M

MAPI
Messaging Application Programming Interface Microsoft and other companies developed MAPI (pronounced "mappy") to enable Windows apps to access a variety of messaging systems, from Microsoft Mail to Novell's MHS.

mbps
megabits per second This abbreviation is used to describe data transmission speeds, such as the rate at which information travels over the Internet. Several factors can influence how quickly data travels, including modem speeds, bandwidth capacity, and Internet traffic levels.

MCA - Micro-channel architecture A bus architecture developed by IBM for its PS/2 computers. Designed for multiprocessing, MCA can function as a 16-bit or a 32-bit bus. It is incompatible with the original ISA bus. Although it was intended to replace ISA, the bus was never widely adopted and was largely overshadowed by the EISA bus, a 32-bit bus that worked with ISA cards.

megabyte                                                                                                                                                                                                                                                                                                                                                                                                               Although mega is Greek for a million, a megabyte actually contains 1,048,576 bytes (1,024 x 1,024 bytes). In other words, a million bytes is actually less than a megabyte.

memory bandwidth                                                                                                                                                                                            Generally, bandwidth refers to data-carrying capacity and is expressed in cycles per second or Hertz (Hz). In the case of RAM, bandwidth is a function of its rated speed and the size of its data path.

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

MHz
megahertz  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, the small computer chip that handles data-related tasks.

Microprocessor                                                                                                                                                                                                     The microprocessor handles the logic operations in a computer, such as adding, subtracting, and copying. A set of instructions in the chip design tells the microprocessor what to do, but different applications can give instructions to the microprocessor as well.

middleware                                                                                                                                                                                                                                                                                                                                                                                                           This software manages the communication between a client program and a database.

MIDI
musical instrument digital interface  Pronounced "middy," this connectivity standard enables to hook together computers, musical instruments, and synthesizers to make and orchestrate digital sound.

millisecond - A millisecond is one-thousandth of a second.

MIME
multipurpose Internet mail extensions It's a way to extend the power of Web browsers to handle graphics, sound, multimedia--anything but text. (Remember, HTML handles nothing but text--everything else is an extension.) MIME is also used for binary email attachments.

MIP                                                                                                                                                                                                         mapping This sophisticated texturing technique is used for 3D animation in games and CAD walk-throughs.

MIPS
millions of instructions per second  Used as a measure of how powerful computer is, MIPS gauge the capability of system to handle instructions.

mirror server                                                                                                                                                                                                                                                                                                                                                                                          Sometimes a Web server will receive more traffic than it can handle. When this happens, the server's administrator may add extra servers--containing identical data--to accommodate the flow. These duplicates are called mirror servers.

mirror site                                                                                                                                                                                                                                                                                                                                                                                                  Because the Internet population has exploded in recent years, a lot of archive servers can't cope with the load. One solution is to create an exact copy of a server--a process called mirroring. Mirror sites divert some of the traffic from the original site.

MMX
multimedia extensions  In late 1996, in an effort to capitalize on the expanding market for multimedia applications, Intel unveiled an enhanced version of its Pentium microprocessor. These MMX processors contain additional instructions, or commands, and other enhancements specifically designed to handle sound, video, and graphics chores.

modem                                                                                                                                                                                                                                                                                                                                                                                                                          A modem is an external box or internal circuitry that converts computer data into sound that can be transmitted over phone lines.

modulation - Modulation refers to the process of encoding digital data into analog signals for transmission.                                                                                                                                            

moiré pattern - Moiré describes the interference pattern you see when, for instance, someone on TV is wearing a herringbone jacket. In images of closely spaced lines or other finely detailed patterns, these ripples or waves appear on color monitors as well as in scanned images. Some monitors and scanners tend to exhibit more moiré patterns than others.

Moore's law - More than 25 years ago, when Intel was developing the first microprocessor, company cofounder Gordon Moore predicted that the number of transistors on a microprocessor would double approximately every 18 months. To date, Moore's law has proven remarkably accurate.

Motherboard - The motherboard is the largest printed circuit board in the computer. It generally houses the CPU chip, the controller circuitry, the bus, and sockets for additional boards, which are called daughter boards.

Mozilla - The original name for Netscape's Navigator browser through version 1.1. Netscape "hacker" Jamie Zawinski claims credit for the name, while artist Dave Titus turned Mozilla into Netscape's original mascot.

MP3
MPEG-1, Layer 3  MP3 is a codec that compresses standard audio tracks into much smaller sizes without significantly compromising sound quality.

MPEG
Moving Pictures Experts Group  MPEG is a standard for compressing sound and movie files into an attractive format for downloading--or even streaming--across the Internet.

MPPP
multilink point-to-point protocol  This is a standard communications protocol used over ISDN to bond separate data-carrying B channels together to transfer data effectively through a larger "pipe." Just as they can under PPP, dissimilar devices can communicate over multilink PPP connections to access the Internet. MPPP also allows both channels to be used for either voice or data transmissions and supports dynamic bandwidth allocation. This means that one of the two channels can be automatically dropped and reallocated for a phone call when calls come in. Once a call has been completed, the channel can be reconnected to continue data transfer over MPPP.

MPP
Multi-Purpose Plenum A kind of cable that is legally approved to be installed in the plenum (the space between a ceiling and the floor above it) in a building. The cable is coated so it won't give off toxic fumes if it burns.

MPR II - The Swedish MPR II standard was developed in response to health concerns about electromagnetic fields given off by monitors. Though these emissions have not been proven harmful to humans, the Swedish government established the stringent standard just in case. MPR II compliance means that a monitor has been tested and shown to have low emissions.

MR
modem ready  This modem light tells you that your modem is on and ready.

MUD
Multiple-User Dimension  Originally known as a Multi-User Dungeon, a MUD is a text-based virtual environment in which users' "characters" interact in real time. Characters can navigate rooms described by text; type to other characters; create shared objects; and engage in games, puzzles, or combat.

multicasting - When you send out data (like television or radio programming) to anyone who cares to tune in, it's broadcasting. When you send out data (such as your voice on a Web phone) to a few receivers you've identified and selected, it's called multicasting.

multiscanning - Multiscanning describes a type of computer monitor that adjusts itself to accommodate signals from different classes of video boards.

Multisession - A feature of many CD-R drives and discs that enables you to add data to a CD-ROM on different occasions. This is an improvement over older CD-Rs, which required you to burn all your data onto the disc at once.

MultiSync - A trademark of NEC, the term MultiSync is widely used (without the capitalization) to describe a monitor that adjusts its scanning rate to accommodate signals from different classes of video graphics boards.

N

NAK
negative acknowledgement  When a modem receives a data packet, it sends back a signal to the sending modem. If everything is in order, the signal is an ACK, or acknowledgement. If some of the data is missing or corrupt, the modem sends back a negative acknowledgement, or NAK, which acts as a request to resend the data.

NC
network computer  This technical-sounding term actually describes a consumer product that could find a mass market. In early 1996, Larry Ellison, CEO of database developer Oracle, called for the development of a less than $500 computing device, or "thin client," that could connect to the Internet. In theory, these non-PCs would use the Internet as a vast storage site for data and applications.

NDIS
Network Device Interface Specification  A device driver for the Windows Operating System that allows multiple network protocols to be used simultaneously with one adapter card.

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.

NetWare Created by Novell to run on Intel-based computers, NetWare is the most widely used network operating system on that platform.

NIC
network interface card An adapter card that physically connects a computer to a network cable.

NID
network interface device Most buildings with multiple phone lines will have a phone line junction, which telephone companies commonly call a NID. At private residences, NIDs are typically small gray boxes mounted outside the buildings, with padlocks to prevent unauthorized access. Service representatives can access the boxes without entering the buildings.

NLM
NetWare Loadable Module Drivers and applications that run under Novell's NetWare are referred to as NLMs

NNTP
network news transfer protocol Usenet news articles can't be just posted and accessed willy-nilly, so they conform to this protocol that runs interference between newsreaders and news servers. NNTP dictates the way in which news articles are distributed, queried, retrieved, and posted.

