[V8i] Configuration Variables: _USTN_INROADS_PREFS vs. CIVIL_XIN_FILE

Question

Hello, I'm working on setting up a command line in a .cfg that will tell inroads/ inrail to load a specific .xin file when it loads. I've seen two different command lines for it: 
 CIVIL_XIN_FILE 
 and 
 _USTN_INROADS_PREFS 
 
 I'd like to understand what difference (if any) there is between these two configuration variables. 
 I've also seen "MS" used, for example: 
 MS_CLIENTCAD_DIR_NAME 
 in configuration files. 
 Does "MS" function the same way as "_USTN?" 
 
 Thank you for your help.

Rod Wing · Answer

Adam, 
 If you are using InRoads SS3 or later (OpenRoads technology), then the CIVIL_XIN_FILE is the variable you should use to define the .xin file. 
 As for the MS vs. _USTN prefix, these are just different variable definitions. The only significance is that any variable that begins with an _ (underscore) character is hidden by default in the configuration variable dialog. Typically the _USTN variables are more internal, system type, variables, hence that's why the all begin with an _ so they are hidden from the user. The MS variables are for user settings and adding additional resources, so no _ in front of those variable definitions. 
 If you are creating your own custom variables I would highly recommend that you do not use the _USTN nor the MS prefix as they tend to become easily confused with the standard MicroStation variables. Using something like an AA prefix on your custom variable works well as then they are grouped together at the top of the list.