| slovo | definícia |
virtual
(mass) | virtual
- virtuálny |
virtual
(encz) | virtual,myšlený adj: Ritchie |
virtual
(encz) | virtual,skutečný adj: Zdeněk Brož |
virtual
(encz) | virtual,virtuální adj: Zdeněk Brož |
Virtual
(gcide) | 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.
[1913 Webster]
Heat and cold have a virtual transition, without
communication of substance. --Bacon.
[1913 Webster]
Every kind that lives,
Fomented by his virtual power, and warmed. --Milton.
[1913 Webster]
2. Being in essence or effect, not in fact; as, the virtual
presence of a man in his agent or substitute.
[1913 Webster]
A thing has a virtual existence when it has all the
conditions necessary to its actual existence.
--Fleming.
[1913 Webster]
To mask by slight differences in the manners a
virtual identity in the substance. --De Quincey.
[1913 Webster]
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.
[1913 Webster] |
virtual
(wn) | virtual
adj 1: being actually such in almost every respect; "a practical
failure"; "the once elegant temple lay in virtual ruin"
[syn: virtual(a), practical(a)]
2: existing in essence or effect though not in actual fact; "a
virtual dependence on charity"; "a virtual revolution";
"virtual reality" |
virtual
(foldoc) | virtual
(Via the technical term {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)
|
virtual
(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
}.
|
| | podobné slovo | definícia |
virtually
(mass) | virtually
- doslova, fakticky, virtuálne |
virtualne
(msasasci) | virtualne
- virtually |
virtualny
(msasasci) | virtualny
- virtual |
virtual image
(encz) | virtual image, n: |
virtual memory
(encz) | virtual memory, n: |
virtual reality
(encz) | virtual reality,virtuální realita n: [it.] |
virtual storage
(encz) | virtual storage, n: |
virtually
(encz) | virtually,doslova adv: Vít Profantvirtually,fakticky adv: Zdeněk Brožvirtually,prakticky adv: Zdeněk Brožvirtually,skutečně adv: Zdeněk Brožvirtually,virtuálně adv: Zdeněk Brožvirtually,vlastně adv: Zdeněk Brož |
virtual environment
(czen) | Virtual Environment,VE[zkr.] [voj.] Zdeněk Brož a automatický překlad |
virtual hug
(czen) | Virtual Hug,VH[zkr.] |
virtual reality
(czen) | Virtual Reality,VR[zkr.] |
virtual time
(czen) | Virtual Time,VT[zkr.] |
Principle of virtual velocities
(gcide) | 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.
[1913 Webster]
Heat and cold have a virtual transition, without
communication of substance. --Bacon.
[1913 Webster]
Every kind that lives,
Fomented by his virtual power, and warmed. --Milton.
[1913 Webster]
2. Being in essence or effect, not in fact; as, the virtual
presence of a man in his agent or substitute.
[1913 Webster]
A thing has a virtual existence when it has all the
conditions necessary to its actual existence.
--Fleming.
[1913 Webster]
To mask by slight differences in the manners a
virtual identity in the substance. --De Quincey.
[1913 Webster]
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.
[1913 Webster] |
Virtual
(gcide) | 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.
[1913 Webster]
Heat and cold have a virtual transition, without
communication of substance. --Bacon.
[1913 Webster]
Every kind that lives,
Fomented by his virtual power, and warmed. --Milton.
[1913 Webster]
2. Being in essence or effect, not in fact; as, the virtual
presence of a man in his agent or substitute.
[1913 Webster]
A thing has a virtual existence when it has all the
conditions necessary to its actual existence.
--Fleming.
[1913 Webster]
To mask by slight differences in the manners a
virtual identity in the substance. --De Quincey.
[1913 Webster]
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.
[1913 Webster] |
Virtual focus
(gcide) | 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.
[1913 Webster]
Heat and cold have a virtual transition, without
communication of substance. --Bacon.
[1913 Webster]
Every kind that lives,
Fomented by his virtual power, and warmed. --Milton.
