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There are 202 names in this directory beginning with the letter V.
v-mail

Video mail. Sending video clips as attachments to e-mail messages.

v-net

The plain old telephone system that uses voice signals for communication.

V.21

An ITU-T modem protocol standard for asynchronous, full-duplex transmission, a data rate of 300 bits per second, and frequency shift keying (FSK) modulation.

V.22

An ITU-T modem protocol standard for synchronous and asynchronous, full-duplex transmission, with data rates of up to 1200 bits per second, and differential phase shift keying (DPSK) modulation.

V.22bis

(V.22bis means V.22 twice). An ITU-T modem protocol standard for synchronous and asynchronous, full-duplex transmission, with data rates of up to 2400 bits per second, and quadrature amplitude modulation (QAM).

V.23

An ITU-T modem protocol standard for synchronous and asynchronous half-duplex transmission at 1200 bits per second, using frequency shift keying (FSK) modulation.

V.24

An ITU-T standard that defines the way circuits are set up for an RS-232 interface between a computer and modem or other data terminal equipment and data communications equipment. It also defines modem carrier frequencies that will not interfere with regular telephone control tones.

V.25

An ITU standard for automatic modems which determines the answer tone and circuitry used.

V.25bis

An ITU standard for equipment that performs automatic calling and answering on dial-up telephone lines.

V.32

An ITU-T modem protocol standard for synchronous and asynchronous bidirectional transmission at 4800 or 9600 bits per second, using Trellis code modulation (TCM).

V.32bis

(V.32 twice). An ITU-T modem protocol standard for synchronous and asynchronous bidirectional transmission at 7200, 12000 and 14400 bits per second, using Trellis code modulation (TCM). The modem changes the speed of transmission as necessary for the transmission line used.

V.32ter

A revision of the ITU-T V.32bis modem protocol standard to allow data transmission at 19000 bits per second.

V.90

An International Telecommunication Union (ITU) standard for 56-Kbps modems.

VAC or V AC

Volts Alternating Current.

vaccine program

A computer program that watches for viruses and alerts the user if a virus is found.

vacuum tube

A sealed glass or metal container, evacuated to a high degree of vacuum, through which a controlled flow of electrons is directed. The first computers used vacuum tubes as on/off switches to indicate the 0s and 1s in digital computations. Now cathode ray tubes (CRTs) are used for computer monitors.

VAD

Value Added Dealer. Same as VAR. A company which sells something made by another company after adding something of value. For example, the VAD might put together a computer, peripherals, and specialized software, all from different companies, as a package.

valid hit

A visit to a web page that delivers all information to the user. Hits such as error messages, redirects, and computer-generated visits are not valid hits.

validation

1. The evaluation of software at the end of its development, to make sure it meets the requirements of the intended user(s). 2. The process of checking data to make sure it is correct and presented in the proper format. 3. The checking of communications packets by the receiving device.

value added dealer

(VAD). Same as VAR. A company which sells something made by another company after adding something of value. For example, the VAD might put together a computer, peripherals, and specialized software, all from different companies, as a package.

value added reseller

(VAR). A company which sells something made by another company after adding something of value. For example, the VAR might put together a computer, peripherals, and specialized software, all from different companies, as a package.

value added retailer

(VAR). A company which sells something made by another company after adding something of value. For example, the VAR might put together a computer, peripherals, and specialized software, all from different companies, as a package.

vaporware

Software that is announced long before it is ready for sale, and that sometimes never materializes.

VAR

Value Added Reseller or Value Added Retailer. A company which sells something made by another company after adding something of value. For example, the VAR might put together a computer, peripherals, and specialized software, all from different companies, as a package.

variable bit rate

(VBR). Asynchronous transfer mode (ATM) service in which bandwidth is guaranteed based on average cell rate.

variable-length field

A database field that can be expanded to the required length. For example, a field such as “Name” or “City” works better as a variable-length field, because names of people and cities vary in length. (A fixed-length field would truncate longer names and leave blank spaces on shorter names). Variable-length fields are harder to program than fixed-length fields, but can be more convenient to the user.

VAX

Virtual Address eXtension. A family of 32-bit computers from Digital which use the VMS operating system. VAXes include mainframes, minicomputers, and microcomputers. The first VAX models were released in 1977.

VAX MIPS

VAX Million Instructions Per Second. A unit of measurement of computer performance, also called VAX Unit of Performance (VUP). One VUP equals the performance of a VAX 11/780. This is also equivalent to one SPECmark.

