Besides basic computer technology, image rendering applicaitons along
with other media development applications, Web Designers and Developers
use a variety of programming scripts and languages to control the layout
of web pages and make them dynamically interactive. Tools that a Web
Developer should be familiar with include:
What is HTML?
HTML (Hypertext Mark-up Language), the simple programming language that most of
the Web is based upon, was originally created as a means to post and
cross-reference academic papers.
HTML works more or less like this: You create a document in plain
text (also known as ASCII text). You save this document with the
".html" extension so that a browser will know that it is a Web
page. Within the document, you write bracketed instructions called
"tags" to tell your browser how and where to render a word or image.
(If you've ever used the "reveal codes" command in an older word
processor, you've seen similar ways of blocking out text to be bolded,
italicized, or underlined --- this is the "markup" of the markup
language.) HTML documents then have to be posted on a server. Once the
document is saved on a server it has an address --- that's the
"http://www.something.com/...", known as the uniform resource locator,
or URL. Browsers, like Netscape Communicator or Internet Explorer,
use this address to locate the Web site on the server and translate
the HTML code into the pictures, words, and links on the Web pages
through which you surf.
HTML severely limits your ability to control the
placement of objects on a Web page --- frames and
tables only get you so far when you want elements to
get up close and personal. And most Web sites are
static. Download time and technological limitations
have made major multimedia effects --- be honest, even
minor multimedia effects --- pretty limited on the Web.
What is DHTML?
Dynamic HTML is an extension of (or addition to)HTML
--- the simple language on which the Web is based. It is not
its own language or script, but a family of scripts and programming
languages used in conjuction with HTML.
New tags in Dynamic HTML, used in conjunction with
other programming languages like Javascript or
component architectures like ActiveX, allow designers
to control the appearance and position of every element
on a page. You'll be able to include dynamic features
like collapsible menus, reactions to mouse rollovers or
keyboard commands, and multimedia animations.
The "dynamic" part of the technology lies in the fact
that, because most of the visual effects are hardcoded
into the page, changes to text, graphics, and
animations can load in on the client side (in your
browser window) without a reload or refresh from the
server. That means you can have page elements loaded
in the browser's memory but not visible until the user
interacts with them in some way. To complete the
multimedia picture, the new tags include display filters
like fades, blends, and wipes, that are more typical of
multimedia development tools than traditional HTML.
What is CSS?
CSS (Cascading Style Sheets) offers Web designers many of the
features commonly found in desktop publishing applications.
With CSS you can specify font point sizes, font
attributes (italics, underline, etc), page margins, colors,
spacing, positioning, visibility, and much more. Using CSS you can
apply different attributes to HTML tags you use in your pages.
The cascading in CSS derives its name from the way a
style cascades down from the general to the specific.
Think of parents passing on traits to their kids; though
the kids can still control their own destiny. Elements
(like paragraphs or footers) inherit properties from
stylesheets (parents), though you can customize or
override them. We'll show you how to do this in this
section, which is designed to help you learn to start
building pages that use stylesheets.
What is XML?
XML (Extensible Markup Language)is more than a markup language.
Like SGML, it's a metalanguage, or a language that allows you
to describe languages. HTML and other markup languages
let you define how the information in a document will
appear in an application that displays it, but SGML and
XML let you define the markup language itself. In this
sense, XML can actually control HTML documents.
Think of HTML as a description system and XML (like
SGML) as a system for defining description systems
and you get the idea. One benefit of SGML is that you
can use it to define and control an unlimited variety of
description systems, HTML being only one of these,
and XML offers this advantage as well.
The Web is getting set for a make-over. Touted as "the second
coming of the Web" at a site maintained by the World Wide Web
Consortium, XML (Extensible Markup
Language) is an important new complement to such
architectural underpinnings of the Web as Java and
HTML. Proponents claim that it can free the Web from
its dependence on inflexible document types and
revolutionize Web searching, Web databases, and Web
information exchange.
XML is designed to tag the locations of critical
information in Web documents. It's based on SGML, an
international standard for defining descriptions of the
structure and content of electronic-document types.
Based on elements such as text parsing, tree
management, and formatting, XML tags can be seen as
a sort of advanced card catalog for a library of Web
pages.
