Computer Science and Networking Glossary-A

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Shortcuts to Common Abbreviations and Acronyms:
AAL
ABIOS
AC
AC-3
ACK
ACR
ADC or A-D
ADPCM
ADSI
ADSL
AGP
AIS
ALT
AM
AMI
AML
ANSI
API
APM
APP
ARA
ARAP
ARP
ARPA
ARPANET
ARLL
ASIC
ASCII
ASL
ASPI
ATA
ATAPI
ATCP
ATM
ATMP
ATU-C ADSL
ATU-R ADSL
AUI
AWG

a-b box: A switching box designed to share a peripheral between two or more computers. It can be switched manually, or under program control.
ABIOS: Acronym for: Advanced Basic Input/Output System. A set of firmware service routines built into the IBM PS/2 series of computers that use the Micro Channel Architecture (MCA) to support multitasking operating systems such as OS/2.
AC-3: 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.
Accelerator board: An add-in printed circuit board that replaces the main processor with a higher-performance processor, so you can upgrade your system without replacing monitor, case, keyboard, and so on.
Using an accelerator board can reduce upgrade costs substantially. However, there are other factors to consider, such as disk access time, in determining the overall performance of your system.
Most modern computers are designed to accept simpler upgrades. Built into the motherboard is a socket in which the CPU sits. It is usually possible simply to remove the CPU and replace it with a faster model. This is particularly easy if the socket is a zero insertion force (ZIF) socket.
Access Bandwidth: The ability of a communications network to provide bandwidth dynamically so users will receive service regardless of the bandwidth their service request requires.
Access Concentrator: A device that efficiently forwards data, handling incoming calls for a network point of presence (POP) In general, an access concentrator supports dial-in modem calls, ISDN connections, nailed-up links, frame relay traffic, and multiprotocol routing.
Access Control: The management of permissions and restrictions for logging onto a computer or network. Systems typically employ individual profiles that specify which network-attached resources are available to which users. The profiles are maintained in a database, such as RADIUS.
Acces mechanism: In a floppy or hard disk drive, the component that positions the read/write head over the surface of the disk, so that data can be read from or written to the disk.
Access Rate: The data rate of the user access channel.
Access Router: An access device with built-in basic routing protocol support, specifically designed to allow remote LAN access to corporate backbone networks. Not designed to replace backbone routers or to build backbone networks.
Access Server: Same as RAS(remote access server) Any device that enables multiple remote users to access a network.
Access time: The period of time that elapses between a request for information from disk or memory, and the information arriving at the requesting device. Memory access time refers to the time it takes to transfer a character from memory to or from the processor, while disk access time refers to the time it takes to place the read/write heads over the requested data. RAM may have an access time of 80 nanoseconds or less, while hard disk access time could be 18 milliseconds or less.
ACK (Acknowledgement): The response from the recipient back to the sender that data was successfully received. TCP uses ACKs as part of its reliable transmission scheme. If an aCK is not received, data is retransmitted. See also NAK and retransmission
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 Interface Specification
ACPI Machine Language: 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.
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.
ACR: Abandon Call and Retry.
Active Directory: Provides the ability to build applications that give a single point of access to multiple directories in a network environment, whether those directories are LDAP,NDS,or NTDS based directories.
Active-matrix screen: An LCD display mechanism that uses an individual transistor to control every pixel on the screen. Active-matrix screens are characterized by high contrast, a wide viewing angle, vivid colors, and fast screen refresh rates, and they do not show the streaking or shadowing that is common with cheaper LCD technology.
Active Open: A client-initiated operation that enables a device to establish a TCP link with a server at a fixed IP address.
Active partition: That part of the hard disk containing the operating system to be loaded when you start or restart the computer.
You can install 2 different operating systems ( perhaps DOS and OS/2) on your hard disk, but each must be in its own separate area, or partition. Only one partition can be active at any given time, and to change from the DOS to the non-DOS partition, you may have to use the DOS FDISK command.
