We need a computer.
Being based on the web and using Java (which works on most machines), App Inventor by design has all three of the major operating systems covered—Windows, Mac, and Linux.
Here are the specific operating system requirements:
Macintosh (with Intel processor): Mac OS X 10.5, or 10.6
Windows: Windows XP, Windows Vista, or Windows 7
GNU/Linux: Ubuntu 8+, or Debian 5+
Web browsers are also important. App Inventor—while doing a lot of its work on our local computers—is controlled from online. Google recommends one of the following:
Mozilla Firefox 3.6 or higher
Apple Safari 5.0 or higher
Google Chrome 4.0 or higher
Microsoft Internet Explorer 7 or higher