[1913 Webster]
2. Being in essence or effect, not in fact; as, the virtual
presence of a man in his agent or substitute.
[1913 Webster]
A thing has a virtual existence when it has all the
conditions necessary to its actual existence.
--Fleming.
[1913 Webster]
To mask by slight differences in the manners a
virtual identity in the substance. --De Quincey.
[1913 Webster]
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.
[1913 Webster] |
Virtual image
(gcide) | Image \Im"age\ ([i^]m"[asl]j; 48), 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.
[1913 Webster]
Even like a stony image, cold and numb. --Shak.
[1913 Webster]
Whose is this image and superscription? --Matt.
xxii. 20.
[1913 Webster]
This play is the image of a murder done in Vienna.
--Shak.
[1913 Webster]
And God created man in his own image. --Gen. i. 27.
[1913 Webster]
2. Hence: The likeness of anything to which worship is paid;
an idol. --Chaucer.
[1913 Webster]
Thou shalt not make unto thee any graven image, . .
. thou shalt not bow down thyself to them. --Ex. xx.
4, 5.
[1913 Webster]
3. Show; appearance; cast.
[1913 Webster]
The face of things a frightful image bears.
--Dryden.
[1913 Webster]
4. A representation of anything to the mind; a picture drawn
by the fancy; a conception; an idea.
[1913 Webster]
Can we conceive
Image of aught delightful, soft, or great? --Prior.
[1913 Webster]
5. (Rhet.) A picture, example, or illustration, often taken
from sensible objects, and used to illustrate a subject;
usually, an extended metaphor. --Brande & C.
[1913 Webster]
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.
[1913 Webster]
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.
[1913 Webster]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.
[1913 Webster]
Heat and cold have a virtual transition, without
communication of substance. --Bacon.
[1913 Webster]
Every kind that lives,
Fomented by his virtual power, and warmed. --Milton.
[1913 Webster]
2. Being in essence or effect, not in fact; as, the virtual
presence of a man in his agent or substitute.
[1913 Webster]
A thing has a virtual existence when it has all the
conditions necessary to its actual existence.
--Fleming.
[1913 Webster]
To mask by slight differences in the manners a
virtual identity in the substance. --De Quincey.
[1913 Webster]
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.
[1913 Webster] |
Virtual moment
(gcide) | 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 that very moment.
[1913 Webster]
In a moment, in the twinkling of an eye. --1 Cor.
xv. 52.
[1913 Webster]
2. Impulsive power; force; momentum.
[1913 Webster]
The moments or quantities of motion in bodies.
--Berkley.
[1913 Webster]
Touch, with lightest moment of impulse,
His free will. --Milton.
[1913 Webster]
3. Importance, as in influence or effect; consequence; weight
or value; consideration.
[1913 Webster]
Matters of great moment. --Shak.
[1913 Webster]
It is an abstruse speculation, but also of far less
moment and consequence of us than the others.
--Bentley.
[1913 Webster]
4. An essential element; a deciding point, fact, or
consideration; an essential or influential circumstance.
[1913 Webster]
5. (Math.) An infinitesimal change in a varying quantity; an
increment or decrement. [Obs.]
[1913 Webster]
6. (Mech.) Tendency, or measure of tendency, to produce
motion, esp. motion about a fixed point or axis.
[1913 Webster]
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.
[1913 Webster]
Syn: Instant; twinkling; consequence; weight; force; value;
consideration; signification; avail.
[1913 Webster]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.
[1913 Webster]
Heat and cold have a virtual transition, without
communication of substance. --Bacon.
[1913 Webster]
Every kind that lives,
Fomented by his virtual power, and warmed. --Milton.
[1913 Webster]
2. Being in essence or effect, not in fact; as, the virtual
presence of a man in his agent or substitute.
[1913 Webster]
A thing has a virtual existence when it has all the
conditions necessary to its actual existence.
--Fleming.
[1913 Webster]
To mask by slight differences in the manners a
virtual identity in the substance. --De Quincey.
[1913 Webster]
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.
