ANSI FORTRAN 77 Standard Support

GNU Fortran supports ANSI FORTRAN 77 with the following caveats. In summary, the only ANSI FORTRAN 77 features g77 doesn't support are those that are probably rarely used in actual code, some of which are explicitly disallowed by the Fortran 90 standard.

• No Passing External Assumed-length: CHAR*(*) CFUNC restriction.
• No Passing Dummy Assumed-length: CHAR*(*) CFUNC restriction.
• No Pathological Implied-DO: No ((..., I=...), I=...).
• No Useless Implied-DO: No (A, I=1, 1).