Runtime corresponding to CAD version

After installing the opendcl runtime, one folder appears in my computer under the common folder. Considering different arx file works well under different CAD version, I'm wondering what cad version suits the following files.
OpenDCL.16.arx
OpenDCL.17.arx
OpenDCL.18.arx
OpenDCL.19.arx
OpenDCL.20.arx
OpenDCL.x64.17
OpenDCL.x64.18
OpenDCL.x64.19
OpenDCL.x64.20

Any help will be appericiated... Thanks in advanced.

Don't worry about this. Just use the Opendcl command which will take care of everything:
(setvar 'cmdecho 0)
(vl-cmdf "_Opendcl")
(setvar 'cmdecho 1)

Thanks. I know the method you provide works well. But I simply want to know the corresponding relationship between the arx file and CAD version. Now i'm trying to program some code which was able to run properly by loading corresponding opendcl arx file, without installing the opendcl install package or the runtime install package, which means i want to zip the code file and the arx and the runtime dll file.
So here comes the topic. Or if other method can be provided will be of great help.

2004 = 16.0
2005 = 16.1
2006 = 16.2
2007 = 17.0
2008 = 17.1
2009 = 17.2
2010 = 18.0
2011 = 18.1
2012 = 18.2
2013 = 19.0
2014 = 19.1
2015 = 20.0

with (atoi (getvar "acadver")) you can get the main version as integer

best regards
marco

Wow, I used the acadver variable before and i did not realize the number shown is the arx number itself. Thanks!