VAX Unit of Performance

(VUP). A unit of measurement of computer performance. One VUP is equivalent to the performance of Digital Equipment Corporation’s VAX 11/780. It is also equivalent to one SPECmark.

VAXstation

A family of VAX workstations from DEC using the VMS operating system.

Vbox

A Sony hardware interface that can connect as many as 7 VCRs, videodiscs and camcorders to one serial port.

VBR

(Variable Bit Rate). Asynchronous transfer mode (ATM) service in which bandwidth is guaranteed based on average cell rate.

VBScript

Visual Basic Scripting Edition. A scripting language that is based on the Visual Basic programming language, but is much simpler and is similar to JavaScript. VBScript makes it possible to add interactive features like buttons and scrollbars to Web pages. This scripting language was developed by Microsoft and works with Internet Explorer.

VBX

Visual Basic Custom Control. A software module that can be used in many different applications. VBXs were originally created to to make it easy to develop Windows applications with Visual Basic, but can be used in other environments. The more versatile ActiveX controls advance the idea of VBX.

Vcache

The disk cache program for Windows 95.

vCard

An electronic business card format.

VCD

Video Compact Disc. A CD that can display full motion video and sound. Using 650/700MB CDs, VCD can hold up to 74/80 minutes respectively. VCDs use MPEG for compression and the quality is similar to VHS based tapes.

VCR

Video Cassette Recorder. An analog videotape player and recorder which is usually connected to a television monitor to record or play tapes. The most commonly used videotape is 1/2-inch VHS format.

VDD

Virtual Device Driver. A virtual device driver is the component of a device driver that communicates directly between an application and a hardware device. Virtual device drivers organize the flow of data to allow more than one application to access the same hardware without conflict. In the device file name, V stands for virtual and D stands for device. The “x” can be replaced with other characters; for example, VmD means a mouse driver.

Vdeck

Video Deck. A Super 8 mm tape drive from Sony which can be connected to a computer via the serial port.

VDT

Video Display Terminal. A computer terminal with monitor and keyboard; sometimes VDT refers to only the monitor.

VDU

Visual Display Unit. A computer terminal with monitor and keyboard.

vector

1. In computer graphics, a quantity represented as a line with a start and end point identified by x-y coordinates which indicate both magnitude and direction. See also vector graphics. 2. Items configured in a single column or row; a one dimensional array.

vector display

A display that uses vector graphics.

vector font

A scalable font composed of vectors (lines drawn between coordinate points).

vector graphics

A way of representing pictures by designating coordinates and drawing lines or geometric shapes in relation to them. Vector graphics are different from raster graphics, in which an image is stored as a collection of pixels. In vector graphics, the image is saved as a file containing instructions for drawing it. One advantage of vector graphics over raster graphics is that a picture can be enlarged or reduced without losing quality. Another difference is that in vector graphics, the elements of a picture (circles, squares, etc.) remain independent objects which can be edited and moved around, whereas in raster graphics, once the elements are drawn they become part of the overall pattern of pixels. A vector graphics image also requires less memory than a raster graphics image, which requires a specific memory location for each pixel.

Vector Markup Language

(VML). An application of Extensible Markup Language (XML) used for the markup of vector graphic information in the same way that HTML is used for the markup of text. VML graphics can be modified with style sheets along with the document which contains them.

vectors per second

(VPS). A measurement of the speed of a vector processor (a processor which can execute instructions in which the operands can be arrays of data rather than only single elements).

Vectra

A family of PCs developed by Hewlett Packard.

Veronica

Very Easy Rodent-Oriented Net-wide Index to Computer Archives. Veronica is a search engine for Gopher sites similar to Archie for FTP sites.

version number

The number before the decimal place in a program number (for example, Netscape Navigator 3.1, Telnet 2.6). A version number indicates a major change in a program (for example, Disinfectant 2 to Disinfectant 3), whereas a release number indicates a minor change (QuickTime 2.0 to QuickTime 2.1).

vertical application

An application created for a specific kind of business or organization, such as hospitals or retail stores. Contrast with horizontal application.

vertical bar

ASCII character 124: | . Also called vertical line.

