-precision64</CODE> indicates that the rounding precision
should be <NOBR>64 bits</NOBR>, equivalent to <NOBR>64-bit</NOBR>
double-precision, and <CODE>-precision80</CODE> indicates that the rounding
precision should be the full <NOBR>80 bits</NOBR> of the
double-extended-precision format.
All these options are ignored for operations not affected by rounding precision
control.
When rounding precision is applicable but not specified, the default assumption
is the full <NOBR>80 bits</NOBR>, same as <CODE>-pre