MICROSOFT Computer Dictionary, Fifth Edition

Microsoft Computer Dictionary, Fifth Edition

n. Memory that appears to an application to be larger and more uniform than it is. Virtual memory may be partially simulated by secondary storage such as a hard disk. Applications access memory through virtual addresses, which are translated (mapped) by special hardware and software onto physical addresses. Acronym: VM. Also called: disk memory. See also paging, segmentation.

virtual monitor

n. An enhanced monitor viewing system for visually impaired users that uses a virtual-reality headset to move enlarged text across the screen in a direction opposite to head motion. See also virtual reality.

virtual name space

n. The set of all hierarchical sequences of names that can be used by an application to locate objects. One such sequence of names defines a path through the virtual name space, regardless of whether the hierarchy of names reflects the actual arrangement of objects around the system. For example, the virtual name space of a Web server consists of all possible URLs on the network on which it runs. See also URL.

virtual network

n. A part of a network that appears to a user to be a network of its own. For example, an Internet service provider can set up multiple domains on a single HTTP server so that each one can be addressed with its company’s registered domain name. See also domain name, HTTP server (definition 1), ISP.

virtual path

n. 1. A sequence of names that is used to locate a file and that has the same form as a pathname in the file system but is not necessarily the actual sequence of directory names under which the file is located. The part of a URL that follows the server name is a virtual path. For example, if the directory c:\bar\sinister\forces\distance on the server miles is shared on the local area network at foo.com under the name \\miles\baz and contains the file elena.html, that file may be returned by a Web request for http://miles.foo.com/baz/elena.html. 2. In Asynchronous Transfer Mode (ATM), a set of virtual channels that are switched together as a unit through the network. See also ATM (definition 1), virtual channel.

virtual peripheral

n. A peripheral that can be referenced but does not physically exist. For example, an application might treat a serial port through which data is being transmitted as a printer, but the device receiving the data might be another computer instead.

virtual printer

n. A feature in many operating systems that allows printer output to be saved to a file until a printer becomes available.

virtual printer device driver n. See virtual device driver.

virtual private network

n. 1. Nodes on a public network such as the Internet that communicate among themselves using encryption technology so that their messages are as safe from being intercepted and understood by unauthorized users as if the nodes were connected by private lines. 2. A WAN (wide area network) formed of permanent virtual circuits (PVCs) on another network, especially a network using technologies such as ATM or frame relay. Acronym: VPN. See also ATM (definition 1), frame relay, PVC.

virtual reality

Microsoft Computer Dictionary, Fifth Edition

n. A simulated 3-D environment that a user can experience and manipulate as if it were physical. The user sees the environment on display screens, possibly mounted in a special pair of goggles. Special input devices, such as gloves or suits fitted with motion sensors, detect the user’s actions. Acronym: VR.

Virtual Reality Modeling Language n. See VRML.

virtual real mode

n. A feature of the Intel 80386 (SX and DX) and later microprocessors that allows them to emulate several 8086 (real-mode) environments at the same time. The microprocessor provides a set of virtual registers and virtual memory space to each virtual 8086 environment. A program running in a virtual 8086 environment is completely protected from other virtual 8086 environments in the system and behaves as if it had control of the entire system. Also called: V86 mode, virtual 8086 mode, virtual 86 mode. See also real mode.

virtual root

n. The root directory that a user sees when connected to an Internet server, such as an HTTP or FTP server. The virtual root is actually a pointer to the physical root directory, which may be in a different location, such as on another server. The advantages of using a virtual root include being able to create a simple URL for the Internet site and to move the root directory without affecting the URL. Also called: v-root. See also pointer (definition 1), root directory, server (definition 2), URL.

virtual route

n. See virtual circuit.

virtual screen

n. An image area that extends beyond the dimensions of the physical screen on the monitor, allowing manipulation of large documents or of multiple documents that lie partially outside the normal screen view. See also monitor.

virtual server

n. A virtual machine that resides on an HTTP server but has the appearance to the user of being a separate HTTP server. Several virtual servers can reside on one HTTP server, each capable of running its own programs and each with individualized access to input and peripheral devices.