Adapter: A printed circuit board that plugs into a computer's expansion bus to provide added capabilities. Common adapters for the PC include display adapters, memory expansion adapters, input/output adapters that provide, serial, parallel, and games peorts, and other devices such as internal modesm, CD-ROMs, or network interface cards. One adapter can often support several different devices; for example, an I/O adapter may support one parallel port, a games or joystick port, and several serial ports. Some PC designs incorporate many of the functions previously performed by these individual adapters on the motherboard.
adaptive compression: Data compression software that continually analyzes and compensates its algorithm, depending on the type and content of the data and the storage medium
Adaptive Differential Pulse Code Modulation: A standard that codes for digitized speech. It samples the sound waves 8,000 times a second; the sample representing the difference between two adjacent samples.
Address: 1.The precise location in memory or on disk where a piece of information is stored. Every byte in memory and every sector on a disk have their own unique addresses. 2. To reference or manage a storage location.
Address bus: The electronic channel, usually from 20 to 32 separate lines wide, used to transmit the signals that specify locations in memory. The number of lines in the address bus determines the number of memory locations that the processor can access, as each line carries one bit of the address. An address bus of 20 lines ( used in early Intel 8086/8088 processors) can access 1MB of memory, one of 24 lines ( as int he Intel 80286) can access 16MB, and an address bus of 32 lines (as used by Intel 80386,80486, and later processors, or the Motorola 68020) can access over 4 GB.
Address Mask: A bit mask used to select bits from an Internet address for subnet address.
Address Resolution: A method for translating one type of address into another -for example, an IP address into a MAC address.
Address Resolution Protocol: The TCP/IP protocol that translates an Internet address into the hardware address of a network interface card(NIC)
add-on devices: Devices that are traditionallya dded 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
Adjunct Processor: A computer outside a telephone switching system that "talks" to the switch and gives it switching commands.
ADSL Asymmetric Digital Subscriber Line: Modems attached to twisted pair copper wiring that transmit from 1.5 Mbps to 9 Mbps downstream (to the subscriber) and from 16 kbps to 800 kbps upstream, depending on line distance.
Asymmetric Digital Subscriber Line is the most popular form of xDSL technology. The key to ADSL is that the upstream and downstream bandwidth is asymmetric, or uneven. In practice, the bandwidth from the provider to the user (downstream) will be the higher speed path. This is in part due to the limitation of the telephone cabling system and the desire to accommodate the typical Internet usage pattern where the majority of data is being sent to the user (programs, graphics, sounds and video) with minimal upload capacity required (keystrokes and mouse clicks). Downstream speeds typically range from 1.5Mbps to 9Mbps. Upstream speeds typically range from 64Kbps to 1.5Mbps.
ADSL Lite: Is a lower data rate version of ADSL This is the dsl in which the POTS splitter is eliminated at the customer premises and the signal is carried over all of the house wiring which lowers bandwidth due to greater noise impairments.A lower data rate version of Asymmetric Digital Subscriber Line (ADSL) has also been proposed as an extension to ANSI standard T1.413 by the UAWG (Universal ADSL Working Group) led by Microsoft, Intel, and Compaq. This is known as G.lite in the ITU standards committee. It uses the same modulation scheme as ADSL (DMT), but eliminates the POTS splitter at the customer premises. As a result, the ADSL signal is carried over all of the house wiring which results in lower available bandwidth due to greater noise impairments.
Advanced Configuration and Power Interface(ACPI): 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 ACPI allows system manufacturers to build systems consistent with the OnNow design initiative for instantly available PCs
Advanced Graphics Port: This is a special interface designed to speed up 3d graphics processing by the computer. Video cards must be specifically designed to plug into the AGP connector, and of course, the motherboard must be designed to have said connector.
Prior to AGP, 3d video cards were connected to the PCI bus. Basically, AGP allows the video card to have a direct connection to the system memory, allowing 3d instructions to bypass the shared (and thus slower) PCI bus. This speeds up 3d video performance. In addition, the data transfer rate of the AGP bus can be 66MHz or more. That is much higher than the 33MHz speed of PCI. Good news for gamers and 3d artists.
Advanced Intelligent Network: A switched voice and data network consisting of a variety of nework elements. It refers to open interfaced, multi-vendor, telecommunications capabilities that let phone companies create and customize their service offerings.
