This is different from g77 (and to all Unix fortran compilers that I know of).
$ cat unit_0.f write (0,*) "hello" end $ rm -f fort.0 $ gfortran unit_0.f $ ./a.out $ cat fort.0 hello $ rm -f fort.0 $ g77 unit_0.f $ ./a.out hello $ cat fort.0 cat: fort.0: No such file or directory -- Summary: unit 0 not preconnected to standard error Product: gcc Version: unknown Status: UNCONFIRMED Severity: normal Priority: P2 Component: libfortran AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: Thomas dot Koenig at online dot de CC: gcc-bugs at gcc dot gnu dot org http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19052