Glossary A

ABSOLUTE URL - The Internet address of a page or other World Wide Web resource that includes the protocol and complete network location of the page or file. The absolute URL includes a protocol, such as "http," network location, and optional path and file name. For example, http://www.acme.com/welcome.html is an absolute URL.

ABSTRACT SYNTAX - A description of a data structure that is independent of machine- oriented structures and encodings.

ABSTRACTION - An abstract representation of the world.

ACCESS TIME - The amount of time it takes a page to load within a browser.

ACK (acknowledgement) - When a modem receives a data packet, it sends a signal back to the sending modem. If all the data is present and correct, it sends an ACK (acknowledgement) signal, which acts as a request for the next data packet. If the modem didn't get all the data, it sends back a negative acknowledgement, or NAK

ACPI (Advanced Configuration and Power Interface) - This power management standard, proposed by Microsoft, Intel, and Toshiba, lets the PC control power to peripherals like CD-ROMs and printers, as well as consumer devices hooked up to the PC. Peripherals can also use ACPI to turn on the PC. For example: you could insert a CD-ROM into a drive, and the computer would automatically boot up.

ACTIVE CHANNELS -  An Active Channel is what Microsoft calls a Web site that has been enabled for push delivery to Internet Explorer 4.0 browsers. To create a channel, developers write and upload a CDF (channel definition format) file to their Web site; new content is delivered to users automatically when the site is updated. Developers and subscribers can control the update frequency; which channels, subchannels, and items (sections) are subscribed to; and other channel characteristics. Most Active Channels use dynamic HTML (DHTML) and other effects to spice up content and make it more interactive.

ACTIVE HYPERLINK -  A hyperlink that is currently selected in a Web browser. Some Web browsers indicate the active hyperlink by changing its color.

ACTIVE MATRIX - Flat-panel displays for laptop computers are created by laying diodes over a superfine grid of wires. The diodes are activated by applying current to various points around the grid. Connect enough of these dots and you get an image. Active-matrix displays use transistors to keep their diodes in an on or off state, unlike their passive-matrix cousins, which rely on the diodes' persistence. As a result, active-matrix displays are brighter and produce better color than passive-matrix displays. However, the additional technology required to build active displays also makes them far more expensive.

ACTIVEX - This set of technologies from Microsoft provides tools for linking desktop applications to the World Wide Web. Using a variety of programming tools--including Java, Visual Basic, and C++--developers can create interactive Web content. For instance, ActiveX technology can allow users to view Word and Excel documents directly in a browser.

ACTIVEX CONTROL - A component that can be inserted in a page to provide functionality not directly available in HTML, such as animation sequences, credit-card transactions, or spreadsheet calculations. ActiveX controls can be implemented in a variety of programming languages from Microsoft and third parties.

AD - (Administrative Domain) A collection of hosts and routers, and the interconnecting network(s), managed by a single administrative authority.

ADDRESS - The location of a computer, file or peripheral device on a network.

ADDRESS BOOK - Address books are used to store frequently used addresses, so that they can be looked up quickly. You can select an address from an address book and paste it in the address field. There are two type of address book:
a) system address books (created by the mail administrator and available to all users - you cannot modify system address books)
b) personal address books (created by you).

ADN - (Advanced Digital Network) -- Usually refers to a 56Kbps leased-line.

ADPCM (Adaptive Differential Pulse Code Modulation) -  This method of encoding sound data files takes up less storage space than the regular PCM format used by WAV and AIFF files--and CD audio for that matter. ADPCM comes in more than one flavor: IMA's ADPCM, for example, is used on the Sony Mini Disc to cram more data onto a smaller platter; Microsoft ADPCM is used as part of Windows 95's canon of audio codecs.

ADSL (Asymmetric Digital Subscriber Line) -  Like ISDN, ADSL uses standard phone lines to deliver high-speed data communications. But while ISDN's transmission speed is limited to 64 kbps, ADSL technology can deliver upstream (from the user) speeds of 640 kbps and downstream (to the user) speeds of more than 6 mbps. Even better, ADSL uses the portion of a phone line's bandwidth not utilized by voice, allowing for simultaneous voice and data transmission. However, as of late 1996, ADSL was still in development and not widely available.