Advanced Power Management: 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. Replaced by ACPI as the system interface under Microsoft� Windows� 98 and Windows 2000
Advanced Research Projects Agency: ARPA. The US government agency that funded the ARPANET, predecessor to the Internet. ARPA is now called DARPA(Defense Advanced Research Projects Agency)
Advanced Research Projects Agency Network: The US government-funded network that evolved into the Internet.
Advanced run-length limited encoding: Abbreviated ARLL. A technique used to store information on a hard disk that increases the capacity of run-lenth limited (RLL) storage by more than 25 %, and increases the data-transfer rate to 9 megabits per second.; Advanced SCSI Programming Interface; The advanced SCSI Programming Interface(ASPI) adapts various SCSI peripherals to a SCSI bus.
agent: 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.
AIS: Alarm Indication Signal. An Unframed All Ones Pattern
Algorithm: A formal set of instructions that can be followed to perform a specific task, such as a mathematical formula or a set of instructions in a computer program.
In compression software, refers to a specific formula used to compress or decompress video or other data.
Alpha: RISC-based 64-bit CPU from DEC (Digital Equipment Corp.) It is designed to run with DOS/Windows, NT and Unix operating systems.
ALT: Automated Loop Test System. The operations system that provides a single comprehensive automated test system for testing international customer POTS lines.
Altair 8800: The first commercially successful microcomputer, based ont he Intel 8080, introduced in 1975 by Micro Instrumentation Telemetry Systems of New Mexico. Over 10,000 were sold, mostly in kit form, and the Altair was packaged with the Microsoft MBASIC interpreter, written by Paul Allen and Bill Gates. The Altair8800 had 256 bytes of memory, received input through a set of switches on the front panel, and displayed output on a row of LEDs.
Alternating Current: (AC) An electrical current that reverse its polarity or direction of flow at regular intervals. AC is usually represented by a sine wave. In the US, domestic wall plugs provide AC at 60 hertz, or 60 cycles persecond.
alt newsgroup: A set of USENET newsgroups that often contain articles on controversial subjects usually considered to be outside of the mainstream.
American Natinal Standards Institue: ANSI. A nonprofit organization of business and industry groups, founded in 1918, devoted to the development of voluntary standards. ANSI represents the USA on the International Standards Organization (ISO). In PC world, ANSI committees have developed recommendations for the C programming language, as well as the SCSI interface and the ANSI.SYS device driver.
AMI: Alternate Mark Inversion A line encoding scheme for transmitting data bits over T1 transmission systems.
Amplitude Modulation (AM): A transmission technique that inserts information onto an electrical carrier wave by varying the amplitude of the carrier.
Analog: Describes any device that represents changing values by a continuously variable physical property such as voltage in a circuit, fluid pressure, liquid level, and son on.
An analog device can handle an infinite number of values within its range. By contrast, a digital device can only manage a fixed number of possible values. For example, an ordinary mercury thermometer is an analog device, and can record an infite number of readings over its range. A digital thermometer, on the other hand, can only display temperature in a fixed number of individual steps.
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. Compare with digital.
Analog Display Services Interface (ADSI): A protocol that allows text messages generated by a remote computer or central office switch to be displayed on a user's telephone or TV set.
Analog Technology: Technology that uses a stream of continuously changing electrical waves to carry voice or low-speed data.
Analog-to-digital converter: ADC or A-D converter. A device that converts continuously varying analog signals into discrete digital signals or numbers.
Once analog signals have been converted into digital form, they can be processed, analyzed, stored, displayed and transmitted by computer. The key to analog-to-digital conversion lies in the amount of digital data created from the analog signal. The shorter the time interval between samples, and the more data recorded from that sample, the more closely the digital signal will modern sound boards can sample and playback at up to 44.1 kHz using a 16-bit analog-to-digital converter.
anamorphic: Unequally scaled in vertical and horizontal dimensions.
Anonymous ftp: A method of accessing an internet computer with the ftp(file-transfer program) which does not require that you have an account on the target computer system. Just log in to the Internet computer with the user name anonymous and use your e-mail address as your password.
anonymous posting: In a USENET newsgroup, a public message posted via an anonymous server in order to conceal the identity of the original author. This server removes all the information from the message that could identify the sender, and forwards the message to its destination.
anti-aliasing: A form of interpolation used in graphics display technology when combining images; pixels along the transitions between images are averaged to provide a smooth transition.
