Java Glossary
Last updated by Roedy Green
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V
- V.17
- FAX standard for 14,400 BPS.
- V.18
- CCITT standard for TDD modems for the deaf.
- V.21
- CCITT standard for 300 BPS Modems, similar to, but incompatible with, the
Bell 103 standard.
- V.22
- CCITT standard for 1200 BPS modems. It is similar to, but incompatible
with, the Bell 212A 1200 BPS standard.
- V.22 bis
- CCITT standard for 2400 BPS modems. Happily Americans use the same standard.
- V.23
- CCITT standard for 1200/75 BPS sometimes used in the UK.
- V.24
- CCITT standard roughly equivalent to RS232-D.
- V.25 ter
- CCITT proposed standard, likely to be some form of the Hayes AT command
set. see also V.at, Hayes command set.
- V.27 ter
- CCITT standard for 4800 BPS FAX.
- V.28
- CCITT standard for power levels, line driver/receiver impedances etc. in
unbalanced double-current interchange circuits. It covers the electrical
characteristics of how two modems talk to each other up to 20,000 BPS.
- V.29
- CCITT standard for 9600 BPS modems used on 4-wire leased lines. These modem
do not work on dial-up lines.
- V.32
- CCITT standard for 9600 BPS full duplex modems. It allows both modems to
talk simultaneously requiring costly echo cancelling circuits. Any two
V.32 modems, even if they were made by different manufacturers, can talk
to each other. The V.32 standard covers modulation. A V.32 modem will also
have V.42 error correction and V.42bis compression.
- V.32 bis
- CCITT standard for up to 14,400 BPS full duplex modems. It allows both
modems to talk simultaneously requiring costly echo cancelling circuits.
Any two V.32 bis modems, even if they were made by different manufacturers,
can talk to each other. V.32 bis modems can also talk to the older 9600
baud V.32 modems. The V.32 bis standard covers modulation. A V.32 bis modem
will also have V.42 error correction and V.42bis compression.
- V.32 terbo
- promoted by AT&T and adopted as an ad-hoc US standard by a number of
companies. Expands V.32 bis by adding 16.8 and 19.2 kbit/s, achieved by
expanding the number of points in the two-dimension constellation (roughly
speaking it uses more tones in composing its sound chords). ZyXEL did a
better job of 19.2 by increasing the symbol rate instead of increasing
the constellation size as "terbo" does to the point where small
impairments become significant contributors to block errors. (By the way
"terbo" was coined to suggest "turbo" and "ter", the
latter being French for "third").
- V.34
- CCITT standard for 28K BPS Modem announced on 1994 June 9. Some older products
can be upgraded to V.34 compatibility. Upwardly compatible with V.32 bis,
V.42 and V.42bis. Provides speeds in 2400 BPS increments from 4.8K to 28.8K
BPS. Originally promoted by a joint contribution of about 30 modem companies.
Heritage can be traced to Motorola Codex for many of the basic features.
- V.35
- CCITT standard for 48K BPS modems in Europe and 56K BPS modems in the USA.
It uses a rectangular 35 pin connector with electrically balanced signals.
It most commonly used for connecting to digital leased lines.
- V.42
- CCITT standard that makes it possible for modems to detect, but not correct,
errors caused by static. It handles MNP-1 through MNP-4 as well as LAPM.
- V.42 bis
- CCITT standard that allows on-the-fly data compression. It also 3.5:1 compression
which is quite a bit better than MNP-5's 2:1. Since the Lepel-Ziv-Welch
compression is complex, transmission speed is usually limited by the speed
of the compression circuitry.
- V.58
- CCITT standard for Modem Information Blocks for network management. This
is not of concern to ordinary users.
- V.8
- CCITT standard for Calling-tone menu (part of the V.34 startup sequence).
Not something to concern the average user.
- V.90
- ITU standard for 56K BPS modems. Replaces K56flex.
