19.4. CGI: Helping Web Servers Process Client Data

19.4.1. Introduction to CGI

The Web was initially developed to be a global online repository or archive of (mostly educational and research-oriented) documents. Such pieces of information generally come in the form of static text and usually in HTML (HyperText Markup Language). [Many documents also exist in plain text, Adobe Portable Document Format (PDF), or Extensible Markup Language (XML) format, a generalized markup language.]

HTML is not as much of a language as it is a text formatter, indicating changes in font types, sizes, and styles. The main feature of HTML is in its hypertext capability, document text that is in one way or another highlighted to point to another document in a related context to the original. Such a document can be accessed by a mouse click or other user selection mechanism. These (static) HTML documents live on the Web server and are sent to clients when and if requested.