Anti-virus program: An application program you run to detect or eliminate a computer virus or infection. Some anti-virus programs are terminate-and-stay-resident programs that can detect suspicious activity on your computer as it happens, while others must be run periodically as part of your normal housekeeping activities.
APP: Ascend Password Protocol
Applet: A small application program, limited in scope to one small but useful task. A calculator program or a card game might be called an applet.A small software module that runs on a Java Virtual Machine (JVM) inside a Web browser.; AppleTalk Control Protocol (ATCP); A protocol that enables you to route Apple Talk packets that are encapsulated in Point-to-Point Protocol (PPP)
Apple Talk Remote Access (ARA): ARA enables a remote Mac workstation to gain access to an IP network. You can use ARA over a modem or V.120 connection. You can also use synchronous PPP when the calling unit is AppleTalk-enabled Lucent unit. A client can dial in using ARA client software or a PPP dialer that supports AppleTalk
appliance server: A relatively low-cost computing device used for specific tasks, including Internet connectivity and file and print. Does not have the full capabilities or software of a typical server that is sold for general-purpose office use, but has an extremely high ease-of-use associated with it.
Application layer: The seventh , or highest, layer in the International Organization for Standardization's Open Systems Interconnection (ISO/OSI) model for computer-to-computer communications. This layer uses services provided by the lower layers, but is completely insulated from the details of the network hardware. It describes how application programs interact with the network operating system, including database management, electronic mail, and terminal emulation programs.
Application program interface: API. the complete set of operting system functions that an application program can use to perform tasks such as managing files and displaying information on the computer screen.
An API is a complete definition of all the operating system functions available to an application program, and it also describes how the application program should use those functions.
In operating systems that support a graphical user interface, the API also defines functions to support windows, icons, pull-down menus, and other components of the interface.
In network operating systems, an API defines a standard method application programs can use to take advantage of all the network features.
Application-specific Integrated Circuit: ASIC. A IC developed for a specific application, designed by incorporating standard cells from a library, rather than designed from scratch. ASICs can be found in VCRs, microwave ovens, automobiles, and security alarms. Manufacturers use it to consolidate many chips into a single package, reducing system board size and power consumption.
ARAP: Apple Talk Remote Access Protocol
Arbitration: The set of rules used to manage competing demands for a computer resource, such as memory or peripheral devices, made by multiple processes or users.
arbitrator: (1) A software module in Windows that handles the allocation of hardware resources among devices. (2) Under Windows, 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 DMA channel resources.
Archie: A system used on the Internet to locate files available by anonymous ftyp. Archie was written by students and volunteers at McGill University's School of Computer Science in Montreal, Canada, and is available worldwide.
Once a week, special programs connect to all the known anonymous ftp sites on the Internet and collect a complete lisint of all th epublicly available files. This listing is kept in an Internet Archive Database, and when you ask Archie to look for a file, only this database is searched rather than the whole Internet; you can then use anonymous ftp to retrieve the file.
Architecture: The overall design and construction of all or part of a computer, particularly the processor hardware an the size and ordering sequence of its bytes. Also used to describe the overall design of software.
artifact: An unintended, unwanted visual aberration in a video image.
Array processor: A group of special processors designed to calculate math procedures at very high speeds, often under the control fo another central processor. Some computers use array processors to speed up video operations or for fast floating-point math operations.
Ascend Inverse Multiplexing Protocol (AIM): An in-band protocol used to manage the interconnection of two remotely located inverse multiplexers. AIM is a feature rich, widely used inverse multiplexing protocol developed and supported by Ascend Communictions. Not to be confused with AOL Instant Messenger.
ASCII: American Standard Code for Information Interchange. A standard coding scheme that assigns numeric values to letters, numbers, punctuation marks, and control characters, to achieve compatibility among different computers and peripherals.
In ASCII each character is represented by a unique integer value. The values 0 to 31 are used for non-printing control codes, and the range from 32 to 137 is referred to as the standard ASCII character set. All computers that use ASCII can understand the standard ASCII character set.
