Browser Teamwork: Applications and Plug-ins

Contents

• Audience and Objectives 
• About this document... 

• Overview: What browsers are expected to do
• Classifying file contents and formats: MIME
• Calling for Assistence: Helper Applications
• Adding Capabilities: Plugins

Overview: What browsers are expected to do

Browsers are expected to display several kinds of materials without help:

• Ordinary, unformatted text
• Formatted HTML text
• GIF and JPEG images

Some browsers display other types of materials, but none can show everything without help!

The early browsers (between about 1993 and 1996) got help in displaying other types of files by launching other programs and letting them run in separate windows. These are called Helper Applications or Helper Apps. Helper apps are still used for some types of files, but increasingly browsers use Plugins that use the browser window and appear to be part of the Web page.

In order to classify file contents for transmission by email in the late 1980s, the MIME system was developed. Browsers use MIME also, in deciding what kind of information they're being asked to display.

Classifying file contents and formats: MIME

MIME is the Multi-Purpose Internet Mail Extensions protocol, defined in RFCs 1521 and 1522. The official keeper-of-the-list is IANA, the Internet Assigned Numbers Authority, where you can see a complete list of MIME types.

Calling for Assistence:
Helper Applications

Helper Apps can include any programs normally found on computers, such as word processors, spreadsheets, photo manipulation programs, and many others. They may also include programs that can be downloaded free from the Internet.

What distinuishes a helper app from a plugin is that helper apps open in windows of their own, and run until you close them.

Browser developers supply their browsers with extensive lists of MIME types and the helper aps or plugins they need. To see what your version of Netscape supports, pull down the Edit menu and select Preferences. Under Navigator in the list at the left, click Applications and you should see something like this:

Notice that you can add new MIME types as they are developed. If you click the New Type button, you should see something like this that will let you tell the browser where to go for help:

You need the official MIME type as listed by IANA, as well as the file extension and the program itself.

Microsoft's Internet Explorer is more closely integrated with the Windows operating system. Explorer on a Windows computer uses the the file types set up through My Computer or Windows Explorer. To determine how types of files will be handled, open My Computer, pull down the View menu and select Options.
Click the File Types tab to see a list of MIME types, their associated extensions, and the program used to handle them.
To add a new type, click the New Type... button and fill in the information:

Adding Capabilities: Plugins

Plugins are programs that can be used to make something appear as part of a Web page. An example would be a video clip that appears, like a GIF or JPEG image, in a box within a page. MS Internet Explorer handles .AVI video files with a plugin, so it appears as part of a Web page, while Netscape handles them with a helper app, so they appear in a window of their own. Actually, Internet Explorer doesn't use the term "plugin", but uses software that is integrated in a similar way.

If a plugin is not available for a page you want to view, you can usually download them from the Internet. Most of them even have a self-installing feature, so that when they arrive at your computer, they automatically install themselves. This saves you from having to find the installation window and filling in all the details yourself.

You can learn a lot about plugins by looking at the Netscape Developer Guide, http://developer.netscape.com/docs/manuals/communicator/plugin/basic.htm

Audience:

This is for people who want to know about plugins and helper applications used in Web browsers. You should already know about browsers in general, as described in module W01c.

Related document: Module W07h, "Installing and Using Browser Plug-ins".

Objectives:

1. Describe plugins
2. Describe helper applications.

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