It is time to begin our journey learning how to program with the Scala language. You can download Scala for free from http://www.scala-lang.org to run on Windows, Mac, or Linux (see the inset below for full instructions on how to install). In this book, we will use the command line to run Scala. If you do not have experience with the command line on your machine, you can refer to Appendix A for a brief introduction. Before looking at the language itself, we need to talk a bit about tools so that you can play along.