DVD disc. As of early 2002 the DVD Forum was struggling to get agreement on a single standard, with rival proposals for formats specifying single-side capacities of between 9MB and 27MB under consideration.

HDLC: High-level Data Link Control: An ISO communications protocol used in X.25 packet switching networks. The HDLC protocol embeds information in a data frame that allows devices to control data flow and correct errors at the data link layer.

HDTV: High Definition TV: a television system with approximately twice the horizontal and twice the vertical resolution of current 525-line and 625-line systems, component colour coding (e.g. RGB or YCbCr) a picture aspect ratio of 16:9 and a frame rate of at least 24 Hz. The principal scanning formats have active vertical scanning lines of 720 progressive (720p), 1080 interlaced (1080i). Though 1080i as higher resolution than 720p, it doesn't render motion quite as well the progressive scanning format.

Head: The tiny electromagnetic coil and metal pole used to create and read back the magnetic pat-terns on the disk. Also known as the read/write head.

Head Crash: Damage to a read/ write head and magnetic media, usually caused by sudden contact of the heads with the disk surface. Head crash also can be caused by dust and other contamination inside the HDA.

Heatsink: Metal device used to cool processors and other components by means of convection or forced air.

Helper App: A "helper application" or add-on program particularly for a web browser that increases the functionality and the type of files that the browser can display. Also see Plug-in.

Hi-8: A video recording and playback system that uses 8mm video cassettes and the S-video technology.

High Colour: Graphics cards that can show 16-bit colour (up to 65,536 colours).

High-Level Formatting: Formatting performed by the operating system's format program (for example, the DOS FORMAT pro-gram). Among other things, the formatting program creates the root directory, file allocation tables, and other basic configurations. See also Low-Level Formatting.

Highlight: The brightest part of an image.

High Sierra Format: The standard logical file format for CD-ROM originally proposed by the High Sierra Group, revised and adopted by the International Standards Organisation as ISO 9660.

Home: Reference position track for recalibration of the actuator, usually the outer track (Track 0).

Home Page: The opening page of a World Wide Web document, sometimes called the welcome page.

HomePNA: Home Phone line Networking Alliance: an association of industry-leading companies working together to ensure adoption of a single, unified phone line networking standard and the development of a range of interoperable home networking solutions.

HomeRF: Home Radio Frequency: a wireless personal area network (PAN) technology from the HomeRF Working Group, founded in 1998 by Compaq, IBM, HP and others. HomeRF uses the Shared Wireless Access Protocol (SWAP) and provides an open standard for short-range transmission of digital voice and data between mobile devices (laptops, PDAs, phones) and desktop devices.

Home Theatre: A home theatre system is a combination of audio-video components - such as a TV, VCR, DVD player and surround-sound speaker system - designed to recreate the experience of watching a movie in a cinema.

Host: A computer connected directly to the Internet. A service provider's computer is a host.

Hop: When accessing a WAN or Internet, data packets often have to travel through several places to reach it's destination, each place the packet lands on is called a hop.

Host Adapter: A plug-in board or circuitry on the motherboard that acts as the interface between the system bus and a peripheral device. IDE and SCSI are examples of peripheral interfaces that call their controllers host adapters.

Hot Plugging: The ability to add and remove devices to a computer while the computer is running and have the operating system automatically recognize the change. Two external bus standards -- Universal Serial Bus (USB ) and IEEE 1394 -- support hot plugging. This is also a feature of PCMCIA.

Hot Swapping: A method in which devices are plugged and unplugged into a computer, usually referring to USB, IEEE, 1394, and similar devices.

HPM: Hyper Page Mode: in DRAM operation, another term for EDO or Extended Data Out.

HRTF: Head-Related Transfer Functions: Refers to the mathematics that models the way a human ear localises the direction of a sound.

HSB: Hue Saturation Brightness: with the HSB model, all colours can be defined by expressing their levels of hue (the pigment), saturation (the amount of pigment) and brightness (the amount of white included), in percentages.

HSCSD: High Speed Circuit Switched Data: the final evolution of circuit switched data within the GSM environment. HSCSD enables the transmission of data over a GSM link at speeds of up to 57.6kbit/s. This is achieved by concatenating consecutive GSM timeslots, each of which is capable of supporting 14.4kbit/s. Up to four GSM timeslots are needed for the transmission of HSCSD.

HSF: Horizontal Scanning Frequency: indicates the speed, measured in kilohertz, at which a single horizontal line is drawn on the screen. Higher scan rates are needed to provide sharper, crisper images at higher resolutions. Also called scan rate.

HSM: Hierarchical Storage Management: System of ranking and storing information across a variety of device types.

HTML (Hyper Text Mark-up Language): This is an acronym for Hyper Text Mark-up Language which is used to format information so that it can be structured and made accessible to the World Wide Web (WWW). The language itself is a simplified derivative of SGML, a widely used standard developed in the mid 1980's. The technique employed is to encase the information in special markers (called tags) which tell the WWW applications how the text is to be interpreted.

HTML+: A proposed new standard which will supersede html. It is a superset of html which is designed to extend the capabilities of the language to incorporate better support for multimedia objects in documents.

HTPS: High Temperature Poly-Silicon: A thin-film transistor (TFT) panel is an active matrix display containing a microscopic thin-film transistor in the corner of each pixel. HTPS panels allow driver ICs to be embedded into their TFTs, thereby allowing greater miniaturisation (higher pixel counts and higher aperture ratios).

HTTP (Hypertext Transfer Protocol): The protocol that forms the basis of World Wide Web technology. HTTP is the set of rules governing the software that transports hyperlinked files along the Internet.

Hub: A common connection point for devices in a network. Often used to describe the device that serves as the centre of a star-topology network.

Hue: The attribute of a visual sensation according to which an area appears to be similar to one of the perceived colours, red, yellow, green and blue, or a combination of two of them. Also referred to as tint.

Huffman Coding: For a given character distribution, by assigning short codes to frequently occurring characters and longer codes to infrequently occurring characters, Huffman's minimum redundancy encoding minimises the average number of bytes required to represent the characters in a text.

HVD: High Voltage Differential: the logic signalling system originally defined in the SCSI-2 standard. HVD has a maximum logic voltage of 5V and uses a paired plus and minus signal level to reduce the effects of noise on the SCSI bus. It was functionally replaced by LVD (Low Voltage Differential) in the SCSI-3 variant of the standard. HVD and LVD SCSI are not directly compatible but can be interconnected by the use of a special adapter.

Hybrid: Under the Orange Book standard for recordable CD, hybrid means a recordable disc on which one or more sessions are already recorded, but the disc is not closed, leaving space open for future recording.

Hypergraphic: In a World Wide Web document, a graphic image coded to form a link to another file. As with hypertext, if you click on a hypergraphic, you will jump to the linked file.

Hyperlink: A code which contains an "address," which when clicked, will take you to that address.

Hypermedia: Like hypertext except that the concept is extended to multimedia objects such as graphics, video and audio.

HyperTransport: The new name for LDT, or Lightning Data Transport. Jointly developed by AMD and API as a replacement to the aging PCI bus.

Hypertext: Electronic text coded to provide instant access, via links, to other hypertext (or hypergraphics) elsewhere within a document or in a separate document.

Hub: Network device that joins all the network devices centrally in a star configuration.

Hz: Hertz - unit of measurement for Frequency.

IA-32: Intel Architecture 32-bit. Intel's 32-bit architecture, also known as x86. IA-32 chips span the early 1990s Intel 486 series to the seventh-generation Intel Pentium 4 and AMD Athlon chips. See also IA-64.

IA-64: Next generation 64-bit architecture made up of the 64-bit Instruction Set Architecture (ISA) jointly developed by HP and Intel and an IA-32 compatibility component. IA-64 supports 32-bit and 64-bit environments, and provides compatibility with PA-RISC and IA-32.

IAB: An acronym for Internet Architecture Board.

IANA: An acronym for Internet Assigned Numbers Authority.

IBM: International Business Machines - IBM is the largest computer company in the world and the first to produce a computer back in 1953. Often IBM compatible is used still to refer to a computer running Windows.

IC: Integrated Circuit: a tiny complex of electronic components and their connections that is produced in or on a small slice of material (such as silicon). Its name results from the integration of previously separate transistors, resistors and capacitors - all on a single chip.

Icon: A small picture on your screen which usually represents a program, folder, file or shortcut.

ICS: Internet Connection Sharing - A method in which 1 internet source can be shared with multiple computers. ICS can be setup with Windows XP or with software like Sygate/Wingate or hardware (routers).

IDE: Integrated Drive Electronics. An interface used mainly by hard drives and CD-ROM drives to connect to the computer.

IEC: International Electrotechnical Commission: the body that attempted to resolve the confusion surrounding the use of "MB" to mean either binary megabytes and decimal megabytes - depending on context - by their approval, in late 1998, of names and symbols for prefixes for binary multiples for use in the fields of data processing and data transmission. The acceptance of the symbols - "Ki", "Mi", "Gi" etc. - by the PC industry has been somewhat disappointing.

IEEE: Institute of Electrical and Electronics Engineers: a membership organisation that includes engineers, scientists and students in electronics and allied fields. Best known for its involvement in setting standards for computers and communications, such as the widely followed IEEE 802 standards for Local Area Networks.

IEEE 1394: An international high-performance serial-bus standard that offers the real-time data transfer of video, audio and peripheral applications through a universal I/O interface. With this technology, digital cameras, CD-ROMs, printers, hard-disk drives and audio/stereo equipment can move data at high speeds to desktops and portable computers through a single cable. Also known as FireWire.

IEEE 802.1: Standard for 11Mbps wireless network operation.

IEEE 802.11b: Standard for 11Mbps wireless network operation.

IEEE 802.1p: Standard for quality of service; network traffic prioritization.

IEEE 802.1Q: Standard relating to VLANs.

IEEE 802.2: Specifies the logical link control for various access methods.

IETF: An acronym for Internet Engineering Task Force

IMA: Interactive Multimedia Association: formed in 1991 (rooted in IVIA, Interactive Video Industry Association), an industry association chartered with creating and maintaining standard specifications for multimedia systems.

iMac: An Apple computer intended for home, school, and small offices, and promoted by Apple as an easy-to-use, stylish computer that outperforms other low-cost options. The computer comes equipped with a 233MHz G3 processor, 32 MB SDRAM, 4GB hard disk drive, a 56K modem, and a Universal Serial Bus (USB), which allows a user to add devices without restarting the computer. Controversially, the iMac does not come with a floppy disk drive. Easily recognisable for its translucent blue casing, the computer sold quickly after its introduction in the summer of 1998.

Image: The computerised representation of a picture or graphic.

Image Pac: In Photo CD, a set of five versions of the same image, at varying resolutions.

Image Resolution: The fineness or coarseness of an image as it was digitised, measured in Dots Per Inch (DPI), typically from 200 to 400 DPI.

Image Type: The different representations of an original that can be captured by a scanner For instance: 24-bit colour, 8-bit greyscale, or 1-bit drawings.

IMT-2000: International Mobile Telecommunications-2000: an ITU initiative to define a standards framework for 3G mobile systems providing access - by means of one or more radio links - to a wide range of telecommunications services supported by the fixed telecommunication networks (e.g. PSTN/ISDN/IP) and to other services which are specific to mobile users.

Incremental writing: A mode of writing supported by DVD-R drives which allows files to be added to a DVD-R disc one recording at a time as an alternative to the disc-at-once method. Similar in concept to the packet writing technology employed by CD-R.

Index: The subset of the CPU address bits used to get a specific location within cache.

Information Area: The space on a CD-ROM where the user data is written. It begins at the address 00:02:00.

Inkjet: A printer technology where ink is splashed onto the printer paper to form an image or character.

Instrument Metamerism: A phenomenon in a scanner in which two colours that look the same to an observer look different to the scanner, or two colours that look different to an observer look the same to a scanner. Instrument metamerism is an no recoverable error because based on the output, there is no way to determine what the input was.

Intensity: The amount of light reflected or transmitted by an object with black as the lowest intensity and white as the highest intensity.

Interface: A hardware or software protocol, contained in the electronics of the disk controller and disk drive, that manages the exchange of data between the drive and computer. The most common interfaces for small computer systems are AT (IDE) and SCSI.

Internet: The global computer network, composed of thousands of WANs and LANs that uses TCP/IP to provide world-wide communications to homes, schools, businesses and governments. The WWW runs on the Internet.

Interpolation: The process of averaging pixel information when scaling an image. Used in scanners and digital cameras to produce an image resolution greater than the resolution of the device's CCD array.

Interactive Video: The fusion of video and computer technology. A video program and a computer program running in tandem under the control of the user. In interactive video, the user's actions, choices, and decisions affect the way in which the program unfolds.

Interframe Coding: Compression techniques which track the differences between frames of video. Results in more compression over a range of frames than intraframe coding.

Interlaced: Scheme to display a video image by displaying alternate scan lines in two discrete fields.

Interleave: Generally refers to the arrangement of data in a non-contiguous way to increase performance. When used in the context of hard disk drives, it describes the way in which sectors are arranged on a track. When used in the context of memory subsystems, it refers to the process of taking data bits (singly or in bursts) alternately from two or more memory pages.

Interleave Factor: Refers to a technique used by older hard disk drives to arrange sectors in a non-contiguous way so as to reduce rotational latency and thereby increase read/write performance. The interleave factor specifies the physical spacing between consecutive logical sectors.

Internal Drive: A drive mounted inside one of a computer's drive bays (or a hard disk on a card, which is installed in one of the computer's slots).

Instruction Cache: The Instruction Cache is a warehouse of instructions right on the chip, so that the microprocessor doesn't have to stop and look in the computer's main memory for instructions. This quick access makes processing fast as instructions are "fetched" to the Prefetch Unit where they are put in the proper order for processing.

Internet: A collection of networks linked together using a common protocol. The global computer network achieved through the interconnection of smaller computer networks around the world.

Integrated: When integrated is used, it means that 2 or more devices have been made into one device. For example, many motherboards have sound cards built into the board making it an integrated sound card.

Invar: Type of metal used in the shadow mask that provides more consistent images over time, by reducing warping of the shadow mask when bright images are displayed.

Inverse Kinematics: In an object hierarchy where there are parent and child objects, grabbing one child object at the end of a chain and automatically calculating the proper movements back to the first object, all according to a series of pre-programmed constraints. An example would be an articulated hand, where moving the tip of a finger causes all the other parts to move together in a properly jointed way.

I/O: Input/Output: refers to data transfer from input devices (keyboard, mouse, scanner, etc.) to output devices (printer, screen, etc.).

I/O Address: Input/Output address - A 3 to 4 digit hexadecimal number used to identify and signal a peripheral device.

Ions: Atoms or molecules that have a net electrical charge. In semiconductor manufacturing, ions are the source of chemical impurities that alter the conductivity of silicon.

IP (Internet Protocol): The standard protocol used by systems communicating across the Internet.

IP Address: Internet Protocol address - The address of a network node in the form of four sets of numbers up to 3 digits each and divided by periods, for example; 127.0.0.1. Everywhere you connect to, and even yourself when you login to your internet provider, is assigned an IP address.

IPC: Instructions Per Clock: a measure of how many instructions a CPU is capable of executing in a single clock. Since different processor architectures have different IPCs, clock frequency x IPC is a much truer measure of processor performance than clock frequency alone.

IPX: Novell network protocol that connects computers running NetWare.

IRC (Internet Relay Chat): A software tool that makes it possible to hold real-time keyboard conversations online.

IrDA: Infrared Data Association: a standard for transmitting data via infrared light. IrDA ports enable the transfer of data between IrDA devices such as computers and printers without using a cable.

IRQ: An IRQ is a signal from a piece of hardware (such as a keyboard or sound card) indicating that it needs the CPU to do something. The interrupt request signals run along the IRQ lines to an interrupt controller that assigns priorities to incoming IRQs and delivers them to the CPU.

ISA: A standard bus architecture associated with the IBM AT motherboards. It's a limited 8-bit and 16-bit bus, but widely compatible.

ISDN (Integrated Services Digital Network): Large bandwidth telephone line. Allows you to transfer information quickly.

ISO: An acronym for International Organization for Standardization.

ISO 9660 Format: An international standard specifying the logical format for files and directories on a CD-ROM. It provides a cross-platform format for storing filenames and directories which restricts the characters used to ensure all CD-ROM drives of all ages can read a data disc. The ISO 9660 data starts at track time 00:02:16 or sector 166 (logical sector 16) of track one. For a multi-session disc the ISO 9660 data will be present in the first data track of each session containing CD-ROM tracks.

ISO 9660 Image: A single large file which is an exact representation of the whole set of data and programs as it will appear on a CD, in terms of both content and logical format.

Isochroous: Refers to processes where data must be delivered within certain time constraints. For example, multimedia streams require an isochronous transport mechanism to ensure that data is delivered as fast as it is displayed and to ensure that the audio is synchronised with the video. Contrast with Asynchronous and Synchronous.

ISP (Internet Service Provider): A company that provides a connection to the Internet. Service providers sell access to the network. Services offered differ between ISPs.

ISRC: International Standard Recording Code: some recorders allow the ISRC to be recorded for each audio track on a disc. The code is made up of: Country Code (2 ASCII characters), Owner Code (3 ASCII characters), Year of Recording (2 digits), Serial Number (5 digits).

Itanium: Brand name for the first product in Intel's IA-64 family of processors, formerly codenamed Merced.

ITU: An acronym for International Telecommunication Union.

Java: Sun Microsystems' Java is a programming language for adding animation and other action to Web sites. The small applications (called applets) that Java creates can play back on any graphical system that's Web-ready, but your Web browser has to be Java-capable for you to see it. According to Sun's description, Java is a "simple, object-oriented, distributed, interpreted, robust, secure, architecture-neutral, portable, high-performance, multithreaded, dynamic, buzzword-compliant, general-purpose programming language.

Java Virtual Machine: The Java Virtual Machine (VM) is a program that interprets Java byte-codes into machine code. The VM is what makes Java portable--a vendor such as Microsoft or Sun writes a Java VM for their operating system, and any Java program can run on that VM.

JavaScript: Designed by Sun Microsystems and Netscape as an easy-to-use adjunct to the Java programming language, JavaScript code can be added to standard HTML pages to create interactive documents. As a result, JavaScript has found considerable use in the creation of interactive Web-based forms. Most modern browsers, including those from Microsoft and Netscape, contain JavaScript support.

Jotter: The interference that occurs - causing a shimmering effect that results in lines and characters to losing their focus - when a TFT panel's clock and phase aren't perfectly synchronised.

JPEG: Joint Photographic Experts Group: A commonly used compression technique for graphics images on the Internet.

Joliet: An extension of the ISO 9660 standard, developed by Microsoft to allow CDs to be recorded using long filenames, and using the Unicode international character set. Joliet allows use of filenames up to 64 characters in length, including spaces.

JPG: Pronounced jay-peg, it is a graphics file format that can be compressed to save file size. Because they can be compressed, they are one of the most popular format of pictures found on websites and can be downloaded quickly at their compressed size, but can also be very high quality and large, when needed.

Jumper: An on/off switch used to alter hardware configurations. A jumper is made of wires and a small metal piece that can connect the wires to turn the jumper on. Jumpers are found on devices such as CD-ROM interface boards, bus expansion boards, controller boards, input/output cards, sound cards, graphics cards, modem cards, and motherboards.

