As distributed, whether as part of f2c or g77,
libf2c accepts file unit numbers only in the range
0 through 99.
For example, a statement such as `WRITE (UNIT=100)' causes
a run-time crash in libf2c, because the unit number,
100, is out of range.
If you know that Fortran programs at your installation require the use of unit numbers higher than 99, you can change the value of the `MXUNIT' macro, which represents the maximum unit number, to an appropriately higher value.
To do this, edit the file `f/runtime/libI77/fio.h' in your
g77 source tree, changing the following line:
#define MXUNIT 100
Change the line so that the value of `MXUNIT' is defined to be at least one greater than the maximum unit number used by the Fortran programs on your system.
(For example, a program that does `WRITE (UNIT=255)' would require `MXUNIT' set to at least 256 to avoid crashing.)
Then build or rebuild g77 as appropriate.
Note: Changing this macro has no effect on other limits
your system might place on the number of files open at the same time.
That is, the macro might allow a program to do `WRITE (UNIT=100)',
but the library and operating system underlying libf2c might
disallow it if many other files have already been opened (via OPEN or
implicitly via READ, WRITE, and so on).
Information on how to increase these other limits should be found
in your system's documentation.
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