Noninterlaced Monitors paint images on a screen by rapidly and repeatedly sweeping their electron guns from top to bottom and left to right across the screen. A noninterlaced display paints every line on the screen each time it scans from top to bottom. Whenever you can, ensure that your monitor and display hardware deliver a screen that's noninterlaced. Interlacing skips every second line on a first pass and fills them in on a second pass.

NS 16550
National Semiconductor 16550 This is the modern UART chip found in standard PCs. The communications port on the first IBM PC was built around a National Semiconductor UART that could hold only 2 bytes of received data. As modem speeds increased, this limit caused problems (any byte of data received before the 2 bytes were processed would be lost).

NSAPI
Netscape Server Application Programming Interface Netscape's API was designed as a more robust and efficient replacement for CGI.

NT-1
network terminator-1 An NT-1 is an interface box that converts ISDN data into something a PC can understand (and vice versa). It works a little like a cable TV descrambler for ISDN signals, and is often built in to ISDN adapters.

NTFS
NT file system With the introduction of Windows NT, Microsoft replaced the aging MS-DOS FAT file system with a faster, more secure, 32-bit way to provide disk and file access. Unfortunately, NTFS is not compatible with FAT, and only Windows NT can read and write NTFS-formatted drives.

National Television Systems Committee (NTSC) It's true--there was a time when TV was just black and white. Eventually, color TV took over, and the Federal Communications Commission established the NTSC standard of 525 lines of resolution per second for broadcasts in the United States. The NTSC standard combines blue, red, and green signals with an FM frequency for audio.

NuBus interface                                                                                                                                                                                                This standard interface (originally designed by Texas Instruments) is a one-piece socket with two rows of pins made for internal Macintosh cards. NuBus uses onboard ROM to configure itself and has bus-mastering capabilities that allow it to take control of the bus for multiprocessing. Power Macintosh computers now use Intel's superior PCI standard, so NuBus interfaces are usually only seen on older Macs.

null-modem cable A special type of computer cable that lets you hook up two computers to communicate via their serial ports. It's called a "null-modem" cable because it eliminates using modems and phone lines for hooking together nearby computers. Null-modem connections are useful for file transfers, remote control, or special applications like the dual-screen mode of Microsoft's PowerPoint 97.

Nvidia The first of what marketing types are calling the "next generation" of 3D ASICs, Nvidia's approach goes one beyond the standard shading, texture mapping, Z-buffering, and acceleration to include a unique algorithm called quadratic texture mapping. This draws scenery using fewer triangles than other 3D ASICs need, making it easier and faster to render a scene.

O

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. It's often now used as a verb, as in this sentence: "This CD-ROM drive is OEM'd by Mitsumi."

object-oriented A method of software-development that groups related functions and data into reusable chunks. Properly handled, object-oriented programming can reduce development time on new projects.

ODBC
Open Database Connectivity This set of application programming interfaces, created by Microsoft, defines how to move information in and out of any PC database that supports the standard.

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.

OH
off hook OH is a modem indicator light that tells you the phone line is open and ready for communications.

OLE
Object Linking and Embedding Microsoft replaced DDE with OLE, a more robust means of integrating applications. DDE allowed "live links" between copied data in different applications or on different systems, but DDE-enabled applications had to know everything about the data format to work properly.

OMG
Object Management Group Formed in 1989, this consortium of software vendors, developers, and users promotes the use of object-oriented technology in software applications. The group also maintains the CORBA software interoperability standard.

OS
operating system A computer by itself is essentially dumb bits of wire and silicon. An operating system knows how to talk to this hardware and can manage a computer's functions, such as allocating memory, scheduling tasks, accessing disk drives, and supplying a user interface. Without an operating system, software developers would have to write programs that directly accessed hardware--essentially reinventing the wheel with every new program. With an operating system, such as Windows NT or Mac OS 8, developers can write to a common set of programming interfaces called APIs and let the operating system do the dirty work of talking to the hardware.

optical fiber                                                                                                                                                                                                                                                                                                                                                                                                Optical fiber cables consist of thin filaments of glass (or other transparent materials), which can carry beams of light. A laser transmitter encodes frequency signals into pulses of light and sends them down the optical fiber to a receiver, which translates the light signals back into frequencies. Less susceptible to noise and interference than other kinds of cables, optical fibers can transmit data greater distances without amplification.

Orange Book                                                                                                                                                                                                      If you ever record a CD-ROM, you'll be using the Orange Book standard. It's the format that enables CD-R drives to record discs that regular CD-ROM players can read.

out-of-band signaling                                                                                                                                                                                          ISDN normally uses a separate wire called the D channel to do all the call setup and signaling. The existence of this separate telephone network intended specifically for call signaling is called "out-of-band." In other words, the call signaling is done independently of the data-carrying B channels, which allows them to utilize their full 64-kbps bandwidth capability.

Over clocking                                                                                                                                                                                              Sometimes "good enough" isn't. Hardware hackers who feel this way often resort to over clocking to boost the speed of their PCs--changing motherboard settings in order to push components beyond their rated speeds. For instance, a 233-MHz Pentium II processor may be over clocked to run at 266 MHz.

P

packet While it may seem as though you send or receive a continuous stream of data every time you use the Internet, you don't. Instead, data is chopped up into pieces called packets. These packets contain information about which computer sent the data and where the data is going. If a packet runs into a problem during its trip, it can attempt to find another route. When all the packets get where they're going, the recipient computer puts them together again.

PAL                                                                                                                                                                                                           Phase Alternate Line The television broadcast standard throughout Europe (except in France, where SECAM is the standard). This standard broadcasts 625 lines of resolution, nearly 20 percent more than the U.S. standard, NTSC, of 525.

PAP
Password Authentication Protocol If you want to verify a user's name and password for PPP Internet connections, you have two choices: PAP and CHAP. PAP is not as secure as CHAP, since it works only to establish the initial link. PAP is also more vulnerable to attack because it sends authentication packets throughout the network.

parallel port                                                                                                                                                                                                                                                                                                                                                                                                  Look on the back of any PC and you'll see a 25-pin RS-232C connector, better known as a parallel port. Theoretically eight times faster than serial ports, parallel ports are also called the printer ports, since that's what you usually find attached to them (although you can get tape backup units, CD-ROM drives, scanners, and other devices in parallel port format these days).

parity                                                                                                                                                                                                                                                                                                                                                                                                                   This is an obsolete method of detecting communication errors. These days, communication ports are almost always set to No Parity, and the modem's internal error detection and correction are used to provide reliable communication.

parity bit                                                                                                                                                                                                                                                                                                                                                                                                      Because old modems transmitted data one character at a time, each character had to have its own individual error check. The usual rule was to add an extra bit (the parity bit) at the end of each character before the stop bit. This bit would be set to 0 or 1 based on the value of the previous data bits.

Partition                                                                                                                                                                                                        A portion of a hard disk that functions as a separate unit. A single hard disk can be divided into several partitions, each of which functions as a separate drive and has its own volume name (such as D:, E:, F:, and so on). The purpose is to make the drive more efficient, as the computer can search smaller sections for a specific file rather than the entire drive.

passive matrix                                                                                                                                                                                                These basic flat-panel displays are created by laying a layer of liquid-crystal diode elements on top of a grid of wires. By applying current to the various intersections, the diodes can be lit to act as pixels. Passive displays simply apply current to the diodes at a specific refresh rate to maintain an image.

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 If you have a Pentium system, it's extremely likely that it runs a self-configuring PC local bus called PCI. Designed by Intel, PCI has gained wide acceptance (even by Apple, in its PowerPC series). It beats out the VESA Local Bus spec from a technical standpoint and will presumably win out in the long run.

 PCMCIA
Personal Computer Memory Card International Association This serious mouthful of acronym stands for the name of a trade association founded in 1989 to establish standards for expansion cards for portable computers. The PCMCIA's 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.