K56flex: A protocol, jointly developed by Lucent Technologies and Rockwell International Corp., to achieve 56 Kbit/s modem transmissions over ordinary phone lines. K56flex allows downloads at up to 56 Kbit/s; uploads are limited to the normal V.34 speed of 33.6 Kbit/s. See also X2.

KB: Kilobyte: a unit of measure consisting of 1000 bytes.

Kbit/s: Kilobits Per Second: a measure of data transfer speed. Modems, for example, are measured in Kbit/s. Note that one Kbit/s is 1,000 bits per second, whereas a kilobyte is 1,024 bytes. Data transfer rates are measured using the decimal meaning of K whereas data storage is measured using the powers-of-2 meaning of K. This measure is often expressed as "Kbps". However, this is also sometimes used to mean "Kilobytes per second" (as well as the more common "KBps"). To avoid confusion the PC Technology Guide uses "Kbit/s" throughout.

KBps: Kilobytes per second: a performance measure used for mass storage devices and memory systems.

KiB: Kibibyte: a unit of measure consisting of 1024 bytes. One of the names and symbols for prefixes for binary multiples for use in the fields of data processing and data transmission approved as an IEC International Standard in December 1998. See also MiB, GiB and TiB.

Kilobyte: 1024 bytes.

Kbps: Kilobits Per Second, a unit of bits that is moved per second. Commonly found used to describe the throughput of analogue modems, i.e.; 56kbps

Kermit: This is a protocol for transferring files during direct dial-up communications that's named after a Muppet (seriously). Kermit is sound but old and can be very slow, slower than Xmodem, Ymodem, and much slower than Zmodem.

Kerr Effect: A change in rotation of light reflected off a magnetic field. The polarity of a magneto-optic bit causes the laser to shift one degree clockwise or counter clockwise.

Keys: Notches in a memory module (DRAM DIMM or SIMM) that prevent them from being plugged into an incompatible system. For example, a DIMM keyed for 3.3V operation cannot be plugged into a socket designed for use with a 5V system.

Keyframe: Most video compression schemes work by taking keyframes at certain intervals and working out the differences between that frame and the following frames. This means that only small pieces of information need to be stored about each frame in order to allow the whole frame to be reconstructed. See also Delta Frame.

Khz: Kilo Hertz - Unit of measurement for 1000 x Frequency.

Kill: An action that can be taken in Usenet to exclude certain words, phrases, subjects, or even specific individual posters, from the list of messages displayed on your screen.

KNI: Katmai New Instructions: the 70 new Single Instruction Multiple Data (SIMD) instructions supported by the Pentium III - formerly codenamed Katmai - which came to market in the spring of 1999 designed to optimise the performance of multimedia and graphics applications.

KVM Switch: Console switch - Controls and scans multiple CPU's from one set of keyboard, video display and mouse.

L2 Cache: Level 2 Cache - The secondary cache memory found on CPU's, L2 Cache uses extremely high speed SRAM coupled with extremely low latencies which helps improve performance.

LAN: Local Area Network - Network of interconnected workstations sharing the resources of a single processor or server, typically within the area of a small office building.

Land: A non-indented area on an optical medium such as a CD-ROM or DVD disc. Contrast with Pit.

Landing Zone: The non-data area set-aside on a hard drive platter for the heads to rest when the system powers down.

LAPM: Link Access Procedure For Modems: one of the two protocols specified by V.42. LAPM provides error control when a modem is communicating with another modem that supports LAPM.

Laser: Light Amplification by Stimulated Emission of Radiation: a means of generating coherent light which can be focused to a very small spot size and ideal for reading compact discs, or writing CD-R and CD-RW discs.

Laser Disc: An optical disk used for full-motion video. In the 1970s, various videodisc systems were introduced, but only the Philips Laser Vision survived. Began being superseded by DVD-ROM during 1998.

Laser Printer: A type of printer that utilises a laser beam to produce an image on a drum. The light of the laser alters the electrical charge on the drum wherever it hits. The drum is then rolled through a reservoir of toner, which is picked up by the charged portions of the drum. Finally, the toner is transferred to the paper through a combination of heat and pressure. This is also the way copy machines work.

Latency: The time between initiating a request for data and the beginning of the actual data transfer. For example, the average latency of a hard disk drive is easily calculated from the spindle speed, as the time for half a rotation. In communications, network latency is the delay introduced when a packet is momentarily stored, analysed and then forwarded.

Latch: Circuit element that stores a given value on its output until told to store a different value.

Lathing: Creating a 3-D surface by rotating a 2-D spline around an axis.

LBA: Logical Block Addressing: the scheme by which the BIOS passes an operating system request for a given sector to a modern hard drive.

LCD: Liquid Crystal Display - Created by sandwiching an electrically reactive substance between two electrodes, LCDs can be darkened or lightened by applying and removing current. Large numbers of LCDs grouped closely together can act as pixels in a flat-panel display.

LCD Printer: Similar to a laser printer. Instead of using a laser to create an image on the drum, however, it shines a light through a liquid crystal panel. Individual pixels in the panel either let the light pass or block the light, thereby creating a dot image on the drum.

LCOS: Liquid Crystal on Silicon: a liquid crystal layer on top of a pixelated, highly-reflective substrate. Below the substrate is a backplane that includes the electronics to drive the pixels. The backplane and liquid crystals are combined into a panel and packaged for use in a projection subsystem or "light engine."

Lead-In: An area at the beginning of each session on a recordable compact disc which is left blank for the session's Table of Contents (track numbers and start points). The lead-in is written when a session is closed, and takes up 4500 sectors on disc (1 minute, or roughly 9 megabytes). The lead-in also indicates whether the disc is Multi Session, and if the disc is not closed, which is the next writable address on the disc.

Lead-Out: The area at the end of a session which indicates that the end of the data has been reached; there is no actual data written in the lead-out. The first lead-out on a disc is 6750 sectors (1.5 minutes, about 13.5 megabytes) long; any subsequent lead-outs are 2250 sectors (.5 minute, about 4.5 megabytes).

LED: Light Emitting Diode: a display technology that uses a semiconductor diode that emits light when charged. LEDs are usually red. It was the first digital watch display, but was superseded by LCD, which uses less power.

LED Printer: An electro photographic printer that uses a matrix of LEDs as its light source. The LED mechanism is much simpler than its laser printer counterpart. A stationary array of LEDs is used instead of numerous moving parts, and the LEDs are selectively beamed onto the drum.

Legacy: Term used to describe an application, architecture, protocol, system or system component etc. that has been in existence for a long time.

LEP: Light-Emitting Polymer: a display technology in which plastics are made to conduct electricity and, under certain conditions, emit light.

Level 1 Cache: Cache that is closest to the processor: typically located inside the CPU chip. Can be implemented either as a unified cache or as separate sections for instructions and data. Also referred to as primary cache or internal cache.

Level 2 Cache: Cache that is second closest to the processor; typically located on the system board. Also referred to as secondary cache and external cache.

Level 3 Cache: Level 3 Cache: a memory reservoir near the processor that boosts performance beyond that possible with traditional two-level cache designs. First seen in early 1999 on AMD's K6-III CPU, a similar system was later used by Intel's 64-bit Itanium processor.

LFB: Linear Frame Buffer: a buffer organised in a linear fashion, so that a single address increment can be used to step from one pixel to the pixel below it in the next scan line in the frame buffer. The entire LFB can be addressed using a single 32-bit pointer.

LGA775: Land Grid Array 775: Intel's proprietary CPU interface form factor introduced in the summer of 2004. Similar to a pin grid array (PGA), the connection between LGA775 chip packaging and the processor chip is via an array of solder bumps rather than pins. Also referred to as Socket T.

LIF: Light Insertion Force - When installing a peripheral, requires light force to insert the device into it's slot/socket. Installing expansion cards (PCI cards and such) require LIF in order to seat it properly.

LIFO: Last In First Out: a queuing method in which the next item to be retrieved is the item most recently placed in the queue. See also FIFO.

Lighting: A mathematical formula for approximating the physical effect of light from various sources striking objects. Typical lighting models use light sources, an object's position & orientation and surface type.

LIMDOW: Light Intensity Modulated Direct Overwrite: a storage technology that works on the same basic principle as MO drives but which uses magnets built into disk itself instead of a magnetic read/write head. This enables data to be written in a single pass of the read/write head rather than two.

Line Art: A type of graphic consisting entirely of lines, without any shading.

Line Dropping: Sub-sampling to reduce the number of raster lines in an image by dropping every nth raster line from the scan. See also Pixel Dropping.

Line Noise: Random signal disturbances that sometimes occur over telephone lines. Noise can disrupt communications and corrupt the transmitted data. The ratio of the usable signal to unusable noise on a communications link is referred to as the signal-to-noise ratio. Fibre optic cables are far less susceptible to noise than metal wire cables.

Line Replication: Creating more raster lines than are actually scanned by replicating every nth raster line from the scan. See also Pixel Replication.

Link Blocks: Blocks created between Track-at-Once and Track Multi-session recording sessions. These are interpreted as "un-correctable errors" on most mastering systems at replication plants.

Liquid Cooling: Method of cooling processors and other devices by liquid cooled water blocks. Similar in operation to heat-sinks, but more efficient due to the high thermal conductivity of water.

Listserv: Mailing list that acts as a newsgroup. Messages sent to a listserv address are sent to everyone who has subscribed to the list. Responses are sent back to the listserv address.

Lithium-ion: Name for an electrochemical cells whose voltages are derived from the electro potential difference of lithium in the anode and cathode. The electrolyte contains lithium ions that are transferred between the anode and cathode on charge and discharge. Unlike earlier systems, lithium-ion does not use unstable lithium metal as the anode material.

Local Bus: A bus which co-exists with the main bus and connects the processor itself to the main memory. PCI is now the standard local bus architecture, having replaced the older VL-Bus.

Local File: A file stored on the hard disk of your computer, as opposed to a file stored on an Internet server or some other remote computer.

Local Loop: The lines between a customer and the telephone company's central office, often called the "last mile." Local loops use copper-based telephone wire.

Logical Block: The smallest addressable space on a disc. Each logical block is identified by a unique Logical Block Number (LBN), assigned in order starting from 0 at the beginning of the disc. Under the ISO 9660 standard, all data on a CD is addressed in terms of Logical Block Numbers.

Logic Gate: A collection of transistors and resistors that implement Boolean logic operations on a circuit board. Transistors make up logic gates. Logic gates make up circuits. Circuits make up electronic systems.

Look Ahead: The technique of buffering data into cache RAM by reading subsequent blocks in advance to anticipate the next request for data. The look ahead technique speeds up disk access of sequential blocks of data.

Loop Qualification: This is a test done by the phone company to make sure the customer is within the maximum ISDN distance of 18,000 feet from the central office that services that customer.

Loopback Test: Diagnostic test where characters that are sent to the modem are immediately sent back from the modem so the computer can compare the characters sent with the characters received.

Lossless: A way of compressing data without losing any information; formats such as GIF are lossless.

Lossy: A way of compressing by throwing data away; this results in much smaller file sizes than with lossless compression, but at the expense of some artefacts. Many experts believe that up to 95 percent of the data in a typical image may be discarded without a noticeable loss in apparent resolution.

Lotus: Lotus Development Corporation the software company responsible for the Notes line of products.

Low-Level Formatting: The process of creating sectors on the disk surface so that the operating system can access the required areas for generating the file structure. Also known as initialisation.

Low Profile: Describes drives built to the 3.5in form factor, which are only 1in high. The standard form factor drives are 1.625in high.

LPT1: The first parallel or printer port on a PC.

LPX: A motherboard form factor which allows for smaller cases used in some desktop model PCs. The distinguishing characteristic of LPX is that expansion boards are inserted into a riser that contains several slots and are therefore parallel, rather than perpendicular, to the motherboard.

LSI: Large Scale Integration: refers to the placement of thousands (between 3,000 and 100,000) of electronic components on a single integrated circuit. VLSI (Very Large Scale Integration) is between 100,000 and one million transistors on a chip.

Luminance: The amount of light intensity; one of the three image characteristics coded in composite television (represented by the letter Y). May be measured in lux or foot-candles. Also referred to as Intensity.

Lurking: Reading chat, forum, newsgroup or listserv messages without responding to them.

Lux: A unit used to measure light.

LVD: Low Voltage Differential - A form of SCSI signalling that was introduced with Ultra2 SCSI. Low Voltage Differential allows cable lengths of up to 12 meters with up to 15 devices. The devices need to be Ultra2 SCSI LVD devices in order to take advantage of the LVD signalling. LVD uses data high and data low signal lines to increase transmission distances over those of single-ended. LVD differs from conventional differential signalling. LVDs advantages are that it consumes less power and it can sense single-ended devices on the bus and revert to single-ended signalling.

LZW: Lempel-Zif-Welch: a popular data compression technique developed in 1977 by J. Ziv and A Lempel. Unisys researcher Terry Welch later created an enhanced version of these methods, and Unisys holds a patent on the algorithm. It is widely used in many hardware and software products, including V.42bis modems, GIF and TIFF files and PostScript Level 2.

MAC: Medium Access Control: general standard for the data link layer in the OSI Reference Model. The IEEE divides this layer into two sub-layers - the logical link control (LLC) layer and the media access control (MAC) layer. The MAC sub-layer is the lower of the two and is responsible for moving data packets to and from one Network Interface Card (NIC) to another across a shared channel. It varies for different network types and is defined by the IEEE 802 family of standards.

Macro Mode: A setting that allows a camera to focus on objects which are very near. It is a feature found on some 35mm, APS, and digital cameras.

Macintosh: Introduced by Apple Computer in 1984, the Macintosh marked a breakthrough in personal computer technology, featuring a graphical user interface (GUI) that utilised windows, icons and a mouse. The success of the Macintosh GUI led heralded a new age of graphics-based applications and operating systems, Microsoft's subsequent Windows interface copying many features from the Mac.

Main Memory: This is the big store house of data located within the main computer outside of the microprocessor. At times the Main Memory may send in data or instructions for the Pre-fetch Unit, which often get stored at an address in the Instruction Cache to be used later.

MAN: An acronym for Metropolitan Area Network.

Manual Dialling: Dialling a remote modem from a telephone connected to the modem. This is in contrast to automatic dialling, where the modem dials the number.

MAPI: Messaging Application Programming Interface: an API developed by Microsoft and other computer vendors that provides Windows applications with an implementation-independent interface to various messaging systems.

Mapping: Placing an image on or around an object so that the image is like the object's skin.

Mask: Used like stencils in the chip making process. When used with the UV light, masks create the various circuit patterns on each layer of the microprocessor. Also used to describe the information in the alpha channel of a graphic that determines how effects are rendered.

Mastering: Technically, refers to the process of creating a glass master from which compact discs will be reproduced in quantity. In desktop recordable CD systems, mastering is done together with pre-mastering by the desktop CD recorder, and the term mastering is used generally to mean recording.

MB: Megabyte: a unit of measure consisting of 1000KB.

Mbit/s: The measure of data transfer speed to mean 1 million bits per second. This is often expressed as "Mbps". But this is also sometimes used to mean "Megabytes per second" (as well as the more common "MBps"). To avoid confusion the PC Technology Guide uses "Mbit/s" throughout.

MBONE: An acronym for Multicast Backbone, an Internet service which gives public access desktop video communications. The quality is poor with only 3-5 frames per second instead of the 30 frames per second of commercial television. Its advantage is that it avoids all telecommunications costs normally associated with teleconferencing. An interesting innovation is the use of MBONE for audio communications and an electronic "whiteboard" where the computer screen becomes a shared workspace where two physically remote parties can draw on and edit shared documents in real-time.

Mbps: Megabits per second - Or one million bits per second. Refers to how fast data packets travel, or network speed.

MCA: Micro Channel Architecture: a 32-bit bus architecture introduced by IBM for their PS/2 series microcomputers. Incompatible with original PC/AT (ISA) architecture.

MCI: Media Control Interface: platform-independent multimedia specification published by Microsoft Corporation and others in 1990. Provides a consistent way to control devices such as CD-ROMs and video playback units.

MDA: Monochrome Display Adapter: the first IBM PC monochrome video display standard supporting 720x350 monochrome text but with no support for graphics or colours.

Media: A component used to store data such as a tape, floppy disk or CD-ROM.

Megabyte (MB): 1 million bytes. A measure of the quantity of data. A megabyte is a lot when you are talking about files containing simple text messages, but it's not much when you are talking about files containing colour photographs.

Memory: Also referred to as RAM, memory is a temporary storage area for programs and data when your computer is on. Anything stored in memory (RAM) is lost when the computer is shut off. Most modern computers have 128, 256, 512 or 1 gig of memory.

Memory Bank: A logical unit of memory in a computer, the size of which the CPU determines. For example, a 32-bit CPU requires memory banks that provide 32 bits of information at a time. A bank can consist of one or more memory modules.

Memory Controller: An essential component in any computer. Its function is to oversee the movement of data into and out of main memory. It also determines what type of data integrity checking, if any, is supported.

Memory Cycle: Minimum amount of time required for a memory to complete a cycle such as read, write, read/write, or read/modify/write.

MEMS: Micro-electromechanical systems: the name for technology that embeds mechanical devices such as fluid sensors, mirrors, actuators, pressure and temperature sensors, vibration sensors and valves in semiconductor chips. MEMS combine many disciplines, including physics, bioinformatics, biochemistry, electrical engineering, optics and electronics.

Mesh Model: A graphical model with a mesh surface constructed from polygons. The polygons in a mesh are described by the graphics system as solid faces, rather than as hollow polygons, as is the case with wire frame models. Separate portions of mesh that make up the model are called polygon mesh and quadrilateral mesh.

Metals: Metals, such as aluminium and copper are used to conduct the electricity throughout the microprocessor. Gold is also used to connect the actual chip to its package.

MFLOPS: Mega-floating point operations per second - Used as a measure of how powerful your computer is, MFLOPS gauge the capability of your system to deal with floating-point math instead of raw instructions.

MFM: Modified Frequency Modulation: the data storage system used by floppy disk drives and older early hard disk drives. Had twice the capacity of the earlier FM method but was slower than the competing RLL scheme.

Mhz: A megahertz is 1 million complete cycles per second. This unit is most commonly used to measure transmission speeds of electronic devices, such as the clock speed of a microprocessor.

MiB: Mebibyte: a unit of measure consisting of 1024KiB.

Microcode: The lowest-level instructions that directly control a microprocessor. A single machine-language instruction typically translates into several microcode instructions. In modern PC microprocessors, the microcode is hard-wired and can't be modified.

Microdrive: An ultra-miniature hard disk technology from IBM that uses a single one-inch diameter platter to provide either 170MB or 340MB storage capacity and either one or two GMR heads, the Microdrive is built into a Type II Compact Flash form factor

Micron: µm: a unit of measure equivalent to one-millionth of a metre; synonymous with micro-metre.

Microsecond: µs: one millionth of a second (.000001 sec.).

Microsoft: The computer industry giant responsible for DOS, Windows, Windows 95 and assorted business and personal software. Now challenging Netscape is the web browser market with Internet Explorer.

