How to run calcoo.jar

Intro

This page is meant for people who do not know how to run software distributed as a .jar file, like the current version of Calcoo. If you do know how to run a .jar, you are unlikely to find anything new here. If you have downloaded (or are going to download) calcoo.jar, and do not know how you could run it, please keep on reading.

Why Java

Version 2 of Calcoo is written in Java, which is a much more modern computer language than C used for version 1 of Calcoo. Java gives developers the huge benefit of their software being able to run on any platform that Java runtime has been ported to by Sun/Oracle. However, this means that a user who wants to run Calcoo needs to have Java runtime installed.

Is Java already there?

To run Calcoo, you need Java, at least Java Version 8. You may already have Java installed on your machine. To check it, open a terminal window aka "command prompt", and type (or copy) "java -version" (without quotes) there and hit "Enter". If you get something like "java version "25.0.2" 2026-01-20 LTS" etc", you have what you need to run Calcoo. If the system cannot recognize the command, or if the version shows as 7 or earlier, you need to install the latest Java.

How to install Java

Get it here (latest, but JDK) or here (JRE only, but 8). It is sufficient to install JRE, though installing JDK (which includes JRE) is also Ok. If your platform is not listed there, you are on your own. You may want to use OpenJDK, for example, if it is available for your platform. After you are done installing, you can verify it by running "java -version" from the command prompt.

How to run calcoo.jar

Once you have a suitable version of Java installed, you can run Calcoo by running command "java -jar calcoo.jar" in a terminal window aka "command prompt" from the folder/directory where you saved it. In Windows and Mac OS, you can also run it by double-clicking on calcoo.jar.