AGP (Accelerated Graphics Port) -  A dedicated graphics bus slot on PC motherboards. Designed by Intel, AGP operates at 66 MHz and transfers data at a rate up to 528 MB/sec. By comparison, the PCI slot that most graphics cards currently use runs at 33 MHz and has a maximum transfer rate of 132 MB/sec. AGP's greater bandwidth will allow game and 3D application developers to store and retrieve larger, more realistic textures in system memory rather than video memory, without incurring a dramatic performance hit.

AIFF  (Audio Interchange File Format) - This audio file format was developed by Apple Computer for storing high-quality sampled audio and musical instrument information. It is also used by Silicon Graphics and in several professional audio packages. Played by a variety of downloadable software on both the PC and the Mac.

AFFORDANCE - A capability in a world. An object may have the affordance of being able to be moved an avatar may have the affordance of being able to gesture.

AGENT - Agents are chunks of software that have certain amount of freedom to move themselves around virtual spaces or computer networks on their own.

ALIAS - A name a user chooses to associate with himself or herself with in a text based or visual virtual world.

ALPHA, ALPHA TESTER - An initial version of a new program which has been made available to a select group of brave and patient users (alpha testers)

ALPHA BLENDING - In computer graphics, each pixel has three channels of color information--red, green, and blue--and sometimes a fourth called the alpha channel. This channel controls the way in which other graphics information is displayed, such as levels of transparency or opacity. Alpha blending is the name for this type of control, and it's used to simulate effects such as placing a piece of glass in front of an object so that the object is completely visible behind the glass, unviewable, or something in between.

ALPHA CHANNEL - In computer graphics, each pixel has three channels of color information--red, green, and blue--in various bit depths. In 24-bit display graphics adapters, there are 8 bits per color per pixel, but when the card has a 32-bit bus, the additional 8 bits are used as an alpha channel to control the color information of the other 24 bits of color

AMBIENT SOUND - Sound that is played as a background to a virtual world.

AMERICA ONLINE - Commercial online service.

AMPLITUDE - Like any wave, analog signals contain peaks and valleys. By measuring the difference between the peaks and the valleys and then dividing by a factor of two, we get the amplitude--or strength--of the wave. The larger the amplitude, the stronger the wave.

ANALOG CONTROLS - Analog controls are dials, knobs, and similar mechanisms that you find on monitors and other devices. They have a potentially infinite number of settings that cannot be stored in a profile and recalled--which means that a monitor's analog controls require readjustment whenever you change the video mode (resolution or refresh rate).

ANALOG LINE - Voice-grade telecommunications line used for telephones. To communicate with a computer on an analog line requires a modem at each end of the connection-to convert digital information to analog, then back to digital.

ANCHOR -  Anchors are the same as hyperlinks--the underlined words or phrases you click on in World Wide Web documents to jump to another screen or page. The word anchor is used less often than hyperlink, but it does maintain the seafaring theme of navigating and surfing the Net.

ANIMATED GIF - This is a graphical animation that is in GIF format. The biggest advantage of GIF animations is that no plug-ins are needed, and most browsers (over 90%) support them.

ANNOTATION -  feature of NCSA Mosaic that lets you add a comment to a document being viewed

ANONYMOUS FTP - FTP (File Transfer Protocol) is a common way to connect to a network, access directories, or obtain files. Usually requires a password and user name.

ANONYMOUS REMAILER- An anonymous remailer is a computer that strips away identifying information (such as your email address) before passing your message on to an email address or a newsgroup. When you send mail using a remailer, the From: field of your message becomes a made-up address like 12xyx@remailer.com. There are actually two kinds of services called anonymous remailers. The first is truly anonymous: no one anywhere knows your identity. With the second, called pseudo-anonymous or sometimes pseudonymous, the owner of the service knows your identity and can be forced in a court of law to reveal it. Most truly anonymous services are free (it's difficult to bill an unknown, unnamed client), but they often require some skill and effort to use. Many pseudo-anonymous services charge a fee, but are more user-friendly.

ANSI  (American National Standards Institute) - This organization of American industry groups works with the standards committees of other nations to develop standards to facilitate international trade and telecommunications. Some of ANSI's greatest hits in the computing field include ASCII, SCSI, and the ANSI.SYS device driver.

