What are helper applications?
Netscape Navigator and other Web browsers can display several file types without any special configuration. These include text (with or without html markup), gif, jpeg, and a few other special types. In fact, the browsers can be configured to view almost any file type for which a viewing application can be specified. These viewing applications are referred to as helper applications.

A number of primary applications such as a program used to view page source, etc. can be set up in the preferences applications menu.

How helper applications work.
In order for the receiving Web browser (the client) to correctly display the file in question, the server and the client applications must be configured to recognize the file type. On the server side, the server software must contain a line in its configuration file to indicate the MIME type, file extension, and creator application (or type) of the files it serves. The MacHTTP.config file handles this in simple text code. For example, the MacHTTP must be configured so that when a file ending in the extension .ppt is served, the client recognizes this as a binary file created by the application PowerPoint. In cases where the server is improperly configured, the wrong application often attempts to open the file and an error message results (for example, if JPEG Viewer tries to open a PowerPoint file, you may get a text looking file in machine code).

Configuring Helper Applications on the Client
Later versions of Netscape make configuring helper applications a snap. A prerequisite, however, is that you have the appropriate helper already installed on the client. Common helper applications include Sound Machine, JPEGView, MPEGView, Sparkle, PowerPoint Viewer, Acrobat Reader, and Stuffit Expander (or their Windows equivalents).

Built in Helper Application Browser
When an unrecognized file type is received by the client, a window pops up that prompts the user to browse for the appropriate helper application. The user then finds the appropriate helper application, clicks to open it and the file is downloaded and viewed by the helper application. The same procedure can be used by entering the correct data into the Edit/Preferences/(Helper) Applications table. Alternatively, this menu may be located under the Options/Preferences menu. See, for example, the helper application configuration settings for the following applications:

Why use helper applications anyway?
Not everything can be displayed as effectively after html markup as it can be in the creating application. You can make a slide presentation from Netscape using the tools you have learned by now, but PowerPoint Viewer delivers PowerPoint slides, quickly, easily, with high resolution and color fidelity. It is easier to copy a .ppt file into the server folder than it is to convert the images and do the html markup!

A special word about Adobe Acrobat
Adobe Acrobat Exchange is a fairly inexpensive application that converts any file from any application into one that can be viewed and printed from the Web. Acrobat Exchange, when installed into your computer, acts as a printer driver, and when chosen, prints from the application (be it Word, PowerPoint, PageMaker, Excel, etc.) to a file of the portable document format type. A client computer that has the FREE and widely available Acrobat Reader installed can display the file, and print the file on the printer attached to the client. This enables rapid preparation of graphically enhanced files for distribution on the Web. See the following examples:


LESSON 9

WebMasters was created and is taught by Dr. Dan Lineberger, WebMaster of Aggie Horticulture, Department of Horticultural Sciences, Texas A&M University, College Station, Texas 77843.