[1913 Webster] |
Virtual velocity
(gcide) | Velocity \Ve*loc"i*ty\, n.; pl. Velocities. [L. velocitas,
from velox, -ocis, swift, quick; perhaps akin to volare to
fly (see Volatile): cf. F. v['e]locit['e].]
[1913 Webster]
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.
[1913 Webster]
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.
[1913 Webster]
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.
[1913 Webster]
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 to 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.
[1913 Webster]
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.
[1913 Webster]
Syn: Swiftness; celerity; rapidity; fleetness; speed.
[1913 Webster]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.
[1913 Webster]
Heat and cold have a virtual transition, without
communication of substance. --Bacon.
[1913 Webster]
Every kind that lives,
Fomented by his virtual power, and warmed. --Milton.
[1913 Webster]
2. Being in essence or effect, not in fact; as, the virtual
presence of a man in his agent or substitute.
[1913 Webster]
A thing has a virtual existence when it has all the
conditions necessary to its actual existence.
--Fleming.
[1913 Webster]
To mask by slight differences in the manners a
virtual identity in the substance. --De Quincey.
[1913 Webster]
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.
[1913 Webster] |
Virtual work
(gcide) | 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.
[1913 Webster]
Heat and cold have a virtual transition, without
communication of substance. --Bacon.
[1913 Webster]
Every kind that lives,
Fomented by his virtual power, and warmed. --Milton.
[1913 Webster]
2. Being in essence or effect, not in fact; as, the virtual
presence of a man in his agent or substitute.
[1913 Webster]
A thing has a virtual existence when it has all the
conditions necessary to its actual existence.
--Fleming.
[1913 Webster]
To mask by slight differences in the manners a
virtual identity in the substance. --De Quincey.
[1913 Webster]
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.
[1913 Webster] |
virtual work
(gcide) | 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.
[1913 Webster]
Heat and cold have a virtual transition, without
communication of substance. --Bacon.
[1913 Webster]
Every kind that lives,
Fomented by his virtual power, and warmed. --Milton.
[1913 Webster]
2. Being in essence or effect, not in fact; as, the virtual
presence of a man in his agent or substitute.
[1913 Webster]
A thing has a virtual existence when it has all the
conditions necessary to its actual existence.
--Fleming.
[1913 Webster]
To mask by slight differences in the manners a
virtual identity in the substance. --De Quincey.
[1913 Webster]
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.
[1913 Webster] |
Virtuality
(gcide) | Virtuality \Vir`tu*al"i*ty\, n. [Cf. F. virtualit['e].]
1. The quality or state of being virtual.
[1913 Webster]
2. Potentiality; efficacy; potential existence. [Obs.]
[1913 Webster]
In one grain of corn, there lieth dormant a
virtuality of many other. --Sir T.
Browne.
[1913 Webster] |
Virtually
(gcide) | Virtually \Vir"tu*al*ly\, adv.
In a virtual manner; in efficacy or effect only, and not
actually; to all intents and purposes; practically.
[1913 Webster] |
virtual image
(wn) | virtual image
n 1: a reflected optical image (as seen in a plane mirror) |
virtual memory
(wn) | virtual memory
n 1: (computer science) memory created by using the hard disk to
simulate additional random-access memory; the addressable
storage space available to the user of a computer system in
which virtual addresses are mapped into real addresses
[syn: virtual memory, virtual storage] |
virtual reality
(wn) | virtual reality
n 1: a hypothetical three-dimensional visual world created by a
computer; user wears special goggles and fiber optic gloves
etc., and can enter and move about in this world and
interact with objects as if inside it |
virtual storage
(wn) | virtual storage
n 1: (computer science) memory created by using the hard disk to
simulate additional random-access memory; the addressable
storage space available to the user of a computer system in
which virtual addresses are mapped into real addresses
[syn: virtual memory, virtual storage] |
virtually
(wn) | virtually
adv 1: in essence or effect but not in fact; "the strike
virtually paralyzed the city"; "I'm virtually broke"
2: (of actions or states) slightly short of or not quite
accomplished; all but; "the job is (just) about done"; "the
baby was almost asleep when the alarm sounded"; "we're almost
finished"; "the car all but ran her down"; "he nearly
fainted"; "talked for nigh onto 2 hours"; "the recording is
well-nigh perfect"; "virtually all the parties signed the
contract"; "I was near exhausted by the run"; "most everyone
agrees" [syn: about, almost, most, nearly, near,
nigh, virtually, well-nigh] |
java virtual machine
(foldoc) | Java Virtual Machine
Java VM
JVM
(JVM) A specification for software
which interprets Java programs that have been compiled into
byte-codes, and usually stored in a ".class" file. The JVM
instruction set is stack-oriented, with variable
instruction length. Unlike some other instruction sets, the
JVM's supports object-oriented programming directly by
including instructions for object method invocation (similar
to subroutine call in other instruction sets).
