English Dictionary: virtual(a) | by the DICT Development Group |
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From Webster's Revised Unabridged Dictionary (1913) [web1913]: | |
Weroole \We*roo"le\, n. (Zo[94]l.) An Australian lorikeet ({Ptilosclera versicolor}) noted for the variety of its colors; -- called also {varied lorikeet}. | |
From Webster's Revised Unabridged Dictionary (1913) [web1913]: | |
Varied \Va"ried\, a. Changed; altered; various; diversified; as, a varied experience; varied interests; varied scenery. -- {Va"ried*ly}, adv. The varied fields of science, ever new. --Cowper. | |
From Webster's Revised Unabridged Dictionary (1913) [web1913]: | |
Varietal \Va*ri"e*tal\, a. Of or pertaining to a variety; characterizing a variety; constituting a variety, in distinction from an individual or species. Perplexed in determining what differences to consider as specific, and what as varietal. --Darwin. | |
From Webster's Revised Unabridged Dictionary (1913) [web1913]: | |
Vertilinear \Ver`ti*lin"e*ar\, a. [Vertical + linear.] Straight; rectilinear. [R.] | |
From Webster's Revised Unabridged Dictionary (1913) [web1913]: | |
Virtual \Vir"tu*al\ (?; 135), a. [Cf. F. virtuel. See {Virtue}.] 1. Having the power of acting or of invisible efficacy without the agency of the material or sensible part; potential; energizing. Heat and cold have a virtual transition, without communication of substance. --Bacon. Every kind that lives, Fomented by his virtual power, and warmed. --Milton. 2. Being in essence or effect, not in fact; as, the virtual presence of a man in his agent or substitute. A thing has a virtual existence when it has all the conditions necessary to its actual existence. --Fleming. To mask by slight differences in the manners a virtual identity in the substance. --De Quincey. {Principle of virtual velocities} (Mech.), the law that when several forces are in equilibrium, the algebraic sum of their virtual moments is equal to zero. {Virtual focus} (Opt.), the point from which rays, having been rendered divergent by reflection of refraction, appear to issue; the point at which converging rays would meet if not reflected or refracted before they reach it. {Virtual image}. (Optics) See under {Image}. {Virtual moment} (of a force) (Mech.), the product of the intensity of the force multiplied by the virtual velocity of its point of application; -- sometimes called {virtual work}. {Virtual velocity} (Mech.), a minute hypothetical displacement, assumed in analysis to facilitate the investigation of statical problems. With respect to any given force of a number of forces holding a material system in equilibrium, it is the projection, upon the direction of the force, of a line joining its point of application with a new position of that point indefinitely near to the first, to which the point is conceived to have been moved, without disturbing the equilibrium of the system, or the connections of its parts with each other. Strictly speaking, it is not a velocity but a length. {Virtual work}. (Mech.) See {Virtual moment}, above. | |
From Webster's Revised Unabridged Dictionary (1913) [web1913]: | |
Virtual \Vir"tu*al\ (?; 135), a. [Cf. F. virtuel. See {Virtue}.] 1. Having the power of acting or of invisible efficacy without the agency of the material or sensible part; potential; energizing. Heat and cold have a virtual transition, without communication of substance. --Bacon. Every kind that lives, Fomented by his virtual power, and warmed. --Milton. 2. Being in essence or effect, not in fact; as, the virtual presence of a man in his agent or substitute. A thing has a virtual existence when it has all the conditions necessary to its actual existence. --Fleming. To mask by slight differences in the manners a virtual identity in the substance. --De Quincey. {Principle of virtual velocities} (Mech.), the law that when several forces are in equilibrium, the algebraic sum of their virtual moments is equal to zero. {Virtual focus} (Opt.), the point from which rays, having been rendered divergent by reflection of refraction, appear to issue; the point at which converging rays would meet if not reflected or refracted before they reach it. {Virtual image}. (Optics) See under {Image}. {Virtual moment} (of a force) (Mech.), the product of the intensity of the force multiplied by the virtual velocity of its point of application; -- sometimes called {virtual work}. {Virtual velocity} (Mech.), a minute hypothetical displacement, assumed in analysis to facilitate the investigation of statical problems. With respect to any given force of a number of forces holding a material system in equilibrium, it is the projection, upon the direction of the force, of a line joining its point of application with a new position of that point indefinitely near to the first, to which the point is conceived to have been moved, without disturbing the equilibrium of the system, or the connections of its parts with each other. Strictly speaking, it is not a velocity but a length. {Virtual work}. (Mech.) See {Virtual moment}, above. | |
From Webster's Revised Unabridged Dictionary (1913) [web1913]: | |
Virtual \Vir"tu*al\ (?; 135), a. [Cf. F. virtuel. See {Virtue}.] 1. Having the power of acting or of invisible efficacy without the agency of the material or sensible part; potential; energizing. Heat and cold have a virtual transition, without communication of substance. --Bacon. Every kind that lives, Fomented by his virtual power, and warmed. --Milton. 2. Being in essence or effect, not in fact; as, the virtual presence of a man in his agent or substitute. A thing has a virtual existence when it has all the conditions necessary to its actual existence. --Fleming. To mask by slight differences in the manners a virtual identity in the substance. --De Quincey. {Principle of virtual velocities} (Mech.), the law that when several forces are in equilibrium, the algebraic sum of their virtual moments is equal to zero. {Virtual focus} (Opt.), the point from which rays, having been rendered divergent by reflection of refraction, appear to issue; the point at which converging rays would meet if not reflected or refracted before they reach it. {Virtual image}. (Optics) See under {Image}. {Virtual moment} (of a force) (Mech.), the product of the intensity of the force multiplied by the virtual velocity of its point of application; -- sometimes called {virtual work}. {Virtual velocity} (Mech.), a minute hypothetical displacement, assumed in analysis to facilitate the investigation of statical problems. With respect to any given force of a number of forces holding a material system in equilibrium, it is the projection, upon the direction of the force, of a line joining its point of application with a new position of that point indefinitely near to the first, to which the point is conceived to have been moved, without disturbing the equilibrium of the system, or the connections of its parts with each other. Strictly speaking, it is not a velocity but a length. {Virtual work}. (Mech.) See {Virtual moment}, above. | |
