The DEFAULTFILE specifier indicates a default file pathname string. It takes the following form:
The default file pathname string is used primarily when accepting file pathnames interactively. File pathnames known to a user program normally appear in the FILE specifier.
DEFAULTFILE supplies a value to the Fortran I/O system that is prefixed to the name that appears in FILE.
If def does not end in a slash (/), a slash is added.
If DEFAULTFILE is omitted, the Fortran I/O system uses the current working directory.