Client(s)

The picture illustrates four pages from a web server (the authors') displayed using the most commonly available client, NCSA's Mosaic. Mosaic is available on Unix and PCs under windows, and Macs.

Mosaic is a screen based client, which is quite sophisticated, so we can use it to illustrate a number of things about clients.

Firstly, the main part of the window shows the page currently being viewed. This is displayed by the client having been retrieved from a server. It is possible to configure a great deal in the way the information is displayed in terms of fonts, colors and so on, depending on which client, and which operating system and windowing system technology you are using.

Next, the server (and page's) location is shown in the second title field "Document URL" (the first shows the title of the document as the author wrote it within the page). A URL is a Uniform Resource Locator: this is the location that hyper-link leads us to and that allows us to go from one page to another. It is made up of three main things, as shown in the table and explained below:

1. The protocol scheme - this is what allows us to choose the right access protocol (if it isn't the basic one, the Hyper Text Transfer Protocol (HTTP.) Many clients programs also implement other protocol clients such as FTP as well as HTTP.
2. The address - this is simply the Domain Name of the server (or perhaps of a caching server - see later).
3. The path - this is the position of the page of information we seek in the tree of data at the server.

Next, there are a number of pull down menu buttons. These allow you to navigate the Web, as well as to make personal annotations, or to save copies of a URL in a bookmark list, or mail the contents of a page. Last but not least, you can even view the source un-marked-up copy of the page

Clients exist for all common systems, from DOS, Windows, Macintosh Systems to Unix and VMS.