Each virtual server has its own domain name and IP address and appears to the user as an individual Web site. Some Internet service providers use virtual servers for those clients who want to use their own domain names. See also domain name, HTTP server (definition 2), IP address.

virtual storefront

n. A company’s point of presence on the Web, providing opportunities for online sales. Also called: electronic storefront.

virtual terminal

n. See terminal emulation.

virtual timer device driver n. See virtual device driver.

virtual world

n. 1. A 3-D modeled environment, often created in VRML, where a user can interact with the viewer to change variables. See also viewer, VRML. 2. An electronic environment that has no basis in the physical world. Multiuser dungeons (MUDs), talkers, and chat rooms are often considered virtual worlds. See also chat1 (definition 1), MUD, talker.

Microsoft Computer Dictionary, Fifth Edition

virus

n. An intrusive program that infects computer files by inserting in those files copies of itself. The copies are usually executed when the file is loaded into memory, allowing the virus to infect still other files, and so on. Viruses often have damaging side effects—sometimes intentionally, sometimes not. For example, some viruses can destroy a computer’s hard disk or take up memory space that could otherwise be used by programs. See also Good Times virus, Trojan horse, worm.

virus signature

n. A portion of unique computer code contained in a virus. Antivirus programs search for known virus signatures to identify infected programs and files. See also virus.

visible page

n. In computer graphics, the image that is being displayed on the screen. Screen images are written into display memory in sections called pages, each of which contains one screen display.

Visio

n. A software application offered by Microsoft that allows users to create diagrams and visual presentations in electronic form. Visio enables users to share ideas and concepts visually by using diagrams to augment written material in documents or by expanding visual elements in a public presentation. Microsoft acquired the Visio application in 1999, when it purchased Visio Corporation.

visit

n. A session during which a person views one or more pages in a particular Web site.

visitor

n. A person who views a Web page or Web site.

Visor

n. A product line of handheld personal digital assistants (PDAs) developed by Handspring Corporation. Features include an address list, an appointments calendar, a to-do list, and memos. Visor also features a 68-pin Springboard socket that allows plug-ins of additional devices offered by Handspring. See also Springboard.

Visual Basic

n. A trademarked name owned by Microsoft Corporation for a high-level, visual-programming version of Basic. Visual Basic was designed for building Windows-based applications. See also Basic, Visual Basic for Applications, Visual Basic, Scripting Edition, visual programming.

Visual Basic Editor

n. An environment in which you write new and edit existing Visual Basic for Applications code and procedures. The Visual Basic Editor contains a complete debugging toolset for finding syntax, run-time, and logic problems in your code.

Visual Basic for Applications

n. A macro-language version of Visual Basic that is used to program many Windows 9x applications and is included with several Microsoft applications. Acronym: VBA. See also macro language, Visual Basic.

Visual Basic Script

n. See Visual Basic, Scripting Edition.

Visual Basic, Scripting Edition

n. A subset of the Visual Basic programming language, optimized for Web-related programming. As with JavaScript, code for Visual Basic, Scripting Edition is embedded in HTML documents.

Microsoft Computer Dictionary, Fifth Edition

This version is included with the Internet Explorer Web browser. Also called: VBScript, Visual Basic Script. See also Visual Basic for Applications.

Visual C++

n. A Microsoft application development system for the programming language C++ that runs under MS-DOS and Windows. Visual C++ is a visual programming environment. See also visual programming. Compare Visual Basic, Visual J++.

