Edits to sections 4.3.1 and 7.1.7 removed conflicts in Fortran 90 with the IEC 559 (IEEE 754/854) standard. Previous Fortran standards appeared to prohibit certain numeric values and numeric operations which were valid when using IEC 559 arithmetic. Fortran 90 requires that the value of a positive zero be the same as that of a negative zero, whereas IEC 559 requires that they be different. Fortran 90 prohibits any mathematically invalid operation, whereas IEC 559 requires such operations to produce +Inf , -Inf or NaNs.
These conflicts were removed to allow processors the ability to implement more of the IEC 559 arithmetic model without violating the Fortran standard.