The JVM itself is written in C and so can be ported to run
on most platforms. It needs thread support and I/O (for
dynamic class loading). The Java byte-code is independent
of the platform.
There are also some hardware implementations of the JVM.
{Specification
(http://javasoft.com/docs/books/vmspec/html/VMSpecTOC.doc.html)}.
{Sun's Java chip
(http://news.com/News/Item/0,4,9328,00.html)}.
[Documentation? Versions?]
(2000-01-03)
|
laboratory virtual instrument engineering workbench
(foldoc) | Laboratory Virtual Instrument Engineering Workbench
LabVIEW
(LabVIEW) A package from National Instruments Corp
originally developed to provide a graphical user interface
to instruments connected by the IEEE 488 (GPIB) bus. It has
powerful graphical editing facilities for defining and
interconnecting "virtual instruments".
(1996-04-24)
|
multiple virtual storage
(foldoc) | Multiple Virtual Storage
MVS
MVS/ESA
MVS/OE
MVS/Open Edition
MVS/SP
MVS/XA
(MVS) Release 2 of OS/VS2, called MVS
because it had multiple 16 MB virtual address spaces, in
contrast to SVS. MVS ran on the IBM 390 series
mainframes. It became MVS/SP, then MVS/XA (with 31-bit
addressing) and then MVS/ESA.
MVS/Open Edition (MVS/OE), aimed at the growing open systems
market, added TCP/IP and Unix support in an MVS address
space, allowing users to run IBM, CICS-type applications,
batch applications and Unix.
MVS/ESA was repackaged as OS/390 as a marketing exercise but
it's basically the same thing.
Version: 5.1.
[Features? Dates?]
(1999-01-20)
|
parallel virtual machine
(foldoc) | Parallel Virtual Machine
PVM
(PVM) 1. A software system
designed to allow a network of heterogeneous machines to be
used as a single distributed parallel processor.
PVM was developed by the University of Tennessee, The {Oak
Ridge National Laboratory} and the Emory University.
(http://epm.ornl.gov/pvm/).
Usenet newsgroup: news:comp.parallel.pvm.
2. The intermediate language used by the Gambit compiler for
Scheme.
[And Multilisp?]
(1995-01-30)
|
permanent virtual circuit
(foldoc) | Permanent Virtual Circuit
Permanent Virtual Connection
(PVC, or in ATM terminology, "Permanent Virtual
Connection") A virtual circuit that is permanently
established, saving the time associated with circuit
establishment and tear-down.
(1997-10-06)
|
permanent virtual connection
(foldoc) | Permanent Virtual Circuit
Permanent Virtual Connection
(PVC, or in ATM terminology, "Permanent Virtual
Connection") A virtual circuit that is permanently
established, saving the time associated with circuit
establishment and tear-down.
(1997-10-06)
|
single virtual storage
(foldoc) | OS/VS2
Single Virtual Storage
SVS
An operating system from IBM, released
with the IBM S/370 and originally known as OS/MVT. OS/VS2
R1 was known as SVS (Single Virtual Storage) as it had a
single 16 MB virtual address space. OS/VS2 R2 was known as
MVS - Multiple Virtual Storage.