Visual Café

n. The Java-based suite of software development tools from Symantec Corporation. Visual Café is available in several product packages. The Standard Edition, intended for beginning Java programmers, includes an integrated editor, debugger, and compiler, as well as a JavaBean library, wizards, and utilities. The Professional Edition provides a larger library of JavaBeans and more sophisticated tools for development and debugging. The Database Edition, as the name indicates, adds support for database functionality. The Enterprise Suite provides a high-end environment for development of enterprise applications. See also Java.

Visual FoxPro Database and Command Language

n. A Microsoft product for developing database applications that includes a rich object-oriented programming language derived from the Xbase language.

Visual InterDev

n. Microsoft’s integrated development environment for Web applications. Visual InterDev includes tools for end-to-end (design through deployment) development, as well as integrated tools for database programming and design. The first version of Microsoft Visual InterDev was released in 1997.

visual interface

n. See graphical user interface.

visualization

n. A feature of an application that displays data in the form of a video image. For example, some databases can interpret and show data in the form of a twoor three-dimensional model.

Visual J++

n. Microsoft’s Java visual programming environment, which can be used to create applets and applications in the Java language. See also applet, Java, Java applet, visual programming.

visual programming

n. A method of programming using a programming environment or language in which basic program components can be selected through menu choices, buttons, icons, and other predetermined methods.

Visual SourceSafe

n. A project-oriented version control system designed by Microsoft to manage software and Web site development. Visual SourceSafe stores files in a secure repository that provides easy access to authorized users and tracks all changes made to files. Visual SourceSafe works with any type of file produced by any development language, authoring tool, or application.

Visual Studio

n. Microsoft’s suite of software development tools for rapid development of business applications and components. Visual Studio is provided in two editions. The Professional Edition, for professional programmers, includes the Visual Basic and Visual C++ languages, Visual FoxPro for database development, Visual InterDev for Web development, and Visual J++ for Java development. The Enterprise Edition, for enterprise-level development, also includes Visual

Microsoft Computer Dictionary, Fifth Edition

SourceSafe (a team-based source code control system) and the Developer Edition of Microsoft BackOffice Server.

Visual Studio .NET

n. A development environment for creating XML Web services and applications on the Microsoft

.NET platform. See also .NET, .NET My Services.

VLAN

n. See virtual LAN.

VLB1

adj. See VESA1.

VLB2

n. See VL bus.

VL bus

n. Short for VESA local bus. A type of local bus architecture introduced by the Video Electronics Standards Association. The VL bus specification allows up to three VL bus slots to be built into a PC motherboard and allows for bus mastering (wherein intelligent adapter cards can do some processing independently of the CPU). A VL bus slot consists of a standard connector plus an additional 16-bit Micro Channel Architecture connector and must be built into the motherboard by the manufacturer. Standard connectors cannot simply be converted to VL bus slots. A non–VL bus adapter card can be used in a VL bus slot, but it cannot use the local bus and so performs as it normally would in a non–VL bus slot. Also called: VL local bus. See also local bus, PCI local bus.

VLF radiation

n. Short for very-low-frequency radiation. Electromagnetic radiation (radio) at frequencies within the range of approximately 300 Hz to 30,000 Hz (30 kHz). Computer monitors emit this type of radiation. A voluntary standard, MPR II, regulates the amount of VLF radiation that a monitor can emit. See also MPR II.

VLIW

n. Acronym for Very Long Instruction Word. An architecture that combines many simple instructions into a single long instruction word that uses different registers.

VL local bus n. See VL bus.

VLSI

n. See very-large-scale integration.

VM

n. Acronym for Virtual Machine. An operating system for IBM mainframes that provides virtualmachine capability. VM was developed by IBM customers and later taken over by IBM itself under the name OS/VM. See also virtual machine, virtual memory.

VML

n. Acronym for Vector Markup Language. An XML-based specification for the exchange, editing, and delivery of 2-D vector graphics on the Web. An application of XML (Extensible Markup Language), VML uses XML tags and Cascading Style Sheets to create and place vector graphics, such as circles and squares, in an XML or HTML document, such as a Web page. These graphics, which are rendered in the native operating system, can include color and are editable in a variety of graphics programs. See also Cascading Style Sheets, XML.