Vertical Redundancy Check

(VRC). A way of error checking by attaching a parity bit to each byte of data to be transmitted, which is then tested to determine if the transmission is correct. See parity bit and Cyclic Redundancy Check.

vertical refresh rate

The maximum number of frames per second that a computer monitor can display, expressed in hertz. Too low a vertical refresh rate causes a flickering screen which is hard on the eyes.

vertical resolution

The number of pixels per vertical line, or the number of rows in a matrix.

vertical scaling

Adding more processors within the same multiprocessing computer system, in contrast to horizontal scaling, in which more computer systems are added.

vertical scan frequency

On a computer monitor, the number of times per second the whole screen is refreshed, expressed in hertz. Beginning at the upper left corner, the electron beam moves across the screen, then down to the next line, and to the next, until it reaches the bottom. The electron gun then moves back to the upper left corner and begins the next frame.

vertical scan rate

(VSR). The maximum number of frames per second that a computer monitor can display, expressed in hertz. Too low a scan rate causes a flickering screen which is hard on the eyes. Each frame begins with the electron gun at the upper left corner of the screen. An electron beam is scanned horizontally across the screen, making one line; it moves down slightly to make the next line, and continues until it reaches the bottom. The electron gun returns to the upper left corner to begin the next frame.

vertical software

Software created for a specific kind of business or organization, such as hospitals or retail stores. Contrast with horizontal software.

very high frequency

(VHF). Electromagnetic frequencies in the range of 30 to 300 megaherz. Used for some television and radio transmission.

very high speed integrated circuit

(VHSIC). A very high-speed computer chip which uses large-scale integration (LSI) and very large scale integration (VLSI) technology.

very large scale integration

(VLSI). The use of integrated circuits with 100,000 to a million logic gates.

very low frequency

(VLF). Electromagnetic frequencies in the range of 3 to 30 kiloherz. VLF radiation has been a source of health concerns in the use of computer monitors; standards were set by MPR II.

Very Small Aperture Terminal

(VSAT). A ground station for a communications satellite that can handle transmission rates of up to 56 kilobits per second.

very-high-level Language

(VHLL). A high-level language that is very structured, having strict rules that must be followed.

VESA

Video Electronics Standards Association. An organization which sets standards for video and multimedia in PCs. VESA established the Super VGA (SVGA) standard and the VESA Local Bus. VESA is headquartered in San Jose, California, and its members are PC vendors.

VESA Local Bus

(VLB). A local bus defined by the Video Electronics Standards Association which provides a high-speed connection between the CPU and peripherals. It allows video cards to communicate faster with the CPU. Computers with VESA Local Bus have two or three VLB slots on the motherboard, along with several ISA or EISA slots, so VESA Local Bus can be used alone or in combination with these other buses.

VFAT

Virtual File Allocation Table. The file allocation table used in Windows 95. It uses Protected Mode, an operational state that allows a PC to address all its memory.

VGA

Video Graphics Array. A video display standard for color monitors that superseded CGA and EGA. VGA monitors display 16 colors at a resolution of 640 x 480 pixels, the minimum standard display. The vertical scan frequency is around 56Hz to 60Hz. For multimedia applications, it is better to have Super VGA.

VHD

Very High Density. A 3.5″ floppy disk that holds 20 MB or more of data.

VHF

Very High Frequency. Electromagnetic frequencies in the range of 30 to 300 megaherz. Used for some television and radio transmission.

VHLL

Very-High-Level Language. A high-level language that is very structured, having strict rules that must be followed.

VHS

Video Home System. The standard home videocassette format, which has 1/2″ videotape and up to 160 minutes playing time.

VHSIC

Very High Speed Integrated Circuit. (Pronounced visik). A very high-speed computer chip which uses large-scale integration (LSI) and very large scale integration (VLSI) technology.

ViaCode

An encrypted and authenticated Internet service for businesses in the U.K., provided by The Royal Mail.

video adapter

Also called graphics adapter, display adapter, video card. A circuit board that enables a computer to display information on its screen. The resolution, number of colours, and refresh rate of a monitor is determined by the kind of video adapter used, plus the limitations of the monitor itself.

video card

Also called graphics adapter, display adapter, video adapter. A circuit board that enables a computer to display information on its screen. The resolution, number of colours, and refresh rate of a monitor is determined by the kind of video card used, plus the limitations of the monitor itself.

video cassette recorder

(VCR). An analog videotape player and recorder which is usually connected to a television monitor to record or play tapes. The most commonly used videotape is 1/2-inch VHS format.

Video CD

Video Compact Disc. A type of compact disc that can store 74 minutes of VHS-quality video along with sound of CD quality, using MPEG compression.

video display terminal

(VDT). A computer terminal with monitor and keyboard; sometimes VDT refers to only the monitor.

