On most modern operating systems (Windows, OS X, and most distributions of Linux), installing Nmap is a very easy task. The official Nmap website (http://insecure.org/) distributes downloadable installers for Windows and Mac OS X that are very easy to run.
For Windows, a full walk-through of the installation process is available at http://nmap.org/book/inst-windows.html.
For Mac OS X, a full walk-through of the installation process is available at http://nmap.org/book/inst-macosx.html.
To install Nmap for Linux, there are several options. The most recent "bleeding edge" builds are always available to install from source (see the following paragraph). There are RPMs that can be downloaded from the http://insecure.org/ website, but most Linux distributions already have Nmap in their standard packages' repositories.
To install from a repository on Debian/Ubuntu is very straightforward. First, run sudo apt-get update to verify that all 'apt sources' lists are up to date. Then, it is as simple as sudo apt-get install Nmap to download and install a working version of Nmap!
Tip
Downloading the example code
You can download the example code files from your account at http://www.packtpub.com for all the Packt Publishing books you have purchased. If you purchased this book elsewhere, you can visit http://www.packtpub.com/support and register to have the files e-mailed directly to you.