MIDI: Musical Instrument Digital Interface: a specification that standardises the interface between computers and digital devices that simulate musical instruments. Rather than transmit bulky digitised sound samples, a computer generates music on a MIDI synthesiser by sending it commands just a few bytes in length. These contain all the information a sound board needs to reproduce the desired sound - the type of instrument, the pitch, duration, volume, attack, decay, etc. are all specified by the protocol. Each channel of a MIDI synthesiser corresponds to a different instrument, or "voice". Programming several channels simultaneously produces symphonic sound.

MIDI Mapper: Windows multimedia translator for MIDI hardware and software.

Mid Span Repeater: A device that amplifies the signal coming or going to the central office. This device is necessary for ISDN service if you are outside the 18,000 feet distance requirement from the central office.

Midtones: Tones in an image that are in the middle of the tonal range, halfway between the lightest and the darkest tones.

Millisecond (ms): A millisecond is one-thousandth of a second. The term is most commonly used to measure data access speeds, such as the amount of time it takes to retrieve data from a hard disk. Milliseconds are sometimes confused with mbps (megabits per second), which describe data transmission speeds.

MIME: An acronym for Multipurpose Internet Mail Extensions.

Mini CD: The 8cm version of the standard 12cm CD format, offering a storage capacity of 185MB. Used as a cheap and convenient form of removable storage in consumer devices such as digital cameras and MP3 players.

MiniDisc: MD: a compact digital audio disc from Sony that comes in read-only and rewritable versions. Introduced in late 1993, the MiniDisc has been popular in Japan. The read-only 2.5in disc stores 140MB compared to 650MB on a CD, but holds the same 74 minutes worth of music due to Sony's Adaptive Transform Acoustic Coding (ATRAC) compression scheme, which eliminates inaudible portions of the signal.

miniDVD: A CD-R(W) disc containing up to 15 minutes of DVD-encoded video.

MIPS: Millions of Instructions Per Second: refers to a computer processor's performance and is the benchmark for comparing standard for CPUs.

Mip Mapping: A sophisticated texturing technique to ensure that 3D objects gain detail smoothly when approaching or receding. This is typically produced in two ways; per-triangle (faster) or per pixel (more accurate).

Mixed Mode: A compact disc which combines computer data and audio. The data is generally all contained in Track 1, and the audio in one or more following tracks.

Mixed-Signal Device: Collects analogue signals and converts them into digital data to be processed. Once a DSP processes and compresses the digital data, a mixed-signal device decompresses, transmits and displays the digital data as either digital or analogue signals.

MMO: Intel's pop-out CPU packaging designed for mobile processors which includes an integrated L2 cache, introduced with Mobile MMX processor launched in early 1998.

MMX: MultiMedia eXtensions: Intel's upgraded Pentium processor which incorporates additional instructions designed specifically for processing multimedia data more efficiently and a larger 32Mb on-board cache. Codenamed P55C.

MNOS: Metal Nitride Oxide Semiconductor: the technology used for EAROMs (Electrically Alterable ROMs); not to be confused with NMOS.

MNP: Microcom Networking Protocol: a series of standards, running from MNP Class 1 to MNP Class 10, designed to improve communications between modems but now superseded by LAPM. They do not stand alone, but operate in conjunction with other modem standards.

Modelling: The process of creating free-form 3-D objects.

Modem (Modulator-Demodulator): A device that converts digital signals from your computer into analogue signals for transmission through a phone line, and vice versa (called demodulation).

Mode: There are two recording modes for compact discs. In Mode 1, used with CD-ROM applications, 288 bytes of each sector are used for storing error correction code, and the remaining 2048 bytes per sector are available for user data. Mode 2, used in CD-I and CD-ROM XA, has two forms: Form 1 is similar to Mode 1, as it is also used to record data that requires error correction; Form 2 is used for recording information such as sound or images which do not require such extreme precision. Since less error correction is needed, more bytes in the sector can be freed for information storage, resulting in a data area of 2336 bytes per sector.

Modem: MOdulator/DEModulator: a modem transforms (modulates) digital information into an analogue signal that can be sent across a telephone line. It also demodulates an analogue signal it receives from the telephone line, converting the information contained in the signal back into digital information.

Modes: Specific frequencies at which the monitor (and/or computer) can display text or graphical information. Most monitors today support several frequencies. This is called multi-frequency or multi-scanning, and it ensures that the monitor will perform with a variety of computers and applications.

Modulation: Converting a data stream into sounds to be sent down a phone line. The opposite is demodulation. See also Modem.

Moire: Moiré pattern describes the interference pattern you see when it appears there are ripples or waves on your monitor.

Moore's Law: It was in 1965, three years before he was to become a co-founder of Intel Corporation, that Gordon Moore made the famous prediction that would thereafter be referred to as "Moore's Law" - that the number of transistors per integrated circuit would double every 18 months. Moore forecast that the trend would continue through 1975; in fact it has been maintained for far longer.

MOPS: Millions of Operations Per Second.

Morph: Short for metamorphosing, morphing refers to an animation technique in which one image is gradually turned into another.

MOS: Metal-Oxide-Semiconductor: layers used to create a semiconductor circuit. A thin insulating layer of oxide is deposited on the surface of the wafer. Then a highly conductive layer of tungsten silicide is placed over the top of the oxide dielectric.

MOSAIC: A software application which runs on UNIX, PC and Macintosh computers. It is an interface to the WWW.

MO Technology: Magneto-Optical Technology: a rewritable optical storage technology that uses a combination of magnetic and optical methods. Data is written on an MO disk by both a laser and a magnet. The laser heats the bit to the Curie point, which is the temperature at which molecules can be realigned when subjected to a magnetic field. A magnet then changes the bit's polarity. Writing takes two passes. Unlike with phase-change drives MO disks do not have to be "reformatted" when full. See also LIMDOW.

Motherboard: Everything attached to your computer connects to the motherboard directly or indirectly. It generally houses the CPU chip, the controller circuitry, the bus, and sockets for additional boards, which are called daughterboard's.

Motion Video: Video that displays real motion by displaying a sequence of images (frames) rapidly enough that the eyes see the image as a continuously moving picture.

Motion-JPEG: A derivative of JPEG that includes some keyframe-based compression to make it suitable for video.

Mount: To install a compact disc so that the computer recognises its presence and can read data from it.

Mouse: A small, handheld device attached to a computer; when moved across any flat surface (such as a desk), it results in the movement of something on the computer screen called a cursor; includes one or more buttons that allow the user to select graphics or text onscreen.

MP: Multilink PPP: a protocol that allows the combination of both B-channels for a total of 128 Kbit/s using synchronous PPP framing. Unlike the older hardware-based BONDING specification, MP is implemented in software and requires only that the communications software support the protocol.

MP3: A very popular compressed audio format. Millions of MP3's can be downloaded on the internet and played on your computer, and MP3 player or even converted to CD Audio to play in most CD players. A song that is 40 megs can often be downloaded as a 4-5 meg MP3 making it accessible to even dial up users.

MPC: Multimedia PC: a specification developed by the Multimedia Council. It defines the minimum platform capable of running multimedia software. PCs carrying the MPC logo will be able to run any software that also displays the MPC logo.

MPEG (Motion Picture Experts Group): A video file compression system used on the web.

MPEG-1: MPEG-1 video, used in Video CDs, is defined for non-interlaced, computer-type data streams. It is the form normally used with PCs. Typical MPEG-1 video compression ranges up to 100:1 for images comprised of 352 pixels (picture elements) by 240 lines at a refresh rate of up to 30 frames per second with 24-bit colour and CD-quality sound.

MPEG-2: The newer MPEG-2 standard offers resolutions of 720x480 and 1280x720 at 60 fps, with full CD-quality audio. This is sufficient for all the major TV standards, including NTSC, and even HDTV. MPEG-2 is used by DVD-ROMs and is capable of compressing a 2 hour video into a few gigabytes.

MPEG-4: A standard for video compression that is targeted at bit rates of tens of kilobytes and below to accommodate applications for digitally-encoded moving pictures and synchronised audio that can be enabled only at very low bit rates. The low bit rates targeted by MPEG-4 are the operating points for widespread communication channels, such as public switched telephone network and low-cost wired and wireless networks.

MPEG Audio: MPEG defined three levels or layers of audio compression. Which layer a type of equipment uses depends on the desired level of compression. These three layers compress audio data streams by roughly four, six and eight times respectively, around 64, 128 and 192Kbit/s per channel. In practical terms, these compression rates make possible radio broadcasting of CD-quality music. All three layers are defined for both monaural and stereo sound. Definitions for surround sound and other high fidelity applications are under consideration.

MPEG-2 Audio: Supplies up to five full bandwidth channels (left, right, centre, and two surround channels), plus an additional low frequency enhancement channel, and/or up to seven commentary/multilingual channels. The MPEG-2 Audio Standard will also extend the stereo and mono coding of the MPEG-1 Audio Standard to half sampling-rates (16 KHz, 22.05 KHz, and 24 KHz), for improved quality for bitrates at or below 64 Kbits/s, per channel.

MPR2: Provides reduced electrostatic and electromagnetic emissions. MPR 1990, or MPR2, is a standard defined to measure emissions from devices such as monitors.

MR: Magneto-resistive heads detect the magnetic flux of a platter by using a sliver of a special material whose resistance changes according to the strength of an applied magnetic field; MR heads are more sensitive than TFI heads, allowing higher areal densities.

MSCDEX: Microsoft DOS extensions for CD-ROM. Allows the DOS operating system to recognise a CD-ROM as a DOS volume.

MTBF: Mean Time Between Failures - The average time from start of use to failure in a large population of identical systems, computers, or devices.

MTF: Modulated Transfer Function: a test that measures the optical frequency response of a scanner or other optical system.

MTTR: Mean Time To Repair: the average time to repair a specific component.

MUD (Multi User Domain): A game or simulation in which multiple participants can engage simultaneously through their connections to the same Internet server.

Multimedia: The way computers display the use of any combination of text, graphics, animation and video.

Multi-Frequency: A monitor's ability to change resolution or refresh rate when signalled by a video adapter. Graphics adapters have the ability to "tell" a monitor to use various display resolutions and refresh rates. If the resolution or refresh rate is within a monitor's scanning range, multi-frequency monitors adjust to the resolutions and refresh rates "ordered" by the video adapter. Also known as multi-scanning. See also Modes.

Multiplexer: A device that integrates serial digital waveforms into a single channel by partitioning the inputted data into segments and combining them together into a bitstream.

Multiplier Lock: What is done to all modern CPU's to prevent overclocking. The multiplier of a locked CPU will remain the same even if it is changed in the BIOS.

MultiRead: An OSTA standard for CD-ROM and DVD-ROM drives. Drives which follow the MultiRead standard can read commercial CDs (audio and data), CD-R discs, and CD-RW discs. They can also read discs written in fixed- or variable-length packets. This applies also to DVD.

Multiscan: A monitor that can display many different resolutions. A single-scan monitor can only display a particular resolution.

MultiSession: The Orange Book specification which allows additional data to be appended to a previously recorded disc. A session is defined as an area including lead-in, program data and lead-out. Contrast the recording structure of a pressed CD-ROM or a CD-R written in Disc at Once mode that contains just. Also referred to as linked session.

Multitasking: The concurrent execution of several jobs.

Multithreading: Multiple concurrent threads of execution within a single application.

Multi-Timbral: The number of simultaneous instruments a synthesiser can play.

MultiTrack: The ability to record more than a single track on a disc. Track numbers are from 1 to 99. They continue to increment across session boundaries. e.g. if session 1 used tracks 1 to 4, session 2 would start at track 5. Track numbers may start at any value, but must be incremented sequentially on the disc.

Munsell Colour System: A system consisting of over 3 million observations of what people perceive to be like differences in hue, chroma, and intensity. The participants chose the samples they perceived to have like differences.

Nanometre: nm: one thousand millionth of a metre.

Nano Seconds: NS for short, Nano seconds refer to the speed of RAM. By looking at the last numbers usually right after a dash (-), it gives the timing for the RAM. When referring with SDRAM, DDR or RDRAM, there sometimes are two numbers. A -75 doesn't mean 75 ns, it means 7.5 ns.

Napster: Created in 1999, Napster is a controversial music indexing service that gives individuals access to one another's MP3 files by creating a unique file-sharing system via the Internet.

NAT: Network Address Translation - A method used by firewalls to keep a network behind under just one IP address for security reasons.

NetBEUI: Network BIOS Enhanced User Interface - IBM developed this standard protocol, which is a set of rules that an operating system uses to control how computers on a network to talk to each other. This protocol is now also used by Microsoft and Novell on many network operating systems including LAN Server, LAN Manager, Windows NT, and Windows 95.

Network: Two or more computers connected to one another for the transfer and sharing of information.

Netiquette: Internet etiquette, the correct form of behaviour to be used while working on the Internet and Usenet. It can be summed up as, "Don't waste computer resources and don't be rude."

Netscape: A computer company in California famous for their Netscape Navigator Internet web browsing software.

Newbie: An individual new to the Internet. Used with both affection and malice--depending on whether you're being welcomed or being flamed.

Newsgroup: Open forums or electronic bulletin boards on the Internet, where readers can share information, ideas, tips, and opinions with each other.

NIC: Network Interface Card - Network cards connect to local area networks via Ethernet cables or some other means of connectivity to bring computers together electronically.

nit: A unit of luminance equal to one candlepower measured at a distance of 1m over an area of 1 square metre. One nit is equal to 1 candela per square metre or 0.2919 fL (foot lamberts).

NLE: Non-Linear Editing: refers to the ability to manipulate digitised video on a computer under software control. The required file segments can be cut, pasted and copied anywhere in the timeline of your project. In the context of AV applications, NLE is to video editing what the word processor was to the typewriter.

NLX: An Intel-designed motherboard form factor. It features a number of improvements over the ATX design providing support for new technologies such as AGP and allows easier access to motherboard components.

NMI: Non-Maskable Interrupt: a high-priority interrupt that cannot be disabled by another interrupt. It is used to report malfunctions such as parity, bus and math co-processor errors.

NMOS: N-channel Metal Oxide Semiconductor: pertains to MOS devices constructed on a P-type substrate in which electrons flow between N-type source and drain contacts. NMOS devices are typically two to three times faster than PMOS devices.

Node: Endpoint of a network connection or a junction common to two or more lines in a network. Nodes can be processors, controllers, or workstations. The term is often used generically to refer to any entity that can access a network, and is frequently used interchangeably with device.

Noise: Interference (static) that destroys the integrity of signals on electronic highways or communications lines. Noise can come from a variety of sources, including radio waves, nearby electrical wires, lightning, and bad connections. Noise is an analogue problem; once a signal is digitised, it is relatively immune to noise.

Non-correlated Noise: A random distortion in an analogue signal causing snow or speckles - random spots throughout the image. The distortion can be the result of electronic noise in the amplifiers, electrical spikes somewhere in the system, or random fluctuations in the scanner lights. Also called random noise. See also Correlated Noise.

Non-Volatile Memory: Types of memory that retain their contents when power is turned off. ROMs, PROMs, EPROMs and flash memory are examples. Sometimes the term refers to memory that is inherently volatile, but maintains its content because it is connected to a battery at all times, such as CMOS memory and to storage systems, such as hard disks.

Northbridge: Refers to the System Controller component of a Pentium chipset, responsible for integrating the cache and main memory DRAM control functions and for managing the host and PCI buses. See also Southbridge.

NOS: Network Operating System: an operating system that includes special functions for connecting computers and devices into a local-area network (LAN). Some operating systems, such as UNIX and the Mac OS, have networking functions built in. The term NOS, however, is generally reserved for software that enhances a basic operating system by adding networking features.

Notes: A group of applications from the Lotus Development Corporation which allows organizations to share documents and exchange email messages.

NSF: An acronym for National Science Foundation.

NS: See Nano Seconds (Above)

nT: nano-Tesla, a unit of measurement for magnetic flux density. A magnetic field of one Tesla is very strong - the earth's magnetic field is only tens of nano-Teslas.

NTFS: NT File System: the file system that is native to Microsoft Windows NT. NTFS is probably the most advanced file system available for personal computers, featuring superior performance, excellent security and crash protection, and the ability to handle large volumes of data.

NTSC: National Television Standards Committee: the industry group that formulated the standards for American television. An NTSC signal is a composite video signal used by televisions and VCRs in North America and some other parts of the world. The NTSC system uses 525 lines per frame, a field frequency of 60 Hz, a 30-frame per second update rate, and the YIQ colour space. Modern NTSC encoders and decoders may also use the YUV colour space.

NURBS: Non-uniform Rational B-Spline: a type of spline that can represent more complex shapes than a Bezier spline.

Nyquist Frequency: The maximum frequency that can be sampled by a digital sampling device such as a scanner. The Nyquist frequency of any digital sampling device is 1/2 the sampling rate of the device. To capture full information about a signal, the frequency content of the signal must be significantly below the Nyquist frequency of the device.

Obstructions: Even when sounds originate in the same room, they are often obstructed by objects like furniture before they reach a person's ears. However, because the sound remains in the same room as the listener, the reverberation effect on these sounds will not be muffled - reverberation will spread round a whole room regardless of individual obstructions.

Occlusions: Sounds that originate from a sound source behind a wall or door or other solitary object. In so doing, they are subtly altered - usually with a volume drop and muffling, depending on the material and thickness of the obstruction.

OCR: Optical character recognition - When your computer gets a fax or scans in text, all it sees are graphical bits on a virtual page. That text is not usable, searchable, or editable. If you pass the page through an OCR program, the software converts the shapes on it into a text document. However, few documents are perfectly recognized and the errors are frequent if the type is small or the scan unclear. But the conversion is often faster than typing text manually.

ODBC: Open Database Connectivity: a standard promulgated by Microsoft that allows databases created by various database management programs-such as DBASE, Microsoft Access, Microsoft FoxPro, and Oracle to be accessed using a common interface independent of the database file format. By relying on ODBC, one can write an application that uses the same code to read records from a DBASE file or a FoxPro file. Internally, ODBC drivers use a form of SQL to carry out database operations. See also SQL and WOSA.

OEM: Original equipment manufacturer - Originally OEM was an adjective used to describe a company that produced hardware to be marketed under another company's brand. Mitsumi, for example, produced CD-ROM drives that dozens of companies would label as their own. When purchasing OEM products you usually get a great price, but little to no warranty, manuals or pretty packaging.

Off-Hook: The condition of a telephone line that corresponds to picking up the telephone receiver. A modem creates an off-hook condition when it tries to communicate on a telephone line.

OFTEL: The UK government regulator for telecommunications, first established in the mid-1980s to oversee the introduction of competition in a market dominated by British Telecom.

OLE: Object Linking and Embedding: an industry-standard method for inserting an object into a document. The document retains a connection, or link, with its original program so that double-clicking on the object in the document opens the object's original program. See also DLL.

OLED: Organic Light-Emitting Diode: a display device invented by Eastman Kodak in the early 1980s. OLEDs sandwich carbon-based films between two charged electrodes, one a metallic cathode and one a transparent anode. The organic films consist of a hole-injection layer, a hole-transport layer, an emissive layer and an electron-transport layer. When voltage is applied to the OLED cell, the injected positive and negative charges recombine in the emissive layer and create electro luminescent light.