Video Electronics Standards Association

(VESA). An organization which sets standards for video and multimedia in PCs. VESA established the Super VGA (SVGA) standard and the VESA Local Bus. VESA is headquartered in San Jose, California, and its members are PC vendors.

video graphic card

An accelerator card to enhance 3D graphics, 2D graphics, videoconferencing, and multimedia. A videographic accelerator card can assist in delivering powerful and high-resolution throughput by performing much of the graphics processing that would otherwise be done by the CPU.

video graphic cards

Accelerator cards that enhance 3D graphics, 2D graphics, videoconferencing, and multimedia. A videographic accelerator card can assist in delivering powerful and high-resolution throughput by performing much of the graphics processing that would otherwise be done by the CPU.

Video Graphics Array

(VGA). A video display standard for color monitors that superseded CGA and EGA. VGA monitors display 16 colors at a resolution of 640 x 480 pixels, the minimum standard display. The vertical scan frequency is around 56Hz to 60Hz. For multimedia applications, it is better to have Super VGA.

Video Home System

(VHS). The standard home videocassette format, which has 1/2″ videotape and up to 160 minutes playing time.

video mail

(V-mail or vmail). Sending video clips as attachments to email messages.

video on demand

(VoD). A system by which viewers can watch video programs on their own television sets at the time they choose. The programs are supplied by cable or ISDN.

video port

The socket on the computer where the monitor cord plugs in.

video RAM

Video Random Access Memory (VRAM). A kind of high-speed memory used for the computer's display. VRAM must be fast to keep up with the speed at which the screen is scanned. The VRAM in a PC is on a display adapter card. VRAM has two ports so it can send the data for text and images to memory and to the display at the same time.

video random access memory

(VRAM). A kind of high-speed memory used for the computer's display. VRAM must be fast to keep up with the speed at which the screen is scanned. The VRAM in a PC is on a display adapter card. VRAM has two ports so it can send the data for text and images to memory and to the display at the same time.

video streaming

Playing video immediately as it is downloaded from the Internet, rather than storing it in a file on the receiving computer first. Streaming is accomplished by way of web browser plug-ins, which decompress and play the file in real time; a fast computer and fast connection are necessary.

video terminal

A cathode ray tube display screen with keyboard for input.

video window

An independent window on a computer screen in which full-motion video is displayed.

videoconferencing

Teleconferencing in which still or moving pictures can be transmitted along with voice and text. The first videoconferencing was done with analog TV and satellites, then digital video systems, using computer networks, evolved.

videodisc

An optical disc that can be used to store full-motion video.

videographer

A person who produces videos.

videographic accelerator card

An accelerator card to enhance 3D graphics, 2D graphics, videoconferencing, and multimedia. A videographic accelerator card can assist in delivering powerful and high-resolution throughput by performing much of the graphics processing that would otherwise be done by the CPU.

videography

The art of recording pictures with a video camera.

videophone

A telephone that sends and receives a video image along with voice transmission; it contains both a camera and a screen.

VideoPhone

The AT&T brand of videophones.

vigintillion

10^63 (U.S. and Canada); 10^120 (Europe).

virtual

1. (Older meaning, before computer era) Being so in essence or effect although not officially recognized (for example, a virtual paradise, meaning a place on Earth that is really like Paradise). 2. (New meaning created by computer technology) Simulated; especially simulated by electronic technology (for example, a virtual paradise, meaning a computer simulation of Paradise, perhaps in a virtual reality or 3-D gaming space).

virtual address

A memory location in a system that uses virtual memory; when an application program needs the data at that location, it is paged in and accessed by means of an address in physical memory.

virtual assistant

A hand-carried device that reads email, screens and forwards telephone calls, and handles voice mail. A virtual assistant may be activated by voice commands.

virtual company

A company that relies a lot on telecommunications and computer technology for its business activities. Some of the work may be done by telecommuting; meetings may take place by videoconferencing; the company's main point of access may be a web page.

virtual corporation

A corporation which exists primarily on the Internet. It may have a website, email address, post office box, or voice mail system which is its main point of access. Its physical resources may consist of a one or more personal computers, modems, telephones, and/or fax machines. It relies mainly on mail, telecommunications, and computer technology for its business activities. Some of the work may be done by telecommuting; meetings may take place by videoconferencing. In this way, a worldwide corporation can be run on a few home computers.

virtual device driver

(VxD). A virtual device driver is the component of a device driver that communicates directly between an application and a hardware device. Virtual device drivers organize the flow of data to allow more than one application to access the same hardware without conflict. In the device file name, V stands for virtual and D stands for device. The “x” can be replaced with other characters; for example, VmD means a mouse driver.

virtual disk

A program which simulates a hard disk drive, using part of the computer's random access memory, for fast processing of data. Files can be copied into the virtual disk and edited. The virtual disk can not store files permanently; the updates must be written to the hard disk or floppy disk before the power is turned off.

