Multimedia Glossary: A

ActionScript

ActionScript is the scripting language of Flash which is derived from ECMA, a European Standard version of JavaScript. ActionScript is a simplified version of ECMA with some additional shortcuts.

Additive color

artificially created color

Also see substractive color.
Color hues cannot be substracted on electronic devices that are used for displaying color. On these devices color ghues are added to one another.

The primary additive colors are: red, green, blue. Secondary additive colors are obtained by mixing primary colors in a 1:1 ratio. The absence of light results in black, while adding all three primary additive colors result in white. Adding the three primary substractive colors in equal ratios would result in brown.

Address Resolution Protocol

See ARP

ADSL

Asymmetric Digital Subscriber Line

ADSL is one kind of Digital Subscriber Line transport systems and can carry as much as 6 Mb/s over a copper line. ADSL thus makes broadband available over copper phone lines.

Advanced Research Projects Agency

See ARPA

AHG

Ad Hoc Group (MPEG)

A group of people established to address a specific topic.

AIFF

Audio Interchange File Format

A sound and video file format developed for the Apple Macintosh platform. Browser plug-ins are available to play files in this format.

Aliasing

The pixels on a CRT are square and result in jagged edges in graphic images. When enlarged a straight line looks like a flight of steps. This effect is called aliasing.
Also see Anti-aliasing.

American National Standards Institute

See ANSI

American Standard Code for Information Interchange

See ASCII

Anchor

An anchor in a markup language is a technical term for what is popularly known as a "link" between web documents, or between locations within the same document (in which case it is identified by a fragment identifier).

• Source Anchor : where the linked anchor starts. In HTML the Source Anchor is specified with the href attribute.
• Destination Anchor : where the link must go to. In HTML the Destination Anchor is specified with the name attribute, and in XHTML with the id attribute.

An anchor in a document such as a DTP document is a fixed point to which a containing box is referenced for layout purposes. For example, the box containing an image in text may be offset at a certain coordinate point from the top of a page. Its anchor point can be measured from this point to the position in which it actually occurs.

ANSI

American National Standards Institute

An organization that defines standards in the information technology industry and participates in defining network protocol standards. ANSI is a member of ISO. The ANSI characters are characters that when preceded with the ESC (Escape) character they function as a command. ANSI escape sequences are used to send commands to monitors or keyboards.

Anti-aliasing

Pixels on CRT screens are square and result in jagged edges where colors meet. To reduce this effect, anti-aliasing is used, which is a technique used for the smooth transition of colors into one another. The smooth transition is achieved by adding a "half-way" color hue in between two bordering colors. This fringe color gives the illusion that the two colors blend smoothly into one another.
Also see Aliasing.

Archie

An older brother of search engines oni the Internet allowing searches of ftp sites.

Archive

A collection of stored files not often used, but nevertheless available. In practice there is no difference between files of current web sites and those in the archive. Both are equally accessible.

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ARP

Address Resolution Protocol

This protocol is broadcast from an internet server and all TCP/IP devices on the local network can hear it. When the machine with the appropriate IP address hears it, it responds to the ARP request.

Each hardware card (.ie. each NIC, Network Interface Card) has a unique hardware address. It is also possible to assign a software address to the card (which would be an IP address). Hardware address information is obtained from the ARP.

Each host has an ARP table that contains software (IP) addresses mapping to hardware (NIC) addresses. ARP looks for a hardware address for a given IP address (the opposite of RARP).

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ARPA

Advanced Research Projects Agency

ARPA is an alliance formed in the 1970s between computer manufacturers and universities to develop communication standards for networks. It designed a protocol that became the basis for TCP/IP. Also see RARP

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ARPANET

The granddaddy of The Internet. This was the original experimental network funded by the US government to determine the feasibility of such a network.

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ASCII

American Standard Code for Information Interchange

This is a character set suited for the characters of a particular language. ASCII is a subset of the UCS (Universal Character Set). As the computer revolution started in the USA ASCII became the standard code set, although there are some systems (such as IBM's EBCDIC) that use a different configuration. Originally ASCII consisted of code for 128 characters, and later this was extended to 256 codes (the extended character set). This extended set included European characters that are not found in English, such as ê é ô and graphic signs such as ¦. Each key on a computer keyboard has an ASCII code and the keyboard can be set to use different configurations of character sets. Languages that use different kinds of alphabets have different kinds of character sets.

More technically, the smallest information unit used by computers are bits, that make up larger units called bytes. There are 8 bits to one byte in an 8-bit system. Using this system there are 128 codes available to represent characters. Some of the codes are reserved for control keys such as the ENTER and space bar keys. There are thus not enough keys on a particular keyboard for all the characters of all the languages of the world. For this reason the language characters are divided into character sets.

The ASCII system is based on the 8-bit system, but the first digit is used for checking and control purposes. ASCII is represented in binary format on the machine level. This table shows how ASCII is represented in the alphanumeric and binary systems:

alphanumeric	binary
1	00110001
2	00110010
3	00110011
4	00110100
5	00110101
6	00110110
7	00110111
a	01000001
b	01000010
c	01000011
d	01000100
e	01000101
f	01000101
g	01000111

Asymmetric Digital Subscriber Line

See ADSL

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ATM

Asynchronous Transfer Mode

This is a method used for high bandwidth data transfer, made possible by hardware switches that create a temporary direct path between two points. This ATM is not to be confused with the Automatic banking machines encountered in shopping malls.

Attribute

Markup language
An attribute is a markup command used together with SGML elements that allow more control over the element. In HTML 4 there are more than 120 attributes. Attribute specify characteristics of specific elements and cannot be used with any element. DTDs specify which attributes can be used with which elements.
Image
An attribute is a property of an image - such as its color, or texture, each of which is an attribute of the image.

AU

AU is a sound file format developed by Sun for the Unix platform for use on The Internet. It is known as the Sparc-audio or u-law format.

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Audio Interchange File Format

See AIFF

Author / web author

A web author is a person who writes the markup (HTML) for web documents. Note that a distinction should be made between a Web Author (who writes the HTML markup code), the Web Graphics Designer (who designs a web page artistically), a Web Designer (who designs the information and information technology of the website; this term is also popularly used for the person responsible for all the authoring aspects mentioned here) and a Web Copy Writer (who writes the text of the document. In some cases these functions may be performed by the same individual, but they are different functions demanding different skills.

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Authoring Tool

An Authoring Tool is a program that enables a multimedia author to create a multimedia product. Authoring tools typically write many of the functions withou the developer having to know the technicalities of programming in a programming language. In its simplest form, an HTML Authoring Tool, for example, automatically completes end tags. A Multimedia tool may simplify ways in which objects are placed on a timeline.

AVI

Audio Video Interleafed

A sound and video file format developed for the Microsoft Windows platform. It is based on the Microsoft Windows Resource Interchange File Format (RIFF) specification. A special player is required to play these files.

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