On-Hook: The condition of a telephone line that corresponds to hanging up the telephone receiver. A modem creates an on-hook condition to break its connection to a telephone line.

Online: Connected. You are online if you are working on your computer while it is connected to another computer. Your printer is online if it is connected to your computer and ready to accept data.

On-Line Mode: One of the two operating modes of the modem, also called data mode. In on-line mode, the modem interprets all information sent to it as data. The only exception is the escape sequence (normally "+++"), which returns the modem to command mode without breaking the connection.

On-The-Fly Switching: A term used regarding the changing of resolution or refresh rates without having to restart a PC.

OpenGL: Open Graphics Library: a standardised 2- and 3D graphics library that has its historical roots in the Silicon Graphics IrisGL library. It has become a de facto standard endorsed by many vendors and can be implemented as an extension to an operating system or a window system and is supported by most UNIX-based workstations, Windows and X Windows. Some implementations operate entirely in software, while others take advantage of specialised graphics hardware.

Optical Frequency Response: A scanner's capability for capturing a given frequency or range of frequencies.

Orange Book: The Philips/Sony specification for Compact Disc Magneto-Optical (CD-MO) and Write-Once (CD-WO) systems. Part II is the primary specification for CD-R media and defines both the physical structure and dimensions of a CD-R disc as well as the use of certain portions of the recording surface: the Program area, the Power Calibration area (PCA), the Program Memory area (PMA), the Lead-in and Lead-out areas. It also Includes the specification for the Hybrid Disc technology on which Photo CD is based.

Orb: Thermatake have adopted this name for a line of conical-finned heat sinks that are based loosely on a design used in HP servers in the 80's. The heat sinks have the fan located in the midst of the fins which allows the unit to offer a good price/performance ratio.

OS (Operating System): The most important program that runs on a computer. Every general purpose computer must have an operating system to run other programs. Operating systems perform basic tasks, such as recognizing input from the keyboard, sending output to the display screen, keeping track of files and directories on the disk, and controlling peripheral devices such as disk drives and printers. Examples: DOS, Windows 95, UNIX, OS/2 Warp, and System 7 (Mac). Windows itself is not an operating system.

Oscilloscope: A test instrument that displays electronic signals (waves and pulses) on a screen. It creates its own time base against which signals can be measured, and display frames can be frozen for visual inspection.

OSD: On Screen Display - How digital monitors can be configured.

OSI: Open System Interconnection: an ISO standard for worldwide communications that defines a framework for implementing protocols in seven layers. Information is passed down through the layers until it is transmitted across the network, where it is passed back up the stack to the application at the remote end.

OSR: OEM Service Release: a version of Windows incorporating bug fixes and new functionality released to PC vendors for bundling with new PCs. Not available as an upgrade to older versions of Windows.

OSTA: Optical Storage Technology Association: an international trade association dedicated to promoting use of writable optical technology for storing computer data and images.

Overclocking: Making a processor run at a higher then normal clock speed. For instance, changing the multiplier so that a 500Mhz chip runs at 667Mhz. This is a way to get more out of your chip then you paid for, but hardware failure is a risk.

OverDrive: A user -installable microprocessor from Intel for the 486 microprocessor. Many PCs 486-based PCs were built with an "OverDrive" socket, which allowed a processor upgrade simply by inserting a faster OverDrive chip.

Overhead: Command overhead refers to the processing time required by the controller, host adapter, or drive prior to the execution of a command. Lower command overhead yields higher drive performance. Disk overhead refers to the space required for non- data information such as location and timing. Disk overhead often accounts for about ten percent of drive capacity. Lower disk overhead yields greater disk capacity.

Overlay: The ability to superimpose computer graphics over a live or recorded video signal and store the resulting video image on videotape. It is often used to add titles to videotape.

Overrun: The condition occurring when data is transmitted to a receiving device at a rate that's too fast for it to handle. See also Underrun and Flow Control.

Oversampling: Scanning at more than an optimum sampling rate. See also Sub-sampling

Overscan: A condition that exists when a created image is larger than the visible portion of the display. Overscan helps relegate the relatively fuzzy perimeter of a CRT image to portions of the screen that are out of sight, and the overscan may disappear over time anyway. On the other hand, monitors with excessive overscan can lose icons and text at the edges of the display.

P5: The Intel codename for the original 60/66MHz Pentiums introduced in 1993. Subsequent faster clock-speed chips were referred to as P54 and the MMX version as P55.

P6: The Intel codename for the Pentium Pro, which is optimised for 32-bit applications. The P6 generation includes the Pentium Pro and Pentium II.

P-channel: One of the CD sub-code channels. The P-channel is used to indicate the gap between tracks on a CD.

PABX: Private Automatic Branch eXchange: an in-house telephone switching system that interconnects telephone extensions to each other, as well as to the outside telephone network. Modern PBXs use all-digital methods for switching and can often handle digital terminals and telephones along with analogue telephones.

Packet: A logical grouping of information that includes a header containing control information and (usually) user data. Packets are most often used to refer to network layer units of data.

Packet Writing: Track at Once writing is a form of incremental write which mandates a minimum track length and a maximum number of tracks per disc. A track written "at once" has 150 blocks of overhead for run-in, run-out, pre-gap and linking. Packet write, on the other hand, is a method whereby several write events are allowed within a track, thus reducing the overhead. These "packets" are bounded by 7 blocks, 4 for run-in, 2 for run-out and 1 link block. Packets can be of fixed or variable length.

Page: On a DRAM, the number of bits that can be accessed from one row address. The size of a page is determined by the number of column addresses. For example, a device with 10 column address pins has a page depth of 1024 bits.

PAL: Phase Alternating Line: video format - used in most of Western Europe, Australia and China as well as in various African, South American and Middle Eastern countries - with a 4:3 image format, 625 lines per frame, a field frequency of 50Hz and 4 MHz video bandwidth with a total 8 MHz of video channel width. PAL has a 25-frame per second update rate and uses YUV colour space.

PAN: Personal Area Network: refers to the ability of small devices such as cellphones, pagers, PDAs, and wearable computers to exchange data wirelessly within the physical limits of someone's personal space.

PanelLink: Developed by Silicon Images Inc. to provide an all digital link between a graphics card and an LCD monitor, PanelLink uses Transition Minimised Differential Signalling (TMDS) signalling technology, allowing a distance of up to 10m between the graphics card and the LCD panel.

Parallelogram Distortion: A type of geometric distortion, where lines are parallel but not perpendicular.

Parallel Port: An I/O channel for a parallel device, like a printer, which sends and receives data eight bits at a time over 8 separate wires. Maximum throughput is around 500 Kbit/s. Increasingly, other devices such as removable storage drives, scanners etc. share the printer parallel port using a "pass through" mechanism.

Particle Animation: Rendering a 3D scene as millions of discrete particles rather than smooth, texture-mapped surfaces. Much more flexible but computer intensive.

Parity: A data encoding scheme that computers (and terminals) use to check the validity of transmitted characters. This scheme adds an extra bit to each character, which the transmitting computer sets or clears based on the type of parity the computers agree to use (odd or even). For example, if the computers use even parity, the transmitting computer sets or clears the parity bit so that there are an even number of bits set in each character it transmits. The receiving computer checks each character and flags a parity error if any character has an odd number of bits set.

Parity Memory: A common method for ensuring the integrity of data stored in memory in which an additional data bit is generated and added to each data byte. Parity is able to detect only single bit errors reliably but cannot perform any correction. If more than one bit has been corrupted, the parity check may not detect a problem. The most commonly used forms of parity are even parity, odd parity, and checksums.

Partition: A portion of a hard disk accessible as a single logical volume, perhaps dedicated to a particular operating system or application.

Passive Matrix: A common LCD technology used in laptops. Passive matrix displays (DSTN, CSTN, etc.) are not quite as sharp and do not have as broad a viewing angle as active matrix (TFT) displays, but they have improved dramatically in recent years.

PC (Personal Computer): Usually refers to what 's commonly known as an IBM-compatible computer, made by any one of dozens of manufacturers or backyard entrepreneurs.

PCA: Power Calibration Area: a space reserved at the beginning of the disc for calibrating the laser to record to that disc.

PCB: Printed Circuit Board: a board upon which there are layers of printed circuits and onto which other integrated circuits can be soldered or otherwise attached.

PC Card: Three (soon to be four) types of credit-card-sized cards plug into portable computers (and some desktop models) to add and remove RAM, modems, network adapters, hard disks, and other devices without requiring that you open the box. These PC Cards conform to several standards set by the PCMCIA.

PCI: Peripheral Component Interconnect - Slot card interface. PCI is a standardized architecture that provides a high-speed data path between peripherals and the CPU.

PCL: Printer Control Language: a protocol designed by Hewlett-Packard to allow PCs to communicate with its laser printers. PCL has become a de facto standard for laser and ink jet printers and is supported by virtually all printer manufacturers. "HP compatible" or "LaserJet compatible" means that a printer supports the PCL command set.

PCM: Pulse Coded Modulation: a technique for converting an analogue signal with an infinite number of possible values into discrete binary digital words that have a finite number of values. The waveform is sampled, then the sample is quantised into PCM codes. PCM is a digitisation technique used by the CCITT V.90 standard , not a universally accepted standard in its own right.

PCMCIA: Personal Computer Memory Card International Association - Based in Sunnyvale, California, the PCMCIA specifications for the PC Card enabled the computer industry to manufacture credit-card-sized removable cards to add RAM, modems, network adapters, hard disks, and even radio devices like pagers and global positioning systems to portable computers. Many people call PC Cards by the longer name PCMCIA cards. The association has trademarked the term PC Card, however, so that's the preferred usage.

PCS: Personal Communications Services: the collective term for US mobile telephone services in the 1900MHz frequency band.

PCX: A popular bitmapped graphics file format originally developed by ZSOFT for its PC Paintbrush program. PCX handles monochrome, 2-bit, 4-bit, 8-bit and 24-bit colour and uses Run Length Encoding (RLE) to achieve compression ratios of approximately 1.1:1 to 1.5:1.

PDA: Personal Digital Assistant: a handheld device that combines computing, telephone/fax, and networking features. A typical PDA can function as a cellular phone, fax sender, and personal organiser. Some PDAs are hand-held PC with tiny keyboards. Another class of device uses a touch-screen and stylus for data entry.

PDC: Personal Digital Cellular: a Japanese standard for digital mobile telephony in the 800MHz and 1500MHz bands.

PDC: Primary Domain Controller.

PD Drive: Refers to the Phase-change Dual optical technology as implemented in Panasonic's patented PD system. Similar to phase-change WORM technology (as used in CD-R) this uses an active layer with reversible properties allowing data to be overwritten in a single pass of the read/write head. This compares with the two-pass operation of conventional MO devices.

PDF: Portable Document Format. A document format read by Adobe System's Acrobat viewer. This format is excellent for displaying instruction manuals and other large documents in a "web-ready" state.

PDL: Page Description Language: a language for describing the layout and contents of a printed page used with laser printers. The best-known PDLs are Adobe PostScript and Hewlett-Packard PCL (Printer Control Language). Both PostScript and modern versions of PCL are object-oriented, describing a page in terms of geometrical objects such as lines, arcs, and circles.

PDP: Plasma Display Panel: a display technology that works on the principle that passing a high voltage through a low-pressure gas creates light.

Peer-to-peer network: A network where there is no dedicated server. Every computer can share files and peripherals with all other computers on the network, given that all are granted access privileges. File sharing programs like Kazaa are a good example of this on a larger scale.

PEM: An acronym for Privacy Enhanced Mail.

Performance: A measure of the speed of the drive during normal operation. Factors affecting performance are seek times, transfer rate, and command overhead.

Peripheral: A hardware component you add to your computer, usually by a cable. When this word is used, it usually refers to hardware such as a mouse, keyboard, monitor or printer.

Perspective Correction: Adjustment of texture maps on objects, viewed at an angle (typically large, flat objects) in order to retain the appearance of perspective.

PGA: Pin Grid Array - The method in which the CPU uses to interact with the CPU socket.

Phase-change Technology: An optical storage technology in which the disk drive writes data with a laser that changes dots on the disk between amorphous and crystalline states. An optical head reads data by detecting the difference in reflected light from amorphous and crystalline dots. When full a phase-change disk can be erased (or "reformatted") using a medium-intensity pulse to restore the original crystalline structure. CD-RW uses phase-change technology.

Phong Shading: A computation-intensive rendering technique that produces realistic highlights while smoothing edges between polygons.

Phosphor: A luminescent substance, used to coat the inside of the cathode-ray tube display, that is illuminated by the electron gun in the pattern of graphical images as the display is scanned.

Phosphor Triad: One red, one green and one blue phosphor that composes a pixel.

Photo CD: A compact disc format developed by Kodak and Philips, based on the CD-i Bridge specification, that allows photographic images to be recorded and viewed on a CD-ROM. Up to 100 high resolution images can be stored on a Photo CD.

Photolithography: The process of reproducing the chip's circuitry pattern onto the wafer surface by using ultraviolet light and stencils or masks to transfer the image photomechanically.

Photometer: An instrument for measuring luminous intensity, luminous flux, illumination, or intensity. See also Correlated Noise.

Photoresist: A material which becomes soluble when exposed to ultraviolet light. Used to help define circuit patterns during chip fabrication where it prevents etching or plating of the area it covers; also called resist.

Physical Format: The actual physical layout of cylinders, tracks, and sectors on a disk drive.

Physical Modelling Synthesis: A revolutionary method for generating sound. This technique emulates the impulse patterns of real-world instruments using a software model.

PIC: Programmable Interrupt Controller: a chip or device that prioritises interrupt requests generated by keyboards, serial ports, and other devices and passes them on to the CPU in order of highest priority. See also IRQ.

PictBridge: A standard aimed at providing a direct connect solution for image input devices and output devices. The first release of PictBridge focuses on the direct print services between a digital still camera and a printer.

Piezo-Electric: The property of certain crystals that causes them to oscillate when subjected to electrical pressure (voltage).

Pigment Inks: While conventional inks are essentially oil-based dyes, pigment inks consist of tiny chunks of solid pigment suspended in a liquid solution. According to their proponents, pigment inks offer richer, deeper colours and have less tendency to run, bleed or feather.

PIM: Print Image Matching: a system created by Epson in partnership with major digital camera manufacturers. PIM embeds colour space, gamma level, sharpness, brightness, shadow and highlight information into the digital file's JPEG header, thereby allowing PIM-enabled devices to work together at their highest level of performance.

Pincushion: Corrects the curve at the vertical edges of a monitors display.

Pincushion Distortion: The opposite of barrel distortion. The vertical lines in a rectangular image curve inwards, with an increase in the distortion towards the edges of the image.

PIO: Mode Programmed Input Output Mode: a method of transferring data to and from a storage device (hard disk or CD device) controller to memory via the computer's I/O ports, where the CPU plays a pivotal role in managing the throughput. For optimal performance a controller should support the drive's highest PIO mode (usually PIO mode 4).

Pipeline: In DRAMs and SRAMs, a method for increasing the performance using multistage circuitry to stack or save data while new data is being accessed. The depth of a pipeline varies from product to product. For example, in an EDO DRAM, one bit of data appears on the output while the next bit is being accessed. In some SRAMs, pipelines may contain bits of data or more.

Pipeline Burst Cache: A type of synchronous cache that uses two techniques to minimise processor wait states - a burst mode that pre-fetches memory contents before they are requested, and pipelining so that one memory value can be accessed in the cache at the same time that another memory value is accessed in DRAM.

Pipeline Processing: A category of techniques that provide simultaneous, or parallel, processing within a CPU. It refers to overlapping operations by moving data or instructions into a conceptual pipe with all stages of the pipe processing simultaneously. For example, while one instruction is being executed, the computer is decoding the next instruction.

Pit: An indentation in an optical medium such as a CD-ROM or DVD. The laser beam is either absorbed in the pit or reflects off the non-indented areas, which are called lands. Using various algorithms, the reflections are converted into 0 and 1 bits.

Pixel: An abbreviation for picture element. In a raster grid, the pixel is the smallest unit that can be addressed and given a colour or intensity. The pixel is represented by some number of bits (usually 8, 16 or 24) in the frame buffer, and is illuminated by a collection of phosphor dots in the CRT that are struck by the beams of the electron gun.

Pixel Clock Speed: The frequency or speed at which individual pixels (picture elements) in an image are written to the screen. The higher the pixel clock speed, the less likely there will be flicker.

Pixel Dropping: Sub-sampling to reduce the number of pixels in an image by dropping every nth pixel from the scan.

Pixelisation: Graininess in an image that results when the pixels are too big. Also referred to as Pixelated.

Pixel Replication: Creating more pixels than are actually scanned by replicating every nth pixel to create the n+1 pixel.

PIXX: PCI ISA IDE Xcelerator: a key component of the Peripheral Bus Controller chipset, responsible for integrating many common I/O functions found in ISA-based PC systems.

Plated Media: Disks that are covered with a hard metal alloy instead of an iron-oxide compound. Plated disks can store more data than their oxide-coated counter-parts.

Platter: A disk made of metal (or other rigid material) that is mounted inside a fixed disk drive. Most drives use more than one platter mounted on a single spindle (shaft) to provide more data storage surfaces in a smaller area.

PnP (Plug And Play): The ability of certain operating systems to automatically detect a new device that has been added to the system, uniquely identify that device, and install the appropriate drivers and system files for that device. Identification is facilitated by means of predetermined identification numbers hard-coded into the device. When the operating system boots up, it polls all installed devices and checks the returned identification numbers against the list of previously installed devices.

Plug-in: A helper application that works within a browser. It adds ore functionality to a browser commonly associated with the Netscape Navigator browser software.

PM: Phase Modulation: a data transmission technique that blends a data signal into a carrier by varying (modulating) the phase of the carrier.

PMA: Program Memory Area: on a recordable disc, an area which temporarily contains track numbers and their starting and stopping points (that is, the session TOC) when tracks are written in a session which is not yet closed. When the session is closed, this same TOC information is written in the session lead-in.

PMOS: P-channel Metal Oxide Semiconductor: pertains to MOS devices constructed on an N-type silicon substrate in which holes flow between source and drain contacts.

PMT: Photomultiplier Tube: a vacuum tube that converts light into electrical energy and amplifies it. Photomultiplier tubes are used in high-end drum scanners, because they are more sensitive to light than the CCD elements used in desktop devices.

Polygon: Any closed shape with four or more sides. In 3D, complex objects like teapots are decomposed, or "tessellated", into many primitive polygons to allow regular processing of the data, and hardware acceleration of that processing.

Polygon-Based Modelling: Representing 3-D objects as a set or mesh of polygons.

Polyphony: The number of voices a synthesiser can play at any one time.

Polysilicon: Conductive material used as an interconnect layer on a chip.

POP: Post Office Protocol - Internet email access standard.

Port: Generally, port refers to the hardware through which computer data is transmitted; the plugs on the back of your computer are ports. On the Internet, port often refers to a particular application. For instance, you might telnet to a particular port on a particular host. The port is actually an application.

POSIX: Portable Operating System Interface for UNIX: a set of IEEE and ISO standards that define an interface between programs and operating systems. By designing their programs to conform to POSIX, developers have some assurance that their software can be easily ported to POSIX-compliant operating systems. This includes most varieties of UNIX.

