Web Interfaces and CGI Programming

The present chapter explains how to build graphical user interfaces as web pages. For example, we shall create an interactive web interface to a computational service and display the results graphically. Interactive or dynamic web pages can be realized in different ways:

• by Java applets that are downloaded and executed on the client's computer system

• by JavaScript code as part of the HTML code in the web page

• by programs on the web server communicating with the web page through a Common Gateway Interface (CGI).

The latter technique has two attractive features: The web page interaction is fast (no need to download applets), and a full-fledged programming language of almost any choice can be used in creating the interactivity. Scripting languages, in particular Perl, have traditionally been popular for CGI programming, basically because CGI programming involves lots of text processing.

Only some basic knowledge of Python from Chapter 2 is required to understand the present chapter. Since we deal with web-based graphical user interfaces and the same examples as in Chapters 6.1 and 6.2, it might be an advantage to have browsed those examples.