Microsoft Computer Dictionary, Fifth Edition

VoATM

n. Short for Voice over Asynchronous Transfer Mode. The transmission of voice and other telephony over an ATM network. See also ATM, VoFR, VoIP.

VoFR

n. Short for Voice over Frame Relay. Voice transmission over a frame relay network. See also frame relay, VoATM, VoIP.

voice answer back

n. The use of sound-recorded messages by a computer in responding to commands or queries. Acronym: VAB.

voice-capable modem

n. A modem that can support voice messaging applications along with its data-handling functions.

voice chat

n. A feature offered by Internet service providers (ISPs) that allows users to converse with each other directly through an Internet connection. See also Internet telephone.

voice coil

n. A device that moves a disk drive actuator arm using electromagnetism. It works more quickly than a stepper motor. See also actuator. Compare stepper motor.

voice-grade channel

n. A communications channel, such as a telephone line, with an audio bandwidth of 300 to 3000 Hz, suitable for carrying speech. A voice-grade channel can also be used for transmitting facsimile, analog, and digital information at rates up to 33 kilobits per second (Kbps).

voice input

n. Spoken instructions that a computer translates into executable commands using speech recognition technology or that are embedded into documents with the aid of a microphone. See also speech recognition.

voice mail

n. A system that records and stores telephone messages in a computer’s memory. Unlike a simple answering machine, a voice mail system has separate mailboxes for multiple users, each of whom can copy, store, or redistribute messages.

voice messaging

n. A system that sends and receives messages in the form of sound recordings.

voice modem

n. A modulation/demodulation device that supports a switch to change between telephony and data transmission modes. Such a device might contain a built-in loudspeaker and microphone for voice communication, but more often it uses the computer’s sound card. See also modem, sound card, telephony.

voice navigation

n. The use of spoken commands to control a Web browser. Voice navigation is a feature of some plug-in applications that embellish Web browsers to allow the user to navigate the Web by means of his or her voice. See also Web browser.

voice-net

n. A term used on the Internet to refer to the telephone system, often preceding the user’s telephone number in an e-mail signature.

Microsoft Computer Dictionary, Fifth Edition

voice output

n. See speech synthesis.

Voice over Asynchronous Transfer Mode n. See VoATM.

Voice over Frame Relay n. See VoFR.

Voice over IP n. See VoIP.

voice recognition

n. The capability of a computer to understand the spoken word for the purpose of receiving commands and data input from the speaker. Systems that can recognize limited vocabularies as spoken by specific individuals have been developed, but developing a system that deals with a variety of speech patterns and accents, as well as with the various ways in which a request or a statement can be made, is more difficult, although advances are being made in this area. Also called: speech recognition. See also artificial intelligence, dictation software, neural network.

voice synthesis

n. See speech synthesis.

VoIP

n. Acronym for Voice over IP. The use of the Internet Protocol (IP) for transmitting voice communications. VoIP delivers digitized audio in packet form and can be used for transmitting over intranets, extranets, and the Internet. It is essentially an inexpensive alternative to traditional telephone communication over the circuit-switched Public Switched Telephone Network (PSTN). VoIP covers computer-to-computer, computer-to-telephone, and telephone-based communications. For the sake of compatibility and interoperability, a group called the VoIP Forum promotes product development based on the ITU-T H.323 standard for transmission of multimedia over the Internet. Also called: Internet telephony. See also H.323.

volatile memory

n. 1. Memory, such as RAM, that loses its data when the power is shut off. Compare nonvolatile memory. 2. Memory used by a program that can change independently of the program, such as memory shared by another program or by an interrupt service routine.

volt

n. The unit used to measure potential difference or electromotive force. One volt is defined as the potential across which 1 coulomb of charge will do 1 joule of work, or the potential generated by 1 ampere of current flowing through 1 ohm of resistance. See also electromotive force.

voltage

n. See electromotive force.

voltage regulator

n. A circuit or circuit component that maintains a constant output voltage despite variations in input voltage.

volts alternating current

n. The measure of the peak-to-peak voltage swing of an electrical signal. Acronym: VAC.

volume

n. 1. A disk or tape that stores computer data. Sometimes, large hard disks are divided into several volumes, each of which is treated as a separate disk. 2. The loudness of an audio signal.