POST: Power On Self Test - A quick test the BIOS does on the components in the computer to make sure everything is working when you first turn it on.

Post-Gap: A space dividing tracks, recorded within the track data area at its end. The post-gap is 150 sectors (2 seconds) long and is required only where successive tracks are of different types.

Posting: A message sent to a newsgroup or the act of sending such a message.

Postmaster: The person at a host who is responsible for managing the mail system. If you need information about a user at a particular host, you can usually send e-mail to the postmaster at postmaster@hostname.

PostScript: A page description language developed by Adobe. Generally used by laser printers, PostScript is becoming increasingly common in high-end inkjets too.

POTS: Plain Old Telephone Service: the basic analogue (nondigital) telephone service - standard single line telephones, telephone lines, and access to the public switched network. There are no added features, such as call waiting or call forwarding, with POTS.

PPI: Pixels Per Inch: ppi is often used interchangeably with dpi, although a dot is a bilevel entity, either on or off, and a pixel can hold multiple levels of information. For instance, for an 8-bit scanner, 1 pixel has 256 possible values (0 to 255).

PPP (Point-to-Point Protocol): A protocol that allows a computer to use the TCP/IP (Internet) protocols (and become a full-fledged Internet member) with a standard telephone line and a high-speed modem. PPP is a new standard for this which replaces SLIP.

Prefetch Unit: The Prefetch Unit decides when to order data and instructions from the Instruction Cache or the computer's main memory based on commands or the task at hand. When the instructions come in the most important task for the Prefetch Unit is to be sure all the instructions are lined up correctly to send off to the Decode Unit.

Pre-Gap: A space dividing tracks, recorded before the track data area. The length of the pre-gap varies with the CD recorder and the types of tracks. Where successive tracks are both of data, one track is separated from another by a track pre-gap of 150 sectors (2 seconds). Where successive tracks are of different types, the pre-gap is usually of 225 sectors (or three seconds). If two successive tracks are audio, there may be no pre-gap at all.

Premastering: The technical process of preparing data to be mastered onto a compact disc. It includes breaking the data into logical blocks and recording those blocks with the appropriate header (address) and error correction information. The result of premastering may be a tape ready to go for mastering, or, in the case of recordable CD systems, premastering and mastering are done in one operation, resulting in a ready-to-read compact disc.

PRI: Primary-Rate Interface: the enhanced ISDN setup, consisting of 23 B-channels (30 in Europe) and one D-channel. See also BRI.

Primitives: Smallest units in the 3D database. Usually points, lines, and polygons representing basic geometric shapes, such as balls, cubes, cylinders, and donuts. Some 3D hardware and software schemes also employ curves, known as "splines".

Printer Dot: The individual pixel in a halftone image. The size of a printer dot is variable, ranging from zero (all white) to the size of the halftone screen (all black).

PRML: Partial Response Maximum Likelihood: a technique used to differentiate a valid signal from noise which achieves improved accuracy by looking at entire waveforms rather than just peaks in isolation, using digital signal processing (DSP) to reconstruct recorded data. On magnetic disks PRML uses RLL encoding to provide a ratio of user data to recorded data of 8:9.

PRNU: Photo Response Nonuniformity: pixel-to-pixel variation in the response of a CCD array to a fixed-intensity light. Ideally, the response to each CCD element in the array is identical; deviations from that response are caused by PRNU.

Process Colours: The four primary ink colours (CMYK) used in colour printing.

Processor: Short for Central Processing Unit or CPU, the brains of any computer. The Intel Pentium line of processors and the AMD Duron and Athlon processors are classed as CPU's.

Program area: The largest area on a CD containing the audio or CD-ROM information.

Protected Mode: A memory-addressing system supporting 32-bit instruction sets. I t mediates between different programs running at once, and keeps them within their memory boundaries.

Protocol: A set of rules computer programmers apply when writing code for a specific software. Computers and networks interact according to standard protocols, which determine the behaviour that each side of a network connection expects from the other side.

PS/2: An IBM personal computer series introduced in 1987, superseding the original PC line. It introduced the 3.5in floppy disk, VGA graphics and Micro Channel bus. The latter has since given way to the PCI bus.

PSK: Phase Shift Keying: a data transmission technique that blends a data signal into a carrier by varying (modulating) the phase of the carrier by a certain number of degrees for each succeeding signal.

PSTN: Public Switched Telephone Network: refers to the international telephone system based on copper wires carrying analogue voice data. This is in contrast to newer telephone networks base on digital technologies, such as ISDN and FDDI.

Psychoacoustics: The study of how the human brain perceives sound. Findings relating to which sounds are and are not heard by the human ear have been used in the formulation of various audio compression techniques, including MP3.

PTT: An acronym for Postal, Telegraph and Telephone.

PSU: Power Supply Unit - The power supply supplies electricity to the motherboard, device drives and any other peripherals in the computer.

Pulse Dialling: A method of dialling the telephone where the modem sends pulses (which you hear through the handset as clicks) to represent the telephone numbers (one pulse for a one, two pulses for a two, etc.). Pulse dialling is normally associated with rotary-dial phones. See also Tone Dialling.

PX64: Similar to MPEG, but adapted to slower bit rate. Typically used for video conferencing over an ISDN phone line.

Q-channel: One of the CD subcode channels. The Q-channel is used to give timecode addresses and, in the lead-in, the Table of Contents.

QAM: Quadrature Amplitude Modulation: modulation technique used by high speed modems combining amplitude and phase modulation of the data signal. QAM generates four bits out of one baud. For example, a 600 baud line (600 shifts in the signal per second) can effectively transmit 2,400 bit/s using the technique.

Quantisation: The process of representing a voltage with a discrete binary digital number. Approximating an infinite valued signal with a finite number system introduces an error called quantisation error or noise.

QuickTime: Apple Computer's video environment (like Microsoft's Video For Windows). QuickTime video files must be converted to .AVI format to run under Microsoft's Video For Windows.

QXGA: Quad XGA: a QXGA display has 2048 horizontal pixels and 1536 vertical pixels giving a total display resolution of 3,145,728 individual pixels - 4 times the resolution of an XGA display.

Radiosity: Complex methods of drawing 3D scenes, which result in photorealistic images. Essentially, they calculate the path that light rays follow from objects to the viewer, and all the accompanying reflections. Also known as ray tracing.

RADIUS: Remote Authentication Dial-In User Service protocol: a client/server security protocol that allows network managers to reduce the risk of distributing security information across many devices by centralising authentication and permission attributes in a single server.

RADSL: Rate Adaptive Digital Subscriber Line: an implementation of ADSL that automatically adjusts the connection speed on start up to adjust for the quality of the telephone line, thereby allowing the service to function over longer distances than does ordinary ADSL.

RAID: Redundant Array of Inexpensive Disks - Several different forms of RAID implementation have been defined. Each form is usually referred to as a "RAID level." RAID provides convenient, low-cost, and highly reliable storage by saving data on more than one disk simultaneously. At its simplest, a RAID-1 array consists of two drives that store identical information. If one drive goes down, the other continues to work, resulting in no downtime for users.

Rainbow Effect: An artefact unique to single-chip DLP projectors which appears as a rainbow or multi-colour shimmer briefly noticeable by some people when they change focus from one part of the projector screen to another. It appears as a secondary image that appears at the viewer's peripheral vision and is typically noticeable when shifting focus from a high contrast area or bright object.

RAM (Random Access Memory): The working space within a computer that may be used at one time; increasing the amount of RAM increases the speed at which a computer works because more of a program may be loaded into the working space at one time, so less time is spent accessing parts of the program from the hard drive. Information stored in RAM is lost when the computer's power is turned off.

RAMDAC: Random Access Memory to Digital Analogue Converter - A chip on video card which turns digital signals to analogue ones which can be output to a monitor. The faster the RAMDAC (measured in MHz), the higher the screen refresh rates that the card will support at each given resolution.

RAM Disk: A "phantom" drive created by setting aside a section of RAM as if it were a group of regular sectors. Access to a RAM disk is very fast but data is lost when the system is reset or turned off.

Random Access: Ability to access any particular block by going directly to it. Memory and disk devices support random access; by contrast, tape storage devices do not.

Random Erase: The ability to erase a single file at a time from a CD-RW disc, freeing up disc space for immediate re-use, just as you would do on a hard or floppy disk. Part of the UDF 1.5 specification and implemented via UDF driver software such as Adaptec's DirectCD V2.0.

RAS: Row Address Select (or Strobe): a control pin on a DRAM used to latch and activate a row address. The row selected on a DRAM is determined by the data present at the address pins when RAS becomes active.

RAS Line: Physical track on motherboard used to select which sides of which SIMMs will be involved in a data transfer. A given chipset supports only a certain number of RAS lines, thereby dictating how many SIMMs can be accommodated. A pair of SIMMs uses one RAS line; a pair of DIMMs uses two.

Raster: A raster is a rectangular grid of picture elements representing graphical data for display. Raster operations (ROPs) can be performed on some portion or all of the raster.

Raster Image: An image defined as a set of dots/pixels in a column-and-row format. Rasterisation is the process of determining values for the dots/pixels in a rendered image. See also Bitmap.

Raster Line: A thin horizontal strip across an image. Raster lines are captured one at a time by the CCD elements in a scanner. When displayed or printed in sequence, raster lines make up the image. Raster lines in a TV or monitor work the same way.

Rasterisation: Rasterisation is the conversion of a polygon 3D scene, stored in a frame buffer, into an image complete with textures, depth cues and lighting.

RCA: Radio Corporation of America: refers to the standard single-ended analogue cables used to connect audio and video devices together. Typically red/white inputs are for the left/right channels of sound and yellow is for video.

RDRAM: Rambus DRAM - A DRAM architecture that has a huge amount of memory bandwidth, however has a high latency penalty. RDRAM is best suited for processors that need high bandwidth like Pentium 4 processors.

Read After Write: A mode of operation that has the computer read back each sector immediately after it is written on the disk, checking that the data read back is the same as recorded. This slows disk operations, but raises reliability.

Read Channel: A drive's read channel performs the vital job of converting the head's analogue signal into accurate digital data.

Read Verify: A disk mode where the disk reads in data to the controller, but the controller only checks for errors and does not pass the data on to the system.

Read/Write Head: A device which uses induction to "write" a data pattern onto magnetic media; and which uses either inductance or magneto-resistance to "read" the data back. Heads come in many different shapes and forms, and are used for both contact and non-contact type recording.

RealAudio: Extreme audio compression scheme used on the Internet to provide streamed audio over ordinary modems.

Real-time: In computing, refers to an operating mode under which data is received and processed and the results returned so quickly as to seem instantaneous.

Rear Projection: With rear projection, the projector is placed behind a translucent screen. See also Front Projection.

Red Book: The Philips/Sony specification for audio (CD-DA) compact discs.

Reflectance: The fraction of the light incident on a surface that is reflected and varies according to the wavelength distribution of the light. Also called reflectivity.

Reflections: Sounds that originate from a sound source and bounce off walls, floors, ceilings and other obstructions before reaching the listener.

Refresh: The process used to restore the charge in DRAM memory cells at specified intervals. The required refresh interval is a function of the memory cell design and the semiconductor technology used to manufacture the memory device. There are several refresh schemes that may be used.

Refresh Rate: The amount of times the monitor refreshes (redraws) the picture on the screen. Lower rates, around 60 Hz will appear to flicker, especially under lighting. Refresh rates above 75 Hz are recommended since anything lower will cause headaches after a prolonged period of time.

Registered Memory: A type of SDRAM memory that uses registers to hold data for one clock cycle before it is moving it on and in so doing increases the reliability of high-speed data access. Registered memory modules are typically used only in server environments and other mission-critical systems. Registered and unbuffered memory cannot be mixed. the design of the processor's memory controller dictating which type is required.

Registers: The Registers are a mini-storage area for data used by the Arithmetic Logic Unit (ALU) to complete the tasks the Control Unit has requested. The data can come from the data cache, main memory or the control unit and are all stored at special locations within the Registers. This makes retrieval for the ALU quick and efficient.

Remote Computer: A computer located somewhere else along a network as, for example, the computer containing the online catalogue of your local public library. Remote is a relative term, relative, that is, to the computer immediately at hand (the local computer). A remote computer can actually be located within the same room, or it can be halfway around the world.

Removable Disk: Generally said of disk drives where the disk itself is meant to be removed, and in particular of hard disks using disks mounted in cartridges. Their advantage is that multiple disks can be used to increase the amount of stored material, and that once removed, the disk can be stored away to prevent unauthorised use.

Rendering: Fundamentally this relates to the drawing of a real-world object as it actually appears. It often refers to the process of translating high-level database descriptions to bitmap images comprising a matrix of pixels or dots.

Replication: Or duplication. Making multiple copies of a compact disc.

Request To Send: RTS: an RS-232C signal that requests the modem to send data. It initiates any data transmission between the computer (or terminal) and the modem. It is answered by a Clear To Send (CTS) signal.

Resampling: A technique used to recalculate an image's pixel data values to produce a different size of image. It involves a process similar to 'interpolation', this being the term used for resampling to a larger image.

Resistor: An electronic component that resists the flow of current in an electronic circuit.

Resolution: Resolution is a measure of graphics that's used to describe what a printer can print, a scanner can scan, and a monitor can display. In printers and scanners, resolution is measured in dots per inch (dpi)--the number of pixels a device can fit in an inch of space.

Response Time: It typically takes around 25ms for the liquid crystal inside a modern TFT panel to respond to the applied current, which is usually more than enough to fool the naked eye into seeing fluid movement. Quoted response times include an element of latency, when a pixel remains lit for a short time after the current has been removed.

RF: Radio Frequency: the range of electromagnetic frequencies above the audio range and below visible light. All broadcast transmission, from AM radio to satellites, falls into this range, which is between 30KHz and 300GHz.

RGB: Red-Green-Blue: a way of encoding images in computer graphics by describing a colour by the amount of the three basic colours Red, Green and Blue. Three bytes are required for "true colour" (three numbers between 0 and 255), giving a theoretical maximum of 16.7 million colours. Computer monitors are generally driven by an RGB signal. The other technique for output display is composite video, which typically offers less resolution than RGB.

RJ11: A common jack type most often used for connecting analogue phones, modems and fax machines to a communications line.

RJ45: The most commonly used connection standard in networks. Its connector looks almost identical to a standard telephone jack, only slightly bigger. Twisted pair cabling is used - comprising two independently insulated wires twisted around each other. One wire carries the data while the other wire is grounded and absorbs any signal interference. This can come in unshielded (UTP) and shielded (STP) versions. Nodes are connected individually to the network, so if one connection fails, the rest of the network can continue to operate.

RIFF: Resource Interchange File Format: platform-independent multimedia specification (published by Microsoft and others in 1990) that allows audio, image, animation, and other multimedia elements to be stored in a common format. See also Media Control Interface (MCI).

RIMM: A form of chip packaging that is similar to DIMMs to be used with the next generation of Direct DRAM memory subsystems.

Ripper: The name given to the specialised software that extracts raw audio data from a music CD. The ability to extract audio digitally relies on a feature of newer CD-ROM drives that allows the digital data from audio CDs to be passed through the computer's bus (IDE, SCSI) just like CD-ROM data.

RISC: Reduced Instruction Set Computer: a microprocessor architecture that recognises a relatively limited number of instructions, favouring the speed at which individual instructions execute over the richness of the instruction set. See also CISC.

Riser: A device that is an add on from another card, takes up an expansion slot however doesn't plug directly into the motherboard.

RJ-11: This is the standard telephone connector--a tab snaps into the socket and has to be pressed to remove the connector from the wall. An ordinary phone circuit uses two wires. The RJ-11 jack has room for up to four wires, but at a glance it's easy to mistake with the larger RJ-45 jack, which can house up to eight wires.

RJ-45: RJ-45 connectors look a bit like a standard phone connector but are twice as wide (with eight wires). RJ-45s are used for hooking up computers to local area networks (LANs) or for phones with lots of lines.

RLE: Run Length Encoding: Microsoft's video compression algorithm for base level multimedia PCs. Compresses 8-bit sequences only. Playback is also in 8 bit and isn't scaleable for higher power PCs.

RLL: Run Length Limited: a method used on some hard disks to encode data into magnetic pulses. RLL requires more processing, but stores almost 50 percent more data per disk than the older MFM (modified frequency modulation) method. The "run length" is the maximum number of consecutive 0s before a 1 bit is recorded.

Rock Ridge: The Rock Ridge extensions to ISO-9660 use some undefined fields in the standard to provide support for Unix-like features such long mixed-case filenames, symbolic links, and deep directories.

Roland GS: Roland General Synthesiser and General MIDI are two overlapping specifications for defining the standard sets of MIDI sounds that are associated with specific commands.

ROM (Read Only Memory): This memory is the core instructions for the computer, it generally cannot be altered (read only) and is burned into the chips making up the specific motherboard.  ROM is a storage chip that typically contains hardwired instructions for use when a computer starts (boots up). The instructions, contained in a small program called the BIOS (basic input/output system) load from ROM and start up the hard disk so that the operating system (OS) can be loaded.

Rotation: Determines how well the image area lines up to the bezel; also called tilt.

Router: A device that forwards data packets along networks. A router is connected to at least two networks, commonly two LANs or WANs or a LAN and its ISP's network. Routers are located at gateways, the places where two or more networks connect. Routers use headers and forwarding tables to determine the best path for forwarding the packets, and they use protocols such as ICMP to communicate with each other and configure the best route between any two hosts.

RPC: Regional Playback Control: restrictions to prevent unauthorised playback of DVD discs in countries they were not intended for.

RPM: Revolutions Per Minute.

RS170A: The EIA standard for the combination of signals required to form NTSC colour video.

RS-232: A standardised connection system for connecting a device to the serial port of a computer or terminal. This is the recommended standard of the Electronic Industries Association (EIA) for exchanging information between DTE (such as computers) and DCE (such as modems).

RTF: Rich Text Format: a format in common use by word processors. It accepts both text and images, and retains text formatting and page layout.

RTV: Real Time Video: single step compression of video.

S-Registers: The RAM in a modem that is used to store its current configuration profile (operating characteristics).

Sampling: The first step in the process of converting an analogue signal into a digital representation. This is accomplished by measuring the value of the analogue signal at regular intervals called samples. These values are then encoded to provide a digital representation of the analogue signal.

Sampling Rate: In digitising operations, the frequency with which samples are taken and converted into digital form. The sampling frequency should be at least twice that of the analogue frequency being digitised. Thus, the sampling rate for hi-fi playback is 44.1kHz, slightly more than double the 20kHz frequency humans can hear.

SAN: Storage Area Network: a high-speed special-purpose network that interconnects different kinds of data storage devices - such as tape libraries and disk arrays- with associated data servers on behalf of a larger network of users.

SATA: Serial Advanced Technology Attachment: a new standard for connecting hard drives into computer systems. An evolution of the Parallel ATA physical storage interface, SATA is based on serial signalling technology, a single cable with a minimum of four wires creating a point-to-point connection between devices. The first implementation of SATA supported a transfer rate of 150 MBps.

Saturated Colours: Strong, bright colours (particularly reds and oranges) which do not reproduce well on video; they tend to saturate the screen with colour or bleed around the edges, producing a garish, unclear image.

