If you upgrade SAO-X by replacing SAOExplorer.jar with newer one, then starting from version 3.5.6 you need to add third-party library exp4j, otherwise SAO-X will be terminated at the very start with message, '%' is not recognized as an internal or external command, operable program or batch file. You can download exp4j from, ftp://umlcar.uml.edu/SAOExplorer/lib/exp4j-0.4.8.jar Steps after downloading: 1. copy exp4j-0.4.8.jar to directory where SAOExplorer is installed 2. add exp4j-0.4.8.jar to the class path of java call line, or, if you use IAnywhere launcher, you have to modify line starting as lax.class.path=.... in the file SAOExplorer.lax, by adding exp4j-0.4.8.jar in the same manner as other jar-libraries.