This Scientific calculator uses RPN Logic (Reverse Polish Notation) similar to the HP Engineering Calculator I used in college. For example: To add 2 and 3 use "2 Enter 3 +." Everytime you press Enter it adds the number to the stack. It's designed for the Zaurus PDA but runs just fine with the Standard Edition (J2SE) so you can run it on your PC as well. It could also be repackaged for the IPAQ with the Jeode JVM installed. To launch this calculator look for the RPN icon in the Jeode Folder.