ANTIALIASING - On computer monitors the pixels themselves aren't curved, but they have to show curves. Using polygons to simulate curves in alphanumeric characters or vector graphics makes the edges of objects appear jagged. The technique for smoothing out these jaggies is called antialiasing, and it usually takes the form of throwing in pixels of washed-out color along the curve. This actually makes text seem a little blurred but, strangely enough, more readable.

ANTIGLARE TREATMENT - The glass face of a monitor has a natural tendency to reflect light, which can be hard on the eyes and can make it difficult to see what's being displayed. An antiglare treatment is a coating on the glass that either absorbs or diffuses the light to prevent reflections. Three types of antiglare treatments are in general use. Most common is a silica-based coating that diffuses light, which tends to decrease the screen's focus. Another approach, using optical lenses, is better because the lenses don't diffuse light. The third technique, mechanical etching (that is, roughing up the surface of the glass), should be avoided because it blurs the onscreen image.

APERTURE GRILLE - In Trinitron monitors, the aperture grille is a series of wires stretched vertically down the inside of the CRT (cathode ray tube) to mask the beams from the electron guns at the back of the tube. In other types of monitors, this function falls to a perforated metal plate called a shadow mask.

APPLICATION - Software, or set of software, which accomplishes a particular task (e.g. a word processor, spreadsheet)

API (Application Programming Interface) -  An API is a series of functions that programs can use to make the operating system do their dirty work. Using Windows APIs, for example, a program can open windows, files, and message boxes--as well as perform more complicated tasks--by passing a single instruction. Windows has several classes of APIs that deal with, messaging, and other issues.

APPLET - A program that can be downloaded over the network and executed on the user’s computer. This usually refers to a Java program that is accessed with a web browser.

ARCHIE - A long-established (read: antiquated) way to find files on the Internet, Archie is a system that gathers, indexes, and helps you find information anywhere on the Internet. Developed at McGill University, Archie started life as an indexed directory of files from archives. However, Archie is a slow boy, and his findings depend on how well maintained the Archie server he connects to is. Found files are retrieved using ftp (file transfer protocol).

ARCHIVE - One large file which contains many compressed smaller files. Files are generally archived when they are stored for future use or reference. They also make it easier to transfer large programs and sets of files from one machine or place to another. Common archive formats include ARJ, TAR, ZIP, and ZOO.

ARJ - A well-known archive program available for PC's.

ARP - (Address Resolution Protocol) Used to dynamically discover the low level physical network hardware address that corresponds to the high level IP address for a given host. ARP is limited to physical network systems that support broadcast packets that can be heard by all hosts on the network.

ARPANET - In the late 1960s--when the U.S. military was desperately afraid of a nuclear attack from the Soviet Union--some government computer scientists in the Advanced Research Projects Agency got together to design a bomb-proof network that would connect military bases and other military agencies. To do so, they created a system based on linking distant computers via a newly developed set of protocols called TCP/IP. This new nuke-proof network (though it was never tested with real nukes, of course) became ARPAnet. In the early 1980s, ARPAnet technology was put to use for nonmilitary purposes and gradually became what we now call the Internet. ARPAnet was taken out of commission in favor of a higher-speed network called NSFNET in 1990.

ARTIFACT - In all kinds of computer graphics, including any display on a monitor, artifacts are things you don't want to see. They fall into many categories (such as speckles in scanned pictures), but they all have one thing in common: they are chunks of stray pixels that don't belong in the image.

ARTIFICIAL INTELLIGENCE (AI) - A general term for software and hardware systems that seek to mimic or extend higher order functions of the human mind, like cognition, vision or locomotion

ASCII - American Standard Code for Information Interchange, the mapping of ordinary letters and numbers to standard numerical representations. It allows computers from different platforms to display, transmit and print textual information. Often used to refer to plain text that does not contain word-processing codes.

ASCEND COMPRESSION - Ascend uses a proprietary data compression implementation, based on STAC Incorporated's standard, with many of its router products. This allows products that support Ascend's STAC compression to achieve greater throughput over Internet connections.

