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J
Glossary of Internet Terms and Phrases
Java Servlet
- A
Java program that runs as part of a network service, typically an
HTTP server and responds to requests from
clients.
The most common use for a servlet is to extend a
web server by generating web content dynamically. For example, a client
may need information from a
database; a servlet can be written that receives the request, gets and
processes the
data as needed by the client and then returns the result to the client.
Applets are also written in Java but run inside the JVM of a
HTML
browser on the client. Servlets and applets allow the
server and client to be extended in a modular way by dynamically loading
code which communicates with the main program via a standard programming
interface.
Servlets are more flexible than
CGI
scripts and, being written in Java, more
portable.
The spelling "servelet" is occasionally seen but JavaSoft spell it "servlet".
There is no such thing as a "serverlet".
Home:
http://java.sun.com/products/servlet/.
Source: Dictionary.com
Java
- A simple, object-oriented, distributed, interpreted, robust, secure,
architecture-neutral,
portable, multithreaded, dynamic, buzzword-compliant, general-purpose
programming language developed by Sun Microsystems in 1995(?). Java
supports programming for the
Internet in the form of platform-independent Java "applets".
Java is similar to
C++ without operator overloading (though it does have method
overloading), without multiple inheritance, and extensive automatic
coercions. It has automatic garbage collection.
Java programs can run stand-alone on small computers. The interpreter and
class support take about 40
kilobytes; adding the standard libraries and thread support (essentially
a self-contained microkernel) adds an additional 175Kb.
Java extends C++'s object-oriented facilities with those of Objective C for
dynamic method resolution.
Java has an extensive library of routines for
TCP/IP
protocols like
HTTP and
FTP.
Java applications can access objects across the Internet via
URLs
as easily as on the local file system.
The Java compiler and linker both enforce strong type checking - procedures
must be explicitly typed. Java supports the creation of
virus-free, tamper-free systems with authentication based on public-key
encryption.
The Java compiler generates an architecture-neutral object file executable
on any processor supporting the Java run-time system. The object code
consists of bytecode instructions designed to be both easy to interpret on
any machine and easily translated into native machine code at load time.
The Java libraries provide portable interfaces. For example, there is an
abstract Window class and implementations of it for Unix, Microsoft Windows
and the Macintosh. The run-time system is written in POSIX-compliant ANSI C.
Java applets can be executed as attachments in
World-Wide Web documents using either Sun's HotJava browser or Netscape
Navigator version 2.0.
Home: http://java.sun.com.
Source: Dictionary.com
JavaScript
- Netscape's simple, cross-platform,
World-Wide Web scripting language, only very vaguely related to Java
(which is a Sun trademark). JavaScript is intimately tied to the World-Wide
Web, and currently runs in only three environments - as a server-side
scripting language, as an embedded language in server-parsed
HTML, and as an embedded language run in web
browsers where it is the most important part of
DHTML.
JavaScript has a simplified {C}-like syntax and is tightly integrated with
the browser Document Object Model. It is useful for implementing enhanced
forms, simple web
database front-ends, and navigation enhancements.
JavaScript originated from Netscape and, for a time, only their products
supported it. Microsoft now supports a work-alike called JScript. The
resulting inconsistencies make it difficult to write JavaScript that behaves
the same in all browsers. This could be attributed to the slow progress of
JavaScript through the standards bodies.
JavaScript runs "100x" slower than {C}, as it is purely interpreted (Java
runs "10x" slower than C code). Netscape and allies say JavaScript is an
"open standard" in an effort to keep Microsoft from monopolising web
software as they have desktop software. Netscape and Sun have
co-operated to enable Java and JavaScript to exchange messages and
data.
Source: Dictionary.com
JPEG (Joint Photographic Experts Group)
- The original name of the committee that designed the standard image
compression algorithm. JPEG is designed for compressing either full-colour
or grey-scale digital images of "natural", real-world scenes. It does not
work so well on non-realistic images, such as cartoons or line drawings.
JPEG does not handle compression of black-and-white (1 bit-per-pixel) images
or moving pictures. Standards for compressing those types of images are
being worked on by other committees, named JBIG and MPEG.
Home: http://www.jpeg.org.
Filename extension: .jpg, .jpeg.
Source: Dictionary.com
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