Mosaic User's Guide

Concepts & Terminology

The World Wide Web (WWW or W3)

The World Wide Web project was initiated by Tim Berners-Lee of CERN, Switzerland. The project attempts to provide an interface to the existing communication protocols (FTP, Telnet, WAIS, Gopher, NNTP, etc.) as well as the existing data formats (GIF images, Postscript documents, AIFF sounds, etc.) in one package.

In addition, the WWW project introduces a new protocol to the global Internet, the HyperText Transfer Protocol (HTTP), and a new file type, the HyperText Markup Language (HTML).

NCSA Mosaic is one WWW client (or browser) that can communicate with HTTP servers, as well as servers of the more traditional protocols.

Uniform Resource Locators (URL)

The mechanism by which Mosaic can retrieve information resources from anywhere on the Net is the Uniform Resource Locator (URL). URLs combine a path and filename with the name of the machine that serves the file to the Net, as well as the protocol to be used to retrieve the data. Here is a Beginner's Guide to URLs.

HyperText Markup Language (HTML)

The HTML documents viewed with Mosaic are simply text files with special markup tags in <brackets>. For example, <b>bold</b> produces the output: bold; and <i>italics</i> produces italics. Hyperlinks are created with the a tag, for anchor, with embedded URLs. To see the HTML source of any document viewed with Mosaic, use the View Source feature under the File menu. For more information, see A Beginner's Guide to HTML.

Hyperlinks & Multimedia (Hypermedia)

NCSA Mosaic can view hypertext HTML documents, in which words or inlined images can act as hyperlinks to other documents. Hyperlinks can also point to images, sound files, movies, HDF files, and more. When a hyperlink is selected that points to a resource which Mosaic cannot handle internally, it attempts to send the data file to an external viewer. For example, GIF images are sent, by default, to the program xv, a commonly-used image viewer. Most sound files are sent, by default, to the showaudio program.

Mosaic's use of external programs to handle specific data types is completely configurable. Click here for more information on the default external viewers and configuring Mosaic's multimedia capabilities.

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National Center for Supercomputing Applications

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