PRISM is free and open source software. You can download both the tool and its source code for free from below. Distribution is under the GNU General Public License (GPL), version 2.
The current version of PRISM is 4.2.1 (first released 4 December 2014). This is a bug fix release. Major new improvements and additions in the latest releases (4.2.x) since the last main release (4.1) are listed below. More details for individual releases are in the CHANGELOG.
To access more recently developed features, try the development versions.
PRISM should run on 32/64-bit versions of all major operating systems. We distribute pre-built binary versions for various architectures. But for non-Windows platforms, it is usually easy to build from source code.
Note: Your version (32- vs 64-bit) of Java must match that of PRISM. In particular, to use the 32-bit Windows binary, make sure you are running a 32-bit version of Java.
If you have any problems, first check the list of common problems and questions.
If you are still stuck, post a message in the forum.
Once you have installed PRISM, you might want to look at: