Dictionary of Computer Terms and Acronyms

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Computer Terms - terms Through Letter B

  • 10Base5 (10 Mbps, baseband, 500 meter): one of several physical media specified by 802.3 for use in an Ethernet local area network LAN); consists of Thickwire coaxial cable with a maximum segment length of 500 meters
  • 10Base2 (10 Mbps, baseband, 185 meter): one of several physical media specified by IEEE 802.3 for use in an Ethernet local area network LAN); consists of Thickwire coaxial cable with a maximum segment length of185 meters
  • 10BaseT (10 Mbps, baseband, unshielded twisted-pair): one of several physical media specified by IEEE 802.3 for use in an Ethernet local area network (LAN); is ordinary telephone twisted pair wire
  • 100BaseT (100 Mbps, baseband, unshielded twisted-pair): one of several physical media specified by IEEE 802.3 for use in an Ethernet local area network (LAN); referred to as Fast Ethernet because of its higher transmission speed
  • AAL (ATM adaptation layer): adapts PDUs passed down from higher layers onto ATM cells
  • Active hub: allows multiple devices to be wired to a central location to share the same media and regenerate the signal; also referred to as multiport repeaters
  • ADSL (asymmetric digital subscriber line): typical form of xDSL telephone companies offer to residences
  • AGP (accelerated or advanced graphics port): a high-speed, point-to-point channel for attaching a graphics card to a computer’s motherboard, primarily to assist in the acceleration of 3D computer graphics
  • ALU (arithmetic logic unit): a digital circuit that calculates an arithmetic operation (e.g., addition, subtraction) and logic operations between two numbers; the fundamental building block of the Central Processing Unit (CPU) or a computer
  • AM (amplitude modulation): a technique used for transmitting information via a radio carrier wave
  • Amplitude: height of the wave at any point in the wave
  • ANSI (American National Standards Institute): a voluntary organization that coordinates the development and use of consensus standards in the United States and represents the needs and views of U.S. stakeholders in standardization forums around the globe
  • API (application programming interface): gives programmers a formal set of routines to call on to use underlying network services
  • Application layer: performs the functions of file transfer, e-mail, etc. (see OSI Model)
  • Architecture: how a system is designed; includes how the components are connected to and operate with each other
  • ARP (address resolution protocol): network layer protocol provided with TCP/IP; used to map an IP (internet protocol) address to a MAC (media access card) address
  • ASCII (American Standard Code for Information Interchange): relates a number from 0 to 255 in the binary (base 2) form to keyboard characters
  • ASIC (application-specific integrated circuit): an integrated circuit designed for a particular use (e.g., a chip designed solely to run a cell phone)
  • Asynchronous communication: describes when devices, such as computers, rely on their own internal clocks; it provides connectivity to printers, modems, fax machines, etc.
  • ATM (asynchronous transfer mode): high bandwidth, cell-switching technology; designed to carry many different types of information, including voice, video, image, data, and graphics; another form of STDM (statistical time division multiplexing)
  • AUI (attachment unit interface): a 15-pin connection that provides a path between a node’s Ethernet interface and the medium attachment unit (MAU); also known as a transceiver
  • AS (Autonomous system): collection of IP networks under the control of a single entity
  • B (bearer) channel: carries voice, video, image, or data traffic, depending upon the equipment and applications available
  • Bandwidth: expressed in a range of frequencies using hertz as the unit of measurement; also called analog capacity
  • Base 2 System: binary number system, only two discrete values (0 and 1) are possible and all numbers are a combination of these two characters; digital signals are numbers sent in the Base 2 system
  • Base 10 System: the decimal system
  • Baseband: describes signals and systems whose range of frequency is measured from 0 to a maximum bandwidth or highest signal frequency; sometimes used as a noun for a band of frequencies starting at 0
  • BGP (border gateway protocol): an interautonomous system routing protocol; a network or group of networks under a common administration and with common routing policies
  • Bit: contraction of the expression “binary digit”; smallest unit of data in a computer
  • BIOS (basic input/output system): the firmware code run by an IBM-compatible PC when first powered on, known as “booting up”; primary function is to prepare the machine so other software programs can load, execute, and assume control of the PC
  • Bluetooth: specification that allows mobile phones, computers, and PDAs to be connected wirelessly over short ranges
  • Bps: bits per second: common measure of data speed for computer modems and transmission carriers
  • BRI (basic rate interface): an integrated services digital network configuration, usually intended for the home and small enterprise (see also PRI)
  • Bricks and clicks: business that existed pre-Internet that now uses e-commerce technology to sell on the Internet
  • Bridge: interprets the LAN hardware adapter address contained in MAC and decide whether to filter or forward the frame; does not change the frame in any way
  • Browsers: client applications that access WWW servers
  • Building backbone: connects LANs within a building
  • Bus: electrical connection between any two components in a computer
  • Bus topology: system layout where electrical signals generated by a device connected anywhere on the bus are received by all other connected devices
  • Byte: the standard size of data in a computer; 8-bits

Computer Terms - Letters C through D

  • Cache: keeps data the processor is likely to need quickly close at hand; increases processor operation speed
  • CAD/CAM (computer-aided design/computer-aided manufacturing): software used to design products such as electronic circuit boards in computers
  • Campus backbone: connects building LANs together
  • CD-R (compact disc - recordable): special type of CD-ROM that can be written onto by any computer with a recording drive; can only be written onto once
  • CD-ROM (compact disc read-only memory): optical storage device read by lasers; can hold up to 700 megabytes of data
  • CD-RW (compact disc - rewritable): special type of CD-ROM that can be written onto by any computer with a recording drive; can be written onto more than once
  • CIR (committed information rate): describes the user information transfer rate the network supports during normal network operations
  • CLEC (competitive local exchange carrier): In the US, a telecommunications provider company (also called a carrier) that competes with other, already established carriers (the local telephone company)
  • Client/server architecture: network where some computers are dedicated clients (workstations) and some are dedicated servers; information is centralized on the server, and an administrator sets policies and manages it
  • CMOS (complementary metal-oxide semiconductor) RAM: requires very little power; maintains information even when the computer is off
  • Collision: occurs when several network users communicate at the same time and interfere (collide) with one another
  • Collision domain: logical network segment where data packets can "collide" with one another for being sent on a shared medium, in particular in the Ethernet networking protocol
  • Computer networking: a combination of hardware and software that lets the various computers in an organization communicate with one another
  • Computer operating system (OS): special computer program that provides an environment in which other programs can use the computer’s central processor and the attached input/output devices
  • Connectivity devices: bring users of the network into contact with one another
  • Constant bit rate (CBR): transmission that uses a set amount of network capacity on a continual basis; used when the arrival of the information is time-sensitive
  • Convergence: the merging and sometimes clashing of voice and data
  • CPE (customer premises equipment): generally refers to telephones, DSL or cable modems, or purchased set-top boxes for use with communication service providers’ services
  • CPS (cycles per second): measure of how frequently an alternating current changes direction; has been replaced by the term hertz (Hz)
  • CPU (Central Processing Unit): the brain of the computer system where calculations and decisions are made; also referred to as the processor
  • CPU Speed: how fast the CPU works
  • CSU (channel service unit): provides a loopback function for telephone company testing, and checks bipolar signal generation
  • CRC (cyclic redundancy check): method of checking for errors in data that has been transmitted on a communications link; a function used to produce a Checksum against a block of data
  • CS (convergence sublayer): particular protocols that are responsible for gathering and formatting higher layer information so it can be processed by the lower layers
  • CSMA/CD (carrier sense multiple access/collision detect): set of rules for determining how network devices response when two devices collide
  • D (data) channel: used for common channel signaling by both the telephone company switch and the customer equipment; provides the call signals that set up B channel connections
  • DACS (digital access and cross-connect system): a piece of telecommunications equipment used for routing T1 lines; can cross-connect any T1 line in the system with any other T1 line in the system
  • Data: information manipulated inside the computer in the form of bits and bytes
  • Datagram: data packet that is sent over an IP network; associated with the network layer when communication protocol is connectionless
  • DCE (data communications equipment OR data circuit-terminating equipment): a device that communicates with a data terminal equipment (DTE) device in a particular standard
  • DDP (datagram delivery protocol): a member of the AppleTalk networking protocol suite, mainly responsible for socket-to-socket delivery of datagrams over an AppleTalk network
  • DE (discard eligibility): signal used to identify less important data traffic that can be dropped during periods of congestion on the system
  • DLCI (data link connection identifier): a channel number that tells the network how to route the data
  • DMA (direct memory access): a feature that allows certain hardware subsystems in a computer to access system memory for reading and/or writing independently of the CPU; can include disk drive controllers, graphics cards, network cards, and sound cards
  • DOS (disk operating system): a family of closely related operating systems (COS) that ran on IBM PC type hardware.
  • DNA (digital network architecture): a set of specifications or protocols created by Digital Equipment Corporation (DECnet) that evolved into one of the first peer-to-peer network architectures
  • DNS (domain name system): service that connects a domain name to an IP address
  • DRAM (dynamic random access memory): primary choice for holding large amounts of information due to its inexpensive cost; must be refreshed or rewritten frequently (about every 386 milliseconds)
  • DS0 (digital signal, level 0): basic digital signaling rate of 64 kbit/s, corresponding to the capacity of one voice-frequency-equivalent channel
  • DS1 (digital signal, level 1): also known as T1; widely used to transmit voice and data between devices
  • DSL (digital subscriber line): technology that delivers digital data transmission over the wires of a local telephone network
  • DVD (digital versatile disc): can hold over seven times as much information as CDs
  • DWDM (dense wavelength-division multiplexing): an optical technology used to increase bandwidth over existing fiber optic backbones (see building backbone, campus backbone)

Computer Terms - Letters E through H

  • EBCDIC (extended binary coded decimal interchange code): 8-bit character encoding table used by ISM mainframes
  • EGP (exterior gateway protocol): a protocol commonly used between hosts on the Internet to exchange routing table information
  • EMI (electromagnetic interference): radiation that causes unwanted signals (interference or noise) to be induced in other circuits; also called radio frequency interference or RFI
  • Enterprise network: connects many types of networks
  • Ethernet: most commonly used protocol designed to change the packets into electrical signals that can be sent out over the wire
  • Exterior protocols: routing protocol used between autonomous systems
  • FAT (file allocation table): table that the operating system uses to locate files on a disk; because a file may be divided into many sections that are scattered around the disk, the FAT keeps track of all the pieces
  • FDDI (fiber distributed data interface): a set of ANSI protocols for sending digital data over fiber optic cable (see ANSI)
  • FDM (frequency-division multiplexing): permits a range of input signals to be carried over a communication line that uses separate carrier frequencies for each signal channel; mostly used for analog information but can carry digital
  • File management systemway to store and retrieve information from disk drives; controls how files can be created, accessed, retrieved, and deleted
  • Firewall: a barrier between a network and the Internet through which only authorized users can pass; set of security policies to screen incoming and outgoing messages; also used to isolate one part of a network from another
  • Floppy drive: early versions were actually floppy; today, they use hard 3.5 inch disk; also referred to as removable drive
  • Frame: data structure that collectively represents the transmission stream (headers, data, and the trailer) and provides the information necessary for the correct delivery of the data
  • Frame relay: service with standards and specifications designed to transmit data; some users have had success at transmitting voice
  • FRAD (frame relay access device): software that frames the customer’s payload with the Frame Relay overhead information, including the first DLCI (data link connection identifier) address, to prepare it for delivery to the network
  • Frequency: number of times a wave repeats a cycle in a one-second period; measured in cycles per second, or hertz
  • FTP (file transfer protocol): application used to transfer a copy of a file from one computer to another computer with one acting as client and the other as server; a login with a user name and password is typically required
  • Full-duplex link: enables both sides to simultaneously send and receive data; could require two separate cables, one in each direction or a single multiplexed cable
  • Gateways: a node on a network that translates (converts protocol) from one operating system environment to another
  • Gateway routers: used to implement exterior protocols and interconnect autonomous systems
  • Gbps (gigabits per second; billions of bits per second): a data transfer speed measurement for highspeed networks
  • GUI (graphical user interface): easy way of accessing applications with the use of a pointing device, such as a mouse; pronounced “gooey”
  • Half-duplex link: enables one side to transmit and receive, but not simultaneously; information only flows in one direction at a time using a control procedure to mediate
  • Host-to-host layer: part of the TCP/IP model that performs the same function as the transport layer in the OSI model
  • Host address: part of an IP address that is uniquely assigned by an administrator
  • HTTP (hypertext transfer protocol): protocol users interact with (by means of a browser) to access Web pages over an internet or intranet
  • Hubs: bring the users of the network into contact with one another
  • Hz (hertz): unit of frequency; one hertz simply means one cycle per second, applied to any periodic event (e.g., one tick of a clock is 1 Hz; the human heart beats at 1.2 Hz)

Computer Terms - Letters I through L

  • ILECs (incumbent local exchange carriers): a telephone company providing local service when the Telecommunications Act of 1996 was enacted (see CLEC)
  • ILP (initial loader program): reads an existing file containing database records; also called a boot-loader
  • Input/output management routines: provide orderly control and flow of information between a computer’s main memory and attached peripheral devices
  • Interface: point in the system where the rules, control codes, formats, and information direction (as dictated by the protocol) are implemented
  • Interior protocols: routing protocol used within/interior to an independent/ autonomous system
  • Internet layer: part of the TCP/IP model that performs the same function as the network layer of the OSI model
  • Internetworking: connecting one network to another network
  • Interprocess communication: allows programs to share information dynamically, whether running locally or remotely
  • I/O (Input/output devices): hardware used to enter and retrieve data from the system
  • IP (internet protocol): network layer protocol provided with TCP/IP; connectionless, unreliable protocol that provides features for addressing, type or service specification, fragmentation and reassembly, and security
  • IP address (internet protocol address): logical address assigned to every workstation, server, printer, and router on any interconnected network
  • IPX/SPX (Internetwork packet exchange/sequenced packet exchange): a networking protocol used by the Novell NetWare operating systems; it is a datagram protocol used for connectionless communications
  • IRC (Internet relay chat): allows groups to communicate interactively via keyboard and screen display
  • ISDN (Integrated Services Digital Network): a circuit-switched telephone network system designed to allow digital transmission of voice and data over ordinary copper telephone wires
  • ISDN PRI: switched-line service from telephone companies that operates over T1 (or E1/J1) facilities
  • IS-IS (intermediate system-to-intermediate system): an interior gateway protocol (IGP) intended for use within an administrative domain or network
  • ISPs (Internet service providers): businesses or organizations that provide consumers with access to the Internet and related services
  • IT (information technology): broad term that can refer to anything from mainframes to PDAs; any technology that moves information (voice, video, or data)
  • ITU-T (ITU Telecommunication Standardization Sector): coordinates standards for telecommunications on behalf of the International Telecommunication Union (ITU)
  • IXC (interexchange carrier): a telephone company that provides connections between local exchanges in different geographic areas
  • Jitter: distortion in a digital signal caused by a shift in timing pulses; can cause data interpretation errors
  • JPEG (Joint Photographics Experts Group): a lossy compression technique for color images; pronounced jay-peg (see Lossy)
  • Kbps (thousands of bits per second): a measure of data transfer speed
  • kHz (kilohertz): a unit of measurement of frequency, also known as cycles per second; e.g., one kilohertz equals 1,000 Hz, or cycles per second
  • LAN (local area network): network that operates within a small geographic area, usually within a building, office, or department
  • LAPB (link access protocol, balanced): a data link protocol in the X.25 stack
  • LATAs (local access and transport areas): In the US, refers to a geographic region assigned to one or more telephone companies for providing communication services
  • Layer 2 switches: interpret and make switching decisions on the LAN hardware adapter address contained in the data link header of MAC frames; forward frames only to the destination hardware address contained in the frame
  • LCI (logical channel identifier): used to define frequencies in use on M/A-COM EDACS (Enhanced Digital Access Communications System) systems and LTR (logic trunked radio) systems; more commonly known as logical channel number (see LCN); also known as virtual channel
  • LCN (logical channel number): used to define frequencies in use on M/A-COM EDACS (Enhanced Digital Access Communications System) systems and LTR (logic trunked radio) systems; also known as the logical channel identifier (see LCI); also known as virtual channel
  • LE (local exchange): a regulatory term in telecommunications for local telephone company
  • Leased lines: another name for private lines, dedicated lines, or permanent circuits
  • LEC (local exchange carrier): a public telephone company in the US that provides local service
  • LGN (logical channel group number): together with the LCN (in the X.25 packet header), identifies the actual logical channel number of the DTE-DCE link; a 4-bit field representing a number between 0 and 15
  • Line layer: layer of the OSI physical layer that is responsible for synchronizing and multiplexing multiple streams of data into one SONET stream within SONET frames; also monitors and administers SONET multiplexers
  • LLC (logical link control): standard interface allowing any combination of MAC techniques and physical media to be used simultaneously in the same workstations; shields higher layer protocols from the peculiarities of the physical medium
  • Logical segmentation devices: allow network designers to maintain separate networks (often for security reasons) that can still communicate with one another
  • Lossy: data compression method where compressing and then decompressing retrieves data that may well be different from the original, but is "close enough" to be useful in some way
  • LU (logical unit): identifies an end-user in IBM's Systems Network Architecture (SNA)

