Source code default file type is ".MSG".

Compiled messages default file type is ".EXE".
    $ mov gibney$:[mdsplus.treeshr]
    $ message tree$messages      !create .obj file
    $ link/share tree$messages   !create .exe file

To examine the meaning of an MDSplus "treeshr" message code:
    $ set message gibney$:[mdsplus.treeshr]tree$messages
    $ exit 265388426
      %TREE$-E-INVDTPUSG, attempt to store datatype which conflicts ...