Most programs will have little reason to access this bit. Since the 80x86 CPUs already support integer data types, these are few reasons why you would want to use the 80x87 integer types. When a floating point number is normalized, the H.O. bit is always one. In the 32 and 64 bit floating point formats, the 80x87 does not actually store this bit, the 80x87 always assumes that it is one. In the extended precision 80 bit floating point format, the 80x87 does not assume that the H.O. bit of the mantissa is one, the H.O. bit of the number appears as part of the string of bits.
Normalized values provide the greatest precision for a given number of bits.
However, there are a large number of non-normalized values which we can represent with the 80 bit format. These values are very close to zero and represent the set of values whose mantissa H.O. bit is not zero. The 80x87 FPUs support a special form of 80 bit known as denormalized values. Denormalized values allow the 80x87 to encode very small values it cannot encode using normalized values, but at a price. Denormalized values offer less bits of precision than normalized values.