Saturation: The colourfulness of an area judged in proportion to its brightness. For example, a fully saturated red would be a pure red. The less saturated, the more pastel the appearance. See also Chroma.

SCA: Single Connector Attachment: Same speed SCSI interface as LVD, but integrates power and IO information into a single 80-pin connector. Used in high-end servers to allow hard disks to be hot-swapped in a RAID array.

Scalability: The ability to vary the information content of a program by changing the amount of data that is stored, transmitted or displayed. In a video image, this translates into creating larger or smaller windows of video on screens (shrinking effect).

Scale: To enlarge or reduce an image by increasing or decreasing the number of scanned pixels, or the sampling rate, relative to the number of samples per inch needed by the printer or other output device. See also Interpolation.

Scaling: Process of uniformly changing the size of characters or graphics

Scanner: A device that reads a printed page and converts it into a graphics image for the computer. It works by digitising an image - converting everything on the page (text and graphics objects) - into one raster graphics image. The resulting matrix of bits, or bitmap, can then be stored in a file, displayed on a screen and manipulated by programs.

SCMS: Serial Copy Management System: a measure introduced to tackle piracy problems which allows the consumer to make a single digital copy, for personal use, from a copyrighted source.

Screen Door Effect: Screen Door Effect (SDE) is common with LCD-based projectors and relates to a viewer's awareness of the grid, or spacing between the pixels. The lines which form the grid are, in fact, where the panel's control electronics are preventing light from shining through the panel.

Screen Regulation: A distortion where the size of the image varies according to the brightness of the screen content. A white rectangle will appear larger when surrounding a solid white rectangle than when surrounding a plain black area.

SCSI: Small Computer System Interface - With SCSI, you can add up to seven new devices to your computer and depend on them to deal with single-interface issues by themselves. It's a robust standard, and it's rendered even more so with its latest implementation, SCSI-2. Pronounced "scuzzy".

SDLC: Synchronous Data Link Control: Proposed by IBM in the 1970's, SDLC is the primary data link protocol used in their SNA networks. It is a bit-oriented synchronous protocol that is a subset of the HDLC protocol.

SDMI: Secure Digital Music Initiative: A secure digital format for distributing music over the Internet. Announced in February 1999, it is backed by the Recording Industry Association of America (RIAA) and Sony, Warner, BMG, EMI and Universal - the top five music production companies. At the time of its announcement, the new format was expected in products by Christmas 1999.

SDRAM: Synchronous dynamic RAM - SDRAM incorporates new features that allow it to keep pace with bus speeds as high as 100 MHz. It does this primarily by allowing two sets of memory addresses to be opened simultaneously. Data can then be retrieved alternately from each set, eliminating the delays that normally occur when one bank of addresses must be shut down and another prepared for reading during each request.

Search Engine: A tool used which matches key words you enter with titles and descriptions on the Internet. It then displays the matches allowing you to easily locate a subject. Similar to a card catalogue, but not as efficient. Common search engines are Webcrawler, Yahoo, Alta Vista, Infoseek, and Lycos.

SEC: Single Edge Connect: a form of processor packaging first used by Intel's Pentium II CPU. Comprising a hardware module (cartridge) that contains the CPU and an external L2 cache, it plugs into a socket (Slot 1, Slot 2, etc.) on the motherboard which bears greater resemblance to a bus slot than an individual chip socket.

SECAM: Sequentiel Coleur A Memoire: European video standard, used in France and Eastern Europe, with image format 4:3, 819 lines per frame, 50 Hz and 6 MHz video bandwidth with a total 8 MHz of video channel width. Like the similar PAL standard, it has a 25-frame per second update rate. The major difference from PAL is that SECAM uses FM-modulated chrominance.

Sector: Describes the minimum segment of track length that can be assigned to store data. Magnetic disks are typically divided into tracks, each which contains a number of sectors. A sector contains a predetermined amount of data, such as 512 bytes. CDs can contain [(75 sectors per second) x (60 seconds per minute) x (number of minutes on disc)] sectors, the capacity of a sector depending on what physical format and mode is used for recording.

Secure Digital: SD: a postage stamp size portable flash memory format developed by Toshiba, Sandisk and Panasonic. Content encoded on an SD card may be encrypted, providing copyright protection of intellectual properties. Expected to the industry standard for the warehousing and transfer of digital media including music, still and moving video, talking books, etc.

Seek Time: The time taken for the actuator to move the heads to the correct cylinder in order to access data.

Semiconductor: A solid-state substance with conductive properties that can be altered with electricity. Silicon performs as a semiconductor when chemically combined with other elements. A semiconductor is also halfway between a conductor and an insulator. When charged with electricity or light, semiconductors change their state from non-conductive to conductive or vice versa. The most significant product built from a semiconductor is the transistor.

Sequencer: Software for recording and editing MIDI files.

Sequential Erase: Erasing, or reformatting, an entire CD-RW disc so that it can be re-used. Contrast with Random Erase.

Serial Port: This is the communications port on your computer; it's also called the COM or RS-232 port. It's called serial because, although it has nine pins and many wires, the PC sends data on only one wire and receives data on one other wire. All the data bits have to follow one another on the single wire, as opposed to the parallel port, where eight separate wires transfer each bit of a byte.

Server: A computer or its software that "serves" other computers by administering network files and network operations. Three types of Internet servers are Web servers, e-mail servers, and Gopher servers.

Servo Data: Magnetic markings written on the media that guide the read/write heads to the proper position.

Servo Motor: A closed-loop control system used to adjust head position and/or tape speed.

Servo Platter: A separate surface containing only positioning and disk timing information but no data. Used only in a dedicated servo system.

Session: As defined under the Orange Book, a recorded segment of compact disc which may contain one or more tracks of any type (data or audio).

Settle Time: The interval between the arrival of the read/write head at a specific track, and the lessening of the residual movement to a level sufficient for reliable reading or writing.

SGRAM: Synchronous Graphics Random Access Memory - A special form of RAM that is designed specifically for graphics cards. SGRAM offers a little more bandwidth then SDRAM, however it costs more as well.

Shading: The process of creating pixel colours. Gouraud is a constant increment of colour from one pixel to the next, while Phong is much more complex and higher quality. Flat shading means no smooth blending of colours, each polygon being a single colour.

Shadow Mask: In monitors, the shadow mask is a metal plate with holes in it that focuses the beams from the electron guns at the back of the CRT. The distance between these holes is called the dot pitch.

Shareware: Software that you can download that is either limited in features, or by how longmany times you can run it. Paying a fee registers the program and releases the limitations.

Sharpening: An option on some scanners that emphasises detail by increasing the contrast of the boundaries between light and dark areas of an image.

Shock Rating: A rating (expressed in Gs) of how much shock a disk drive can sustain without damage. Operating and non-operating shock levels are usually specified separately.

Shutter Speed: The shutter speed controls how long the digital sensor is exposed to light. The faster it is, the less susceptible the camera is to movement.

SIF: Standard Interchange Format: format for exchanging video images of 240 lines with 352 pixels each for NTSC, and 288 lines by 352 pixels for PAL and SECAM. At the nominal field rates of 60 and 50 fields/s, the two formats have the same data rate.

SIG: An acronym for Special Interest Group.

Signature: A short piece of text transmitted with an e-mail or newsgroup message. Some systems can attach text from a file to the end of a message automatically. Signature files contain detailed information on how to contact someone.

Silicon Dioxide: Grown on a wafer during chip fabrication to serve as an insulating layer.

Silicon Ingot: A large, cylindrical, single crystal made from purified silicon. The cylinder is sliced into thin wafers which are used for making computer chips.

Silicon Wafer: Intel uses wafers of pure silicon cut from a silicon ingot to make microprocessors. Silicon, the primary ingredient of beach sand, is a semiconductor of electricity. Semiconductors are materials that can be altered to be either a conductor or an insulator.

Silver Disc: A disc which is mastered by a stamping process. It is Read-Only and can not be modified.

SIM: Designed to be inserted into a mobile telephone, a SIM or "smart" card contains all subscriber-related data, such as phone numbers, service details, and memory for storing messages. With a SIM card, calls can be made from any valid mobile phone because the subscriber data--not the telephone's internal serial number--is used to make the call.

SIMD: Single Instruction Multiple Data: a method of efficiently processing data in which a single instruction is applied to multiple pieces of data simultaneously rather than to each piece of data individually. Repetitive tasks are effectively consolidated into a single one, greatly increasing the speed of data processing. Instructions of this nature are often associated with 3D graphics and multimedia. See also SSE.

SIMM: Single In-Line Memory Module - RAM generally used in older 486 and Pentium computers. Denoted by either 30 or 72 pin configurations, available from 1-32 megs.

Single Session: The smallest collection of information that can be read by a CD-ROM compatible device. It contains the ISO 9960 file structure and files. A single session can contain a single track or multiple tracks. Contrast Multi Session and Multi Track.

Slave: A device that gets its instructions from another device, for example 2 hard drives or 2 CD-ROM's on the same cable. First in line is considered master and the second in line slave.

Sledgehammer: Codename for AMD's x86-64 design for extending the iA-32 architecture to support 64-bit code and memory addressing.

SLIP (Serial Line Internet Protocol): A protocol that allows a computer to use the Internet protocols (and become a full-fledged Internet member) with a standard telephone line and a high-speed modem. SLIP is being superseded by PPP, but is still in common use.

Slot 1: Intel's proprietary CPU interface form factor for Pentium II CPUs. Slot 1 replaces the Socket 7 and Socket 8 form factors used by previous Pentium processors. It is a 242-contact daughter card slot that accepts a microprocessor packaged as a Single Edge Contact (SEC) cartridge. Communication between the Level 2 cache and CPU is at half the CPU's clock speed.

Slot 2: An enhanced Slot 1, which uses a somewhat wider 330-way connector SEC cartridge that holds up to four processors. The biggest difference from Slot 1 is that the Level 2 runs at full processor speed.

Slot A: AMD's proprietary 242-way connector SEC cartridge used by their original Athlon processor. Physically identical to Slot 1 but electrically incompatible.

Slotted Mask: A variation on the aperture grill phosphor triad approach which uses the slot-mask design used on many non-Trinitron TV sets.

SmartMedia: An ultra-compact flash memory format developed by Toshiba. About the size of Compact Flash, but as thin as a credit card, SmartMedia cards can be plugged into a SmartMedia socket or into a standard Type II PC Card slot with an adapter.

Smiley: A symbol in e-mail and newsgroup messages used to convey emotion, or simply amusement. Create a smiley by typing various keyboard characters. For example, :-) means happiness. See also, Emoticon.

SMDS: Switched Multimegabit Data Service: a high-speed, switched data communications service offered by telephone companies for interconnecting separate local area networks (LANs) into a single wide area network (WAN). Prior to SMDS's arrival in 1995, the only way to connect LANs was through a dedicated private line. SMDS is becoming an increasingly attractive alternative because it is more flexible and usually more economical.

SMTP (Simple Mail Transfer Protocol): One method a computer uses to send e-mail from one computer to another. Other methods include Multi-purpose Internet Mail Extensions (MIME) and Privacy Enhanced Mail (PEM).

SMP: Symmetric Multiprocessing: a computer architecture that provides fast performance by making multiple CPUs available to complete individual processes simultaneously (multiprocessing). Unlike asymmetrical processing, any idle processor can be assigned any task, and additional CPUs can be added to improve performance and handle increased loads.

SMPTE Timecode: An 80-bit standardised edit time code adopted by SMPTE, the Society of Motion Picture and Television Engineers. See also Time Code, for measuring video duration. Each frame is identified in the form hours:minutes:seconds:frames.

SNA: Systems Network Architecture: a mainframe network topology introduced by IBM in 1974. Originally designed as a centralised architecture with a host computer controlling many terminals, SNA has evolved over the years so that it now also supports peer-to-peer networks of workstations. SNA incorporates data protocols, network interface cards and just about every facet of communication.

SNR: Signal-to-Noise Ratio: a measure of link performance arrived at by dividing signal power by noise power. Typically measured in decibels. The higher the ratio, the clearer the connection.

Socket: Socket usually refers to where the processor is placed. Examples are Socket A, Socket 370 and Socket 462.

Socket 370>: Intel's proprietary CPU interface form factor first introduced for its Celeron line of CPUs and subsequently adopted for later versions of the Pentium III family.

Socket 423: Intel's proprietary CPU interface form factor used by its early Pentium 4 processors.

Socket 478: Intel's proprietary CPU interface form factor which replaced Socket 423 with the advent of the 0.13-micron Pentium 4 Northwood core.

Socket 7: The CPU interface form factor for fifth-generation Pentium-class CPU chips from Intel, Cyrix, and AMD.

Socket 754: AMD's 754-pin CPU interface form factor introduced with its 64-bit Athlon 64 processor in the autumn of 2003.

Socket 8: Intel's proprietary CPU interface form factor used exclusively by their sixth-generation Pentium Pro CPU chip. Socket 8 is a 387-pin ZIF socket with connections for the CPU and one or two SRAM dies for the Level 2 cache.

Socket 939: AMD's 939-pin CPU interface form factor introduced in the summer of 2004. The Socket 939 marked the convergence of the mainstream and FX versions of the Athlon 64 CPU, which had previously used different interfaces, the Socket 754 and Socket 940 respectively.

Socket A: AMD's 462-pin CPU interface form factor which replaced Slot A at the time of the introduction of the Thunderbird and Spitfire cores used by AMD's Athlon and Duron desktop processor ranges respectively.

Soft Error: A faulty data reading that does not recur if the same data is reread from the disk or corrected by ECC. Usually caused by power fluctuations or noise spikes.

Soft-Sectored: Disks that mark the beginning of each sector of data within a track by a magnetic pattern.

SOHO: Small Office/Home Office: refers to the small business or business-at-home user. This market segment has benefited greatly from recent technological advances, allowing it to compete on a level playing ground with the bigger companies.

SOI: Silicon-On-Insulator: silicon wafer with a thin layer of oxide - into which integrated circuits are built - buried in it. SOI substrates achieve superior isolation between adjacent devices in CMOS devices.

SOJ: Small Outline J-Lead package: this plastic package, designed for memory chips, is a surface mount package with turned under leads that look like the letter J.

Sound Blaster: A family of sound cards from Creative Labs. The Sound Blaster protocol has become the de facto audio standard for PCs. Monaural versions of Sound Blaster cards were introduced in 1989, and a stereo version three years later. The Sound Blaster AWE32 and AWE64 are 16-bit sound cards that provide WaveTable MIDI with 32 and 64 voices respectively.

Sound Card: Also called sound board and audio adapter, this is an expansion board that records and plays back sound, providing outputs directly to speakers or an external amplifier. The de facto standard for sound card compatibility in PCs is Creative Labs' Sound Blaster.

Southbridge: Refers to the Peripheral Bus Controller component of a Pentium chipset, responsible for implementing a PCI-to-ISA bridge function and for managing the ISA bus and all the ports. See also Northbridge.

Spam: Mass emailings that are used to market products or websites. Keeping your email private and using a free email address service for anywhere you post your email publicly goes a long way to avoiding this mess.

Specular Highlights: A lighting characteristic that determines how light should reflect off an object. Specular highlights are typically white and can move around an object based on camera position.

S/PDIF: Sony/Philips Digital Interchange Format: an interface standard that lets users connect sound equipment (such as sound boards and speakers) via a pure digital signal.

Spindle: The drive's centre shaft, on which the hard disk platters are mounted.

Spindle Speed: Velocity at which the disk media spins within a hard disk, measured in rpm (revolutions per minute). By the late 1990s EIDE hard disks generally features a 5,400rpm or 7,200 mechanism, while SCSI drives were usually either 7,200rpm or 10,000rpm.

Spline: A 3D bezier curve used in modelling.

Spline-Based Modelling: Representing 3-D objects as surfaces made up of mathematically derived curves (splines).

Sprite: A small graphic drawn independently of the rest of the screen.

Spyware: Cookies or programs that track your surfing habits and use your internet connection to send this data to a third party. They can profile your shopping preferences, hijack your browser start page or pages, alter important system files, and can do this without your knowledge or permission. The security and privacy implications of these exploits should be quite obvious and undesirable on any system or network.

SQL, Structured Query Language: an official ANSI language for retrieving information from a database. Most database software providers add extensions. The "official" pronunciation is "sequel"

SRAM: Static RAM, extremely high speed RAM that doesn't need a constant refresh unlike DRAM. Because it is very expensive, SRAM is usually used as cache RAM on CPU's.

sRGB: Standardised Red, Green and Blue: the colour space standard established by the International Electrotechnical Commission which forms the basis of colour matching hardware devices such as CRT monitors, LCD panels, projectors, printers, scanners and digital cameras and applications, including the World Wide Web.

SSA: Serial Storage Architecture: a peripheral interface from IBM whose ring configuration allows remaining devices to function if one fails. SCSI software can be mapped over SSA allowing existing SCSI devices to be used.

SSE: Streaming SIMD Extensions: Intel's SSE and SSE2 technologies are effectively sets of instructions for accelerating multimedia applications. SSE is found on Intel Pentium III processors; SSE2 is an incremental supported on Intel Pentium 4 processors. Some of the benefits of SSE/SSE2 include rendering higher quality images, high quality audio, MPEG2 video, simultaneous MPEG2 encoding and decoding and reduced CPU utilisation for speech recognition. See also SIMD.

SSL: Secure Sockets Layer - Secure encrypted communication between a network (Internet). Used often by online stores for security. Developed by Netscape Communications.

ST506: Introduced in 1979, Seagate's ST506 was the first hard disk drive for personal computers. Supporting 5.25in full-height drives with a capacity of between 5MB and 40MB, the ST506 interface became an industry standard for the IBM PC and its successors, eventually being superseded by the IDE interface.

Start/Stop Bits: The bits at the beginning and end of a data block when using asynchronous data transmission. See also Asynchronous Communication.

Stepper Motor: A type of motor that moves in discrete amounts with each electrical pulse. Steppers were originally the most common type of actuator engine, since they can be geared to advance a read/ write head one track per step. However, they are not as fast, reliable, or durable as voice coil actuators.

Streaking: A visual effect which is related to 'white level shift' and 'black level shift', where the difference in intensity between neighbouring white and black areas results in a discoloration. Occurs when a CRT's electron gun does not switch on and off quickly enough.

Stream: Audio or video transfer of signals in digital form. It is then downloaded on your computer and played back using various tools.

Streaming: A technique for transferring data such that it can be processed as a steady and continuous stream. Streaming allows the user to play media from the Internet immediately, without having first to download the entire media file.

Stripe Pitch: This is similar to dot pitch, but applicable tubes which the aperture grille method to separate phosphors. Dot stripe is measured as the distance between the vertical stripes that result. Measures of dot pitch and dot stripe are not directly comparable.

Strobe: An input that allows parallel data to be entered asynchronously.

StrongARM: A family of high-performance RISC-based microprocessors from Intel. StrongARM chips are used in handheld devices such as PDAs and palmtops. The StrongARM technology was jointly developed by Digital Equipment Corporation and Advanced RISC Machines (ARM). In 1997, Intel acquired Digital's chip manufacturing facilities and continues to make the Alpha and StrongARM chips.