From Webster's Revised Unabridged Dictionary (1913) [web1913]: | |
Image \Im"age\, n. [F., fr. L. imago, imaginis, from the root of imitari to imitate. See {Imitate}, and cf. {Imagine}.] 1. An imitation, representation, or similitude of any person, thing, or act, sculptured, drawn, painted, or otherwise made perceptible to the sight; a visible presentation; a copy; a likeness; an effigy; a picture; a semblance. Even like a stony image, cold and numb. --Shak. Whose is this image and superscription? --Matt. xxii. 20. This play is the image of a murder done in Vienna. --Shak. And God created man in his own image. --Gen. i. 27. 2. Hence: The likeness of anything to which worship is paid; an idol. --Chaucer. Thou shalt not make unto thee any graven image, . . . thou shalt not bow down thyself to them. --Ex. xx. 4, 5. 3. Show; appearance; cast. The face of things a frightful image bears. --Dryden. 4. A representation of anything to the mind; a picture drawn by the fancy; a conception; an idea. Can we conceive Image of aught delightful, soft, or great? --Prior. 5. (Rhet.) A picture, example, or illustration, often taken from sensible objects, and used to illustrate a subject; usually, an extended metaphor. --Brande & C. 6. (Opt.) The figure or picture of any object formed at the focus of a lens or mirror, by rays of light from the several points of the object symmetrically refracted or reflected to corresponding points in such focus; this may be received on a screen, a photographic plate, or the retina of the eye, and viewed directly by the eye, or with an eyeglass, as in the telescope and microscope; the likeness of an object formed by reflection; as, to see one's image in a mirror. {Electrical image}. See under {Electrical}. {Image breaker}, one who destroys images; an iconoclast. {Image graver}, {Image maker}, a sculptor. {Image worship}, the worship of images as symbols; iconolatry distinguished from idolatry; the worship of images themselves. {Image Purkinje} (Physics), the image of the retinal blood vessels projected in, not merely on, that membrane. {Virtual image} (Optics), a point or system of points, on one side of a mirror or lens, which, if it existed, would emit the system of rays which actually exists on the other side of the mirror or lens. --Clerk Maxwell. | |
From Webster's Revised Unabridged Dictionary (1913) [web1913]: | |
Virtual \Vir"tu*al\ (?; 135), a. [Cf. F. virtuel. See {Virtue}.] 1. Having the power of acting or of invisible efficacy without the agency of the material or sensible part; potential; energizing. Heat and cold have a virtual transition, without communication of substance. --Bacon. Every kind that lives, Fomented by his virtual power, and warmed. --Milton. 2. Being in essence or effect, not in fact; as, the virtual presence of a man in his agent or substitute. A thing has a virtual existence when it has all the conditions necessary to its actual existence. --Fleming. To mask by slight differences in the manners a virtual identity in the substance. --De Quincey. {Principle of virtual velocities} (Mech.), the law that when several forces are in equilibrium, the algebraic sum of their virtual moments is equal to zero. {Virtual focus} (Opt.), the point from which rays, having been rendered divergent by reflection of refraction, appear to issue; the point at which converging rays would meet if not reflected or refracted before they reach it. {Virtual image}. (Optics) See under {Image}. {Virtual moment} (of a force) (Mech.), the product of the intensity of the force multiplied by the virtual velocity of its point of application; -- sometimes called {virtual work}. {Virtual velocity} (Mech.), a minute hypothetical displacement, assumed in analysis to facilitate the investigation of statical problems. With respect to any given force of a number of forces holding a material system in equilibrium, it is the projection, upon the direction of the force, of a line joining its point of application with a new position of that point indefinitely near to the first, to which the point is conceived to have been moved, without disturbing the equilibrium of the system, or the connections of its parts with each other. Strictly speaking, it is not a velocity but a length. {Virtual work}. (Mech.) See {Virtual moment}, above. | |
From Webster's Revised Unabridged Dictionary (1913) [web1913]: | |
Moment \Mo"ment\, n. [F. moment, L. momentum, for movimentum movement, motion, moment, fr. movere to move. See {Move}, and cf. {Momentum}, {Movement}.] 1. A minute portion of time; a point of time; an instant; as, at thet very moment. In a moment, in the twinkling of an eye. --1 Cor. xv. 52. 2. Impulsive power; force; momentum. The moments or quantities of motion in bodies. --Berkley. Touch, with lightest moment of impulse, His free will. --Milton. 3. Importance, as in influence or effect; consequence; weight or value; consideration. Matters of great moment. --Shak. It is an abstruse speculation, but also of far less moment and consequence of us than the others. --Bentley. 4. An essential element; a deciding point, fact, or consideration; an essential or influential circumstance. 5. (Math.) An infinitesimal change in a varying quantity; an increment or decrement. [Obs.] 6. (Mech.) Tendency, or measure of tendency, to produce motion, esp. motion about a fixed point or axis. {Moment of a couple} (Mech.), the product of either of its forces into the perpendicular distance between them. {Moment of a force}. (Mech.) (a) With respect to a point, the product of the intensity of the force into the perpendicular distance from the point to the line of direction of the force. (b) With respect to a line, the product of that component of the force which is perpendicular to the plane passing through the line and the point of application of the force, into the shortest distance between the line and this point. (c) With respect to a plane that is parallel to the force, the product of the force into the perpendicular distance of its point of application from the plane. {Moment of inertia}, of a rotating body, the sum of the mass of each particle of matter of the body into the square of its distance from the axis of rotation; -- called also {moment of rotation} and {moment of the mass}. {Statical moment}, the product of a force into its leverage; the same as {moment of a force} with respect to a point, line, etc. {Virtual moment}. See under {Virtual}. Syn: Instant; twinkling; consequence; weight; force; value; consideration; signification; avail. | |
