On a particular computer the range for reals is 10-38 to 10+38.

a) What value does the expression (A/B) have when A = 1.0, B = 0.0?

    Division by zero.

b) What value does the expression (5.3E+25 * 6.4E+28) have?

    Overflow.

c) What value does the expression (5.3E-50 * 6.4E-35) have?

    Underflow.

Programs containing such expressions may crash, may deliver a special
value or may otherwise misbehave.  In general, underflow will cause the
result to be quietly replaced by zero, but that is not required by the
Fortran standard.