PCM
pulse code modulation Sound is analog, and computers are digital. So for a computer (and that includes CD and DAT players) to deal with sound, the sound needs to be digitized. The most common technique for doing so is pulse code modulation.

PCS
Personal Communications Services A generic description of cellular communications services that combine voice, data, and paging features into a single device. The GSM and CDMA digital cellular standards can both be used for PCS.

PCX                                                                                                                                                                                                             This PC graphics format, developed by Zsoft for its pioneering DOS-based paint program PC Paintbrush, was the de facto standard for bitmapped graphics before Windows took hold.

PDF
Portable Document Format This Adobe technology is a popular way of formatting documents in such a way that they can be viewed and printed on multiple platforms using the freely available Adobe Acrobat reader.

PDP
Programmed Data ProcessorIn the '60s and '70s before it developed the VAX minicomputer, Digital Equipment Corporation sold and maintained several lines of minicomputers under the PDP label. The best-known families in the PDP line were the PDP-10 and PDP-11

PDP
Plasma display panel These futuristic displays send an electrical current through thousands of tiny sealed gas packets (usually housing a mixture of xenon and neon). They require little space and are generally used in flat-panel TVs.

Perl
practical extraction and report language The programming language of choice for writing Web server applications Perl is used for creating interactive forms and a slew of other CGI programs.

 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. Such a network is practical only for small workgroups of less than a dozen computers. .

perspective correction                                                                                                                                                                                           In 3D graphics, quick-and-dirty rendering can make straight lines vanishing into the distance, appear to bend. Perspective correction is the generic term for techniques used to counteract this distortion.

perspective correct texture mapping This texture-mapping process keeps scenery looking realistic, particularly when looking down a long hallway or corridor that's been rendered with large polygons. Without perspective correction, the hallway might appear to bend into the vanishing point.

Persistence The amount of time a phosphor or diode pixel stays lit after current has been applied to it. A pixel's persistence is what allows an image to remain on the screen between screen refreshes.

Phase Basic waves--such as analog signals--consist of a series of repeating peaks and valleys. In its simplest form, the wave starts at a zero point on a line, gradually climbs to a peak a bit further down the line, dips down past the zero point to a valley, and then finally returns to the zero point.

Phong shading In 3D graphics, the polygons that make up the graphics need to be shaded. Phong shading is one of the more sophisticated techniques for doing this. It works like Gouraud shading but requires more computer horsepower and yields better results.

Photo CD Photo CD is a proprietary system developed by Kodak for storing photographic images from film onto CD-ROMs. People use the term Photo CD to refer to two distinct entities: the Orange Book CD-ROMs that contain pictures, and the graphics file format with the file extension . pcd that stores the data, which can also be found on magnetic disks--floppy or hard.

PICS
Platform for Internet Content Selection PICS is a specification in the latest official versions of HTML that allows Web developers to include HTML tags with information about their site's content.

PICT PICT is the native graphics format used by the Macintosh Operating System. Any time you do a screen capture using the Shift-Command-3 key combination, you're creating a PICT file.

PIF
program information file This data file contains settings such as memory allotments and program locations for DOS programs running under Windows. In Windows 3.x and earlier versions, these files are often required for creating enough resources in a virtual DOS machine to run demanding DOS programs. But many programs can run just fine without them.

pincushioning On computer screens, lines that should be straight don't always appear that way. Lines that look bowed or curved are evidence of a pincushion error. Such problems are common at the right and left edges of a displayed image, resulting in a screen that appears to be bowed inward at the centers (thus the source of the name).

Ping
packet Internet groper When submarine crews wanted to test the distance of an object, they would send a sonar "ping" and wait to hear the echo. In the computer world, Ping is a program that "bounces" a request off of another computer over a network to see if the remote computer is still responding. If the ping comes back, the remote computer is still alive

pipeline burst cache This type of secondary cache is an advanced type of SRAM installed on the motherboard to boost computer performance. Pipeline burst SRAM is commonplace now in motherboard market, where it replaced the older Sync Burst cache, which works less efficiently with fast processors.

pixel
picture element The image displayed on monitors or in a graphic produced by a scanner or paint program is made up lots of dots called pixels. Collectively, the number of pixels displayed is referred to as the image's resolution.

A pixel on a monitor is a number of red, green, and blue phosphor dots. These dots are "excited" to varying degrees by the monitor's three electron guns, and the results mix additively to generate a specific color. By manipulating large numbers of pixels in precise ways, patterns emerge to make up an identifiable picture.

Plug and Play The Plug and Play (PnP) standards were developed by Microsoft, Intel, and other industry leaders to simplify the process of adding hardware to PCs. The standard's intention is to conceal unpleasant details, such as IRQ and DMA channels, from people who just want to add a new board, drive, or other chunk of hardware to their system. Some devices that don't seem that difficult to install also take advantage of PnP standards. A Plug and Play monitor, for example, can communicate with both Windows 95 and the graphics adapter to automatically set itself at the maximum refresh rate supported for a chosen resolution. PnP also ensures that the monitor will not be driven beyond its capabilities.

plug-in This term refers to a type of program that tightly integrates with a larger application to add a special capability to it. The larger app must be designed to accept plug-ins, and the software's maker usually publishes a design specification that enables people to write plug-ins for it. Two notable applications designed around a plug-in architecture are Adobe Photoshop and Netscape Navigator.

PNG
Portable Network Graphics A lossless graphics file format that combines many of the benefits of GIF and JPEG. PNG also allows for many features that the GIF format doesn't, including 254 levels of transparency (GIF supports only one), more control over image brightness, and support for more than 256 colors. PNG also supports progressive rendering, as interlaced GIF?s do, and tends to compress better than a GIF.

point sample texture filtering The simplest technique for adding texture to a 3D model, point sampling selects a single texel to place on an appropriate pixel, then puts the same texel on pixels with similar properties. Since this technique can make a scene look blocky, it's unacceptable for true 3D gaming.

PPTP
Point-to-Point Tunneling Protocol PPTP is a protocol developed by a number of companies, including Microsoft, that allows secure transmission of data in TCP/IP packets. PPTP and similar protocols are used to carry secure communications over Virtual Private Networks that use public phone lines.

POP
Post Office Protocol The current champ in Internet email mailbox access standards, but its limitations--basically, you connect to a server and download all your messages, which are then deleted from the server--discourage flexibility. Of course, some clients let you leave all messages on the server, and/or refuse to download messages above a certain size. Still, as messages become longer--with multimedia (such as sound or video) objects and the likes--we'll want some flexibility in what we retrieve and when we retrieve it. That's where IMAP comes in. The current version of POP is POP3.

PoP
point of presenceSo that your Internet access provider can offer a local dial-up number to give you access to the Net, it either maintains or leases PoPs throughout the areas it serves. A PoP (pronouced "pop") is likely to contain modems, digital leased lines, and multiprotocol routers.

POSIX
Portable Operating System Interface for UnixWith an eye toward buying programs that would run on a variety of systems, the U.S. government created POSIX. POSIX-compliant programs are designed to be easily ported, and run on any POSIX-compliant operating system, including many Unix variations and Windows NT.

POTS
plain old telephone service If you're logging on to the Net using a regular modem that employs your phone line, you have a POTS connection. POTS is the basic voice phone service you get from Ma Bell and her kids, and the term is used to differentiate this type of connection from ISDN or a leased line like T1.

ppi
pixels per inch The ppirating is a measure of resolution that's used interchangeably with the more common term dpi(dots per inch).

PPP
point-to-point protocol PPP is the Internet standard for serial communications. Newer and better than its predecessor, SLIP, PPP defines how your modem connection exchanges data packets with other systems on the Internet.

