What Does Free Mean

Open source software is free in the sense that you do not have to pay money to use it, but it carries the wish that users will pay for it in other ways, such as by participating in discussion boards, offering to test new features, and possibly even contributing to the code base itself. In addition, you may have other costs for customization, support, and the hardware on which to run it.

Like much software that powers the web, Drupal doesn't run in the way that a word-processing program or spreadsheet runs. It sits on a web server ready for action, and it flies into action when that web server receives a request to display a page. Drupal responds to the request by interacting with the rules and information that have been stored in its database; the result of this response is almost always a web page that is returned to the user's browser. For the most part, input to Drupal consists of requests for pages (sent via Hypertext Transfer Protocol [HTTP]) that, after processing, are returned as pages of Hyper text Markup Language (HTML).

The database that powers Drupal (which can be MySQLor PostgreSQL and, in Drupal 7, SQLite) also lies in wait most of the time. It springs to action when Drupal sends a request for data or, in the case of developing a site, when Drupal sends a request to store information or rules about how the site is to be structured and displayed.

The primary exception to this is an optional job that runs periodically on the web server (a cron job) to do maintenance, such as indexing the site for searching. If you do not have access to cron on your site, Drupal provides poormanscron, which does the same sort of periodic processing, although it is actually triggered by events on Drupal.

Thus, to access a Drupal website or build one, you use a browser to communicate with the site, which must be installed on a web server. (The web server can be your own computer identified as localhost or with its own IP address.)

More technical information on how Drupal functions and how you build, manage, and use websites is provided throughout this book.

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