(1999-01-13)
|
switched virtual circuit
(foldoc) | virtual circuit
switched virtual circuit
A connection-oriented network service which
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)
|
switched virtual connection
(foldoc) | switched virtual connection
(SVC) A virtual connection in an ATM network
set up on demand by the signalling control point.
Contrast with permanent virtual connection.
(2001-06-29)
|
virtual 86 mode
(foldoc) | virtual 86 mode
(Or "virtual mode" or "virtual 8086
mode") An operating mode provided by the Intel 80386 and
later processors to allow real mode programs to run under
operating systems 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 registers exhibit the same behaviour as in
real mode. The paged MMU, however, still operates. This
means that the one megabyte address space of real mode can
be remapped in four kilobyte pages 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 interrupts)
switches the processor back into protected mode. It is
therefore possible to have multiple tasks in virtual mode
which run concurrently under the control of an operating
system which runs in protected mode.
Most operating system services in MS-DOS systems are called
by software interrupts, 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 programs can run.
|
virtual address
(foldoc) | virtual address
logical address
1. A memory location accessed by an
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)
|
virtual cache
(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)
|
virtual circuit
(foldoc) | virtual circuit
switched virtual circuit
A connection-oriented network service which
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)
|
virtual circuit identifier
(foldoc) | Virtual Circuit Identifier
VCID
(VCID) An identifier used for the routing of a
virtual circuit. An ATM switch may route according to a
Virtual Circuit Identifier, a Virtual Path Identifier, or a
combination.
(2001-05-16)
|
virtual connection
(foldoc) | virtual connection
1. (VC) A connection or a path through an ATM
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)
|
virtual control program interface
(foldoc) | Virtual Control Program Interface
VCPI
(VCPI) An alternative, and incompatible method for doing the
same thing as DOS Protected Mode Interface (DPMI).
(1995-01-12)
|
virtual device driver
(foldoc) | Virtual Device Driver
VxD
(VxD) A device driver under {Windows
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)
|
virtual device location
(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)
|
virtual disk
(foldoc) | RAM disk
RAM drive
virtual disk
A memory-resident program which
mimics a hard disk drive. It uses part of computer's RAM
to store data which can be accessed as files. Unlike a real
disk drive, this drive forgets all stored data when the
computer is turned off.
(1995-03-14)
|
virtual home environment
(foldoc) | Virtual Home Environment
VHE
(VHE) A tool for using NFS on HP UX.
(1994-12-07)
|
virtual host
(foldoc) | virtual host
vhost
Most computers on the Internet have a single
IP 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" web or other services for
several of their customers on one computer but giving the
appearence that they are separate servers.
(1997-09-11)
|
virtual lan
(foldoc) | Virtual LAN
Software defined groups of host on a {local
area network} (LAN) that communicate as if they were on the
same wire, even though they are physically on different {LAN
segments} 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 addresses used by IP, IPX, and other
network layer protocols to normally identify physical
networks. Administrators assign one subnet address to a
number of switch ports (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)
|
virtual loadable module
(foldoc) | Virtual Loadable Module
(VLM) Novell's term for software modules that
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)
|
virtual local area network
(foldoc) | Virtual Local Area Network
VLAN
(VLAN) A logical grouping of two or more nodes
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)
|
virtual machine
(foldoc) | Virtual Machine
Virtual Machine/ESA
Virtual Machine/System Product
Virtual Machine/XA
VM
VM/ESA
VM/SP
VM/XA
(VM) An IBM pseudo-operating system
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.
(http://vmdev.gpl.ibm.com/).
["History of VM"(?), Melinda Varian, Princeton University].
(1999-10-31)
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)
|
virtual machine environment
(foldoc) | Virtual Machine Environment
(VME) ICL's mainframe operating system.
(1995-06-28)
|
virtual machine manager
(foldoc) | hypervisor
virtual machine manager
(Or "virtual machine manager") A program that
allows multiple {operating
systems} to share a single "host" computer. The hypervison allows
each operating system
to behave as though it had the host's processor, memory and other
resources all to itself.