From Webster's Revised Unabridged Dictionary (1913) [web1913]: | |
Velocity \Ve*loc"i*ty\, n.; pl. {Velocities}. [L. velocitas, from velox, -ocis, swift, quick; perhaps akin to v[?]lare to fly (see {Volatile}): cf. F. v[82]locit[82].] 1. Quickness of motion; swiftness; speed; celerity; rapidity; as, the velocity of wind; the velocity of a planet or comet in its orbit or course; the velocity of a cannon ball; the velocity of light. Note: In such phrases, velocity is more generally used than celerity. We apply celerity to animals; as, a horse or an ostrich runs with celerity; but bodies moving in the air or in ethereal space move with greater or less velocity, not celerity. This usage is arbitrary, and perhaps not universal. 2. (Mech.) Rate of motion; the relation of motion to time, measured by the number of units of space passed over by a moving body or point in a unit of time, usually the number of feet passed over in a second. See the Note under {Speed}. {Angular velocity}. See under {Angular}. {Initial velocity}, the velocity of a moving body at starting; especially, the velocity of a projectile as it leaves the mouth of a firearm from which it is discharged. {Relative velocity}, the velocity with which a body approaches or recedes from another body, whether both are moving or only one. {Uniform velocity}, velocity in which the same number of units of space are described in each successive unit of time. {Variable velocity}, velocity in which the space described varies from instant, either increasing or decreasing; -- in the former case called accelerated velocity, in the latter, retarded velocity; the acceleration or retardation itself being also either uniform or variable. {Virtual velocity}. See under {Virtual}. Note: In variable velocity, the velocity, strictly, at any given instant, is the rate of motion at that instant, and is expressed by the units of space, which, if the velocity at that instant were continued uniform during a unit of time, would be described in the unit of time; thus, the velocity of a falling body at a given instant is the number of feet which, if the motion which the body has at that instant were continued uniformly for one second, it would pass through in the second. The scientific sense of velocity differs from the popular sense in being applied to all rates of motion, however slow, while the latter implies more or less rapidity or quickness of motion. Syn: Swiftness; celerity; rapidity; fleetness; speed. | |
From Webster's Revised Unabridged Dictionary (1913) [web1913]: | |
Virtual \Vir"tu*al\ (?; 135), a. [Cf. F. virtuel. See {Virtue}.] 1. Having the power of acting or of invisible efficacy without the agency of the material or sensible part; potential; energizing. Heat and cold have a virtual transition, without communication of substance. --Bacon. Every kind that lives, Fomented by his virtual power, and warmed. --Milton. 2. Being in essence or effect, not in fact; as, the virtual presence of a man in his agent or substitute. A thing has a virtual existence when it has all the conditions necessary to its actual existence. --Fleming. To mask by slight differences in the manners a virtual identity in the substance. --De Quincey. {Principle of virtual velocities} (Mech.), the law that when several forces are in equilibrium, the algebraic sum of their virtual moments is equal to zero. {Virtual focus} (Opt.), the point from which rays, having been rendered divergent by reflection of refraction, appear to issue; the point at which converging rays would meet if not reflected or refracted before they reach it. {Virtual image}. (Optics) See under {Image}. {Virtual moment} (of a force) (Mech.), the product of the intensity of the force multiplied by the virtual velocity of its point of application; -- sometimes called {virtual work}. {Virtual velocity} (Mech.), a minute hypothetical displacement, assumed in analysis to facilitate the investigation of statical problems. With respect to any given force of a number of forces holding a material system in equilibrium, it is the projection, upon the direction of the force, of a line joining its point of application with a new position of that point indefinitely near to the first, to which the point is conceived to have been moved, without disturbing the equilibrium of the system, or the connections of its parts with each other. Strictly speaking, it is not a velocity but a length. {Virtual work}. (Mech.) See {Virtual moment}, above. | |
From Webster's Revised Unabridged Dictionary (1913) [web1913]: | |
Virtual \Vir"tu*al\ (?; 135), a. [Cf. F. virtuel. See {Virtue}.] 1. Having the power of acting or of invisible efficacy without the agency of the material or sensible part; potential; energizing. Heat and cold have a virtual transition, without communication of substance. --Bacon. Every kind that lives, Fomented by his virtual power, and warmed. --Milton. 2. Being in essence or effect, not in fact; as, the virtual presence of a man in his agent or substitute. A thing has a virtual existence when it has all the conditions necessary to its actual existence. --Fleming. To mask by slight differences in the manners a virtual identity in the substance. --De Quincey. {Principle of virtual velocities} (Mech.), the law that when several forces are in equilibrium, the algebraic sum of their virtual moments is equal to zero. {Virtual focus} (Opt.), the point from which rays, having been rendered divergent by reflection of refraction, appear to issue; the point at which converging rays would meet if not reflected or refracted before they reach it. {Virtual image}. (Optics) See under {Image}. {Virtual moment} (of a force) (Mech.), the product of the intensity of the force multiplied by the virtual velocity of its point of application; -- sometimes called {virtual work}. {Virtual velocity} (Mech.), a minute hypothetical displacement, assumed in analysis to facilitate the investigation of statical problems. With respect to any given force of a number of forces holding a material system in equilibrium, it is the projection, upon the direction of the force, of a line joining its point of application with a new position of that point indefinitely near to the first, to which the point is conceived to have been moved, without disturbing the equilibrium of the system, or the connections of its parts with each other. Strictly speaking, it is not a velocity but a length. {Virtual work}. (Mech.) See {Virtual moment}, above. | |