The extended ASCII character set (from code 128 through code 255) is assigned bariable sets of characters by computer hardware manufacturers and software developers, and is not necessarily compatible between different computers. The IBM extended character set includes mathematical symbols and characters from the PC line drawing set.
ASCII file: A file that only contains text characters from the ASCII character set. An ASCII file contains letters, numbers, and punctuation symbols, but does not contain any hidden text-formatting commands. Also known as a text file, and aSCII text file.
ASL: 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.
Assembly: In the chip making workd , the process of enclosing a device in a plastic or ceramic package.
Assembly Language: A symbolic language that is converted by a computer into executable machine-language programs. Assembly language is easier to manipulate and remember than machine language.
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.
asymmetrical compression: 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.
asynchronous: An operation that proceeds independent of any timing mechanism, such as a clock. Compare with synchronous.
Asynchronous Communications Server: A LAN server that enables a network user to dial out of the network and into the public switched telephone network (PSTN), or to access nailed-up lines for asynchronous communications. An asynchronous communications server is also called a dial-in/dial-out server or a modem server.
AT Attachment: A disk drive implementation that integrates the controller on the disk drive itself. Also known as IDE.
ATA-2 is an extension of ATA that was beefed up to include performance enhancing features such as fast PIO ( programmed input/output) and DMA (direct memory access) modes. It also got an improved Identify Drive command. This features lets a hard drive tell the software exactly what its characteristics are, and is the basis for both Plug and Play hard drive technology and compatibility with any new version of the standard that may come.
Fast ATA supports high speed data transfers specified by ANSI-standardized Programmed Input/Output(PIO) Mode3 and multi-word Direct Memory Access(DMA) Mode 1 protocols. Fast ATA enables the drive to transfer data at speeds as high as 13.3MB/s.
Fast ATA-2 is like Fast ATA, but is a standard that will allow manufacturers to create products that support ANSI PIO Mode 4 and multi-word DMA Mode 2 protocols. With Fast ATA-2, its possible to get data transfers as high as 16.6 MB/s.
AT Attachment Packet Interface: A hardware and software specification that documents the interface between a host computer and CD-ROM drives using the ATA bus.
AT Bus: The 16-bit bus started with the IBM-AT (Advanced Technology) systems. It is still the standard interface for most PC expansion cards. It is also known as the ISA (Industry Standard Architecture) bus.
AT command set: A set of standard instructions used to activate features on a modem.
The code AT is short for ATtention, and precedes most of the modem commands.
ATM Asynchronous Transfer Mode: This high speed network protocal is composed of 53 byte "cells" having 5 byte headers and 48 byte payloads. Because of its short packet length, it is especially good for real time voice and video.
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.
ATM Adaption Layer(AAL): The AAL enables engineers to adapt the asynchronous transfer mode layer to particular services. Lies between the ATM layer and the higher layers and maps or adapts the functions or services of the higher layers onto a common ATM bearer service.
(ATMP) Ascend Tunnel Management Protocol: A vpn protocol. VPNs provide low-cost remote access to private LANs via the Internet. The tunnel to the private corporate network may be from an ISP, enabling mobile nodes to dial-in to a corporate network, or between two corporate networks that use a low-cost Internet connection to access each other.
ATU-C ADSL Termination Unit - Central Office: The device at the end of an ADSL line that stands between the line and the first item of equipment in the telephone switch. It may be integrated within an access node.
ATU-R ADSL Termination Unit - Remote: The device at the end of an ADSL line that stands between the line and the first item of equipment in the subscriber's premises. It may be integrated within an access node.
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 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.
Attachment Unit Interface: The portion of the Ethernet standard that specifies how a cable is to be connected to an Ethernet card. AUI specifies a cable connected to a transceiver that plugs into a 15-pin socket on the network adapter.
authority zone: The part of a DNS domain for which a name server has responsibility. Authority is sometimes called "knowing the truth" about network name/address translation.
AWG American Wire Gauge: A measure of the thickness of copper, aluminum and other wiring in the U.S. and elsewhere. Copper cabling typically varies from 18 to 26 AWG. The higher the number, the thinner the wire. The thicker the wire, the less suceptible it is to interference. In general, thin wire cannot carry the same amount of electrical current the same distance that thicker wire can.

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