(2022-02-23)
|
virtual machine/conversational monitor system
(foldoc) | Virtual Machine/Conversational Monitor System
Conversational Monitor System
VM/CMS
(VM/CMS) An IBM time-sharing and
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 APIs 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)
|
virtual machine/esa
(foldoc) | Virtual Machine
Virtual Machine/ESA
Virtual Machine/System Product
Virtual Machine/XA
VM
VM/ESA
VM/SP
VM/XA
(VM) An IBM pseudo-operating system
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.
(http://vmdev.gpl.ibm.com/).
["History of VM"(?), Melinda Varian, Princeton University].
(1999-10-31)
|
virtual machine/system product
(foldoc) | Virtual Machine
Virtual Machine/ESA
Virtual Machine/System Product
Virtual Machine/XA
VM
VM/ESA
VM/SP
VM/XA
(VM) An IBM pseudo-operating system
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.
(http://vmdev.gpl.ibm.com/).
["History of VM"(?), Melinda Varian, Princeton University].
(1999-10-31)
|
virtual machine/xa
(foldoc) | Virtual Machine
Virtual Machine/ESA
Virtual Machine/System Product
Virtual Machine/XA
VM
VM/ESA
VM/SP
VM/XA
(VM) An IBM pseudo-operating system
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.
(http://vmdev.gpl.ibm.com/).
["History of VM"(?), Melinda Varian, Princeton University].
(1999-10-31)
|
virtual memory
(foldoc) | virtual memory
A system allowing a computer program to
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)
|
virtual memory system
(foldoc) | Virtual Memory System
OpenVMS
VAX/VMS
VMS
(VMS) DEC's proprietary {operating
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://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)
|
virtual path
(foldoc) | virtual path
The location of a file or directory on a
particular server, as seen by a remote client accessing it
via 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)
|
virtual point of presence
(foldoc) | virtual point of presence
virtual PoP
(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 modems 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)
|
virtual pop
(foldoc) | virtual point of presence
virtual PoP
(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 modems 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)
|
virtual private network
(foldoc) | Virtual Private Network
VPN
(VPN) The use of encryption in the
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://cisco.com/univercd/cc/td/doc/product/lan/cat5000/cnfg_nts/rsm/rsm_pa/4801encr.htm)}.
(1999-11-15)
|
virtual reality
(foldoc) | virtual reality
VR
(VR) Computer simulations that
use {3D
graphics}, often displayed in a VR headset or goggles and {hand
controllers},
e.g. the data glove, that allow the user to interact with the
simulation.
(2021-12-02)
|
virtual reality modeling language
(foldoc) | Virtual Reality Modeling Language
VRML
(VRML) A draft specification for
the design and implementation of a platform-independent
language for virtual reality scene description.
VRML 1.0 was released on 1995-05-26.
(http://vrml.org/).
Wired (http://vrml.wired.com/).
Hypermail Archive (http://vrml.wired.com/arch/).
Mailing list: (message body: "subscribe
www-vrml your-email-address").
(1995-07-20)
|
virtual sequential access method
(foldoc) | Virtual Storage Access Method
Virtual Sequential Access Method
VSAM
(VSAM) An IBM disk file storage scheme first used
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)
|
virtual server
(foldoc) | virtual server
A configuration of a web
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 website, 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 websites while allowing the
owner of each website to use and administer the server as
though they had complete control.
(2003-06-23)
|
virtual shredder
(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 pipes and
I/O redirection.
[Jargon File]
(1995-01-30)
|
virtual software factory
(foldoc) | Virtual Software Factory
VSF
(VSF) A product from Systematica which
allows users to develop CASE tools appropriate to any
software engineering methodology.
(1997-06-09)
|
virtual storage access method
(foldoc) | Virtual Storage Access Method
Virtual Sequential Access Method
VSAM
(VSAM) An IBM disk file storage scheme first used
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)
|
virtual storage extended
(foldoc) | Virtual Storage Extended
VSE
(VSE, formerly DOS/VSE) is a
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 4381s and a significant
proportion of IBM 9370s 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)
|
|