From Webster's Revised Unabridged Dictionary (1913) [web1913]: | |
Virtual \Vir"tu*al\ (?; 135), a. [Cf. F. virtuel. See {Virtue}.] 1. Having the power of acting or of invisible efficacy without the agency of the material or sensible part; potential; energizing. Heat and cold have a virtual transition, without communication of substance. --Bacon. Every kind that lives, Fomented by his virtual power, and warmed. --Milton. 2. Being in essence or effect, not in fact; as, the virtual presence of a man in his agent or substitute. A thing has a virtual existence when it has all the conditions necessary to its actual existence. --Fleming. To mask by slight differences in the manners a virtual identity in the substance. --De Quincey. {Principle of virtual velocities} (Mech.), the law that when several forces are in equilibrium, the algebraic sum of their virtual moments is equal to zero. {Virtual focus} (Opt.), the point from which rays, having been rendered divergent by reflection of refraction, appear to issue; the point at which converging rays would meet if not reflected or refracted before they reach it. {Virtual image}. (Optics) See under {Image}. {Virtual moment} (of a force) (Mech.), the product of the intensity of the force multiplied by the virtual velocity of its point of application; -- sometimes called {virtual work}. {Virtual velocity} (Mech.), a minute hypothetical displacement, assumed in analysis to facilitate the investigation of statical problems. With respect to any given force of a number of forces holding a material system in equilibrium, it is the projection, upon the direction of the force, of a line joining its point of application with a new position of that point indefinitely near to the first, to which the point is conceived to have been moved, without disturbing the equilibrium of the system, or the connections of its parts with each other. Strictly speaking, it is not a velocity but a length. {Virtual work}. (Mech.) See {Virtual moment}, above. | |
From Webster's Revised Unabridged Dictionary (1913) [web1913]: | |
Virtuality \Vir`tu*al"i*ty\, n. [Cf. F. virtualit[82].] 1. The quality or state of being virtual. 2. Potentiality; efficacy; potential existence. [Obs.] In one grain of corn, there lieth dormant a virtuality of many other. --Sir T. Browne. | |
From Webster's Revised Unabridged Dictionary (1913) [web1913]: | |
Virtually \Vir"tu*al*ly\, adv. In a virtual manner; in efficacy or effect only, and not actually; to all intents and purposes; practically. | |
From Webster's Revised Unabridged Dictionary (1913) [web1913]: | |
Virtueless \Vir"tue*less\, a. Destitute of virtue; without efficacy or operating qualities; powerless. Virtueless she wished all herbs and charms. --Fairfax. | |
From U.S. Gazetteer (1990) [gazetteer]: | |
Veradale, WA (CDP, FIPS 74725) Location: 47.64945 N, 117.20752 W Population (1990): 7836 (2724 housing units) Area: 8.0 sq km (land), 0.0 sq km (water) Zip code(s): 99037 | |
From U.S. Gazetteer (1990) [gazetteer]: | |
Verdel, NE (village, FIPS 50335) Location: 42.81148 N, 98.19294 W Population (1990): 59 (37 housing units) Area: 0.5 sq km (land), 0.0 sq km (water) Zip code(s): 68760 | |
From Jargon File (4.2.0, 31 JAN 2000) [jargon]: | |
virtual adj. [via the technical term `virtual memory', prob. from the term `virtual image' in optics] 1. Common alternative to {logical}; often used to refer to the artificial objects (like addressable virtual memory larger than physical memory) simulated by a computer system as a convenient way to manage access to shared resources. 2. Simulated; performing the functions of something that isn't really there. An imaginative child's doll may be a virtual playmate. Oppose {real}. | |
From Jargon File (4.2.0, 31 JAN 2000) [jargon]: | |
virtual beer n. Praise or thanks. Used universally in the Linux community. Originally this term signified cash, after a famous incident in which some some Britishers who wanted to buy Linus a beer and sent him money to Finland to do so. | |
From Jargon File (4.2.0, 31 JAN 2000) [jargon]: | |
virtual Friday n. (also `logical Friday') The last day before an extended weekend, if that day is not a `real' Friday. For example, the U.S. holiday Thanksgiving is always on a Thursday. The next day is often also a holiday or taken as an extra day off, in which case Wednesday of that week is a virtual Friday (and Thursday is a virtual Saturday, as is Friday). There are also `virtual Mondays' that are actually Tuesdays, after the three-day weekends associated with many national holidays in the U.S. | |
From Jargon File (4.2.0, 31 JAN 2000) [jargon]: | |
virtual reality n. 1. Computer simulations that use 3-D graphics and devices such as the Dataglove to allow the user to interact with the simulation. See {cyberspace}. 2. A form of network interaction incorporating aspects of role-playing games, interactive theater, improvisational comedy, and `true confessions' magazines. In a virtual reality forum (such as Usenet's alt.callahans newsgroup or the {MUD} experiments on Internet), interaction between the participants is written like a shared novel complete with scenery, `foreground characters' that may be personae utterly unlike the people who write them, and common `background characters' manipulable by all parties. The one iron law is that you may not write irreversible changes to a character without the consent of the person who `owns' it. Otherwise anything goes. See {bamf}, {cyberspace}, {teledildonics}. | |
From Jargon File (4.2.0, 31 JAN 2000) [jargon]: | |
virtual shredder n. The jargonic equivalent of the {bit bucket} at shops using IBM's VM/CMS operating system. VM/CMS officially supports a whole bestiary of virtual card readers, virtual printers, and other phantom devices; these are used to supply some of the same capabilities Unix gets from pipes and I/O redirection. | |
