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List of Names
Short Form
Full Form
- V
-
VBScript
- See:
- Language type:
- Description:
Visual Basic Scripting Edition is a
subset dialect of Visual Basic; it is
an interpreted, procedural language intended
for creating application extension scripts
and for adding interactivity to web pages.
VBScript's syntax resembles that of
Visual Basic: statements are bounded by
end-of-line, and normal Basic keywords
are used for control structures and
code modularity. VBScript supports a
modest set of data types: various numeric
types, strings, dates, booleans, arrays, and
object references. Variables in VBScript
are typed, but the interpreter does not
do strong type enforcement. VBScript
supports subroutines and functions, and
can interact with objects provided by its
environment (usually a scriptable application).
VBScript does not support the definition of
new object classes, nor does it support
overloading or polymorphism. The language
has fairly good support for handling time, dates,
and strings.
The newest version of VBScript also supports
a dictionary object, an associative array
for storing string data.
VBScript is most commonly employed in
web browsers and web servers from Microsoft.
Under the 32-bit Windows environment, any
application can employ VBScript if it
is installed; Microsoft intends VBScript
to be the baseline or typical scripting
language for simple OLE applications.
The first release of VBScript was part of
Microsoft's Internet Explorer 3.0 product; in
1997 they released VBScript 2.0.
Good information about VBScript, including
a hyperlinked reference manual, in available
from Microsoft's web site. Many good books
about it are also available.
- Origin:
Microsoft Corporation, 1995 ?
- See Also:
- Remarks:
In the web browser niche, VBScript
and JavaScript are the two main
competitors. They are comparable
in terms of functionality, although
in most respects JavaScript is a
more powerful programming language.
In web browsers, VBScript is often
employed to validate HTML form data and
to make forms more responsive. It
can also be used, in web browsers and
elsewhere, to configure and manipulate
ActiveX controls.
VBScript has not language-defined
I/O facilities; any I/O that it supports
must be provided by object classes
supplied from the controlling application
environment. In a web browser client,
these objects are not available, but in a
web server environment they are.
- Links:
- Date:
- Sample code:
An example of using VBScript to check
form data.
Function isSSN(ssns)
isSSN = False
If (len(ssns) = 9 or len(ssns) = 11) Then
isSSN = True
End If
End Function
Sub submit_OnClick
dim namestr, ssnstr, psw, req
set form = document.form1
namestr = Trim(form.NameStrField.Value)
ssnstr = Trim(form.SSNStrField.Value)
If (len(namestr) = 0) Then
msgbox "Name is empty, please type in your name"
Exit Sub
ElseIf (not isSSN(ssnstr)) Then
msgbox "SSN field is not the right length, please fix it"
Exit Sub
Else
psw = InputBox("Enter your password:","Form Password","")
End If
req = "http://test.org/cgi/start.cgi?ssn=" &
ssnstr & "&passwd=" psw
loc.href = req
End Sub
-
VHDL
- Language type:
M - Mathematical or Simulation
- Description:
VHDL is a modeling and simulation language
intended for study and design of digital
integrated circuits. The name is an
acronym for VHSIC Hardware Description
Language. The syntax and general
appearance of VHDL are similar to that of
Ada, but the semantic structure is quite
different.
A VHDL model consists of a
hierarchy of entities, these entities
usually directly correspond to the parts of
the digital system under study.
Entities operate in parallel during
simulation; the simulations use a
kind of timed dataflow model that is adjustable
by the user (so as to accurately
represent a real circuit or chip).
The
operation of the various entities
can be very simple, like a small
expression, or very complex. VHDL
supports subroutines and functions as
well as conventional sequential
control structures.
Data types in VHDL include bits,
enumerated sets,
integers, reals, time, arrays,
and records. The support for enumerated
types and their use is very good. (Because
most simulations of digital circuits model the
state of a digital signal with more than just
a bit.)
VHDL has good support for modularity and
for separation of
interface and implementation of entities.
First, it support generics for entities;
and second, the interface to an entity
is always separate from the description
of its operation.
This allows simulation's structure to be
built up once, but simulated for several
different hardware technologies.
A variety of VHDL implementations are
available from commercial CAD vendors.
