To follow along with the examples in this book, you will need a computer that can run MySQL, PHP, and the Apache web server, which are all prerequisites for Drupal. Drupal is written in PHP and can run on many platforms and environments including Windows, Mac OS X, and Ubuntu Linux.
You may want to create an account with a website hosting company to test your work, although you can also use a regular desktop or a laptop computer. But all that is required is a development environment set up on your computer; some of the most popular development environment bundles are Acquia Drupal, WAMP, XAMPP, and MAMP.
You will also need the Drupal 7 core, which is available at http://www.drupal.org