Virtual File Allocation Table

(VFAT). The file allocation table used in Windows 95. It uses Protected Mode, an operational state that allows a PC to address all its memory.

virtual hosting

The ability of a single machine to act like multiple systems, hosting more than one domain.

virtual interface

A user interface based on virtual reality; the user’s whole body interacts with the computer.

virtual LAN

Virtual Local Area Network. A division of a local area network by software rather than by physical arrangement of cables. Division of the LAN into subgroups can simplify and speed up communications within a workgroup. Switching a user from one virtual LAN to another via software is also easier than rewiring the hardware.

virtual library

A library on the Internet. There are many books and publications available online; some can be viewed on the World Wide Web and some can be downloaded via FTP.

Virtual Machine

(VM). An IBM virtual data processing system, in which multiple operating systems and programs can be run by the computer at the same time. Each user appears to have an independent computer with its own input and output devices.

virtual machine

1. (VM). A computer that does not exist as a physical device, but is simulated by another computer. 2. (VM). An IBM virtual data processing system, in which multiple operating systems and programs can be run by the computer at the same time. Each user appears to have an independent computer with its own input and output devices.

virtual machine

(VM). A computer that does not exist as a physical device, but is simulated by another computer.

virtual machine/conversational monitor s

(VM/CMS). The combination of Virtual Machine with CMS (Conversational Monitor System) to provide interactive capability. VM/CMS supports many interactive users at a time, and was designed for IBM 43xx and 30xx series computers.

virtual memory

A way of using disk storage space to make the computer work as if it had more memory. When a file or program is too big for the computer to work with in its memory, part of the data is stored on disk. This virtual storage is divided into segments called pages; each page is correlated with a location in physical memory, or RAM. When an address is referenced, the page is swapped into memory; it is sent back to disk when other pages must be called. The program runs as if all the data is in memory. The computer uses a hardware device called a memory management unit (MMU) to manage virtual memory.

Virtual Memory System

(VMS). Digital Equipment Corporation's multi-user, multitasking operating system for the VAX series of computers. As the name indicates, VMS makes use of virtual memory.

virtual office

An office that exists more in virtual space than physical space. The actual office may be little more than a computer, a telephone, a modem, and/or a fax machine. Its only communication with the outer world may be through a post office box, a voice mail system, a web page, or an email address.

virtual operating system

An operating system run by another operating system. The host computer may be able to run multiple operating systems at the same time, each giving the appearance of an independent computer with its own input and output devices.

virtual point of presence

(virtual PoP). A remote point through which a user can connect to an Internet service provider, which is not maintained by the ISP. The virtual PoP is usually established to avoid long distance telephone charges. The user calls to the virtual point of presence and the called is relayed to the ISP by a third party.

virtual printer

A way of saving printer output when the user wants to print a file but the printer is busy. The file can be “printed” to disk, where it is saved and then sent to the printer when it is no longer busy.

Virtual Private Network

(VPN). A network which has the appearance and functionality of a dedicated line, but which is really like a private network within a public one, because it is still controlled by the telephone company, and its backbone trunks are used by all customers.

virtual private networking

(VPN). A means by which certain authorized individuals (such as remote employees) have secure access to an organization's intranet by means of an extranet (a part of the internal network that is accessible via the Internet). VPN can be far less expensive than using actual private lines in a wide area network (WAN).

virtual reality

(VR). A computer simulation of reality, using 3D graphics and sound effects, often with user interfaces such as special goggles and gloves, to create a lifelike environment for entertainment, experimentation, and training.

virtual reality markup language

(VRML; also called Virtual Reality Modeling Language). A programming language which used to create the illusion of three-dimensional objects for onscreen virtual reality environments. The computer shows an apparently three-dimensional object from a certain position, and then creates the illusion of movement by gradually changing the viewpoint. The objects can be programmed to respond to mouse clicks.

virtual reality modeling language

(VRML; also called Virtual Reality Markup Language). A programming language which used to create the illusion of three-dimensional objects for onscreen virtual reality environments. The computer shows an apparently three-dimensional object from a certain position, and then creates the illusion of movement by gradually changing the viewpoint. The objects can be programmed to respond to mouse clicks.

virtual screen

A viewing area that extends beyond the physical boundaries of the computer display screen. The extended area can be seen by scrolling, allowing the user to look at very large documents or multiple documents placed side by side.

Virtual Sequential Access Method

(VSAM). A data storage system used in IBM mainframes. VSAM was designed to improve access time by searching indexes instead of actual files, and organizing data efficiently.