PRI
Primary Rate InterfaceThis ISDN service is used mainly by Internet service providers (ISPs) and businesses. Why? Because it provides a lot of bandwidth: 23 B channels with 64-kbps throughput capability and one 64-kbps D channel for call signaling and setup. It was designed for transmission through a standard North American T1 trunk and has throughput capability to 1.472 mbps. If you see the notation 23B+D, that's another way of saying the same thing.

primary cache By caching data in fast, pricey memory, you speed up your system performance. Primary cache is fast, usually integrated into the CPU chip, and not very large (typically 16K). While it's useful for storing some instructions, it usually relies on a secondary (L2) cache for an all-around boost of system performance.

Primitive In graphics, a primitive is one of a basic group of shapes, such as circles, polygons, and squares.

progressive JPEG Unlike normal JPEG images, which are displayed one line at a time from top to bottom, progressive JPEGs are displayed in alternating lines, then filled in on a second pass. Depending on which graphics viewer or Web browser is being used, progressive JPEGs may produce a "venetian blind" effect or simply a blurry or blocky image that gradually sharpens.

progressive scan Most computer monitors and some high-resolution TV sets display all the lines of a picture at the same time, in one quick burst. This is known as progressive scanning, which stands in contrast to interlacing, in which every other line is displayed in two successive "swoops" to form a complete picture. Analog TVs and some really low-resolution monitors use interlacing.

protected mode An operating mode of x86 chips that lets the PC access the largest possible amount of memory. In protected mode, different parts of memory are assigned to different programs. This way, memory is "protected" in the sense that only the assigned program can access it.

protocol  Computers can't just throw data at each other any old way. Because so many different types of computers and operating systems connect via modems or other connections, they have to follow communications rules called protocols.

proxy servers A proxy server is a system that caches items from other servers to speed up access. On the Web, a proxy first attempts to find data locally, and if it's not there, fetches it from the remote server where the data resides permanently.

public domain  Of all the kinds of software or information you can download, public domain has the fewest strings attached. With shareware, you're expected to pay a fee. With freeware, you may face other restrictions, and there's still a copyright attached.

public method In object-oriented languages such as Smalltalk or Java, public is one of several modifiers you use to control access to a method. A public method is available to any class in any file. If you use no modifier, only classes declared in the same file have access to the method.

Push                                                                                                                                                                                                             The Internet and the Web started as communications media through which users could request data. But it didn't take long for some enterprising souls to see the value in "pushing" data to users based on predefined preferences.

Q

QPSK
quadrature phase shift keying                                                                                                                                                                                                                                                                                                                                                                 QPSK is a digital frequency modulation technique used for sending data over coaxial cable networks. Since it's both easy to implement and fairly resistant to noise, QPSK is used primarily for sending data from the cable subscriber upstream to the Internet.

quadratic texture mapping                                                                                                                                                                                      This technique, used with Nvidia-based 3D graphics boards, speeds up texture mapping and redrawing by reducing the amount of work required. Nvidia chips use fewer polygons to render an acceptable-looking rounded object.

QuickTime Developed by Apple Computer, QuickTime is a method of storing sound, graphics, and movie files. If you see a MOV file on the Web or on a CD-ROM, you'll know it's a QuickTime file. Although QuickTime was originally developed for the Macintosh, player software is now available for Windows and other platforms.

R

RAD
rapid application development  The generic name for tools and techniques designed to make it easy to quickly assemble the skeleton of an application, especially the user interface.

RAID
redundant array of independent (or inexpensive) disks  A 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.

RAM
random access memory When you run an application like Microsoft Word, the program is called up from its permanent storage area (like the hard drive, floppy disk, or CD-ROM) and moved into the RAM, where it sends requests to the CPU. Using the faster PC100 memory preferred by 350-, 400-, and 450-MHz Pentium II processors means your information spends less time in line before being processed.

RAMDAC
random access memory digital-to-analog converter This microchip sits on a VGA card or other graphics display board and translates the digital representation of a screenful of information into an analog signal that the monitor can display. The faster the RAMDAC (measured in MHz), the higher the screen refresh rates that the card will support at each given resolution.

RCA connectors                                                                                                                                                                                                   In the days before CD players, the Radio Corporation of America (RCA) developed RCA connectors to connect turntables to stereo systems.

RD
receive data This modem light flashes off and on during data transfers, telling you that the modem is receiving signals from a remote computer.

RDO
Remote Data Objects A Microsoft technology for accessing remote databases. You can write programs that run on one computer while accessing data stored in a separate computer

real mode An operating mode of x86 chips that replicates the memory management used by 8086 or 8088 chips. Real mode limits the processor to 1MB of memory and provides no memory management or memory protection features.

Red Book Another name for the CD-DA audio CD format introduced by Sony and Philips, the Red Book standard defines the number of tracks on the disc that contain digital audio data and the error correction routines that save sound from minor data loss.

Registry The Windows Registry stores system configuration details so that Windows looks and behaves just as you want it to. The Registry stores user profile information such as wallpaper, color schemes, and desktop arrangements in a file called user.dat. And it stores hardware- and software-specific details, such as device management and file extension associations, in a file called system.dat.

refresh rate The image on your computer monitor doesn't just appear fully formed on the screen's phosphors: it's drawn line by line with beams fired from three electron guns at the back of the CRT. (The three guns are for different colors--red, green, and blue. The colors blend to build all the colors you see.) The frequency at which they redraw the image is called the refresh rate, and it's an important measure of how steady the image will appear. A refresh rate of 60 Hz (in which the screen is redrawn 60 times per second) will almost always look flickery--especially under fluorescent lights, which refresh at about the same rate. This causes eye fatigue. Refresh rates of 70 Hz and higher are preferable. Since refresh rates can vary depending on the screen resolution you pick, check that both the monitor and display adapter you run can manage a 70-Hz or higher refresh rate.

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.

results listing                                                                                                                                                                                                 An HTML page generated by a search engine in response to a search request sent when a user typed search terms into a search form. The results listing contains links to the pages that matched the search term, with the links usually sorted by order of relevance

RGB                                                                                                                                                                                                             RGB refers to the so-called scientific hues--the additive primary colors red, green, and blue--that, when mixed together in equal amounts, create white light. Television sets and computer monitors display their pixels based on values of red, green, and blue.

RISC
reduced instruction set computer In the mid-1970s, the microprocessor started to come under scrutiny. While the original complex instruction set computing (CISC) chips had accomplished amazing things, chip designers were asking themselves, "How can we do even more?" In 1974, John Cocke of IBM Research decided to try an approach that dramatically reduced the number of instructions a chip performed.

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                                                                                                                                                                                                            This file format uses the run-length encoding technique for reducing the size of a graphics file. But not all such files have the .rle file extension: PCX files, as well as some flavors of TIFF and BMP, are run-length encoded, even though they keep their own extension and format.

ROFL (or ROTFL) 
rolling on the floor laughing  This shorthand term is used in postings and online chat to show enthusiastic appreciation of a witticism in a previous posting.

ROM
read-only memory  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 and the whole shooting match can begin.

rotation error Not all screen images appear squarely in a monitor's display. The entire image may tilt clockwise or counterclockwise from the vertical position. Many monitors include a dial to correct this rotation error so that the image is displayed straight up and down. Also called tilt error.

router
This piece of hardware does what it says: it routes data from a local area network (LAN) to a phone line's long distance line. Routers also act as traffic cops, allowing only authorized machines to transmit data into the local network so that private information can remain secure.

RS-232
Recommended Standard 232 This was originally a nine-wire interface standard for teletype machines from the Electronics Industry Association. Now in its third revision (RS-232-C), it's the standard for computer serial-port transfers.

RSA                                                                                                                                                                                                                                                                                                                                                                                                                       RSA refers to public key encryption algorithms created by Ron Rivest, Adi Shamir, and Leonard Adleman, and licensed by their company, RSA Data Security.

RTF
rich text format This file format, developed by Microsoft, enables you to save text files in your word processor with formatting, font information, text color, and some page layout information intact.

RTFM
read the f---ing manual Not to be confused with RTF (Rich Text Format), this acronym is the classic response of overworked technical support consultants to stupid user questions.