From The Free On-line Dictionary of Computing (15Feb98) [foldoc]: | |
virtual memory}, probably from the term "virtual image" in optics) 1. Common alternative to {logical}; often used to refer to the artificial objects (like addressable {virtual memory} larger than physical memory) created by a computer system to help the system control access to shared resources. 2. Simulated; performing the functions of something that isn't really there. An imaginative child's doll may be a virtual playmate. Opposite of {real} or physical. [{Jargon File}] (1994-11-30) | |
From The Free On-line Dictionary of Computing (15Feb98) [foldoc]: | |
virtual 86 mode mode") An operating mode provided by the {Intel 80386} and later processors to allow {real mode} programs to run under {operating system}s which use {protected mode}. In this sub-mode of protected mode, an operating environment is created which mimics the address calculation in real mode. In virtual 86 mode the segment {MMU} is practically turned off and the {segment register}s exhibit the same behaviour as in real mode. The {page}d MMU, however, still operates. This means that the one megabyte {address space} of real mode can be remapped in four kilobyte {page}s to anywhere in the 32 bit {physical address} space. Each page can be protected separately from read or write accesses. Virtual mode is handled on a per-task-basis, so each {exception} (from protection violations or {interrupt}s) switches the processor back into protected mode. It is therefore possible to have multiple tasks in virtual mode which run {concurrent}ly under the control of an operating system which runs in protected mode. Most operating system services in {MS-DOS} systems are called by {software interrupt}s, which are a kind of exception. If an MS-DOS application runs in virtual mode under the control of a protected mode operating system, each call to MS-DOS causes a switch to protected mode. The operating system emulates the MS-DOS service and switches back to the application in virtual mode. From the viewpoint of the application nothing differs from real mode. {Microsoft Windows}, {Windows NT}, and {OS/2} use this feature to implement "DOS-boxes" in which both MS-DOS and real mode {application program}s can run. | |
From The Free On-line Dictionary of Computing (15Feb98) [foldoc]: | |
virtual address 1. {application program} in a system with {virtual memory} such that intervening hardware and/or software maps the virtual address to real ({physical}) memory. During the course of execution of an application, the same virtual address may be mapped to many different {physical addresses} as data and programs are {paged out} and {paged in} to other locations. 2. In {IBM}'s {VM} {operating system}, {Virtual Device Location}. (2001-01-02) | |
From The Free On-line Dictionary of Computing (15Feb98) [foldoc]: | |
virtual cache A {cache} which uses {virtual address}, i.e. it is between the processor and the {memory management unit}. A virtual cache cannot recognise external access to physical address, e.g. from {DMA}. The whole cache must be flushed when swapping between tasks which share same virtual {address space}. (1994-11-30) | |
From The Free On-line Dictionary of Computing (15Feb98) [foldoc]: | |
virtual circuit is implemented on top of a network which may be either connection-oriented or {connectionless} ({packet switching}). The term "switched virtual circuit" was coined needlessly to distinguish an ordinary virtual circuit from a {permanent virtual circuit}. (One of the perpetrators of this confusion appears to be ["Networking Essentials", 1996, Microsoft Press, ISBN 1-55615-806-8], a book aimed at people preparing for the {MCSE} exam on {LANs} and {WANs}). Not to be confused with {switched virtual connection}. (2001-10-26) | |
From The Free On-line Dictionary of Computing (15Feb98) [foldoc]: | |
Virtual Circuit Identifier {virtual circuit}. An {ATM} {switch} may route according to a Virtual Circuit Identifier, a {Virtual Path Identifier}, or a combination. (2001-05-16) | |
From The Free On-line Dictionary of Computing (15Feb98) [foldoc]: | |
virtual connection network. The word "{virtual}" indicates that the connection is {logical} rather than {physical}. Nothing to do with a {virtual circuit} on a {packet switching} network. [Fred Halsall, "Data Communications, Computer Networks and Open Systems", 1996, Addison Wesley]. 2. A communications link that appears to be a direct connection between sender and receiver, although physically the link can be routed through a more circuitous path, running over {virtual circuits} instead of a private network built primarily with {dedicated lines}. A virtual connection can provide full-time connection among many sites, including those configured for {SNA}/{SDLC} {protocol}. A virtual connection can handle any transmission protocol and is supported worldwide. It can provide high throughput and low delay for {LAN} and {Internet} applications, peer-to-peer connectivity, client-server computing, and other distributed processing applications. [Same as {virtual circuit}?] (2001-10-26) | |
From The Free On-line Dictionary of Computing (15Feb98) [foldoc]: | |
Virtual Control Program Interface (VCPI) An alternative, and incompatible method for doing the same thing as {DOS Protected Mode Interface} (DPMI). (1995-01-12) | |
From The Free On-line Dictionary of Computing (15Feb98) [foldoc]: | |
Virtual Device Driver 3.x}/{Windows 95} running as part of the {kernel} and thus having access to the memory of the kernel and all running processes as well as raw access to the hardware. VxD's usually have the {filename extension} .386 under Windows 3.x and .vxd under Windows 95. VxD's written for Windows 3.x can be used under Windows 95 but not vice versa. (1997-02-27) | |
From The Free On-line Dictionary of Computing (15Feb98) [foldoc]: | |
Virtual Device Location (Or "Virtual Address") The address of a device (e.g. disk, printer, terminal) belonging to a "guest" {operating system}. Such an address is mapped to a physical device. VM may remap several virtual disks to different parts of a single physical disk. (1995-02-22) | |
From The Free On-line Dictionary of Computing (15Feb98) [foldoc]: | |
virtual disk {RAM disk} | |
From The Free On-line Dictionary of Computing (15Feb98) [foldoc]: | |
