Computer Science

AC
Alternating Current

Access Method
A way of accessing the network/Disk Drives(I/O).

Access speed
The time required to complete read or write instructions as required by the memory controller chip. Usually measured in nanoseconds (ns).

ACK
Acknowledgment message confirming receipt of the data packet.

Active Hub
Regenerates or amplifies a signal when it is passed through.

ActiveX
ActiveX is a model for writing programs. ActiveX technology is used to make interactive web pages that look and behave like computer programs, rather than static pages. With ActiveX, users can ask or answer questions, use push buttons, and interact in other ways with the web page.

Adapter Card
A card that provides the connection between the PC expansion bus and the network cabling.

Address Bus
A group of parallel conductors (circuit traces) found on the motherboard, which are used by the CPU to "address" memory locations. Determines what information or code is to or received from the data bus.

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

Affiliate Marketing
Small companies or individuals whose Web pages link to larger sites, like Amazon.com, and earn a commission on the purchases of referrals.

ALU
Arithmetic Logic Unit

Analog Signal
A continuously variable signal, or a circuit or device designed to handle such signals; opposite of digital.

AppleShare
The file server on an AppleTalk network.

Applet
A small Java program that can be embedded in an HTML page.

AppleTalk
The Apple networking protocol.

Application
Software, program; these three terms are often used interchangeably.

Application Layer
The highest layer of the OSI Model, it supplies functions to applications, or computers on the network (nodes), so they can communicate with other applications or nodes.

Application Server
A dedicated server for applications.

Archie
A tool (software) for finding files stored on anonymous FTP sites.

ARCNet
Attached Resource Computer Network

ARP
Address Resolution Protocol

ARPANet
(Advanced Research Projects Agency Network) -- The forerunner of the Internet. Developed in the late 60s and early 70s by the US Department of Defense as an experiment in wide-area-networking that could be utilized for communication in the event of a nuclear war.

ASCII
American Standard Code for Information Interchange - the basis for computer communication. Basic ASCII consists of 128 codes that represent the English alphabet, punctuation and certain control characters. Most systems today recognize 256 codes, the original 128 plus an additional 128 codes called the extended character set.

Asynchronous
Not Synchronized, the computer is free to transmit any number of characters at any time. The bits constituting a single character are transmitted at a fixed rate, but the pauses between transmission can be of any duration.

ATA/CAM
AT Attachment/Common Access Method

Attenuation
The signal loss due to the physical properties of copper wire that happens over distance.

Auditing
A third-party company will audit the number of visitors sent from a Web site during a given time. When you try to sell advertising, auditing gives the potential advertiser proof for site popularity. This service can often be obtained free of charge from various Internet sites such as eXTReMe tracking at http://www.extreme-dm.com/tracking/.

AWG
American Wire Gauge AWG is the standard that describes wire thickness. The AWG wire number decreases as the wire thickness increases.