RTP
routing table protocol RTP is a communications protocol that uses a list of steps or instructions (called the routing table) for handling incoming calls. Accessing a network of phones may be as simple to the caller as dialing a number, but behind the scenes, it's not as straighforward (and with Web phones, it's usually not even that simple to dial a number). Routing tables are also used for directing outgoing calls across long-distance networks.

RTS
ready to send One of the nine wires in a serial port used in modem communications, RTS carries a signal from the computer to the modem saying "I'm ready to start when you are."

run-length encoding Bitmapped graphics files are typically larger than they need to be. Run-length encoding is a compression technique that reduces file sizes, especially for black-and-white or cartoon-style line art graphics. It works by replacing "runs" of the same color with a single character.

S

sandbox A protected, limited area in computer memory where applications (generally Java-based) are allowed to "play" without risking damage to the system that hosts them.

S-CDMA
Synchronous Code Division Multiple Access A proprietary version of code division multiple access (CDMA), S-CDMA was developed by Terayon Corporation for data transmission across coaxial cable networks. S-CDMA scatters digital data up and down a wide frequency band and allows multiple subscribers connected to the network to transmit and receive concurrently. This method of data transmission was developed to be secure and extremely resistant to noise.

scene graph The scene graph is the data structure defined in VRML. Files using a WRL extension describe the three-dimensional world, including the objects it contains, their properties, and how they interact. As in HTML, developers can link external media--such as graphic textures or sound files. Also like HTML, scene graph files are simple text files.

screen geometry Screen geometry is a general term describing a monitor's ability to reproduce various shapes accurately and without distortion. Monitors are subject to numerous problems with geometry, including pincushioning, trapezoid error, rotation (or tilt) error, and inadequate linearity.

SCSI
Small Computer System Interface While the PC was settling for rankly inferior alternatives, the Mac adopted SCSI as its expansion standard. 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. But it requires some system overhead, slows down your computer's start-up, and demands that during installation you handle device ID administration and a process called termination that closes the SCSI circuit. Pronounced "scuzzy" by those in the know.

SD
send data This modem light flashes off and on during data transfers, telling you that the modem is sending signals to a remote computer.

SDRAM
synchronous dynamic RAM  Sending data from main memory to the system processor is consistently one of the biggest performance bottlenecks in any PC. Even the fastest standard DRAM and EDO memory cannot keep up with the 66-MHz bus speeds used on many Pentium systems. SDRAM incorporates new features that allow it to keep pace with bus speeds as high as 100 MHz.

search engine When a user enters text into a search form, a program called a search engine analyzes the text and searches for matching terms in an index file, which was created using a search indexer. The search engine returns the results of its search using a result listing.

search form An HTML page that lets users type in search terms and set various search options. For example, the main page on  snap contains a search form.

search indexer A program that analyzes documents such as Web pages and creates a searchable index file. The resulting index file is used by a search engine to locate files containing specific words or phrases.

SECAM
Sequential Couleur avec Mémoire The television broadcast standard in France, the Middle East, and most of Eastern Europe, SECAM broadcasts 819 lines of resolution per second. SECAM is one of three main television standards throughout the world.

secondary cache  By caching data in fast, pricey memory, you speed up your system performance. A secondary cache is bigger than the primary cache (usually in the same chip as the CPU) and fits between it and main memory (RAM). It's faster than main memory, but slower than primary cache memory. It's typically around 256K in size.

Selector In cascading style sheets, the selector is the string used to identify a declared style value. It can be an HTML element or a defined class or ID. The selector is attached to objects on the page (either as an HTML tag or as an attribute of a tag), and it determines what style the HTML elements receive.

Semiconductor A class of materials that allow electrical current to flow through them under certain conditions. Semiconductors are used to create common electronic components, such as diodes and transistors.

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  The business end of a client/server setup, a server is usually a computer that provides the information, files, Web pages, and other services to the client that logs on to it. (The word server is also used to describe the software and operating system designed to run server hardware.) The client/server setup is analogous to a restaurant with waiters and customers. Some Internet servers take this analogy to extremes and become inattentive, or even refuse to serve you.

Session A connection between a user agent and a server where information is exchanged between the two computers. HTTP handles only sessions that consist of a page. Therefore, to maintain state on the Web, it is necessary to use cookies to store state information.

SGRAM
synchronous graphics RAM  SGRAM contains the speed-enhancing features of SDRAM and adds graphics capabilities that enhance 3D graphics performance. Like SDRAM, SGRAM can work in sync with system bus speeds up to 100 MHz.

Shading In 3D graphics, every shape you see is built on a framework of polygons. The process of coloring the polygons is called shading, and the techniques for doing it are often more complicated than just flooding a shape with a single color.

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 Shareware is the wonderful alternative to commercial software. Available from centralized archives on the Internet and local bulletin board systems (or sometimes via CD-ROM or floppy), shareware is copyrighted but works on the honor system. Shareware that doesn't involve a fee is called freeware.

Shift key The Shift key is so called because on manual typewriters, it shifts the position of the carriage, causing the upper portion of each key's hammer--the part that contains the capital letter--to strike the paper through the ribbon.

SHTTP
secure hypertext transfer protocol This protocol was developed by Enterprise Integration Technologies to keep your moolah safe on its way from your wallet to a commercial transaction on the Internet.

sideband addressing A feature of AGP. Sideband addressing provides additional channels for transmitting data requests between the graphics processor and the system.

Signed applet  An applet whose source and integrity are guaranteed by its author. This is done by attaching a digital signature to the applet that indicates who developed the applet, when, and whether it has been tampered with since that time.

SIM
Subscriber Identity Module 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.

SIMM
single in-line memory module SIMMs are the most widespread form of RAM available. They're about 10cm by 2cm, and they sit in rows at either 90 degrees or 45 degrees to your motherboard. You can generally get them in 1MB to 32MB configurations.

SIT                                                                                                                                                                                                             SIT files are created by Aladdin System StuffIt compression and decompression software. If you see a file with the extension .sit, you'll need a decompression program to open it. And although such files are typically compressed using Macintosh Software for other Mac users, you can also open them using some PC programs, too.

Skins Similar to desktop themes, skins are interface enhancements that alter the appearance of a program.

SLIP
serial line Internet protocol  SLIP is a standard for connecting to the Internet with a modem over a phone line. It has serious trouble with noisy dial-up lines and other error-prone connections, so look to higher-level protocols like PPP for error correction.

SMIL SMIL is an HTML-like programming language proposed by the World Wide Web Consortium (WC3) that synchronizes multiple media types for effects such as dissolve transitions between images and integrated hyperlinked text and graphics in video streams-even over low-bandwidth connections.

S/MIME
Secure Multipurpose Internet Mail Extensions  S/MIME defines a means to make email messages more secure by adding both digital signatures and encryption. Using S/MIME-compliant email packages, users can make sure that a message in fact comes from the supposed sender (thanks to the signature), and that no one else could read the message before it arrived (thanks to encryption).

SMTP
simple mail transfer protocol When you're exchanging electronic mail on the Internet, SMTP is what keeps the process orderly. It's a protocol that regulates what goes on between the mail servers.

snail mail This term is used by supercilious fans of email to describe the regular paper-based mail service. Since the delay between sending email and receiving it can be as little as a few seconds, regular mail seems a lot slower by comparison.

Solid state Refers to any electronic circuit made of solid, singular components, such as chips and transistors. Solid state devices function exclusively with internal electromagnetic signals, and don't use any mechanical action

sound  Even if you ignore the beeping noise a PC makes when you boot it up (and who can blame you for wanting to?), the computer still has three ways of generating sound. One is to play CD audio--either by putting, say, a Dire Straits disc into your CD-ROM drive or by using a CD-ROM title like 7th Level's Tuneland that makes use of CD audio tracks. The second method is waveform sound, which is a digital recording of any kind of sound or music (for example, Windows' warning-sound file ding.wav). The third is MIDI--a kind of digital sheet music that instructs synthesizer chips on the notes, tempo, and instrumentation of a musical passage.

spam
spiced ham Hormel's famous can o' additives has given its name to something almost as disgusting: junk email. Spam can be a mass mailing to bulletin boards, newsgroups, or lists of people. But spam is never welcome: if you spam or get spammed, flame wars can ensue.