Computer Terms - Letters M through O

  • MAC (media access control) address: unique 6-byte address associated with and coded into each network interface card (NIC); address assignment is controlled by the IEEE
  • MAN (metropolitan area network): connects sites in and around a large city
  • MB (megabyte): unit of information or computer storage equal to either exactly one million bytes or, in some cases, 1,048,567 bytes, or more rarely, 1,024,000 bytes; not to be confused with Mb, which stands for megabits
  • Mbps (megabits per second): a unit of information storage; not to be confused with MB or megabytes
  • Medium: transmission, or system that carries the message or data
  • MAU (medium attachment unit): converts signals on an Ethernet cable to and from AUI signals
  • Memory: desk space of the computer system; microchips located on the motherboard that hold data and instructions for the CPU (central processing unit)
  • Memory management: allocates memory to separate tasks and protects data from corruption
  • Menu: used in some DOS shells and early versions of Windows; an improvement on the command line but cumbersome when a task requires the submenu of a submenu of a submenu of a menu item
  • Message: information content to be shared
  • MHz (megahertz): one hertz is one cycle per second; a megahertz is equal to one million cycles per second
  • MIB (management information base): a type of database used to manage the devices in a communications network
  • MPEG (Motion Picture Experts Group): digital video format identified by “.mpg” extension after the file name; a working group of ISO/IEC charged with the development of video and audio encoding standards; pronounced m-peg
  • MPLS (multiprotocol label switching): an initiative that integrates Layer 2 information about network links (bandwidth, latency, utilization) into Layer 3 (IP) within a particular autonomous system to simplify and improve IP packet exchange
  • Mpps (millions of packets per second): a measurement of information sent per second
  • Multiplexing: process of putting multiple signals on a wire simultaneously
  • Multiport repeaters: allow multiple devices to be wired to a central location, share the same media, and regenerate (repeat) the signal; also referred to as active hubs
  • Multitasking routines: permit two or more distinct tasks to be performed concurrently by the computer
  • Name resolution: process by which the peer-to-peer name used on each conversational level is related to other levels
  • NAP (network access point): transitional data communications facilities at which Network Service Providers (NSPs) would exchange traffic, in replacement of the publicly-financed NSFNet Internet backbone; now replaced by modern IXPs
  • NAT (network address translator): involves re-writing the source and/or destination addresses of IP packets as they pass through a router or firewall; also called network masquerading, native address translation, or IP-masquerading
  • NetBIOS (network basic input/output system): allows applications on separate computers to communicate over a local area network (LAN)
  • Network access layer: allows a computer to exchange data with another computer over a common network medium; part of the TCP/IP model that performs the same functions as the data link and physical layers of the OSI model.
  • Network address: part of an IP address that is uniquely assigned by one of the ICANN-sanctioned agencies
  • Network design: how the various clients and servers are arranged for purposes of connectivity, performance, and security
  • NOS (network operating system): optimizes the client/server architecture; provides and supports network services such as file services, e-mail, Internet and intranet services, and applications
  • NIC (network interface card): hardware adapter that provides communication capabilities; responsible for building, transmitting, receiving, and decoding frames in a LAN environment; serves as the interface between the networked devices and the connecting wires
  • NNTP (network news transfer protocol): makes USENET possible; protocol for the distribution, inquiry, retrieval, and posting of news articles using a reliable stream-based transmission of news among the ARPAInternet community
  • Nonvolatile memory: chips that hold information even when the system is turned off
  • NRZ-L (non-return to zero level): form of digital encoding; negative voltage is used to represent a binary 1, and a positive voltage is used to represent a binary 0
  • NSP (network service provider): a business or organization that sells bandwidth or network access by providing direct backbone access to the Internet, and usually access to it’s network access points (see NAP)
  • OC1 (optical carrier, level 1): a fiber optic connection capable of transferring data at 51.85 Mbps
  • Operating environment: how the OS controls the hardware and application programs
  • OS (operating system): interface between the application (word processor, spreadsheet, etc.) and the computer hardware
  • OSI (open systems interconnection) model: developed to provide a view of the distinct functionalities that are required to implement each protocol layer; defines a complete range of functions that can be achieved with data communications equipment
  • OSPF (open shortest path first): a link-state hierarchical interior gateway protocol (see IGP) for network routing protocol