Simredo is a Java program - it needs the Java Runtime Environment (JRE) in order to run. Simredo 4.9 requires JRE version 1.8 or higher.

To find out what version your system has, or if it has Java at all, open a Terminal window, and enter the command shown below.

In Windows 10, you can find Terminal by typing 'terminal' in the search field of the task bar, at the bottom of the screen. In Linux/Gnome, the terminal may be located under System Tools. For Mac users, it can be found in the folder Application/Utilities.

If you get a 'command not found' message, or your version is less than 1.8, you will need to install the latest JRE. Go to http://java.com/ and click on 'Free Java Download'.