ASDL - (Asymmetric Digital Subscriber Line) New technology to carry high speed data over ordinary phone lines. It will be up to 70 times as fast as a 28.8 modem, and can be used concurrently with voice over the same line. Expected to be offered to homes commercially beginning in 1998.

ASIC (Application Specific Integrated Circuit) - As its full name implies, an ASIC is a custom microchip designed for a specific application. Of course, the chip doesn't reinvent the wheel: ASIC design involves taking common functions from a library and integrating them onto a circuit.

ASPECT RATIO -  The physical proportions of the width of your screen to its height. Aspect ratios affect how images are displayed. The number of pixels that are shown across the width and height of your screen must be factored into aspect ratios. Square aspect ratios mean that an image will not be distorted when displayed on your screen.

ASYNCHRONOUS COMMUNICATION - This term describes how your computer uses a modem to connect with other computers. Back in the days of teletypes and dumb terminals, computers sent data synchronously--they operated using a shared timer that marked the transmission of each character. This didn't work very efficiently for large blocks of data over phone lines, however. So modern modems use asynchronous rules: instead of synching up to a time signal to mark a character, transmitting computers use a start bit, a stop bit, and an optional error-checking parity bit to indicate to receiving computers the boundary of each character. (The term is a bit of a misnomer, though, since all modems synch up with one another before they transmit data.)

ATAPI  (Attachment Packet Interface) -  The Enhanced IDE standard by itself works wonders for hooking up disk drives to PCs. But that's not enough. People want to attach tape drives and CD-ROMs to the same controller. Thanks to EIDE's support for the ATAPI standard, they can. Using ATAPI-capable hardware and software drivers, you can mix and match different types of drives on the same EIDE controller, which is both a convenience and a savings in hardware costs.

AT COMMANDS - AT is a contraction of attention, a command used to program SmartModems from Hayes Microcomputer Products. AT commands program a variety of modem hardware settings and were adopted by other modem manufacturers who wanted to market their wares with the coveted phrase Hayes-compatible. At one time, you couldn't call yourself an online aficionado if you didn't know that ATL0 turned your modem speaker way down and ATM0 turned it off. Now the commands are usually hidden under a menu option in your communication software.

ATM - (Asynchronous Transfer Mode) A method for the dynamic allocation of bandwidth using a fixed-size packet (called a cell). ATM is also known as "fast packet".

ATTACHMENT - An included file: ex. you can send an E-Mail with an attachment. The attachment can be any file allowed by that E-Mail system (ex. data file, an image file etc.).

ATTRIBUTE - A setting for a tag, that affects the way the tag is displayed.

AU - When a Sun Microsystems or other Unix computer makes a noise, it does so in AU file format. And because the Internet is dominated by Unix boxes, you'll find a lot of AU files there. Luckily, Macintosh and PC browsers such as Netscape Navigator are usually able to play AU files, which have the extension .au. A sound file that originated on a PC is likely to be in WAV or MIDI format instead.

AUP - (Acceptable Use Policy) - Many transit networks have policies which restrict the use to which the network may be put. A well known example is NSFNET's AUP which does not allow commercial use. Enforcement of AUPs varies with the network.

AUTHENTICATION - Verification that a user is who she says she is. This can be done by password or any other means. Outside the Internet, fingerprinting or signatures are standard techniques.

AUTHENTICATION DATABASE - A database on a server that matches user
names to passwords.

AUTO ANSWER - A modem indicator light that tells you the modem is ready to pick up the phone, so long as there's a communication program running and prepared to handle the call. The light is often not shining even when the modem is prepared to take a call, so it's not a useful light.

AVABUSE - Verbal abuse of a user while using their avatar in a virtual world.

AVADDICTION - Addiction to life and interaction in avatar virtual worlds

AVATAR - Originally the term avatar came from Hindu mythology and is the name for the temporary body a god inhabits while visiting Earth. Avatar can also denote an embodiment or concrete manifestation of an abstract concept. The ancient Sanskrit term avatara meant "a passing down". Avatar was first coined for use in describing users' visual embodiment in Cyberspace by Chip Morningstar in the early days of Habitat back in 1985.

AVI - Audio Video Interleave, a popular format for video files.  

©2008 ITS Systems. All rights reserved.