?? refers to the variant abbreviation

Base Serial Runs
??test.key - these keyword files contain 4 test runs for a specific base variant
??test.tre - input tree data for a specific base variant
??test.rsp - response file for a specific base variant

Climate Extension
??test.rsp - response file for running FVS-Climate

Parallel Processing Extension
??pp.key - keyword file for running the parallel processing extension to FVS
??pp.tre - input tree data file for running the parallel processing extension
pp??test.rsp - response file for running the parallel processing extension
??serial.key - keyword file for running the parallel processing extension in serial mode
ser??test.rsp - response file for running the parallel processing extension in serial mode
