To support legacy codes, GNU Fortran allows the comma separator to be omitted immediately before and after character string edit descriptors in FORMAT statements. A comma with no following format descriptor is permitted if the -fdec-blank-format-item is given on the command line. This is considered non-conforming code and is discouraged.

PRINT 10, 2, 3
10     FORMAT ('FOO='I1' BAR='I2)
       print 20, 5, 6
20     FORMAT (I3, I3,)