The following are used as internal file unit numbers and cannot
be changed by the user:
Number     Description
 0          Standard error
 5          Standard input and NAMELIST unit when not using OPNFI
 6          Standard output
15          NAMELIST unit when using OPNFI
34          Units conversion table verbose units labels 
35          Units conversion table abbreviated units labels 
36          Units conversion table plotting/graphics units labels 
37          Units conversion table conversion factors
38          Units conversion table conversion terms
39          Units conversion table index lookup table
41          Restart file input file unit number (42 also used if pnrg1=2)
43          Restart file output file unit number (44 also used if pnrg1=2)
48          Model diagnostics available table
49          Model diagnostics desired diagnostics table