- V.at
- CCITT "Question" It is a topic of debate during the next "Study Period"
with the goal of accepting a form of the Hayes AT command set as V.25 ter
sometime in the future. In a related item, Hayes has formally announced
that they would license the Heatherington "+++" patent in a non-discriminatory
manner. The formal announcement isn't anything new -- Hayes has been issuing
licenses in that manner ever since the Bytecom decision -- but it crosses
the official "t" on the subject. Hayes managed to patent the idea of a
pause before and after the string +++ to gain the modem's attention. The
required pause helps avoid inadvertently attracting the modem's attention
when you send files (such as this one) containing the string +++.
- V.FAST
- CCITT preliminary work on the V.34 standard for modems to run at 28.8K
uncompressed. Supplanted by the official V.34 standard.
- V.FC
- V.Fast Class promoted by Rockwell as a proprietary implementation of "V.Fast"
now officially called V.34. US Robotics has developed an independent implementation
of V.FC.
- valid
- A component is valid if its size and position relative to its
enclosing container have been calculated. A container is valid if it
is valid with respect to its container, and all its enclosed children
are valid. A container might be marked invalid because a
subcomponent had been added/removed or shown/hidden and the positions
of the remaining elements need to be adjusted in position and size.
An individual component might be marked invalid because it now
contains an image that takes more room to display. Valid does imply
the component is currently or even will be displayed on the screen.
Standard layout managers ignore hidden components. Custom ones
could well leave room for them. See also validate, invalidate,
visible.
- validate
- check that a container is valid and if not, calls layout() or
validateTree() to calculate the exact positions and sizes of all the
contained components. validate() was formerly known as
pack, (though they are not exactly the same). It redoes the layout if
necessary deciding on new sizes and locations of all the components
in the container. Most often it gets called directly by application
programmers, after a frame or other container been composed, but just
before the Frame.setVisible(true). validate() is also called as the second
step in processing a COMPONENT_RESIZED event. Invoking
validate() by itself will not
schedule a repaint. If your
recent layout changes (e.g. button adding/removing) are not showing
up, make sure you do a validate() prior to any repaint().
Even though validate() does nothing
if the layout is already valid, don't call validate() unnecessarily. Wait until just
before the setVisible() or repaint() to avoid the overhead of calculating
the entire layout just to deal with some tiny change. See valid,
invalidate.
- value type
- In Java a = b makes a copy of b and puts it in a when a is a
primitive e.g. int, long, float or double. Otherwise a is a
reference value and receives a pointer (reference) to the same
object that b points to. In Java there are no equivalent to C++
structs whose entire structure would be copied to a.
- vaporware
- Software announced before it has even been written. Software
mired in extended beta-test would not usually be termed vapourware.
A vendor may announce a product only to test if there is any market
interest, or to spoil the actual product announcement of a
competitor. That might be termed pernicious vapourware.
- variable
- There are several types of variables. My personal preferred
terms for each are show in bold. Variables take on different
values at different stages in the execution. You can have variables
that are part of the class (static class variables),
variables that are part of an object (instance
variables). Collectively static variables and instance variables
are called member variables, or just members.
Variables defined inside a method are called local,
temporary or stack variables. Static final variables
are called constants by normal humans and values
by the Java Language spec. Fields collectively refer
to static class variables, instance variables and static final
constants defined inside classes, but outside methods. There is one
copy of each static variable per class, one copy of each
instance variable per instantiated object, and one copy of
each local variable for each incarnation of its enclosing
method currently executing. Static is a strange word,
inherited from C. I use it in preference to class variable because
it matches the keyword used in code. There is no corresponding
explicit keyword for instance. A variable is declared
instance by the lack of the keyword static. There is
similarly no keyword local. You create local declarations
using identifiers otherwhere declared as types
in the middle of a method. There is no obvious visual clue. See
field, local variable, constant, literal, instance variable, static
variable.
-
VasJavaToHTML
- Converts Java source code to HTML, colouring it.
- vCard
- The IMC, Internet Mail Consortium Versit's
interchange format for electronic business cards. The format is done using
only printable ASCII characters. Have a look at my
electronic business card which includes a digitised logo and photo,
your address for both domestic and international mail, your latitude and
longitude, your telephone numbers, your email addresses, how your name is
pronounced, a wav or au file of you pronouncing your name ... You can view
it properly with the vCard viewer. There is a primitive one inside
Netscape Communicator. You can download a quite
detailed composer/viewer free. See Bustel.