For example, you might XML-tag a page containing a
Shakespeare play so that not just the page but precise
passages in it and references associated to it could be
searchable by a search engine or a database.
Information in HTML-based table format on the Web
now (such as stock-price tables) will also be
XML-tagged, so spreadsheets and databases will easily
be able to import and sort such tables.
What is JavaScript?
If you've been on the Web for a while, you've probably run into
JavaScript. Netscape developed the JavaScript language (originally
called LiveScript) to help developers add interactivity to
otherwise static Web sites. You can use it to create everything from
calculators to search engines to interactive order forms on your Web
pages--if you know how.
Designed by Sun Microsystems and Netscape as an easy-to-use adjunct
to the Java programming language, JavaScript code can be added to
standard HTML pages to create interactive documents. As a result,
JavaScript has found considerable use in the creation of interactive
Web-based forms. Most modern browsers, including those from
Microsoft and Netscape, contain JavaScript support.
What is Java?
Sun Microsystems' Java is a programming language for adding
animation and other action to Web sites. The small applications
(called applets) that Java creates can play back on any graphical
system that's Web-ready, but your Web browser has to be Java-capable
for you to see it. According to Sun's description, Java is a "simple,
object-oriented, distributed, interpreted, robust, secure,
architecture-neutral, portable, high-performance, multithreaded,
dynamic, buzzword-compliant, general-purpose programming
language." And Sun should know.
What is an ASP?
We are used to thinking in terms of languages, but ASP does not
fit that model. Although we talk about ASP scripts, ASP is not a
language. Instead, Microsoft refers to it as a server-side scripting
environment. To work in that environment, ASP coders commonly use
VBScript or JScript, both of which are automatically supported by ASP.
It is possible to use other scripting languages with ASP as long as
you have an Active X scripting engine for the language installed. For
example, if you're a longtime Perl coder, you may want to check out
PerlScript, which lets you write ASP scripts in Perl.
What is ActiveX?
This set of technologies from Microsoft provides tools for linking
desktop applications to the World Wide Web. Using a variety of
programming tools--including Java, Visual Basic, and C++--developers
can create interactive Web content. For instance, ActiveX technology
can allow users to view Word and Excel documents directly in a browser.
What is VBScript?
Microsoft VBScript (Visual Basic Scripting Edition) is a lightweight
version of Microsoft Visual Basic for Applications. Launched with
Microsoft Internet Explorer 3.0, VBScript is fast becoming one of
the most widely used server-side scripting languages for the
Windows environment:
- It is the major scripting language for Active Server Pages (on the
Microsoft IIS Web server)
- It is the automation language built into Microsoft Outlook
- It will be the language for programming administrative tasks in
both SQL Server 7.0 and Microsoft Windows 2000 (NT 5.0) when released
What is Perl?
Perl (practical extraction and report language) is both a workhorse
for back-end data processing and a prototype development tool. Before
the Web, Unix administrators and developers embraced Perl as an
improvement over traditional scripting languages such as awk and sed.
Perl creator Larry Wall never intended for it to take the place of
robust compiled languages like C, but developers found that Perl let
them accomplish many of the same tasks with much less code.
Perl is now a decade old, but it's hardly old news. The devoted
members of the Perl community are constantly finding new ways to
modularize Perl, link it to other common languages, and make it work
with various operating systems. In fact, efforts are underway to make
Perl the top scripting language for XML.
Perl's facility for automating system administration tasks and
processing interactive Web sites--as well as its powerful regular
expressions engine and its strong process, file, and text manipulation
functionalities--makes it ideal for quick prototyping, creating system
utilities, developing software tools, system management, database
access, graphics manipulation, networking, gluing other applications
together.
What is CGI?
If you want your site to do something dynamic or interactive, like
handling information in an HTML form, you have to run a separate
program outside your Web server. That's where CGI (common gateway
interface)comes in--it's the interface between these applications and
the Web server.
These external programs can do just about anything: handle incoming
forms, grab records from a database, save data to a file, and so on.
As long as you conform to the CGI specification, you have a wide
choice of tools for writing your CGI applications. Typically, you use
Perl (practical extraction and report language), although you can
write CGI applications in just about any programming language,
including Java and C/C++.
