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Glossary of Computer Hardware Terms - The Letter A

written by: Jesma•edited by: Michele McDonough•updated: 12/26/2008

Complete definitions for Computer and Network hardware terms that begin with the letter A. Covers beginning and advanced terms that impact your life as a computer user, like Applications, ACPI, AGP, Antistatic, and more.

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    All Things A

    AC - Alternating Current

    Electricity running from the wall outlet. 120 Volts at 60Hz through a fuse or circuit breaker that can typically handle around 15-20 Amps.

    Access Light

    The LED on the front of a device indicating that it is reading or writing data.

    Access Time

    The time that elapses from the moment information is requested and the information is delivered. Usually given in nanoseconds (ns) for memory chips and milliseconds (ms) for disk drives.

    ACPI - Advanced Configuration and Power Interface

    A standard developed by Intel, Toshiba, and Microsoft that implements advanced power managment functions through the operating system. Also known as APM (advanced power management).

    Active Matrix

    A type of LCD (liquid crystal display) screen containing at least one transistor for every pixel on the screen. Also known as TFT.


    A device that serves as an interface between dissimilar devices. Often also called a circuit board, or card, but can also refer to a connector or cable adapter that changes connection types from one to another.


    The location of a particular piece of data or other information found on a computer.

    Address Bus

    One or a series of electrical conductors that are used to carry the binary address from the microprocessor to the rest of the system.

    ADSL - Asymmetric Digital Subscriber Line

    High speed transmission technology commonly used for Internet access. ADSL sends information asymmetrically, meaning data travels faster one way than the other. Original application was a T1 line, though it is now available in many different speeds and configurations.

    AGP - Accelerated Graphics Port

    A dedicated interface between the video adapter and the motherboard's North Bridge. AGP is 32 bits wide and runs at 66MHz base speed. It can transmit 1, 2, 4, or 8 bits per cycle - marketed as 1x, 2x, 4x or 8x. This is an older standard that is quickly becoming entirely unsupported.

    Ampere - AKA Amp

    Basic unit for measuring electrical current.


    Software designed to make diagonal or curved lines appear smooth and continuous. Aliasing refers to undesirable visual effects in computer generated images caused by low sampling. Antialiasing seeks to correct this.

    Anti-Static Mat

    A pad on which computer components should be placed to prevent damage through electro-static discharge (ESD). May also refer to a large floor mat placed below a computer desk to discharge static from the technician while he is servicing the computer and components.


    Software that prevents files containing viruses from being executed on a computer, as well as detects, repairs, and removes infected files.


    Software for the end-user like office productivity, games, web browsers, etc.

    Archive Bit

    The bit in a file's attribute byte that indicates whether the file has been modified since the last time it was backed up.

    ASCII - American Standard Code for Information Interchange

    The commonly used 256 character set containing letters, numbers, and special characters. The graphical representation of a single byte. eg: the letter N contains 8 bits (1 byte) indicating how it should be displayed on screen.

    ATAPI - AT Attachment Packet Interface

    A specification that defines device-side characteristics for IDC peripherals like CD-ROM and tape drives.

    ATM - Asynchronous Transfer Mode

    A high-bandwidth low delay transmission technology.


    A common motherboard form factor that has been in use since 1995 characterized by a double row of rear external I/O (input/output) connectors. Memory and CPU locations are designed not to interfere with the installation of expansion cards.

    Available Memory

    Memory not currently in use by the operating system, drivers, or applications.

    Average Access Time

    The average time it takes for a disk drive to begin reading data placed anywhere on the drive. This includes seek time and latency.

    Average Seek Time

    The average amount of time it takes to move the heads of a hard disk from one random cylinder location to another. Often defined as the seek time across one third of the total number of cylinders.