The default I/O units,
specified by READ fmt,
READ (UNIT=*),
WRITE (UNIT=*), and
PRINT fmt,
should not be units 5 (input) and 6 (output),
but, rather, unit numbers not normally available
for use in statements such as OPEN
and CLOSE
.
Changing this would allow a program to connect units 5 and 6
to files via OPEN
,
but still use READ (UNIT=*) and PRINT
to do I/O to the “console”.
This change probably requires the libg77
project.