STT (Secure Transaction Technology): Technology developed by software companies and credit companies to protect financial dealings over the Internet and prevent fraud.

STP: Shielded Twisted Pair: telephone wire that is wrapped in a metal sheath to eliminate external interference. See also UTP.

Subcode channel: A separate low speed data channel on every CD. The subcode comprises 8 channels, designated "R" through "W".

Subsampling: Bandwidth reduction techniques which reduce the amount of digital data used to represent an image. Part of a compression process.

Substrate: The underlying material on which a microelectronic device or storage media is built. Silicon is the most widely used substrate for chips, fibreglass for printed circuit boards and ceramic for multichip modules. Aluminium is commonly used for hard disks, glass for optical disks and mylar for floppy disks.

Superscalar: A CPU architecture that allows more than one instruction to be executed in one clock cycle. Processors can do this by fetching multiple instructions in one cycle, deciding which instructions are independent of other instructions, and executing them.

Surface: The top or bottom side of the platter that is coated with the magnetic material for recording data. On some drives one surface may be reserved for positioning information.

Surfing: Same as "cruise." The random, aimless exploration of web pages achieved through following links that look interesting within a document.

Sustained Transfer Rate: The amount of data a drive can continuously read or write per second.

SVCD: Super VCD: an evolution of the VCD format that uses MPEG-2 compression to store between 35 and 80 minutes (depending on bit rate) of SVHS quality video on a CD. Also known as Chaoji VCD.

S-Video: Type of video signal used in Hi8, S-VHS and some laserdisc formats. S-Video is a hardware standard for the way a signal is carried on the cable itself and also defines the physical cable jacks. It transmits luminance and colour portions separately, using multiple wires, and avoids composite video encoding (such as NTSC) and the resulting loss of picture quality. Also known as Y-C Video.

SVGA: Super-VGA; when SVGA first came out it was used to describe graphics adapters capable of handling a resolution of 800x600 with support for 256 colours or 1024x768 with 16-colour support. It subsequently came to be used to indicate a capability of 800x600 or greater, regardless of the number of colours available.

Switch: A device that operates at the data link layer (Layer 2) of the OSI reference model and whose function is to filter and forward packets of information according to their destination address.

Switched Ethernet: An Ethernet network that runs through a high-speed switch. Changing to switched Ethernet means replacing the Ethernet hub with a switch. As a result the full bandwidth - 10 Mbit/s for Ethernet or 100 Mbit/s for Fast Ethernet - is made available to each sender and receiver pair.

SXGA: Super XGA: a screen resolution of 1280x1024 pixels, regardless of the number of colours available.

Synchronous: Refers to events that are synchronised, or co-ordinated, in time. Communication within a computer is usually synchronous and is governed by the microprocessor clock. Signals along the bus, for example, can occur only at specific points in the clock cycle.

Synchronous Cache: An SRAM that requires a clock signal to validate its control signals. This enables the cache memory to run lockstep with the CPU. Can be either Burst or Pipelined Burst.

System Bus: The primary pathway between the CPU, memory and high-speed peripherals to which expansion buses, such as ISA, EISA, PCI and VL-Bus, can connect. Also referred to as the external bus or host bus, and came to be used interchangeably with frontside bus (FSB) following the introduction of Intel's Dual Independent Bus (DIB) architecture in 1997.

T1 Line: A line connecting a computer to a high-speed, high-bandwidth, digital electronic communication carrier.

T&L: Transform and Lighting: two separate engines on the GPU that provide for a powerful, balanced PC platform and enable extremely high polygon count scenes. Transform performance determines how complex objects can be and how many can appear in a scene without sacrificing frame rate. Lighting techniques add to a scene's realism by changing the appearance of objects based on light sources.

Tag: The subset of the CPU address bits used to compare the tag bits of the cache directory to the main memory address being accessed.

Tag RAM: Cache is physically divided into two sections. The Tag RAM section stores the Tag address of the location of the data in cache. This section is smaller than the Data RAM section, which stores the actual data or instruction.

TAPI: Telephony Application Programming Interface: permits Windows applications to program telephone-line-based devices such as modems and fax machines in a device-independent manner.

Taskbar: The long horizontal bar at the bottom of your screen that houses your Start button, for example. It may also have the quick launch next to the start button and to the far right more icons of running programs. It be customized to suit your needs and preferences.

TB: Terabyte: a unit of measure for storage capacity 1,000,000,000,000 (1 trillion) bytes, or 1,000,000 (1 million) megabytes or 1,000 (1 thousand) gigabytes.

TCP-IP: Transmission Control Protocol/Internet Protocol - These two protocols were developed by the U.S. military to allow computers to talk to each other over long distance networks. IP is responsible for moving packets of data between nodes. TCP is responsible for verifying delivery from client to server. TCP/IP forms the basis of the Internet, and is built into every common modern operating system.

TDM: Time Division Multiplexing: a data communications technique that interleaves separate data streams into one high-speed transmission by assigning each stream a different time slice in a set. The receiving end then divides the single stream back into its original constituent signals.

TDMA: Time Division Multiple Access: a mobile communications technique in which a radio frequency channel is divided into time slots, each of which lasts for a fraction of a second. TDMA divides a 30KHz channel into six time slots that are allocated in pairs, resulting in three usable TDMA channels. Any given conversation can use one or more of every third time slot on an ongoing basis during a call.

Tearing: Video artefact in which portions of a video window are not updated in time for the next frame.

Telnet: An Internet protocol used for logging on to a remote computer, as well as the software that implements it. Telnet makes all Internet hosts appear to the user as if they use the same techniques for presenting information on screen and the same commands for performing tasks (such as typing and editing commands).

Terabyte: 1 trillion bytes or 1000 Gigabytes. In binary, 1 TB is 2 to the power of 40.

Tesla: Magnetic fields, or more specifically, magnetic flux densities historically have been measured with a unit called the milligauss - 1 milligauss(mg) being equal to 0.001 Gauss(g). Electrical engineers and physicists use the Tesla as a unit of international standard, one Tesla being the equivalent to 10,000 Gauss or 10,000,000 milligauss. Typically the Tesla is used in technical journals and the milligauss unit is used in information for the general public.

Tessellation: The process of dividing an object or surface into geometric primitives (triangles, quadrilaterals, or other polygons) for simplified processing and rendering.

Texel: A textured picture element; the basic unit of measurement when dealing with texture-mapped 3D objects.

Texture: A (2 dimensional) bitmap pasted onto objects or polygons, to add realism.

Texture Filtering: Bilinear or trilinear filtering. Also known as sub-texel positioning. If a pixel is in between texels, the program colours the pixel with an average of the texels' colours instead of assigning it the exact colour of one single texel. If this is not done, the texture gets very blocky up close as multiple pixels get the exact same texel colouring, while the texture shimmers at a distance because small position changes keep producing large texel changes.

Texture Mapping: The application of a bitmap onto a 3D shape to give the impression of perspective and different surfaces. Texture maps can vary in size and detail, and can be 'projected' on to a shape in various different ways: cylindrically, spherically and so on.

Texture Memory: Memory used to store or buffer textures to be mapped on to 3D polygon objects.

TFI: Thin film inductive heads use a minute coil deposited onto a thin film using the photo-etching techniques employed to create integrated circuits; as the magnetic flux of the platter cuts the coil it induces a detectable current.

TFT: Thin-Film Transistor - A technology for building the LCD screens that are commonly found on laptop computers. TFT screens are brighter and more readable than dual-scan LCD screens, but consume more power and are generally more expensive.

Thermal Recalibration: The periodic sensing of the temperature in hard disk drives so as to make minor adjustments to the alignment servo and data platters. In an AV drive, this process is performed only in idle periods so that there is no interruption in reading and writing long streams of digital video data.

Thermal Transfer: A printer technology that uses heat to transfer coloured dye onto paper.

Thermo Autochrome: A print technology which has emerged in digital camera companion printers and which is claimed to produce photographic-quality output on a par with the more well-known dye-sublimation technique.

Thin Film: A type of coating allowing very thin layers of magnetic material used on hard disks and read/write heads. Hard disks with thin film surfaces can store greater amounts of data.

Threaded: Organized according to thread, or line of discussion, in a newsgroup or on a discussion board. A thread is a more or less continuous chain of postings on a single topic.

TiB: Tebibyte: a unit of measure consisting of 1024GiB.

TIFF: Tagged Image File Format: a popular file format for bitmapped graphics that stores the information defining graphical images in discrete blocks called tags. Each tag describes a particular attribute of the image, such as its width or height, the compression method used (if any), a textual description of the image, or offsets from the start of the file to "strips" containing pixel data. The TIFF format is generic enough to describe virtually any type of bitmap generated on any computer.

Time Code: A frame-by-frame address code time reference recorded on the spare track of a videotape or inserted in the vertical blanking interval. It is an eight-digit number encoding time in hours, minutes, seconds, and video frames (e.g.:02:04:48:26).

Time Line: A scale measured in either frames or seconds; it provides an editable record of animation events in time and in sequence.

TLB: Translation Lookaside Buffer: a small piece of associative memory within a processor which caches part of the translation from virtual addresses to physical addresses. Such translations can often be very large and complex and the data structures that implement them too large to store efficiently on the processor. Instead, a few elements of the translation are stored in the TLB, which the processor can access extremely quickly. If a required translation for a particular virtual address is not present in the TLB the address will be resolved using the more general mechanism. Also referred to as Address Translation Cache.

TN: Twisted Nematic: the first LCD technology. It twists liquid crystal molecules 90 degrees between polarises. TN displays require bright ambient light and are still used for low-cost applications.

TOC: Table Of Contents: shows the number of tracks, their starting locations, and the total length of the data area of the disc.

Token Ring: A local area network (LAN) technology developed by IBM (IEEE 802.5). Packets are conveyed between network end stations by a token moving continuously around a closed ring that uses twisted wire cable to connect nodes.

Tone Dialling: One of two methods of dialling the telephone. (The other is pulse dialling.) With tone dialling, the modem sends tones of different frequencies to represent the telephone numbers. Tone dialling is normally associated with push-button (touch-tone) phones and is also called Dual Tone Multi-Frequency (DTMF) dialling.

Tonal Resolution: The number of bits per pixel used in the digital representation of an image. The intensity and colour of each pixel in the image are represented by an integer value or set of integer values. Tonal resolution is a measure of a scanner's resolution capability for small changes in intensity. Also called pixel depth or bit depth.

Toner: A special type of ink used by copy machines and laser printers. Toner consists of a dry, powdery substance that is electrically charged so that it adheres to a drum, plate, or piece of paper charged with the opposite polarity.

Toolbar: Icons grouped together within a program, usually in a strip across the top of the window. Each toolbar icon provides a shortcut to one of the programs commands or features such as help or a website link.

Topology: The pattern of interconnection between nodes in a communications network.

Toslink: A fibre optic digital audio connection used to connect a digital source component (e.g., DVD player, CD player, etc.) to a receiver or pre-amplifier. By passing the "raw" digital audio signal using laser (light) pulses, interference and degradation are minimised. The means of interconnect used for connecting MiniDisc players to stereos and certain sound cards.

TPI: Tracks Per Inch: the number of tracks written within each inch of a storage medium's recording surface. In the context of hard disk drives, EIDE drives generally have a higher TPI than SCSI drives. Also referred to as Track Density.

Track: Sub-division of the recording area of storage media, such as magnetic disks, optical discs and magnetic tape.

Track At Once: A writing mode that allows a session to be written in a number of discrete write events, called tracks. The mode mandates a minimum track length of 300 blocks (4 seconds), which equates to around 700KB, and a maximum of 99 tracks per disc. The disc may be removed from the writer and read in another writer before the session is fixated.

Track MultiSession: This write mode is very similar to Track At Once. In the Multisession environment, each "session" must contain at least one track. Again, the size of the track must be at least 300 blocks. Track Multisession mode allows tracks to be incrementally added to a disc (this should not to be confused with Incremental Writing). Each session will take up about 13.5MB of disc space in overhead; the so-called Lead-in and Lead-out areas.

Transceiver: A term used to describe a combination of transmitter and receiver. In the context of networking, a transceiver is an electronic interface or adapter between the Ethernet coaxial cable and the drop cable that attaches to network devices to provide the drive, reception, and collision detection between physical network media.

Transfer Rate: The rate at which the disk drive sends and receives data from the controller. The sustained transfer rate includes the time required for system processing, head switches, and seeks, and accurately reflects the drive's true performance. The burst mode transfer rate is a much higher figure that refers only to the movement of data directly into RAM.

Transparency: The quality of being able to see through a material. The terms transparency and translucency are often used synonymously; however, transparent would technically mean "seeing through clear glass," while translucent would mean "seeing through frosted glass."

Transistor: One of the most important inventions in history, the transistor can be found in nearly every common electronic device manufactured today--radios, TV sets, cellular phones, computers, and so on. Originally created in the late 1940s by Bell Labs, the transistor was hailed as a smaller, less-expensive, and cooler-running replacement for the vacuum tubes then commonly used to amplify current in electronic devices. Today, millions of transistors are often packed into silicon chips to create the processors used in modern computers.

Trapezoidal Distortion: A type of geometric distortion where the vertical edges of an image slant inwards towards the top horizontal edge. Also called keystone distortion.

Trichromatic: The technical name for RGB representation of colour to create all the colours in the spectrum.

True Black: Black produced by a separate black ink rather than the "composite black" produced from a mixture of cyan, magenta and yellow. See also Composite Black.

True Colour: The ability to generate 16,777,216 colours (24-bit colour).

TruForm: Found only in ATi's Radeon 8500 series and above, TruForm allows for the GPU to draw many more triangles for objects on the screen without a performance hit. This allows for rendered objects to have a more realistic look to them since curves and such will be smoother.

TWAIN: The interface used by a input device such as a scanner to import images (generally graphics) into the computer.

Tweening: Also known as in-betweening; calculating the intermediate frames between two keyframes to simulate smooth motion.

Twisted Pair: Two insulated wires, usually copper, twisted together and often bound into a common sheath to form multi-pair cables. In ISDN, these cables are the basic path between a subscriber's terminal or telephone and the PBX or the central office.

UART: Universal Asynchronous Receiver Transmitter: the chip that drives a serial port. IBM chose the National INS8250, better known simply as "the 8250", for the serial ports in its original PC. The subsequent 16550 UART provided support for speeds of 9,600 bps and greater.

UDF: Universal Disk Format: a file system for optical media developed by the Optical Storage Technology Association (OSTA). It was designed for read-write interoperability between all the major operating systems as well as compatibility between re-writable and write-once media. The standard allows for efficient recording of small packages of data, using incremental packet writing.

UDMA: Ultra Direct Memory Access - UDMA defines a new protocol for the interface between the hard drive and the computer. It improves upon the ATAPI/EIDE standard by doubling data transfer rates to 33MB/sec, which translates into faster disk reads and writes. For users to take advantage of UDMA, both their system and hard drive must support the protocol. UDMA retains backwards compatibility for previously existing hardware.

Ultra DMA: A hard drive protocol which doubled the previous maximum I/O throughput to 33 MBps.

ULSI: Ultra Large Scale Integration: more than one million transistors on a chip.

UMTS: Universal Mobile Telecommunications System: a 3G standard, being developed under the auspices of ETSI, and intended mainly for the evolution of GSM networks.

Unbalanced Pin: Describes concave and convex lines on opposite sides of the screen.

Underrun: The condition occurring when the rate at which data is transmitted to a receiving device is insufficiently fast to avoid the device going into a "wait" state. Buffer underrun is best known in the context of CD recording, where if a recorder's buffer becomes completely emptied, the recordable CD is irretrievably damaged. See also Overrun.

Unformatted Capacity: The total number of usable bytes on a disk, including the space that will be required later to record location, boundary definitions, and timing information. See also formatted capacity.

UNIX: A computer operating system, popular with high-end computer users, academics and the research community. Most hosts connected to the Internet run UNIX.

Unzip: To decompress a file that has been compressed using the zip format. Tools like WinZip or WinRar can extract these.

Uplink Port: Special port on a hub or switch that connects to another hub or switch to expand port density.

Upload: The process of transferring information from one computer to another, generally from a client to a server. For example, you upload a file from your computer to another.

URL (Universal Resource Locator): The specific path to a World Wide Web file, including filename and extension.

USB: Universal Serial Bus - High speed plug and play standard that supports data transfer rates of 12 Mbps. A single USB port can be used to connect up to 127 peripheral devices, such as mice, modems, and keyboards. USB also supports Plug-and-Play installation and hot plugging.

USB-IF: USB Implementers Forum: a non-profit corporation founded by the group of companies that developed the Universal Serial Bus specification to provide a support organization and forum for the advancement and adoption of USB technology. The Forum facilitates the development of high-quality compatible USB peripherals (devices), and promotes the benefits of USB and the quality of products that have passed compliance testing.

Usenet: Usenet is a worldwide network of thousands of Unix systems with a decentralized administration. The Usenet systems exist to transmit postings to special-interest newsgroups covering just about any topic you can imagine (and many you wouldn't even want to imagine).

UTP: Unshielded Twisted-Pair: a four-pair wire medium used in a variety of networks. UTP does not require the fixed spacing between connections that is necessary with coaxial-type connections. See also STP.

UTRAN: UMTS Terrestrial Radio Access Network: the name of the WCDMA radio network in UMTS.

UV Light: Ultraviolet Light has very short wavelengths and is just beyond the violet end of the visible spectrum. It is used to expose patterns on the layers of the microprocessor in a process much like photography.

UXGA: Ultra XGA: a screen resolution of 1600x1200 pixels.

V.34: An ITU modem standard for data transmission at up to 33.6 Kbit/s. V.34 is the successor to several earlier ITU standards, and most V.34 modems can interoperate with older, slower modems.

V.90: An ITU's modem standard, agreed on 4 February 1998, which brought to an end a year-long 56 Kbit/s standards battle between the rival proprietary X2 and K56Flex standards.

VAR: Value Added Reseller: a company which resells hardware and software packages to developers and/or end-users.

VBR: Variable Bit Rate: maximum throughput set in advance, but data not always sent evenly.

VCR: Video Cassette Recorder: a videotape recording and playback machine that is available in several formats. Sony's Beta tape was the first VCR format, but is now defunct. VHS 1/2in tape is the most commonly used format. Although VCRs are analogue recording machines, adapters allow them to store digital data for computer backup. See also VHS.

VDI: Video Device Interface: a software driver interface that improves video quality by increasing playback frame rates and enhancing motion smoothness and picture sharpness. VDI was developed by Intel and will be broadly licensed to the industry.

VDRV: Variable Data Rate Video: in digital systems, the ability to vary the amount of data processed per frame to match image quality and transmission bandwidth requirements. DVI symmetrical and asymmetrical systems can compress video at variable data rates.

Vector Graphics: Images defined by sets of straight lines, defined by the locations of the end points.

Veronica: The Very Easy Rodent-Oriented Net-wide Index to Computerized Archives is a service that's built into Gopher. Veronica allows you to search all Gopher sites for files, directories and other resources.

Vertex: A dimensionless position in three- or four-dimensional space at which two or more lines (for instance, edges) intersect.

VESA: Video Electronic Standards Association - This industry organization formed to create various personal computer standards, including those for Super VGA video displays and the VLB bus standard.

