Adapter - A network interface card or external device that lets a PC connect to a network.

Address - In online terms this commonly refers to a particular machine or computer system connected to the Internet. Machine 'addresses' exist on the Internet for servers for e-mail sending and receiving, web page or web site access, and almost everything functioning on the Internet. Internet users encounter two important types of addresses: Web page addresses (more properly called URLS) and E-mail addresses (for sending e-mail to someone. E-mail addresses almost always contain an @).

Applet - A type of computer program that allows animation and other interactive functions on a file or Web page.

ARQ - Automatic Repeat Request. A general term for error control protocols featuring hardware detection and retransmission of defective data. This term is used primarily by US Robotics.

ARPANet - (Advanced Research Projects Agency Network) - The precursor to the Internet. Developed in the late 60’s and early 70’s by the US Department of Defense as an experiment in wide-area-networking that would survive a nuclear war.

ASCII - American Standard Code for Information Exchange. A 7-bit binary code representation of letters, numbers and special characters. It is universally supported in computer data transfer.

ASP (Application Service Provider) - A network technology provider that provides business productivity applications and processing infrastructure to small and medium size businesses that want to avoid the business of physical and human costs for non-core information technologies. ASPs host and deliver accounting, payroll, customer service, education, etc. usually using web-browser based technology.

Asynchronous - Data transmission in which the actual data is preceded by a start bit and followed by a stop bit since the time between transmitted characters varies. Compare Synchronous.

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 term Hayes-compatible. It was considered a must to know that ATL0 turned your modem speaker down and ATM0 turned it off. Now, however, the commands are usually hidden under a menu option in your communication software.

Attachment - A computer file electronically “paper clipped” to an e-mail message and sent along with it.

Authentication - A security measure for checking a user’s identity (userID). Some Web sites require a user’s identity to be authenticated before they can enter. This is usually done with a password and/or username.

Auto Answer - The modem feature which enables detection of a ring and answering without assistance from a program.

AVI (Audio/Video Interleaved) - a common video file format (.avi). Video quality can be very good at smaller resolutions, but files tend to be rather large.