Virtual Home Environment (VHE) A tool for using {NFS} on {HP UX}. (1994-12-07) | |
From The Free On-line Dictionary of Computing (15Feb98) [foldoc]: | |
virtual host {Internet address}; however, often via special {kernel} patches, a given computer can be made to respond to several {IP} addresses and provide different {services} (typically different {Web} services) on each. Each of these different IP addresess (which generally each have their own {hostname}) act as if they were distinct hosts on distinct machines, even though they are actually all one host. Hence, they are {virtual} hosts. A common use is when an {Internet Service Provider} "hosts" {World-Wide Web} or other services for several of their customers on one computer but giving the appearence that they are separate servers. (1997-09-11) | |
From The Free On-line Dictionary of Computing (15Feb98) [foldoc]: | |
Virtual LAN area network} (LAN) that communicate as if they were on the same wire, even though they are physically on different {LAN segment}s throughout a site. To define a virtual LAN, the {network administrator} uses a virtual LAN management utility to establish membersip rules that determine which hostss are in a specific virtual LAN. Many models may exist but two seem to dominate: (1) Vitual Segment (or Port-Group) Virtual LAN. These are switched at the {data link layer} ({OSI} layer 2). Virtual segments turn an arbitrary number of physical segments into a single virtual segment that funtions as a self-contained traffic domain. (2) Virtual Subnet Virtual LAN: These are switched at the {Network Layer} ({OSI} layer 3). Subnet-oriented virtual LANs are based on {subnet address}es used by {IP}, {IPX}, and other {network layer} {protocol}s to normally identify physical networks. Administrators assign one subnet address to a number of switch {port}s (which may be on different switches and over a backbone). Once identified as a virtual subnet, the selected LANs function as a {bridge group} - traffic is bridged at Layer 2 within the virtual subnet and routed at Layer 3 between virtual subnets. ["The many faces of virtual LANs", Steven King, Network World, 1994/5?]. (1995-04-03) | |
From The Free On-line Dictionary of Computing (15Feb98) [foldoc]: | |
Virtual Loadable Module can be dynamically loaded to extend the functionality of the "VLM" {NetWare Requester} for {MS-DOS} that became standard beginning with {Novell NetWare} 4. (1995-01-11) | |
From The Free On-line Dictionary of Computing (15Feb98) [foldoc]: | |
Virtual Local Area Network which are not necessarily on the same physical {network segment} but which share the same {IP} {network number}. This is often associated with {switched Ethernet}. IEEE 802.1Q is a VLAN standard. [Confirm? Better description? Reference?] (2002-08-30) | |
From The Free On-line Dictionary of Computing (15Feb98) [foldoc]: | |
virtual machine 1. An {abstract machine} for which an {interpreter} exists. Virtual machines are often used in the implementation of portable executors for {high-level languages}. The HLL is compiled into code for the virtual machine (an {intermediate language}) which is then executed by an {interpreter} written in {assembly language} or some other portable language like {C}. Examples are {Core War}, {Java Virtual Machine}, {OCODE}, {OS/2}, {POPLOG}, {Portable Scheme Interpreter}, {Portable Standard Lisp}, {Parallel Virtual Machine}, {Sequential Parlog Machine}, {SNOBOL Implementation Language}, {SODA}, {Smalltalk}. 2. A software emulation of a physical computing environment. The term gave rise to the name of {IBM}'s {VM} {operating system} whose task is to provide one or more simultaneous execution environments in which operating systems or other programs may execute as though they were running "on the bare iron", that is, without an eveloping Control Program. A major use of VM is the running of both outdated and current versions of the same operating system on a single {CPU} complex for the purpose of system migration, thereby obviating the need for a second processor. (2002-04-15) | |
From The Free On-line Dictionary of Computing (15Feb98) [foldoc]: | |
Virtual Machine {hypervisor} running on {IBM 370}, {ESA} and {IBM 390} architecture computers. VM comprises CP ({Control Program}) and CMS ({Conversational Monitor System}) providing Hypervisor and personal computing environments respectively. VM became most used in the early 1980s as a Hypervisor for multiple {DOS/VS} and {DOS/VSE} systems and as IBM's internal operating system of choice. It declined rapidly following widespread adoption of the {IBM PC} and hardware partitioning in {microcode} on IBM {mainframes} after the {IBM 3090}. VM has been known as VM/SP (System Product, the successor to {CP/67}), VM/XA, and currently as VM/ESA (Enterprise Systems Architecture). VM/ESA is still in used in 1999, featuring a {web} interface, {Java}, and {DB2}. It is still a major IBM operating system. {Home (http://vmdev.gpl.ibm.com/)}. ["History of VM"(?), Melinda Varian, Princeton University]. (1999-10-31) | |
From The Free On-line Dictionary of Computing (15Feb98) [foldoc]: | |
virtual machine 1. An {abstract machine} for which an {interpreter} exists. Virtual machines are often used in the implementation of portable executors for {high-level languages}. The HLL is compiled into code for the virtual machine (an {intermediate language}) which is then executed by an {interpreter} written in {assembly language} or some other portable language like {C}. Examples are {Core War}, {Java Virtual Machine}, {OCODE}, {OS/2}, {POPLOG}, {Portable Scheme Interpreter}, {Portable Standard Lisp}, {Parallel Virtual Machine}, {Sequential Parlog Machine}, {SNOBOL Implementation Language}, {SODA}, {Smalltalk}. 2. A software emulation of a physical computing environment. The term gave rise to the name of {IBM}'s {VM} {operating system} whose task is to provide one or more simultaneous execution environments in which operating systems or other programs may execute as though they were running "on the bare iron", that is, without an eveloping Control Program. A major use of VM is the running of both outdated and current versions of the same operating system on a single {CPU} complex for the purpose of system migration, thereby obviating the need for a second processor. (2002-04-15) | |
From The Free On-line Dictionary of Computing (15Feb98) [foldoc]: | |
