6.1.7 Default widths for F, G and I format descriptors

To support legacy codes, GNU Fortran allows width to be omitted from format specifications if and only if -fdec-format-defaults is given on the command line. Default widths will be used. This is considered non-conforming code and is discouraged.

REAL :: value1
       INTEGER :: value2
       WRITE(*,10) value1, value1, value2
10     FORMAT ('F, G, I')