Virtual Software Factory

(VSF). A tool for Computer Aided Software Engineering (CASE) from Systematica.

virtual storage

A way of using disk storage space to make the computer work as if it had more memory, also called virtual memory. See virtual memory.

Virtual Storage Access Method

(VSAM). An IBM program that controls communication and data flow in SNA networks.

Virtual Telecommunications Access Method

(VTAM). Software for controlling communications between terminals and application programs in IBM and IBM-compatible systems. It is compatible with Systems Network Architecture.

Virtual Terminal

(VT). The OSI Virtual Terminal Service. Similar to Telnet, it allows users of one host to log into a remote host and interact as if they are normal terminal users of that host.

virus

A program that infects a computer by atttaching itself to another program, and propagating itself when that program is executed. A computer can become infected by files downloaded over a network, or by the installation of new software or floppy disks that are infected with viruses. Some viruses are only pranks, and perform harmless actions like displaying a screen with a joke message on it. Others can destroy files or wipe out a hard drive. To avoid damage from viruses, write-protect the boot disk and other important disks, check new software or disks for viruses, and have virus protection software installed on the computer at all times. Disinfectant programs must be updated periodically because new viruses get into circulation over time. There are some virus protection programs available on the Internet for free. Disinfectant for Macintosh, written by John Norstad of Northwestern University, is freeware; McAfee Anti-Virus for the PC is a shareware program. Knowingly spreading a computer virus is a crime punishable by law. See also Trojan horse and worm.

virus signature

The binary pattern of a virus, used by the antivirus program to detect and eliminate the virus.

VisiCalc

The first spreadsheet program for computers, created by Dan Bricklin and Bob Frankston in 1978 for the Apple II.

Visual Basic

A visual programming environment from Microsoft, used for developing Windows applications. Visual Basic makes it possible to develop practical programs very quickly. The programmer designs windows graphically, then drags program elements, represented by icons, from the Visual Basic Toolbox, and writes Basic code for each element. Visual Basic is event-driven; procedures are called automatically when the end-user chooses menu items, clicks the mouse, moves objects on the screen, etc.

Visual Basic Custom Control

(VBX). A software module that can be used in many different applications. VBXs were originally created to to make it easy to develop Windows applications with Visual Basic, but can be used in other environments. The more versatile ActiveX controls advance the idea of VBX.

Visual C++

A development environment for C and C++ from Microsoft .

Visual dBASE

A version of dBASE designed to enable developers to present data on the World Wide Web.

visual display unit

(VDU). A computer terminal with monitor and keyboard.

Visual User Environment

(VUE). A graphical user interface for UNIX from Hewlett-Packard.

Visual User Interface Tool

(VUIT). A Digital Equipment Corporation tool for creating applications interfaces with OSF/Motif.

VLB

VESA Local Bus. A local bus defined by the Video Electronics Standards Association which provides a high-speed connection between the CPU and peripherals. It allows video cards to communicate faster with the CPU. Computers with VESA Local Bus have two or three VLB slots on the motherboard, along with several ISA or EISA slots, so VESA Local Bus can be used alone or in combination with these other buses.

VLF

Very Low Frequency. Electromagnetic frequencies in the range of 3 to 30 kiloherz. VLF radiation has been a source of health concerns in the use of computer monitors. The Swedish guidelines called MPR II define acceptable levels; some monitors are designed to meet these guidelines.

VLSI

Very Large Scale Integration. The use of integrated circuits with 100,000 to a million logic gates.

VM

1. Virtual Memory. A way of using disk storage space to make the computer work as if it had more memory. When a file or program is too big for the computer to work with in its memory, part of the data is stored on disk. This virtual storage is divided into segments called pages; each page is correlated with a location in physical memory, or RAM. When an address is referenced, the page is swapped into memory; it is sent back to disk when other pages must be called. The program runs as if all the data is in memory. The computer uses a hardware device called a memory management unit (MMU) to manage virtual memory. 2. Virtual machine. A computer that does not exist as a physical device, but is simulated by another computer. 3. Virtual Machine. An IBM virtual data processing system, in which multiple operating systems and programs can be run by the computer at the same time. Each user appears to have an independent computer with its own input and output devices.

VM/CMS

Virtual Machine/Conversational Monitor System. The combination of Virtual Machine with CMS (Conversational Monitor System) to provide interactive capability. VM/CMS supports many interactive users at a time, and was designed for IBM 43xx and 30xx series computers.

VmD

Virtual device driver for a mouse.