SPID
Service Profile Identifiers These numbers identify the services and features the telephone central office switch provides to ISDN devices. When a new ISDN line is added, the telephone company assigns a SPID for each directory number (DN) so that the switch will sync up correctly with the customer's ISDN device. SPIDs are needed for configuring the ISDN device and are usually entered when the device is installed.

Spider Also known as a Web spider, this class of robot software explores the World Wide Web by retrieving a document and following all the hyperlinks in it. Web sites tend to be so well linked that a spider can cover vast amounts of the Internet by starting from just a few sites.

spread spectrum  Spread spectrum is a type of modulation that scatters data transmissions across the available frequency band in a pseudorandom pattern. Spreading the data across the frequency spectrum makes the signal resistant to noise, interference, and snooping.

SQL
Structured Query Language A type of programming language used to construct database queries and perform updates and other maintenance of relational databases, SQL is not a full-fledged language that can create standalone applications--but it is strong enough to create interactive routines in other database programs.

SRAM
static RAM  SRAM is like DRAM on steroids. Since it stores its data in capacitors that don't require constant recharging to retain their data, it performs better (though it is pricier to produce). SRAM is typically used for secondary caches because its speed falls somewhere between that of DRAMs and a CPU-based cache (typically 8ns to 20ns, as opposed to 60ns to 80ns for DRAM).

S-Registers The only way a modem can handle the mind-boggling array of telecommunications settings adopted by phone companies across the world is to make them programmable. Options are programmed in the modem's S-Registers--hardware settings that can be programmed using AT command strings. The functions of S-Registers vary from modem to modem, which is why communications software and some operatings systems (like Windows 95) insist on knowing the manufacturer and model of your modem.

SSI
server-side include SSIs allow for dynamic additions, such as a clock with the current time, to be easily attached to Web pages.

SSL
Secure Sockets Layer SSL is a transaction security standard developed by Netscape Communications to enable commercial transactions to take place over the otherwise notoriously nonsecure Internet. It's one of a few competing security standards.

STAC LZS compression
STAC Lempel-Ziv standard compression  This data compression standard is developed and marketed by STAC Incorporated to be used over PPP (Internet) connections. STAC LZS is widely supported by many types of equipment and can triple data rates with highly compressible files. Though STAC LZS compression is currently supported by many ISDN routers, it is a rare feature of ISDN modems and adapters.

start bit Ancient modems alternated between two tones. One tone represented 0 and the other represented 1, which covered the entire binary language. Silence was not an option: to a modem, silence meant the phone call had been cut off. So when a modem had nothing to say, it continuously transmitted the 1 tone to tell the other modem that it was in an idle state.

state  The state of a system or a Web page is its condition: its attributes, configuration, or content. For a Web page, state is maintained only as long as the page is in the browser, unless a cookie is set to retain information over time.

stateless A stateless server (for example, a World Wide Web server) considers each page request independently. A request specifies the entire document, without requiring any context or memory of previous requests. Unless a cookie is set, no information is carried across requests.

S/T interface The S/T interface is the part on the ISDN modem to which all other ISDN devices connect in order to communicate over ISDN. An additional piece of hardware called an NT1 must be placed between the ISDN device and the wall jack to terminate the line.

stop bit  The opposite of the start bit.

streaming Data is streaming when it's moving quickly from one chunk of hardware to another and doesn't have to be all in one place for the destination device to do something with it. When your hard disk's data is being written to a tape backup device, it's streaming.

swap file  A swap file is an area on your hard disk used as virtual memory. It's called a swap file because virtual memory management software swaps data between it and main memory (RAM).

synchronous communication
Synchronous communication is the technique of choice for ISDN lines because it handles data more efficiently than the typical modem's asynchronous technique. While asynchronous communication sends smallish blocks of data with lots of control bits for error correction, synchronous techniques use big blocks of data with control bits only at the start and end of the entire transmission.

T

T1 If ISDN isn't enough digital carrier for you, T1 offers faster speeds. T1 is a term coined by AT&T for a system that transfers digital signals at 1.544 megabits per second (as opposed to ISDN's mere 64 kilobits per second). Of course, if T1 doesn't cut it, there's always T3. (T2 seems to have been bypassed altogether.)

T3  When you're transferring data across a digital carrier, T3 is the premium way to go. It's not just three times the capacity of T1, as the name suggests--it's almost 30 times the capacity. It can handle 44.736 megabits of digital data per second.

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 (including all flavors of Unix, the Mac OS, and the latest versions of Windows).

TDMA
Time Division Multiple Access A method of digital wireless communications transmission allowing a large number of users to access a single radio-frequency channel without interference. Each user is given a unique time slot within each channel.

telephone company central office switching
All phone calls (including those over ISDN) are routed through the telephone company's central office. These offices form a central location for all calls within a particular area. The switch type refers to the equipment the telephone company uses to receive and transmit data over ISDN.

Telephony An adjective that covers a multitude of communications issues, telephony has recently permeated the world of small computing, as add-in boards that combine the functions of modems, sound boards, speakerphones, and voice mail systems have begun to proliferate.

Telnet  Telnet is an application that lets you log on to a Unix computer. Provided you have an account on that Telnet server, you can then use its resources. A drawback of Telnet is that it's character-based, so you need to speak Unix to the other computer.

TEOTWAWKI An acronym for the end of the world as we know it--frequently used on news groups and Web sites dealing with the Year 2000 bug, survivalism, and other similar and alarming topics.

terminal adapter
This chunk of hardware converts the data it receives over ISDN to a form your computer can understand. Sometimes mistakenly called an ISDN modem or a digital modem, a terminal adapter handles data digitally and does not need to modulate or demodulate an analog signal. Terminal adapters can be an internal board or an external box that connects to the computer through the serial port.

texel
texture element Like its cousin the pixel, a texel is the base unit of a graphic. While pixels are the basic elements in any graphic, texels are their equivalent in a texture map.

texture mapping In 3D graphics, texture mapping is the process of adding graphics to scenery. Unlike shading, which adds color to the underlying polygons, texture mapping applies simple textured graphics to simulate walls, sky, and so on.

Texturing A shorthand term for texture mapping.

TFB
too f---ing bad Often used in flame mail and postings, this acronym indicates sneering, sarcastic "pity."

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.

TIFF
tagged image file format  This graphics file format was designed to be the universal translator of the graphics world back in the 1980s when sharing graphics across computing platforms was a great headache.

TR
terminal ready  This is a signal sent during modem communications indicating that the computer is running a communications program. That serial port's wire is called DTR (data terminal ready). External modems usually match this with an indicator light labeled TR.

Traceroute Originally a Unix program, Traceroute is now available on most platforms. Traceroute is a utility that allows you to see how and where information travels on the Net. It traces the path a packet takes as it is sent from your computer to a destination computer (such as the server for a Web site).

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.

transparent GIF A feature of the GIF89a graphics standard, a transparent GIF lets the background show through selected parts of an image. When creating the GIF, the designer can designate one color in the image's palette as transparent. When the GIF is displayed, areas using that color reveal whatever is underneath. Transparency is most often applied to a GIF's background color to let the page's own background show through, so that images appear to float on the page.

trapezoid error  In computer monitors, the screen sometimes distorts an image so that it appears wider at the top of the display than at the bottom--or vice versa. Because this trapezoid error is a common problem, many monitors include controls to help correct the image so that it is truly rectangular.

trilinear texture filtering Like its less sophisticated cousin, bilinear texture filtering, trilinear filtering is a complex technique used by 3D graphics cards to make movement through rendered landscapes realistic even in fast-moving games.

