What are plug-ins?
Which Web browsers support plug-ins
Introducing ActiveX
How plug-ins & ActiveX work
Be careful
Best of the bunch

What are plug-ins?

Today's Web browsers have more muscle than Schwarznegger but you can pump them up even further with `plug-in' modules. Plug-ins are miniature applications which integrate themselves with Web browsers to add enhanced functionality, mostly in the area of multimedia.

Which Web browsers support plug-ins?

Netscape pioneered the use of plug-ins for Navigator 2.0 and later, but Internet Explorer 3.0 now offers plug-ins too.

Introducing ActiveX

But as well plug-ins, Microsoft has added a similar technology called ActiveX to IE 3.0.

ActiveX is actually a variation of OLE (object linking and embedding) Windows functionality where you can click on an icon in a document and start a separate application which supports it.

Although the result is often the same -- say, a calendar appears in the middle of your Web page -- ActiveX controls are not really plug-ins -- nor are they Java applets for that matter. They're inserted into pages like an applet, so when you hit a page that contains one, it's automatically downloaded. Once downloaded, however, it acts like a plug-in.

It stays permanently on your system so that when a Web page requires it, that specific control, the code for it gets pulled off of your local disk rather than off the Net.

The idea is that instead of having a spellchecker built into every application, you just have a system-wide, spellchecker 'object', which can be called up by any application. Thus, when you upgrade just the spellchecker object, every program will 'automagically' get an all-new spellchecker, with no extra work.

Lotus has also introduced similar technology, called Components, for its Notes groupware applications.

The downside to ActiveX is that unlike Java and Netscape plug-ins, it only works (surprise, surprise!) in Windows 95, whereas Netscape plug-ins work on most hardware platforms including Macintosh and Unix.

Both Netscape's plug-in and Microsoft's ActiveX technology enables third-party developers and users to extend the capabilities of their browsers.

They include native support for new data types and additional features. ActiveX has a lot of potential but it will not be fully realised until the release of Internet Explorer 4.0 at the end of this year. IE 4.0 will turn the desktop into one big browser and ActiveX will be its major feature.

How plug-ins & ActiveX work

For the user, both ActiveX and Netscape plug-ins operate similarly. When the browser starts up, it checks for plug-in or ActiveX modules in the \NETSCAPE\PLUGINS folder or IE directory.

Plug-ins can work various ways:

• During a user's normal navigation through the Web, the plug-in is loaded as needed when a specified data file is encountered for a registered plug-in. Plug-ins are automatically triggered as the user loads an HTML page that includes the specific data type. It works as if a GIF or JPEG image is embedded, except the image can be live or can respond to user events such as mouse action. An example of such a plug-in is an MPEG player.
• A full-page plug-in is a viewer for a particular data type that is not a part of an HTML document. In this mode, a plug-in fills the inner frame of a Netscape window with its representation of some data type. An example of this kind of plug-in is an Adobe Acrobat viewer.
• A hidden plug-in, currently unimplemented, runs in the background. An example of such a plug-in might be a MIDI player.

Be careful

Theoretically all these should operate equally well with Internet Explorer 3.0 as with Netscape 2.0 and above.

One headache to watch for is that as you upgrade your browser, there is a likelihood the plug-ins that worked nicely with your current browser may not work with a later release. You should resist deleting your old version of the browser before you are sure the new one works, and keep abreast of the latest plug-ins.

Best of the bunch

Currently there are almost a hundred plug-ins, most of which are on the November PC User Offline CD-ROM (see the Plug-in List). They can also be freely downloaded from various sites on the Internet. Some run only under Windows 95, however many run happily on Windows 3.1.

The three plug-ins I've found most useful or entertaining are:

• RealAudio, a plug-in that gives you live AM-radio like sound over the Net. (URL: http://www.realaudio.com/products/player2.0.html#download)
• Macromedia's ShockWave for Director, for mind-blowing animation, sound and interactivity. (URL: http://www-1.macromedia.com/Tools/Shockwave/Plugin/ plugin.cgi)
• Netscape's Live3D, which opens the door to 3D virtual reality worlds written using the virtual reality mark-up (VRML) language, although it will give even a high-end Pentium a work-out. (URL: http://home.netscape.com/comprod/products/navigator/ live3d/download_live3d.html)

By John Hilvert

Where to now

• The Plug-in List. A comprhensive listing of Netscape and ActiveX plug-ins, with links to their Web sites.
• Using the Internet. We've got plenty more tutorials.