- An audio standard for delivering 5.1 audio developed by Dolby
Laboratories. This system compresses six channels of digital audio into 384
Kbps versus 4 Mbps uncompressed.
- Advanced Configuration and Power Interface. A specification that defines a
new interface to the system board that enables the operating system to
implement operating-system directed power management and system configuration.
Following the ACPI allows system manufacturers to build systems consistent
with the OnNow design initiative for instantly available PCs.
- ACPI hardware
- Computer hardware with the features necessary to support operating system
power management and with the interfaces to those features described using the
Description Tables as specified in Advanced Configuration and Power
- ACPI Name Space
- A hierarchical tree structure in operating-system–controlled memory that
contains named objects. These objects can be data objects, control method
objects, bus and device package objects, and so on. All the information in the
ACPI Name Space comes from the Differentiated System Description Table.
- See device.
- adaptive compression
- Data compression software that continually analyzes and compensates its
algorithm, depending on the type and content of the data and the storage
- add-on devices
- Devices that are traditionally added to the base PC system to increase
functionality, such as audio, networking, graphics, SCSI controller, and so
on. Add-on devices fall into two categories: devices built onto the system
board and devices on expansion cards added to the system through a system
board connector such as PCI.
- Adaptive Differential Pulse Code Modulation. An encoding format for
storing audio information in a digital format.
- Asymmetric Digital Subscriber Line. A method for moving data over regular
phone lines. An ADSL circuit is much faster than a regular phone connection,
and the wires coming into the subscriber's premises are the same (copper)
wires used for regular phone service.
- Acoustic echo cancellation.
- Software that runs on a client computer for use by administrative software
running on a server. Agents are typically used to support administrative
actions, such as detecting system information or running services.
- In compression software, refers to a specific formula used to compress or
decompress video or other data.
- ACPI Machine Language. Pseudocode for a virtual machine supported by an
ACPI-compatible operating system and in which ACPI control methods are
written. The AML encoding definition is provided in section 16 of the
Advanced Configuration and Power Interface Specification.
- A method of signal representation by an infinitely smooth universe of
numeric values. Measurements that are characterized as analog include readings
of voltage and current. Analog devices are characterized by dials and sliding
mechanisms. Compare with digital.
- analog video
- A video signal that represents an infinite number of smooth gradations
between given video levels. Compare with digital video.
- Unequally scaled in vertical and horizontal dimensions.
- American National Standards Institute. A standards-setting,
non-governmental organization that develops and publishes standards for
voluntary use in the United States.
- A form of interpolation used in graphics display technology when combining
images; pixels along the transitions between images are averaged to provide a
- Application programming interface. A set of routines that an applications
program uses to request and carry out lower-level services performed by a
computer operating system.
- Advanced Power Management. 1. A software interface (defined by Microsoft
and Intel) between hardware-specific power management software (such as that
located in a system BIOS) and an operating system power management driver. 2.
An abridgment of the APM BIOS Interface Specification title.
- 1. A software module in Windows that handles the allocation of
hardware resources among devices. 2. Under Windows 95, the Plug and
Play device driver responsible for allocating a specific resource among all
drivers that require the resource. For example, VDMAD is a DMA-channel
arbitrator, and VPICD has services for allocating IRQ lines. Windows 95
provides arbitrators for standard I/O, memory, hardware interrupt, and
- A general term referring to the structure of all or part of a computer
system. Also covers the design of system software, such as the operating
system, as well as referring to the combination of hardware and basic software
that links machines on a computer network.
- An unintended, unwanted visual aberration in a video image.
- American Standard Code for Information Interchange. The most popular
coding method used by small computers for converting letters, numbers,
punctuation, and control codes into digital form.
- Application-specific integrated circuit.
- ACPI Source Language. The programming-language equivalent for AML. ASL is
compiled into AML images. The ASL statements are defined in section 15 of the
Advanced Configuration and Power Interface Specification.
- aspect ratio
- The relationship of width and height. When an image is displayed on
different screens, the aspect ratio must be kept the same to avoid either
vertical or horizontal stretching.
- assigned configuration
- Drivers examine this portion of the device node to determine which
resources have been allocated for the device. For Plug and Play cards, the
assigned resources for a device can change dynamically or from one system
start-up to the next.
- A system that requires more processing capability to compress than to
decompress an image. It is typically used for the mass distribution of
programs on media such as CD-ROM, where significant expense can be incurred
for the production and compression of the program, but the playback system
must be low cost. Compare with symmetrical compression.
- An operation that proceeds independent of any timing mechanism, such as a
clock. Compare with synchronous.
- AT Attachment. An integrated bus usually used between host processors and
disk drives. Used interchangeably with IDE.
- AT Attachment Packet Interface. A hardware and software specification that
documents the interface between a host computer and CD-ROM drives using the
- Asynchronous transfer mode. A transmission protocol that segments user
traffic into small, fixed-size units called cells, which are transmitted to
their destination, where they are reassembled into the original traffic.
During transmission, cells from different users may be intermixed
asynchronously to maximize utilization of network resources.
- audio class
- The class of filters that deals with pulse code modulation or similar
digitized data or analog signals. A WDM audio minidriver provides support for
audio devices under the WDM digital audio architecture.
- audio mixing
- The method of combining multiple streams of audio data into a single
stream through some method such as addition and clipping.