Microsoft Computer Dictionary, Fifth Edition

volume label

n. A name for a disk or tape. MS-DOS systems, which seldom use disk names except in directory listings, use the term volume label. Apple Macintosh systems, which often refer to disks by name, use the term volume name.

volume name

n. See volume label.

volume reference number

n. See volume serial number.

volume serial number

n. The optional identifying volume number of a disk or tape. MS-DOS systems use the term volume serial number. Apple Macintosh systems use the term volume reference number. A volume serial number is not the same as a volume label or volume name. Compare volume label.

VON

n. Acronym for voice on the net. A broad category of hardware and software technology for realtime voice and video transmission over the Internet. The term was coined by Jeff Pulver, who formed a group called the VON Coalition, which opposes regulation of VON technology and promotes VON to the public.

von Neumann architecture

n. The most common structure for computer systems, attributed to the mathematician John von Neumann. It uses the concept of a program that can be permanently stored in a computer and manipulated or made self-modifying through machine-based instructions. Sequential processing is characteristic of von Neumann architecture. Parallel architectures have evolved to improve on the encumbrances of sequential instructions. See also parallel computer.

von Neumann bottleneck

n. Competition between data and instructions for CPU time. Mathematician John von Neumann was the first to show that a computer based on architecture linking a single processor with memory will actually spend more time retrieving data from memory than processing it. The bottleneck arises when the processor has to trade off between executing a large number of instructions per second and reading in a large amount of data in the same time. See also CPU.

VPD

n. Acronym for virtual printer device driver. See virtual device driver.

VPN

n. See virtual private network.

VR

n. See virtual reality.

VRAM

n. See video RAM.

VRC

n. Acronym for vertical redundancy check. A method for checking the accuracy of transmitted data. VRC generates an extra bit (parity bit) for each character transmitted. The parity bit indicates whether the character contains an odd or an even number of 1 bits. If its value does not match the type of the character, that character is assumed to be incorrectly transmitted. See also parity. Compare LRC.

Microsoft Computer Dictionary, Fifth Edition

V-sync

n. See vertical bandwidth.

VT-52, VT-100, VT-200

n. A popular set of control codes used in terminals with those model numbers that were originally manufactured by Digital Equipment Corporation. Appropriate software can enable a microcomputer to use these codes to emulate such terminals.

VTD

n. Acronym for virtual timer device driver. See virtual device driver.

Vulcan death grip

n. A warm boot by pressing the Alt+Crl+Delete keys. The name is a reference from Star Trek. See also three-finger salute, warm boot.

VxD

n. See virtual device driver.

W: w3 - WYSIWYG

w3

n. See World Wide Web.

W3

n. See World Wide Web.

W3C

n. Abbreviation for the World Wide Web Consortium, a standards body based in the United States, Europe, and Japan. The W3C is dedicated (in part) to encouraging the development of open Web standards, such as the HTML and XML document markup languages, to promote interoperability and assist the Web in achieving its potential.

wafer

n. A thin, flat piece of semiconductor crystal used in the fabrication of integrated circuits. Various etching, doping, and layering techniques are used to create the circuit components on the surface of the wafer. Usually multiple identical circuits are formed on a single wafer, which is then cut into sections. Each integrated circuit then has leads attached and is packaged in a holder. See also integrated circuit, semiconductor.

wafer-scale integration

n. The fabrication on a single wafer of different microcircuits that are then connected to form a single circuit the full size of the wafer. See also wafer.