AC (Alternating Current) - A current, or flow of electrical charge, that has alternately positive and negative values.
Accelerator board - An adapter card containing a microprocessor that is faster and more powerful than CPU on the motherboard, used to upgrade a PC system. Also, an adapter card containing a special-purpose microprocessor used to speed up specific operations, such as displacing graphics. These were common with 80286 computers.
Access time - The time that elaspes from the moment that information is requested to the moment it is required.
Active partition - On a hard disk, the partition containing the operating system, and used to boot the system on power up.
Adapter card - A circuit board that serves as an interface between the system bus and some device such as a disk drive or video monitor.
Address - The physical location in computer memory where a particular segment of information is stored.
Address bus - A bus that is dedicated to the transmission of storage addresses associated with the data being concurrently transmitted on the data bus.
ADSL (Asychronous Digital Subscriber Line) - This is a special type of hardware that uses the existing copper phone wire to achieve higher bandwidth along the Internet.
Alphanumeric characters - A character set that contains only letters (A-Z) and digits (0-9).
Alphanumeric mode - A video mode in which control is limited to the display of a complete character, composed of a matrix of horizontal and veritcal pixels.
Ampere (amp) - The basic unit for measuring electrical current.
Analog - Information contained in a continuosly varying form, analoguous to some physical property.
ANSI (American National Standards Institute) - An industry - sponsored organization founded in 1918 to propose, approve, and publish data- processing standards for voluntary use in the United States.
Application program - A software program written for a specific application, such as word processing, database management or spreadsheet generation.
Arbitration - A method by which multiple devices attached to a single bus can bid or arbitrate to get control of that bus.
Archive bit - A data bit that indicates whether or not a file has been changed since it last was backed up.
ASCII (American Standard Code for Information Interchange) - The accepted standard for keyboard character codes. The code defines 128 control and graphic characters, representing the key codes 0 to 127.
Aspect ratio - The ratio of active screen width to height, or of horizontal to vertical pixels.
Asynchronous communication - Data transmission in which the lenght of time between transmitted characters is not fixed. Timing is dependent on the actual time for the transfer to take place, plus the addition of start bits to each character.