VML

Vector Markup Language. An application of Extensible Markup Language (XML) used for the markup of vector graphic information in the same way that HTML is used for the markup of text. VML graphics can be modified with style sheets along with the document which contains them.

VMS

Virtual Memory System. Digital Equipment Corporation's multi-user, multitasking operating system for the VAX series of computers. As the name indicates, VMS makes use of virtual memory.

vmsnet

Top-level newsgroup category for a VAX/VMS system newsgroup.

VoD

Video on Demand. A system by which viewers can watch video programs on their own television sets at the time they choose. The programs are supplied by cable or ISDN.

voice activated

Activated by spoken commands rather than by typing commands into a keyboard, clicking with a mouse, or pushing buttons.

voice channel

A communications channel used to transmit human voice.

voice grade

The bandwidth necessary for transmitting the human voice, usually about 4,000 Hz.

voice mail

A computerized system for receiving, recording, and sometimes forwarding audio messages. A voice mail system plays a prerecorded message to the caller when the line is not answered, and may provide choices such as paging, talking to an operator, or selecting a number by touchtone to choose between message boxes.

voice messaging

The recording of voice messages, even when the receiver of the message is available to listen; used as an alternative to email.

voice recognition

The ability of a computer to recognize spoken words. A computer with voice recognition software can respond to simple spoken commands. In some voice recognition systems, the computer can be programmed to respond only to a particular speaker, by comparing spoken commands with a sound sample.

voice-activated dialing

A feature that allows a user to dial a telephone by speaking; the phone responds to the user’s spoken commands to dial telephone numbers that are pre-programmed in its memory.

voice-net

The plain old telephone system.

voice-over IP

Also called Internet telephony, Voice-over IP (VoIP) uses the Internet Protocol (IP) to transmit voice communications over intranets, extranets, and the Internet. VoIP provides an alternative to standard telephone communication, especially for Internet users with free or fixed-price Internet access, as they can essentially call anywhere around the world for free using Internet telephony software). VoIP sends digitized audio in packet form.

volatile memory

Memory that loses its content when the power is shut off. The main memory (Random Access Memory or RAM) of the computer is volatile memory. Any changes made to files must be saved to disk before the power is turned off or they will be lost. ROM (Read-Only Memory) is non-volatile memory.

volatile storage

Storage or memory which is not permanent; with volatile storage the data is lost when the electrical power is off. A computer’s main memory (RAM) is ordinarily volatile, although there is non-volatile RAM.

volatile storage

Storage that loses its content when the power is shut off, such as Random Access Memory (RAM). Disks and tapes are non-volatile storage media.

volt

The International System unit of electric potential and electromotive force. (Named after Count Allesandro Volta, Italian physicist, 1745-1827). If one volt is applied to a resistance of one ohm, a current of one ampere will flow across the resistance.

volt-amperes

Volts times amperes; an electrical measurement. For direct current, one volt-ampere equals the same power as one watt.

volt-amps

Volts times amperes; an electrical measurement. For direct current, one volt-amp equals the same power as one watt.

voltage regulator

A device which maintains constant voltage in an electrical line in case of brownout.

volume

1. Sound level. 2. A data carrier, such as a disk, a reel of magnetic tape, or a unit of logical storage.

Volume Table of Contents

(VTOC). A table of contents on a disk or diskette that describes the location and size of each file. VTOC is generally a term used with mainframes; personal computers use the term File Allocation Table.

von Neumann architecture

The architecture of computers in which one instruction is processed at a time, also called serial architecture. John von Neumann (1903-1957), Hungarian mathematician, outlined this idea in 1945. Since then, other concepts have evolved, and parallel processing, in which many instructions are processed similtaneously, is often used for faster results.

von Neumann, John

A Hungarian mathematician (1903-1957) who outlined the basic structure of digital computers when working at Princeton in 1945. Von Neumann envisioned the computer with 5 basic units: 1. an arithmetic unit to perform calculations.; 2. a central processing unit; 3. a memory unit to store data and instructions; 4. an input unit to receive data and instructions; 5. an output unit. The von Neumann concept included serial architecture, which means the computer processes one instruction at a time, although very quickly. The first all-electronic computer, ENIAC, realized von Neumann's vision in 1946.

Voodoo

The chip used by 3DFX, for more powerful 3D graphics.

Voters Telecommunications Watch

(VTW). An organization concerned with the rights of Internet citizens; VTW has supported free speech on the Internet and opposed restrictions on encryption technology. VTW is known for the “Free Speech” fireworks icon displayed on web pages.

voxel

(Volume pixel, or volume picture element). A three-dimensional pixel; a concept used in three-dimensional modeling. The smallest division of a three-dimensional space or image.