At least one free implementation is
available for Unix systems as
part of the ALLIANCE
educational VLSI package.
- Origin:
M.R. Shahdad et al, 1985; IEEE Standard 1076, 1987.
- See Also:
- Remarks:
VHDL is a remarkable complete procedural
block-structured language, considering
that it was not intended for application
programming.
VHDL was originally standardized in 1987 as
IEEE 1076, and revised six years later as
IEEE 1076-1993; there
is also an analog modeling extension which
is IEEE 1076.1. Unfortunately, there does
not seem to be a copy of the standard
available as HTML.
- Links:
-
-
-
- Date:
- Sample code:
-- Behavioral model of a D flip-flop, from
-- the US Army FCIM VHDL Tutorial.
USE WORK.std_logic_1164.ALL
ENTITY mydff IS
GENERIC(q_out, qb_out :time);
PORT(preset, clear, din, clock: :IN std_logic;
q, qb : :OUT std_logic);
END mydff
ARCHITECTURE behavioral OF mydff IS
BEGIN
mydff_proc : PROCESS(preset, clear, clock)
VARIABLE int_q :std_logic;
BEGIN
IF preset = '0' AND clear = '0' THEN
IF(clock'EVENT) AND (clock = '1') THEN
int_q := din;
END IF;
ELSEIF preset = '1' AND clear ='0' THEN
int_q := '1';
ELSEIF clear = '1' AND preset = '0' THEN
int_q := '0';
ELSE
int_q := 'X';
ENDIF;
q <= int_q AFTER q_out;
int_q := NOT(int_q);
qb <= int_q AFTER qb_out;
END PROCESS mydff_proc;
END behavioral;
-
Visual Basic
- See:
- Language type:
- Description:
Visual Basic is an advanced
structured dialect of Basic
developed by Microsoft, and intended for
application development.
The syntax of Visual Basic is similar to that
of other modern Basic dialects, but with
many additional features.
The
following primitive data types are
supported: integers, reals, strings,
booleans, currency, dates, and
object references. Variables may
be declared, but need not be. Type
checking can be performed, but is enforced
only for declared variables and parameters.
Composite data
types include arrays and
user-defined records. Control
structures include various conditional
and iteration constructs, and rudimentary
error handling mechanisms.
Memory management in Basic is automatic.
Visual Basic is nominally an interpreted
language, but newer implementations
include native code compilers. During
execution, Visual Basic programs are
normally supported by a run-time library.
Visual Basic is a commercial product.
A subset edition is available free,
the full development environment must
be purchased. Visual Basic runs on
Microsoft Windows platforms. Information
about the language and other resources
for developers are widely available
on the Internet and in print media.
- Origin:
- See Also:
- Remarks:
As a language, Visual Basic has evolved
enormously since its commercial introduction
in 1990. Version 5, 1997, supports
object oriented programming, a wide
variety of data types and type checking,
function pointers, and assertions.
The "Visual" in the name Visual Basic
does not really refer to the language, but
to the development environment. The VB
integrated development environment that
Microsoft distributes has extensive
facilities for on-screen design of
graphical user interfaces: dialog boxes,
window interfaces, menus, etc. It also
provides a rich but complicated interface
for code management and debugging.
GUI programs are easy to write in Visual
Basic, and the development environment
provides copious support for coding the
necessary event handling subroutines.
The popularity of Visual Basic is derived
partly from its extensibility. New
components, especially GUI elements,
can be added to the language
run-time system and transparently used
by application developers. There is a
large community of programmers who design
and distribute "Visual Basic Controls" (VBXs)
and "ActiveX Controls" for use in Visual
Basic.
- Links:
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- Date:
- Sample code:
- 3 entries retrieved.
Descriptions in this dictionary are ©1997-99 Neal Ziring. Some
examples copyright of their respective authors. Some
technologies and languages are trademarked. Permission to
copy descriptions is granted as long as authorship credit is preserved.
Comments on this dictionary, corrections and suggestions, are all welcome.
Please use email, the address is ziring@home.com
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Dictionary and script maintained by Neal Ziring, last major modifications 3/18/98. Most recent
additions to dictionary and master list, 1/00.