Virtual Machine {hypervisor} running on {IBM 370}, {ESA} and {IBM 390} architecture computers. VM comprises CP ({Control Program}) and CMS ({Conversational Monitor System}) providing Hypervisor and personal computing environments respectively. VM became most used in the early 1980s as a Hypervisor for multiple {DOS/VS} and {DOS/VSE} systems and as IBM's internal operating system of choice. It declined rapidly following widespread adoption of the {IBM PC} and hardware partitioning in {microcode} on IBM {mainframes} after the {IBM 3090}. VM has been known as VM/SP (System Product, the successor to {CP/67}), VM/XA, and currently as VM/ESA (Enterprise Systems Architecture). VM/ESA is still in used in 1999, featuring a {web} interface, {Java}, and {DB2}. It is still a major IBM operating system. {Home (http://vmdev.gpl.ibm.com/)}. ["History of VM"(?), Melinda Varian, Princeton University]. (1999-10-31) | |
From The Free On-line Dictionary of Computing (15Feb98) [foldoc]: | |
Virtual Machine Environment system}. (1995-06-28) | |
From The Free On-line Dictionary of Computing (15Feb98) [foldoc]: | |
Virtual Machine/Conversational Monitor System personal computing environment executing under {Virtual Machine} (VM) in a virtual machine environment. VM/CMS is designed to support large numbers of {interactive} users. It relies on numerous {API}s into the {Control Program} (CP) to provide very efficient single-user processing VM/CMS was only adopted some time after the original design of {Virtual Machine} as a more efficient personal computing environment than {MVS/TSO}. (1999-01-19) | |
From The Free On-line Dictionary of Computing (15Feb98) [foldoc]: | |
Virtual Machine/ESA {Virtual Machine} | |
From The Free On-line Dictionary of Computing (15Feb98) [foldoc]: | |
Virtual Machine/System Product {Virtual Machine} | |
From The Free On-line Dictionary of Computing (15Feb98) [foldoc]: | |
Virtual Machine/XA {Virtual Machine} | |
From The Free On-line Dictionary of Computing (15Feb98) [foldoc]: | |
virtual memory behave as though the computer's memory was larger than the actual {physical} {RAM}. The excess is stored on {hard disk} and copied to RAM as required. Virtual memory is usually much larger than physical memory, making it possible to run programs for which the total code plus data size is greater than the amount of RAM available. This is known as "{demand paged} virtual memory". A page is copied from disk to RAM ("paged in") when an attempt is made to access it and it is not already present. This paging is performed automatically by collaboration between the {CPU}, the {memory management unit} (MMU), and the {operating system} {kernel}. The program is unaware of virtual memory, it just sees a large {address space}, only part of which corresponds to physical memory at any instant. The virtual {address space} is divided into {pages}. Each {virtual address} output by the {CPU} is split into a (virtual) {page} number (the most significant bits) and an offset within the page (the N least significant bits). Each page thus contains 2^N {bytes} (or whatever the unit of addressing is). The offset is left unchanged and the {memory management unit} (MMU) maps the virtual page number to a {physical} page number. This is recombined with the offset to give a {physical address} - a location in {physical memory} ({RAM}). The performance of a program will depend dramatically on how its memory access pattern interacts with the paging scheme. If accesses exhibit a lot of {locality of reference}, i.e. each access tends to be close to previous accesses, the performance will be better than if accesses are randomly distributed over the program's {address space} thus requiring more paging. In a {multitasking} system, physical memory may contain pages belonging to several programs. Without {demand paging}, an OS would need to allocate physical memory for the whole of every active program and its data. Such a system might still use an {MMU} so that each program could be located at the same {virtual address} and not require run-time relocation. Thus virtual addressing does not necessarily imply the existence of virtual memory. Similarly, a {multitasking} system might load the whole program and its data into physical memory when it is to be executed and copy it all out to disk when its {timeslice} expired. Such "swapping" does not imply virtual memory and is less efficient than paging. Some {application programs} implement virtual memory wholly in software, by translating every virtual memory access into a file access, but efficient virtual memory requires hardware and operating system support. (2002-11-26) | |
From The Free On-line Dictionary of Computing (15Feb98) [foldoc]: | |
Virtual Memory System system} originally produced for its {VAX} {minicomputer}. VMS V1 was released in August 1978. VMS was renamed "OpenVMS" around version 5.5. The first version of VMS on {DEC Alpha} was known as OpenVMS for AXP V1.0, and the correct way to refer to the operating system now is OpenVMS for VAX or OpenVMS for Alpha. The renaming also signified the fact that the {X/Open} consortium had certified OpenVMS as having a high support for {POSIX} standards. VMS is one of the most secure operating systems on the market (making it popular in financial institutions). It currently (October 1997) has the best {clustering} capability (both number and distance) and is very scalable with {binaries} portable from small desktop {workstations} up to huge {mainframes}. Many {Unix} fans generously concede that VMS would probably be the {hacker}'s favourite commercial OS if Unix didn't exist; though true, this makes VMS fans furious. {FAQ (http://www.cis.ohio-state.edu/hypertext/faq/bngusenet/comp/os/vms/top.html)}. {Usenet} newsgroup: {news:comp.os.vms}. [How does its performance compare with other OSes?] (1999-06-03) | |
From The Free On-line Dictionary of Computing (15Feb98) [foldoc]: | |
virtual path particular {server}, as seen by a remote {client} accessing it via {World-Wide Web} (or similar distributed document service). A virtual path provides access to files outside the default directory and subdirectories. It appears in the form ".../~name/..." where "~name" is replaced with actual path configured by the administrator. An {access control list} can be associated with a virtual path. (1995-04-13) | |
From The Free On-line Dictionary of Computing (15Feb98) [foldoc]: | |
