Configuration Variables are organized into Framework Configuration Variables, which start with the "_USTN_" prefix, and Operational Configuration Variables, most of which start with the "MS_" prefix. In general, the Framework Configuration Variables are used in configuration files, while Operational Configuration Variables are used to direct program behavior within MicroStation. A few of the Framework Configuration Variables are determined by the MicroStation installation directory. Other Framework Configuration Variables default to locations relative to the installation directory, but can be changed in Configuration Files provided by the user.