Voyager

A virtual reality modeling language (VRML) viewer for Macintosh.

VPN

Virtual Private Networking . A means by which certain authorized individuals (such as remote employees) have secure access to an organization's intranet by means of an extranet (a part of the internal network that is accessible via the Internet). VPN can be far less expensive than using actual private lines in a wide area network (WAN).

VPS

Vectors Per Second. A measurement of the speed of a vector processor (a processor which can execute instructions in which the operands can be arrays of data rather than only single elements).

VR

(Virtual Reality). A computer simulation of reality, using 3D graphics and sound effects, often with user interfaces such as special goggles and gloves, to create a lifelike environment for entertainment, experimentation, and training.

VRAM

Video Random Access Memory. A kind of high-speed memory used for the computer's display. VRAM must be fast to keep up with the speed at which the screen is scanned. The VRAM in a PC is on a display adapter card. VRAM has two ports so it can send the data for text and images to memory and to the display at the same time.

VRC

Vertical Redundancy Check. A way of error checking by attaching a parity bit to each byte of data to be transmitted, which is then tested to determine if the transmission is correct. See parity bit and Cyclic Redundancy Check.

VRML

Virtual Reality Modeling Language or Virtual Reality Markup Language. A programming language which used to create the illusion of three-dimensional objects for onscreen virtual reality environments. The computer shows an apparently three-dimensional object from a certain position, and then creates the illusion of movement by gradually changing the viewpoint. The objects can be programmed to respond to mouse clicks.

VRML Consortium, Inc.

The VRML Consortium, Inc. is a nonprofit corporation dedicated to promoting VRML (Virtual Reality Modeling Language) as the open standard for 3D multimedia and shared virtual worlds on the Internet.

VSAM

1. Virtual Storage Access Method. An IBM program that controls communication and data flow in SNA networks. 2. Virtual Sequential Access Method. A data storage system used in IBM mainframes. VSAM was designed to improve access time by searching indexes instead of actual files, and organizing data efficiently.

VSAT

Very Small Aperture Terminal. A ground station for a communications satellite that can handle transmission rates of up to 56 kilobits per second.

VSF

Virtual Software Factory. A tool for Computer Aided Software Engineering (CASE) from Systematica.

VSR

Vertical Scan Rate. The maximum number of frames per second that a computer monitor can display, expressed in hertz. Too low a scan rate causes a flickering screen which is hard on the eyes. Each frame begins with the electron gun at the upper left corner of the screen. An electron beam is scanned horizontally across the screen, making one line; it moves down slightly to make the next line, and continues until it reaches the bottom. The electron gun returns to the upper left corner to begin the next frame.

VT

1. Vertical Tab; ASCII character 11. 2. Virtual Terminal. The OSI Virtual Terminal Service. Similar to Telnet, it allows users of one host to log into a remote host and interact as if they are normal terminal users of that host.

VT100

A video terminal from DEC, released in the 1980s, that became a standard. VT200 and VT300 models followed.

VTAM

Virtual Telecommunications Access Method. Software for controlling communications between terminals and application programs in IBM and IBM-compatible systems. It is compatible with Systems Network Architecture.

VTOC

Volume Table of Contents. A table of contents on a disk or diskette that describes the location and size of each file. VTOC is generally a term used with mainframes; personal computers use the term File Allocation Table.

VTW

Voters Telecommunications Watch. An organization concerned with the rights of Internet citizens; VTW has supported free speech on the Internet and opposed restrictions on encryption technology. VTW is known for the “Free Speech” fireworks icon displayed on web pages.

vtwm

An extended version of Tab Window Manager, which provides a virtual desktop.

VU/Text Information Services, Inc.

An online service based in Philadelphia, Pennsylvania, that provides access to newspapers.

VUE

Visual User Environment. A graphical user interface for UNIX from Hewlett-Packard.

VUIT

Visual User Interface Tool. A Digital Equipment Corporation tool for creating applications interfaces with OSF/Motif.

VUP

VAX Unit of Performance. A unit of measurement of computer performance. One VUP is equivalent to the performance of Digital Equipment Corporation’s VAX 11/780. It is also equivalent to one SPECmark.

VxD

Virtual Device Driver. A virtual device driver is the component of a device driver that communicates directly between an application and a hardware device. Virtual device drivers organize the flow of data to allow more than one application to access the same hardware without conflict. In the device file name, V stands for virtual and D stands for device. The “x” can be replaced with other characters; for example, VmD means a mouse driver.

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