When a Fortran program attempts to write to a hard drive that is completely full, the operating system will prevent the write operation from succeeding. This is not a limitation of Fortran itself but rather a function of the operating system's handling of disk space. On systems like DOS and Windows, if a write request exceeds available disk space, the operation will fail, and the program will receive a return value indicating that fewer bytes were written than requested, or zero if the disk is entirely full. No existing files will be overwritten in this scenario.