VFAT: Virtual File Allocation Table: the 32-bit file system that Windows 95 uses to manage information stored on disks. An extension of the FAT file system, VFAT supports long filenames and 32-bit Protected Mode access while retaining compatibility with FAT volumes.

VfW: Video for Windows: a standard established by Microsoft for the integration of digital video, animation and sound which uses the .AVI file format. The necessary software drivers are incorporated into the Windows operating system.

VGA: Video Graphics Array: also referred to as Video Graphics Adapter. VGA quickly replaced earlier standards such as CGA (Colour Graphics Adapter) and EGA (Enhanced Graphics Adapter) and made the 640x480 display showing 16 colours the norm. Other manufacturers have since extended the VGA standard to support more pixels and colours. See also SVGA.

VGA Feature Connector: A standard 26-pin plug for passing the VGA signal on to some other device, often a video overlay board. This feature connector cannot pass the high-resolution signal from the card and is limited to VGA.

VHS: A VCR format introduced by JVC in 1976 to compete with Sony's Beta format. VHS subsequently become the standard for home and industry, and Beta became obsolete. S-VHS (Super VHS) is a subsequent format that improves resolution.

VidCap: Microsoft's Video For Windows program to capture video input to RAM or hard disk memory.

Video1: The default video compression algorithm in Microsoft's Video for Windows. Can produce 8- or 16-bit video sequences.

Video Capture: Performed by an expansion board that digitises full-motion video from a VCR, camera or other video source. The digital video is then stored in a compressed format on hard disk.

VideoCD: Format that allows the viewing of MPEG-1 (also known as the ISO IEC 11172 compression standard) video on CD-ROM. Originally devised by Philips, it allows for more than an hour of compressed video, the audio also being compressed and giving hi-fi standard. The whole point of VideoCD is cross-platform compatibility. The discs should work on suitably equipped PCs, Macs, dedicated VideoCD players, and CD-i systems. Video CD is based on the White Book standard developed by Philips and other industry leaders. Also referred to as VCD.

Video Mapping: A feature allowing the mapping of an AVI, MPEG movie or animation on to the surface of a 3D object.

Video Memory: The graphics card RAM used in the frame buffer, the Z-buffer and, in some 3D graphics cards, texture memory. Common types include DRAM, EDO DRAM, VRAM and WRAM.

Video Scaling and Interpolation: When scaled upwards, video clips tend to become pixelated, resulting in block image. Hardware scaling and interpolation routines smooth out these jagged artefacts to create a more realistic picture. Better interpolation routines work on both the X and Y axis to prevent stepping on curved and diagonal elements.

Virtual Desktop: When a graphics card is capable of holding in its memory a resolution greater than that being displayed on the screen, the monitor can act as a 'window' onto the larger viewing area which may be panned across the "desktop".

Virtual Image: A database of files to be written to CD, created by dragging and dropping files into the main window. Can be used to write directly to CD, or to master a real ISO 9660 image to hard disk.

Virtual Memory: Virtual memory is really a part of your hard disk called a swap file, dedicated as a storage area for bits of data in RAM that aren't being used much. By freeing up RAM, you're virtually increasing the amount of working memory available to you.

Virtual Reality: Technology that allows the user to experience 3D interaction with the computer. Some VR systems may incorporate special visors, helmets, gloves, and special 3D graphics technology to simulate the real world environment.

Virus: A program or piece of code that uses various techniques for duplicating itself and travelling between computers. Viruses vary from harmless nuisances to serious problems that can cause millions of dollars' worth of damage. A virus is often designed so that it is automatically spread to other computer users. Viruses can be transmitted as attachments to an e-mail or files, for example.

VLB: VESA Local Bus or VL-Bus: the 32-bit local-bus standard created by the Video Electronics Standards Association (VESA) to provide a fast data connection between CPUs and local-bus devices. The VL-Bus was widely used in 486 PCs, but has since been replaced by the Intel PCI Bus.

VLSI: Very Large Scale Integration: the process of placing hundreds of thousands (between 100,000 and one million) of electronic components on a single chip. Nearly all modern chips employ VLSI architectures, or ULSI (ultra large scale integration).

VM Channel: Vesa Media Channel, VESA's video bus which avoids the main system bus.

VOB: Video Object File: the file format and extension specified for DVD-Video used files - such as DVD movies - that contains MPEG video, audio and navigation data.

Voice Coil: A fast and reliable actuator motor that works like a loudspeaker, with the force of a magnetic coil causing a proportionate movement of the head. Voice coil actuators are more durable than their stepper counterparts, since fewer parts are subject to daily stress and wear and also provide higher performance.

VoIP: Voice over IP: The technology used to transmit voice conversations over a data network using the Internet Protocol. The data network involved might be the Internet itself, or a corporate intranet, or managed networks used by local or long distance carriers and ISPs. The technique promises drastically reduced costs to carriers and therefore prices to end users. Also referred to as IP Telephony.

Volatile Memory: Memory that loses its contents when the power is turned off. A computer's main memory, made up of dynamic RAM or static RAM chips, loses its content immediately upon loss of power. Contrast ROM, which is non-volatile memory.

Volume: A logical division of data, comprising of a number of files. In the context of hard disk drives, a volume is formatted by using a file system - such as FAT or NTFS - and has a drive letter assigned to it. A single hard disk can have multiple volumes and, unlike partitions, volumes can span multiple disks. Under the ISO 9660 standard, a "volume" refers to a single CD-ROM disc.

Volume Descriptors: In ISO 9660, a set of information on the disc containing vital information about the CD and how the computer should read it.

VPN: Virtual Private Network - A Virtual Private Network, or VPN, is a private network of computers that's at least partially connected by public phone lines. A good example would be a private office LAN that allows users to log in remotely over the Internet (an open, public system). VPNs use encryption and secure protocols like PPTP to ensure that data transmissions are not intercepted by unauthorized parties.

VR (Virtual Reality): A simulated three-dimensional environment, displayed in real time with interactive capabilities. VR applications have been developed for the World Wide Web, although the technology is still at an early stage.

VRAM: Video Random Access Memory: a dual-ported DRAM designed for graphics and video applications. One port provides data to the CRT, while the other is used for read/write transfers from the graphics controller. See also WRAM.

VRM: Voltage Regulator Module: used to absorb the voltage difference between a CPU which may be added in the future and the motherboard.

VRML (Virtual Reality Mark-up Language): Protocol language which allows 3-D representation of graphics. Chat rooms are increasingly using VRML to represent chatters graphically with avatars.

VUMA: VESA Unified Memory Architecture: a standard which establishes the electrical and logical interface between a system controller and an external VUMA device enabling them to share physical system memory.

W3: An acronym for the World Wide Web.

Wafer Fab: Also known as a semiconductor fabrication plant, this is where all of a semiconductor's electronic components are interconnected onto a single die of silicon.

WAIS (Wide Area Information Search): Software that is used to index large text files in servers. On the client side, it finds and retrieves documents in databases, based on user defined words.

WAN: An acronym for Wide Area Network. A larger computer network that is geographically dispersed, such as one that stretches across a large company or global sites like the Microsoft Corporation.

WAP: Wireless Application Protocol: a protocol that enables Internet services to be delivered to small-screen mobile devices. The application via which WAP-enabled devices access Web content is referred to as a "micro-browser".

Watermark: A background image. Typically used to decorate and identify pages in a Web site, a watermark remains stationary as the page scrolls.

WAV: Waveform Audio: the native digital audio format used in Windows. WAV files use the .wav file extension and allow different sound qualities to be recorded. Either 8-bit or 16-bit samples can be taken at rates of 11025Hz, 22050Hz and 44100Hz. The highest quality (16-bit samples at 44100Hz) uses 88KB of storage per second.

Wave Table Synthesis: A common method for generating sound electronically on a PC. Output is produced using a table of sound samples -actual recorded sounds - that are digitised and played back as needed. By continuously rereading samples and looping them together at different pitches, highly complex tones can be generated from a minimum of stored data without overtaxing the processor.

WCDMA: Wideband Code Division Multiple Access: a 3G wideband radio technique which makes highly efficient use of radio spectrum and is capable of supporting data rates of up to 2 Mbit/s, sufficient to allow simultaneous access to several voice, video and data services at once.

Web: see World Wide Web (WWW).

Web Browser: A client application that fetches and displays Web pages and other WWW resources to the user. The most popular browsers are Microsoft's Internet Explorer and Netscape's Navigator.

Web Page: A single screen (document) on a Web site.

Web Site: The location of published hypertext content. Physically, a Web site can occupy an entire Web server or a part of a server; or it can be spread out among different servers as long as its sections are all linked, directly or indirectly, to the same home page.

WECA: The Wireless Ethernet Compatibility Alliance is a non-profit international association formed in 1999 to certify interoperability of wireless Local Area Network products based on IEEE 802.11 specification.

WEP: Wired Equivalent Privacy data encryption is defined by the 802.11 standard to prevent access to the network by "intruders" using similar wireless LAN equipment and capture of wireless LAN traffic through eavesdropping. WEP allows the administrator to define a set of respective "Keys" for each wireless network user based on a "Key String" passed through the WEP encryption algorithm. Access is denied by anyone who does not have an assigned key.

White Book: The White Book defines the VideoCD specification. First published in 1993.

White Point: The colour that when scanned produces values of 255, 255, 255 in an 8-bit scanner. Ideally the white point is 100% neutral reflectance or transmittance. See also Reflectance.

Wi-Fi: Branding that denotes products that have been certified as being interoperable. The scheme was originally operated by WECA - the Wireless Ethernet Compatibility Alliance - and applied to products conforming to the IEEE 802.11b wireless networking standard. WECA was subsequently renamed the Wi-Fi- Alliance and the brand applied also to IEEE 802.11a products.

Winchester Disk: The term "Winchester" comes from an early type of disk drive developed by IBM that stored 30MB and had a 30-millisecond access time; so its inventors called it a Winchester in honour of the .30-calibre rifle of the same name. Although modern disk drives are faster and hold more data, the basic technology is the same, so "Winchester" has become synonymous with "hard".

Wireframe: All 3D models are constructed from lines and vertices forming a dimensional map of the image. Then texture, shading or motion can be applied. Also referred to as Polygon Mesh.

WLAN: Wireless LAN: a local area network that transmits over the air typically in an unlicensed frequency such as the 2.4GHz band. Wireless access points (base stations) are connected to an Ethernet hub or server and transmit a radio frequency over an area of several hundred to a thousand feet which can penetrate walls and other non-metal barriers.

WMF: Windows Meta File: a vector graphics format used mostly for word processing clip art.

WML: Wireless Markup Language: XML is a meta-language defined by the World Wide Web Consortium. This means that it is a series of rules for how to create other languages for specific applications. Content is not directly encoded in XML, but in a specific markup language defined using XML. WML is an example of a specific language for wireless applications that is fully compliant with XML's rules. WML is thus an XML application.

Wobble Groove: Refers to the undulating "wobble" signal moulded into the pre-grooved spiral track on recordable DVD media which is used to guide the recording laser beam during the writing process.

Worm (Write Once Read Many): An optical disk technology that allows the drive to store and read back data but prevents the drive from erasing information once it has been written.

WOSA: Windows Open Services Architecture: a collection of APIs that provide standard ways for Windows applications to access databases, telephony devices, messaging services, and other services. ODBC and MAPI are two examples of APIs that fall under the WOSA umbrella.

WPS: Windows Print System: the scheme supported by Windows 95 in which the operating system spools data from an application in Enhanced Metafile Format (EMF), instead of raw printer data. The spooler interprets the data in the background and then passes appropriate commands to the printer. Like with GDI, all the processing is done on the PC.

WRAM: Windows Random Access Memory: a form of VRAM used exclusively by Matrox Graphics. WRAM has added logic designed to accelerate common video functions such as bit-block transfers and pattern fills. It can substantially speed up certain graphical operations such as video playback and screen animation.

Write Back: Data written into the cache by the CPU is not written into main memory until that data line in the cache is to be replaced. Also referred to as Copy Back.

Write Direct: The data referenced in a virtual image are written directly to the CD without first writing a real ISO 9660 image. This is temporarily written to the hard disk. Also referred to a on-the-fly.

Write First To HD: Everything is written to the hard disk first. Contrast it to Write Direct. Also called ISO image.

Write Through: A technique for writing data from the CPU simultaneously into the cache and into main memory to assure coherency.

WWW (World Wide Web): An acronym for the World Wide Web. The WWW is a hypermedia retrieval system for information. The newest medium of the Internet. Based on hypertext, the Web provides a quick and easy method of delivering and receiving information files which are read by a browser. The Webs ability to transfer files containing not just text but also graphics, sound, and video makes it the most versatile of all the Internet services.

WYSIWYG (What You See Is What You Get): Pronounced "wizzywig," it is a generic term meaning what you see on your screen is what is going to print out on your printer.

X.10: A communications protocol for remote control of electrical devices designed for operation over standard household electrical wiring. It transmits data using Amplitude Modulation.

X.25: An ITU standard for packet-switching networks approved in 1976, X.25 defines layers 1, 2, and 3 in the OSI Reference Model. Such networks are widely used for point of sale (POS) terminals, credit card verifications and automatic teller machine (ATM) transactions. New packet-switched networks employ frame relay and SMDS technologies rather than X.25.

X2: Technology developed by U.S. Robotics for achieving modem transmissions at close to 56 Kbit/s over ordinary phone lines. See also K56flex.

X-direction Sampling Rate: A scanner's sampling rate in the horizontal direction (across the page). The x-direction sampling rate is determined by the number of CCD elements in the CCD array.

xDSL: Digital Subscriber Line: it shares the same phone line that the telephone service uses, but because it uses a different part of the phone line's bandwidth, it does not interfere with normal phone service. This is possible because there is a significant amount of unused capacity in current phone wires. The technology will allow subscribers to hook up DSL modems to a local Internet Service Provider (ISPs) and still be able to talk on the phone - all using the same phone line. The "x" represents a variety of possible methods and information rates that can be handled through DSL.

XG: Yamaha's extension of General MIDI that provides many instrument variations and more digital effects. Many instrument parameters can be controlled in real-time.

XGA: eXtended Graphics Array: also referred to as Extended Graphics Adapter. An IBM graphics standard introduced in 1990 that provides screen pixel resolution of 1024x768 in 256 colours or 640x480 in high (16-bit) colour. It subsequently came to be used to describe cards and monitors capable of resolutions up to 1024x768, regardless of the number of colours available.

Xmodem: This is a protocol for transferring files during direct dial-up communications. Developed by Ward Christensen in 1977, Xmodem has basic error checking to ensure that information isn't lost or corrupted during transfer; it sends data in 128-byte blocks. Xmodem has undergone a couple of enhancements: Xmodem CRC uses a more reliable error-correction scheme, and Xmodem-1K transfers data faster by sending it in 1,024-byte blocks.

XON/XOFF: A way of controlling the flow of data between a modem and its host computer and between two modems, also called software flow control. XON stands for "Transmitter On" and XOFF stands for "Transmitter Off". If the modem receiving data needs time to process the data or do some other task, it sends an XOFF signal to the host computer (or sending modem). The host computer (or sending modem) then waits until it receives an XON signal before sending more data.

X Windows Protocol: A network terminal standard developed at MIT that enables a user to run and display multiple network applications at the same time.

XYZ Planes: The three dimensions of space; each is designated by an axis. The x- and y-axes are the 2D co-ordinates, at right angles to each other. The z-axis adds the third dimension. Z-buffers accelerate the rendering of 3D scenes by tracking the depth position of objects and working out which are visible and which are hidden behind other objects.

Y-direction Sampling Rate: A scanner's sampling rate in the vertical direction (down the page). The y-direction sampling rate is determined by the mechanical motion of the scanner's carriage as it moves down the page. Some scanners vary the y-direction sampling rate in steps of lines pairs per inch (Lppi), offering more sampling rates to scale a document. Scanners with fixed, y-direction sampling rates offer fewer sampling rates or use interpolation, line dropping, or line replication to supply more sampling rates.

YCrCb: The colour space used in the CCIR601 specification. Y is the luminance component, and the Cr and Cb components are colour difference signals. Cr and Cb are scaled versions of U and V in the YUV colour space.

Yellow Book: The book which sets out the standard developed by Philips and Sony for the physical format of compact discs to be used for information storage - CD-ROM.

YIQ: The colour space used in the NTSC colour system. The Y component is the black-and-white portion of the image. The I and Q parts are the colour components; these are effectively nothing more than a "watercolour wash" placed over the black and white, or luminance, component.

Ymodem: This is a protocol for transferring files during direct dial-up communications. So named because it builds on the earlier Xmodem protocol, Ymodem sends data in 1,024-byte blocks and is consequently faster than Xmodem. However, it doesn't work well on noisy phone lines, unlike its successor, Zmodem. Ymodem has undergone a few enhancements: Ymodem-Batch can send several files in one session; Ymodem-G drops software error correction, which speeds up the process by leaving hardware-based error correction in modems.

YUV: A colour encoding scheme for natural pictures in which luminance and chrominance are separate. The human eye is less sensitive to colour variations than to intensity variations. YUV allows the encoding of luminance (Y) information at full bandwidth and chrominance (UV) information at half bandwidth. YUV is used by the PAL colour system.

Z-buffer: In a graphics card, this section of video memory keeps track of which onscreen elements can be viewed and which are hidden behind other objects.

ZIF: Zero Insertion Force: a socket allows a processor to be upgraded easily and without the need for specialist tools. It clamps down on the microprocessor pins using a small lever located to the side of the socket. Socket 5 and Socket 7 are common types of ZIF socket.

Zine: Electronic magazines, published on the Internet.

Zmodem: This file transfer protocol should be your first choice for sending and receiving files using dial-up connections. Zmodem's speed and error checking recommend it, and it can resume a file transfer after a break in communications, so make sure this protocol is available in your communications software and any BBS you dial into. In case you couldn't tell, it's so named because it's intended to supersede Xmodem and Ymodem.

Zones: Because outer tracks are longer than inner tracks they can store more data; consequently disks are divided into zones, each zone having a certain number of sectors per track.

100Base T: 100 Mbps Ethernet. There are three types of physical wiring that can carry signals: 100BASE-T4, 100BASE-TX, and 100BASE-FX. This designation is an IEEE shorthand identifier. The "100" in the media type designation refers to the transmission speed of 100 Mbps. The "BASE" refers to baseband signalling, which means that only Ethernet signals are carried on the medium. The "T4," "TX," and "FX" refer to the physical medium that carries the signal.

10Base T: The most widely installed Ethernet local area networks use ordinary telephone twisted-pair wire. When used on Ethernet, this carrier medium is known as 10BASE-T. 10BASE-T supports Ethernet's 10 Mbps transmission speed.

3D Accelerator: Referring to the graphics cards or video card, today's video cards also incorporate some form of 3D acceleration, rendering images faster then the CPU would by itself.

3D API: 3D Application Programming Interface - This generic term refers to any API that supports the creation of standard 3D objects, lights, cameras, perspectives, and so on. Such APIs include Argonaut's BRender and Microsoft's Reality Lab.

802.11: 802.11 refers to a family of specifications developed by the IEEE for wireless LAN technology. 802.11 specifies an over-the-air interface between a wireless client and a base station or between two wireless clients. The IEEE accepted the specification in 1997.