Trinitron  The Trinitron tube is a type of CRT (cathode ray tube) developed by Sony Corporation. It differs from the standard tube types because it employs an aperture grille (wires stretched vertically down the screen) instead of the usual shadow mask (a metal plate with holes in it).

TrueSpeech When it comes to sound compression, the DSP Group's TrueSpeech codec is about as small as it gets. This codec reduces the signal to 8,000 Hz, in mono, with a bit depth of 1. This means that the sound goes through at a rate of 1K per second--an eighth the size and rate of the smallest PCM audio files (like WAV and AIFF files) and a quarter the size of the smallest ADPCM files.

Turing experiment Named for computing pioneer Alan Turing, this is one element of testing the robustness of artificial intelligence; it's also called a Turing test. Back in the 1950s, Turing believed that by the end of this century a computer with the right program could engage in a written conversation, and for 5 minutes pass for a real human about 70 percent of the time.

TWAIN  While there are some who claim that TWAIN stands for toolkit without an interesting name, in fact it stands for nothing but itself. But what is it? TWAIN is an interface standard that should be on the checklist of anyone buying a scanner or OCR, graphics, or fax software.

tweedler One who has a deep and abiding, sometimes overwhelming, love for all computer related technology and gadgets. Believed to have been inspired by the sound a tunic-worn Star Trek communicator makes when activated.

twisted pair  Telephone companies commonly run twisted pairs of copper wires to each customer household. The pairs consist of two insulated copper wires twisted into a spiral pattern. Although originally designed for plain old telephone service (POTS), these wires can carry data as well as voice. New services such as ISDN and ADSL also use twisted-pair copper connections.

U

UART
Universal Asynchronous Receiver Transmitter This chip was one of the first really successful integrated circuits. In your PC, the UART is the key component of the serial communications port. Data is tranferred within the computer in units of 1 to 8 bytes, with a separate wire for each bit within the byte. The UART receives a byte and converts it to a sequence of voltage changes to represent the 0s and 1s on a single wire. The modem takes the signal on this wire and converts it into sound. At the other end, a modem converts the sound back to voltages, and another UART converts the stream of 0s and 1s back into bytes of data.

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.

U interface
The U interface connects NT1 terminated ISDN devices to the telephone company's ISDN network. Many ISDN devices have a U interface option, which means they have the NT1 termination device built into their hardware. These U-type devices can be connected directly to the ISDN wall jack. A device that doesn't have a built-in NT1 has an S/T interface. (Note that in Europe S/T devices can be connected directly to the ISDN wall jack.)

uniformity  An ideal monitor will deliver equal brightness across the entire screen. In practice, however, many monitors have darker areas or appear patchy, demonstrating a lack of uniformity. These problems are particularly easy to spot on a white background.

Unix                                                                                                                                                                                                        Described by one of its developers as "a weak pun on Multics" (which was an experimental, time-sharing operating system at Bell Labs in the 1960s), Unix took off in the early 1970s as a general-purpose operating system. Since much of the Internet is hosted on Unix machines, the OS took on a new surge of popularity in the early 1990s. Unix comes in many flavors--including Xenix, Ultrix, GNU, and Linux--and runs on a variety of platforms, which makes its development a subject of widespread discussion. But the truly great debate involves how to style the word itself: should it have an initial capital (Unix)? Or should it be in all caps (UNIX)? Since the operating system itself is case-sensitive, the debate rages. Bell Labs' implementation of Unix is trademarked in all caps; for the other implementations, it's optional.

URL
uniform resource locator
universal resource locator  URLs are the Internet equivalent of addresses. How do they work? Like other types of addresses, they move from the general to the specific (from zip code to recipient, so to speak)..

USB
universal serial bus Imagine replacing all those ports on the back of your PC--mouse, keyboard, serial, parallel, joystick, and more--with a single port. Now imagine you can daisy-chain as many as 127 peripherals off that port and use them all at once. Finally, imagine that the port supports data transfer rates up to 12MB/sec, making it suitable for even high-bandwidth applications such as video. Imagine no more.

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 kind of cable that has one or more pairs of wires twisted together to improve its electrical properties. Unshielded refers to the fact that there is no metal shield around the cable.

Uuencode Like MIME, UUencode lets you send binary files over the Internet. UUencode--or Unix-to-Unix encoding--converts binary data into ASCII text format, which can then be inserted into an email message. The recipient must use a UUdecode utility to convert the text back to binary format.

V

V.120 Protocol
This protocol allows ISDN modems to transfer files using familiar protocols such as X-, Y-, and Zmodem. V.120 can only make a connection on one of the two data-carrying channels at a time over ISDN, so it is limited to a maximum throughput of 64 kbps. It is mostly used to connect to ISDN-capable BBSs. Connecting to an Internet service provider over ISDN uses PPP or MPPP rather than V.120 to establish communications.

V.32                                                                                                                                                                                                                                                                                                                                                                                                                      This is the modem standard (pronounced "v-dot 32") for error correction and compression at speeds of 9,600 bits per second.

V.32bis This is the modem standard (pronounced "v-dot 32 biss") for error correction and compression at speeds of 14.4 kpbs. Bis (French for encore) is an international designation for the first revision to a standard.

V.34 This is the modem standard (pronounced "v-dot 34") for error correction and compression at speeds of 28.8 kbps.

V.42bis This is the modem standard (pronounced "v-dot 42 biss") for error correction and compression at speeds of 28.8 kbps. Bis (French for encore) is an international designation for the first revision of a standard.

VAT  This Unix audio teleconferencing tool enables you to talk to one or more people over an Internet connection. In most cases, all you need is the Unix VAT program, IP connection, and sound hardware. The VAT program's window is divided into two parts: the right pane controls the local audio and the left pane displays the status of the other parties participating in the conference.

VBScript Visual Basic Scripting Edition (VBScript) is a programming language developed by Microsoft for creating scripts (miniprograms) that can be embedded in HTML Web pages for viewing with Internet Explorer. These scripts can make Web pages more interactive.

vCalendar The vCalendar specification defines a format for exchanging calendaring and scheduling information. You can distribute vCalendars as email attachments or make them available for downloading from a Web page. vCalendars hold information about event and to-do items that are normally used by personal information managers (PIMs) and group schedulers.

vCard   The vCard specification defines a sort of electronic business card that can be sent via an email attachment or as a link on a Web page. vCards can store information such as your name, address, telephone number, email address, and so on. A recipient of your vCard can easily add your information to their electronic address book (as long as it's vCard-compliant) with a single click.

vector graphics Computer-aided design (CAD) programs and drawing applications such as Adobe Illustrator and CorelDraw produce graphics that don't look blocky when you zoom in on them. They scale up easily because they store geometric information about shapes and lines called vectors. These images are unlike pictures from paint programs or scanners,

Veronica
very easy rodent-oriented Netwide index to computerized archives  This contrived acronym is really the name of a front end for searching Gopher servers. A Veronica search looks for filenames and produces a menu of items linked to a Gopher data source. It's really named for a character from the Archie comics, because Veronica searches Gopher sites in the same way that Archie searches ftp archives.

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.

VFW                                                                                                                                                                                                           Video for Windows Video for Windows, or VFW, is the multimedia technology that ships as part of Windows 95. It can be added to earlier versions of Windows when you install a CD-ROM title or other program that uses VFW. Its playback files have the extension .avi and can be played using Windows' Media Player.

video bandwidth Video bandwidth refers to a monitor's ability to refresh the screen. High bandwidths allow more information to be painted across the display in a given amount of time, which translates into support for higher resolutions and higher refresh rates.

viewable area  Monitor sizes aren't as straightforward as they seem. A 17-inch CRT monitor measures 17 inches diagonally across the glass face of its picture tube. However, the viewable area of the monitor--the diagonal measurement of the largest possible picture the screen can display--is never as large as the actual tube size.

viewer  A viewer assists your Web browser by handling files that the browser itself can't. Viewers can be any type of application, since they may be called upon to handle any kind of file--even sound files.