virtual point of presence (virtual PoP) A point, via which users can connect to an {Internet access provider}, which is not operated by the provider. The user is charged by the telephone company for the call to the virtual point of presence which relays his call via some third party circuit to the Internet provider's central location. This is in contrast to a physical {point of presence} (PoP) which is operated by the Internet provider themselves. The advantage of a virtual PoP is that the provider can keep all their {modem}s in one location, thus improving availability and maintenance, but users do not have to pay long-distance call charges to that point. (1994-12-13) | |
From The Free On-line Dictionary of Computing (15Feb98) [foldoc]: | |
virtual PoP {virtual point of presence} | |
From The Free On-line Dictionary of Computing (15Feb98) [foldoc]: | |
Virtual Private Network lower {protocol layers} to provide a secure connection through an otherwise insecure network, typically the {Internet}. VPNs are generally cheaper than real private networks using private lines but rely on having the same encryption system at both ends. The encryption may be performed by {firewall} software or possibly by {routers}. Link-level (layer 2 and 3) encryption provides extra protection by encrypting all of each {datagram} except the link-level information. This prevents a listener from obtaining information about network structure. While link-level encryption prevents traffic analysis (a form of attack), it must encrypt/decrypt on every {hop} and every path. Protocol-level encryption (layer 3 and 4) encryption encrypts protocol data but leaves protocol and link headers clear. While protocol-level encryption requires you to encrypt/decrypt data only once, and it encrypts/decrypts only those sessions that need it, headers are sent as clear text, allowing traffic analysis. Application (layer 5 up) encryption is based on a particular application and requires that the application be modified to incorporate encryption. {Cisco (http://www.cisco.com/univercd/cc/td/doc/product/lan/cat5000/cnfg_nts/rsm/rsm_pa/4801encr.htm)}. (1999-11-15) | |
From The Free On-line Dictionary of Computing (15Feb98) [foldoc]: | |
virtual reality (VR) 1. devices such as the {data glove} to allow the user to interact with the simulation. 2. of role-playing games, interactive theater, improvisational comedy, and "true confessions" magazines. In a virtual reality forum (such as {Usenet}'s {news:alt.callahans} newsgroup or the {MUD} experiments on {Internet} and elsewhere), interaction between the participants is written like a shared novel complete with scenery, "foreground characters" that may be personae utterly unlike the people who write them, and common "background characters" manipulable by all parties. The one iron law is that you may not write irreversible changes to a character without the consent of the person who "owns" it, otherwise, anything goes. See {bamf}, {cyberspace}. [{Jargon File}] (1995-01-30) | |
From The Free On-line Dictionary of Computing (15Feb98) [foldoc]: | |
Virtual Reality Modeling Language the design and implementation of a {platform}-independent language for {virtual reality} scene description. VRML 1.0 was released on 1995-05-26. {Home (http://www.vrml.org/)}. {Wired (http://vrml.wired.com/)}. {Hypermail Archive (http://vrml.wired.com/arch/)}. Mailing list: www-vrml your-email-address"). (1995-07-20) | |
From The Free On-line Dictionary of Computing (15Feb98) [foldoc]: | |
Virtual Sequential Access Method {Virtual Storage Access Method} | |
From The Free On-line Dictionary of Computing (15Feb98) [foldoc]: | |
virtual server {server} that appears to {clients} as an independent server but which is actually running on a computer that is shared by any number of other virtual servers. Each virtual server can be configured as an independent {web site}, with its own {hostname}, content, and security settings. {DNS} maps the hostnames of all virtual servers on one physical server to its {IP address}. The web server software then uses the "Host" header in the {HTTP} request to determine which virtual server the request was for, and then processes the request using that virtual server's configuration. Virtual servers allow {Internet Service Providers} to share one computer between multiple {web sites} while allowing the owner of each web site to use and administer the server as though they had complete control. (2003-06-23) | |
From The Free On-line Dictionary of Computing (15Feb98) [foldoc]: | |
virtual shredder The jargon equivalent of the {bit bucket} at shops using {IBM}'s {VM/CMS} {operating system}. VM/CMS officially supports a whole bestiary of virtual card readers, virtual printers, and other phantom devices; these are used to supply some of the same capabilities {Unix} gets from {pipe}s and {I/O redirection}. [{Jargon File}] (1995-01-30) | |
From The Free On-line Dictionary of Computing (15Feb98) [foldoc]: | |
Virtual Software Factory allows users to develop {CASE} tools appropriate to any software engineering methodology. (1997-06-09) | |
From The Free On-line Dictionary of Computing (15Feb98) [foldoc]: | |
Virtual Storage Access Method in {S/370} and virtual storage. VSAM comprises three access methods: {Keyed Sequenced Data Set} (KSDS), {Relative Record Data Set} (RRDS), and {Entry Sequenced Data Set} (ESDS). Both {IMS/DB} and {DB2} are implemented on top of VSAM and use its underlying data structures. ["Storage" or "Sequential"?] (2002-07-26) | |
From The Free On-line Dictionary of Computing (15Feb98) [foldoc]: | |
Virtual Storage Extended {multitasking}, {IBM 370}-architected {operating system} similar to {Multiple Virtual Storage} (MVS). VSE run jobs in {partitions} rather than {address spaces}, and uses {POWER} for input/output rather than {JES}, but is largely similar to MVS. Subsequent VSE/{ESA} releases gave VSE the {XA-370} channel architecture, 31-bit virtual and real storage support, and data spaces. VSE is the {IBM} operating system on one-third of installed {IBM 4381}s and a significant proportion of {IBM 9370}s as well. It offers {transaction processing} and {batch processing} capabilities well beyond {Virtual Machine}'s current capabilities, and has a close affinity with MVS. (1997-06-09) | |
From The Free On-line Dictionary of Computing (15Feb98) [foldoc]: | |
Virtual Telecommunications Access Method (VTAM) A data communications access method compatible with {IBM}'s {Systems Network Architecture}. [More detail?] (1995-01-30) |