- verifier
- A program that checks JVM byte codes in class files to make sure
the stack won't overflow, and that operands will always be the correct
type. Applet classes downloaded over the Internet automatically
go through a verification. You can also explicitly test by submitting
your classes to the
Kimera verifier.
- Veronica
- Internet speak for a program that provides you with a list of gopher
servers. See Archie.
-
VIBE
- Visix's visual Java IDE RAD. It runs on Windows 95, Mac and Solaris.
See springs and struts. I think they went out of business.
- virtual
- "Virtual" in C++ means "overrideable". In Java
all methods are assumed overrideable unless marked final (or private which
implies final). Virtual has yet another meaning in C++. When you inherit
from several classes, which may share a common subclass, in C++ you have
to decide how many copies of the base class variables you want -- a shared
or separate embedded in this new object. "virtual" refers to
using a single shared copy. In Java you can inherit from only one class,
so the problem never comes up. See also pure virtual. See JVM.
- virtual machine
- See JVM.
-
Visaj
- a RAD for developing Java applications. See RAD.
- Visblock
- A Java obfuscacator. Visionary Solutions don't seem to still be
marketing it. See shroud, obfuscate.
- visible
- a component is visible if in on any repainting cycle it should be repainted.
It might not actually be visible on the screen right now because it is
occluded, or because CardLayout is not currently displaying the panel in
which the component lives. See Layout, valid, enabled.
- visitor
- a design pattern where work gets done as a side effect of an object
visiting others, e.g. traversing all the nodes in a tree. See design patterns.
- Visual Café Database Development Edition
- Symantec marketing's new name for the version of Café that
comes bundled with Sybase SQLAnywhere SQL engine and dbAnywhere. I have
written an essay giving some tips on how to use
it and bugs to watch out for. I have written a second essay particularly on installing dbAnywhere. See
Symantec.
- Visual Café Pro
- Symantec's Java development package that includes a compiler,
editor, debugger, dbAnywhere, and Sybase SQL. It is the same code as
Visual Café Database Development Edition, but with a few things
left out. See See Visual Café Database Development Edition,
Symantec.
- Visual Programming
- We are moving away from text based representations of computer programs
to more visual forms just as JavaBeans components, Delphi and CPX. Prograph
CPX is an entirely visual, iconic, dynamic, object oriented, data-flow,
interpreted IDE, compiled executable programming language. It is currently
available on the Macintosh platform. They are well into the beta of their
Windows 95/NT version. There is no textual syntax. The only text is the
name on the icon. Everything else is represented graphically. Icons are
linked by lines. The input nodes on top are called terminals. The output
nodes on the bottom are called roots. You may visit Pictorius Incorporated's
home page.
- VisualParse++
- A parser that parses interactively. You can watch it build the tree visually.
- VLIW
- Very long Instruction Word. Intel is working on a new type of CPU that
uses very long instruction words instead of microcode. The instruction
words give it hints on branch prediction etc. The processors are very fast,
but need recompilation even for different variants of same processor. Its
as if you needed a totally different exe file for 80386, 80486, Pentium,
and Pentium Pro processors. The Java JIT solves the code distribution problem
neatly, since the common JVM class files can be compiled as the last minute
into the required VLIW format.
-
VoiceType
- IBM's $15 add in for Netscape that lets you browse the
web using voice commands. Its main use is nicknames for
common websites you like to visit, rather than searching
long lists of bookmarks.
- Volano
- a package for creating chat room software
applications.
- Voyager
- A ORB/Agent product, free for commercial use. See ORB.
- vqserver
- A free, 350K, personal web server written in Java. It
supports password protection, file uploading, Java servlets and
CGI scripts.
- VRML
- Virtual Reality Markup Language.
An ASCII-based language for describing simple three dimensional
objects and their interactions. The intent of the language is to
use as little bandwidth as possible in the descriptions, by have
the scenes rendered from mathematical descriptions rather than
from bit maps.