VIM
Vendor Independent Messaging  Just as MAPI lets email clients communicate with Windows applications, VIM, a Lotus standard, allows cc:Mail and Notes to communicate with other applications.

virtual memory What do you do when you run out of real random access memory (RAM)? Easy. Pass it off to virtual memory. To do this you need a virtual memory manager (usually a function of the operating system) that maps chunks of data and code to storage areas that aren't RAM.

Visual Basic A high-level programming language from Microsoft that's graphically oriented and relatively easy to learn, Visual Basic can be used to create everything from simple database applications to commercial software packages.

VLB
VESA Local Bus This 32-bit, far speedier improvement over the IBM PC's 8-bit and 16-bit ISA bus architecture gained popularity with the advent of Intel's 80486 processor. However, VLB has been superceded recently with the introduction of the Pentium and Intel's superior PCI bus.

VOC   VOC is an audio file format developed by Creative Labs for use with the earliest Sound Blaster cards under DOS. With the continued preeminence of Windows, the VOC file format has lost much ground to the Windows-native WAV file format.

von Neumann architecture                                                                                                                                                                                       Most computers use the stored-program concept designed by Hungarian mathematician John von Neumann. In it, you store programs and data in a slow-to-access storage medium (such as a hard disk) and work on them in a fast-access, volatile storage medium (RAM).

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).

VRAM
video RAM  This type of RAM sits on the better class of graphics display adapters. Unlike its general-purpose cousin dynamic RAM (DRAM), VRAM has dual ports--a design that can read and write data at the same time and is thus faster than DRAM.

VRML
Virtual Reality Modeling Language  The World Wide Web isn't a linear experience like leafing through and reading a book. The Web enables you to jump around from place to place. But in most cases, you jump from one page-based site to another. HTML is the specification for page-oriented Web navigation. VRML is a 3D navigation specification, hammered out by Silicon Graphics, Intervista Software, and other organizations and individuals.

VSB
vestigial side band  VSB is a digital frequency modulation technique used to send data over a coaxial cable network. Used by Hybrid Networks for upstream digital transmissions, VSB is faster than the more commonly used QPSK, but it's also more susceptible to noise.

VSL
virtual software library  Searching for files to download over the Internet isn't easy. Scanning ftp sites directories is inefficient. Older search techniques like Archie began to show their age pretty quickly.

V. standards                                                                                                                                                                                                                                                                                                                                                                                                     These standards were established by CCITT for modem manufacturers to follow (voluntarily) to ensure compatible speeds, compression, and error correction. These include V.34 (pronounced "v-dot 34"), the standard for 28.8-kbps communication.

VxD
virtual device driver  A VxD, or virtual device driver, is a specific type of Windows device driver that has direct access to the operating system's kernel. The x stands for extended, as the driver is basically an extension of the kernel.

W

.wad                                                                                                                                                            The file extension for Doom plug-ins, a .wad is used to add new levels of play or additional images to the regular game from iD Software.

WAIS
wide area information servers  A software system used to search indexed databases on remote servers, WAIS returns a ranked list of pages or files that you can retrieve from the server. Another plus to WAIS searching is that it enables you to use so-called natural language input; in other words, you can ask simply "Why is the sky blue?" instead of having to master Boolean AND/OR constructs.

WAN
wide area network Take two local area networks, hook them together, and you've got a WAN. Wide area networks can be made up of interconnected smaller networks spread throughout a building, a state, or the entire globe.

WAV                                                                                                                                                                                                       Pronounced "wave," this is the Windows standard for waveform sound files. WAV files predictably have the extension .wav.

waveform                                                                                                                                                                                                                                                                                                                                                                                                           Waveform is a type of sound that works like a tape recording: speak into a computer's microphone, and your voice becomes a waveform sound file (typically stored in WAV, AIFF, or AU format).

wavetable synthesis If you're aiming to re-create the sound of an existing instrument or other sound using a sythesizer, the easiest way is to make a digital sample and then modify it to change the pitch. Sample-based synthesis is often called wavetable synthesis because of the way samples are stored and retrieved.

Webmaster The fanciful name for anyone in charge of managing the hardware and software that make up a company's Web site. Less fun-loving companies may use a more mundane term, such as Internet systems administrator.

whiteboard Like the laminated conference-room board it gets its name from, an electronic whiteboard is used for collaborating on documents. Electronic whiteboards are programs that allow multiple users teleconferencing at their own computers to draw and write comments on the same document.

White Book   This is the fourth major extension to the audio CD (Red Book) standard. Unlike those for CD-ROM, CD-I, and CD-R, however, White Book is a very medium-specific format (similar to the original CD format, which handled only audio data).

Whois An Internet directory service, similar to finger, used to look up names of people on a remote server. You can use whois through third-party utilites on Windows and Macintosh machines, and through the command-line interface in Unix.

wildcards  Computer software often uses wildcards to act as placeholders for missing characters in filenames. For example, if you search for a file named r?te in Unix, the operating system will consider the files rite, rote, and rate matches.

WinISDN
Windows ISDN  This API is an open standard created by NetManage, ISDN*tek, and Performance Systems Incorporated (PSI). It allows ISDN adapter cards to use a dialer to initiate an Internet connection using PPP and MPPP. Major Internet software packages like NetManage Chameleon and Ftp Software OnNet use WinISDN to communicate over ISDN. The WinISDN API runs on Window 3.1, Windows 95, and Win/OS2 operating systems.

WinSock
Windows socket services  WinSock is a piece of software that acts as the middleman between Windows applications (such as ftp, a Web browser, Telnet, and so forth) and the Internet protocol. As the name implies, WinSock is used with Microsoft Windows, and most commonly with TCP/IP (though other protocols are also supported).

Wireframe In computer-aided design and 3D graphics, the image you see is built on a skeleton called a wireframe. During development, graphics designers use wireframes because they render onscreen a lot faster. The images are previewed by covering the frame with shading or a texture map.

World Wide Web  Also known as the WWW, the W3, or most often simply as the Web, it originally developed by CERN labs in Geneva, Switzerland. Continuing development of the Web is overseen by the World Wide Web Consortium. The Web can be described (dryly) as a client/server hypertext system for retrieving information across the Internet. On the Web, everything is represented as hypertext (in HTML format) and is linked to other documents by their URLs.

WRAM
window RAM  No, it has nothing to do with Microsoft's operating environment. Instead, WRAM is a variation on dual-ported memory technology that includes a larger bandwidth and more graphics-handling features than VRAM has, making WRAM useful for graphics applications.

WYSIWYG
What You See Is What You Get  A catchphrase from the old TV show Rowan and Martin's Laugh-In that became a desktop publishing byword, WYSIWYG (pronounced "whizzy-wig") refers to any technology that enables you to see images onscreen exactly as they will appear when printed out.

X

XML
Extensible Markup Language  XML is the Extensible Markup Language, a system for defining specialized markup languages that are used to transmit formatted data. XML is conceptually related to HTML, but XML is not itself a markup language.

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.

Y

Yellow Book  The industry standard that defines the format of CD-ROMs, Yellow Book was the first extension of the audio CD (Red Book) standard, and it enables CDs to contain 650MB of computer data instead of only digital sound. Because neither of the standard's defining companies--Philips and Sony--were major players in the personal computer market, Yellow Book needed some further definition.

YMMV
your mileage may vary  An acronym often used in email and postings, this disclaimer removes any sense of endorsement from a claim the writer has made.

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.

Z 

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 socket
zero insertion force socket  Here's the problem: when you're swapping microprocessor chips in and out of their sockets (as you do when you're upgrading your CPU), you're in danger of bending a pin or a whole row of pins with the pressure you exert.

ZIP  An open standard for compression and decompression used widely for PC download archives, ZIP was developed by Phil Katz for his DOS-based program PKZip, and it is is now widely used on Windows-based programs such as WinZip and Drag and Zip.