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[This is preliminary documentation and subject to change.]

ActiveX control

A reusable software component that can quickly add specialized functionality to World Wide Web sites, desktop applications, development tools, and interactive video programs. These controls typically provide user interface elements, such as buttons. Microsoft® ActiveX® controls were previously known as OLE custom controls or OCXes.

Address Resolution Protocol

(ARP) The protocol that maps Internet Protocol (IP) addresses to the physical hardware addresses of specific networks. This protocol operates at the level of network operating systems and is not generally accessible to applications.

ADSL

See Asymmetrical Digital Subscriber Line.

analog television tuner card

A type of broadcast receiver card that receives and processes analog video signals.

analog video

Video transmitted by an analog signal, such as an NTSC, PAL, or SECAM transmission.

announcement filter

In the Announcement Listener, one of a collection of dynamic-link libraries (DLLs) or executable files that act as Automation servers. An announcement filter distinguishes between announcements that are of interest to a particular broadcast client's user and those that are not. Multiple filters can exist for different kinds of data; for example, in Broadcast Architecture Internet channel broadcasting and enhancements have their own filters.

Announcement Listener

A operating-system service that receives announcements of upcoming data. Using Announcement Listener, the broadcast client can filter incoming data at the network interface (that is, at the broadcast receiver card) so the client only receives data of interest.

API

See application programming interface.

application

A computer program designed to help people perform a certain type of work. An application differs from an operating system (which runs a computer), a utility (which performs maintenance or general-purpose chores), and a programming language (with which computer programs are created). An application can manipulate text, numbers, graphics, or a combination of these elements. In the context of Broadcast Architecture, potential applications might enable users to shop at home, find information, order movies, and so on.

application layer

The seventh and highest layer in the International Organization for Standardization's Open Systems Interconnection (OSI) model. The application layer contains the signals sent during interaction between user and application and that perform useful work for the user, such as file transfer. See also data link layer, transport layer.

application programming interface

(API) An interface exposed by a software module as a means for other software modules to interact with it. For example, applications generally interact with an operating system by way of the APIs the operating system exposes. In the case of Microsoft® Windows® 98 and Microsoft® Windows NT®, the APIs consist of functions that an application uses to request operating-system services, such as screen management, keyboard input, printer output, and so forth.

ARP

See Address Resolution Protocol.

ASCII

(American Standard Code for Information Interchange) A coding scheme that assigns numeric values to letters, numbers, punctuation marks, and certain other characters. By standardizing the values used for these characters, ASCII enables computers and computer programs to exchange information. Although it lacks accent marks, special characters, and non-Roman characters, ASCII is the most universal character-coding system.

Asymmetrical Digital Subscriber Line

(ADSL) A technology that allows data to be sent over ordinary twisted-pair telephone lines at T1 trunk-line speeds, currently up to 1.544 megabits per second, and to be returned at a current rate of 16 kilobits per second. ADSL provides a bidirectional voice signal while data is sent.

authorization key

A Triple DES key used to encrypt session keys.