Hour 21. Introduction to CGI

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What You'll Learn in This Hour:

The basics of how the Web works
What you need to know before writing CGI
How to write your first CGI program

There's no question in anyone 's mind that the explosion in popularity of the Internet is mostly due to the World Wide Web. Since the introduction of the first graphical web browser in 1993, the Internet has expanded at a phenomenal rate ”going from the number of hosts doubling every 20 months around 1993 to doubling every 12 months currently. The growth of private networks ” intranets ”has increased even more rapidly .

The content of the web has become more sophisticated since 1993, and the users of the web expect each web page to do more than simply show static (unchanging) web pages. A successful web site requires dynamic web pages ”web pages that provide up-to-date information. Complex pages with rapidly changing content would be almost impossible to keep current if not for Common Gateway Interface ( CGI ) .

By the Way

The next four hours require you to have some knowledge of Hypertext Markup Language (HTML). If you're unfamiliar with HTML, don't despair. It's really not hard to learn, and you won't need much to complete this book.

HTML is a markup language commonly used for constructing web pages. HTML consists of plain text with formatting codes embedded in the text to indicate how a web browser should display the text. For example, the text HTML is <I>not</I> hard to learn. is normal text except for the <I></I> markers. They are called tags and describe the formatting used to display the text. In this case, the word not should be displayed in italic by a web browser, if it can. (Remember, not all browsers are graphical.)

A full lesson in HTML is well beyond the scope of this book. It's not difficult; there's just a lot of material to cover. The specification for HTML is maintained by the World Wide Web Consortium (W3C) at http://www.w3c.org, and you can find some nice tutorials there as well. One good book on HTML is Sams Teach Yourself HTML in 24 Hours .

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