IST129, Ch 13: Executable Content

This chapter deals with programming issues and the WWW, specifically detailing how to embed objects into HTML. In the current HTML specification (4.0), objects include:

• graphic files
• sound files
• video files
• programs
• ... and anything else that may be included in WWW pages in the future (wireless communications like automatic beeper messages, medical monitoring devices, etc).

Applets:

Applets are server-side programs that are downloaded to and executed on your PC. Applets differ from JavaScript program source code embedded in HTML because the applets:

1. reside on the server
2. are written in JAVA (or Active-X)
3. are compiled modules, not source code
4. are executed by the JVM (or Windows in the case of Active-X)

OBJECT tag (pg.429-437):

The <object>...</objectGt tag replaces a number of tags including:

• <bgsound>
• <embed>
  The embed tag is non-standard and confusing since the attributes it needs are dynamic in that you must find them out from the plug-in author.
• <applet>
  The APPLET tag is deprecated in HTML4.0. It's purpose is to allow loading of JAVA applets by the browser.

And oddly enough, the OBJECT tag can be used in place of the IMG and MAP tags for image maps (see p. 435 for details):

<object data="usmap.gif" shapes>

<a shape=rect coords="140,70,200,100" href="stateofva.htm">
</object>

Versus the more common form of:

<img src="usmap.gif" usemap="#map1">
. . .
<map name="map1">
<area coords="140,70,200,100" href="stateofva.htm">

</map>

Click here for a simple example of how to use the OBJECT tag to play a sound file.

There are many attributes associated with the OBJECT tag as it is the new do-all-be-all multi-media tag. I will leave in depth study of this tag to your reading.

JavaScript (p446-461):

JavaScript is Netscape's HTML scripting language, allowing you to pump up HTML and make it do things it was not designed to do.

Some features of JavaScript include:

• very much like the 'C' programming language
• it is not JAVA
• program source code is embedded as text within an HTML document
• executed by the borwser, not the JVM
• lengthy program code = lengthy HTML

Not to be outdone by archrival Netscape, Microsoft introduced their own HTML scripting language - vbScript. It functions just like JavaScript, but the code is Visual BASIC, not 'C'.

Beyond what little we have done with JavaScript (use of the window.alert function to pop up a window), I leave the exploration of JavaScript as a programming language to you and the next semester of Advanced HTML.