If your program crashes at run time with a message including
the text `illegal unit number', that probably is
a message from the run-time library, libg2c.
The message means that your program has attempted to use a
file unit number that is out of the range accepted by
libg2c.
Normally, this range is 0 through 99, and the high end
of the range is controlled by a libg2c source-file
macro named `MXUNIT'.
If you can easily change your program to use unit numbers in the range 0 through 99, you should do so.
Otherwise, see section Larger File Unit Numbers, for information on how
to change `MXUNIT' in libg2c so you can build and
install a new version of libg2c that supports the larger
unit numbers you need.
Note: While libg2c places a limit on the range
of Fortran file-unit numbers, the underlying library and operating
system might impose different kinds of limits.
For example, some systems limit the number of files simultaneously
open by a running program.
Information on how to increase these limits should be found
in your system's documentation.
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