Convert to Signed Binary-Coded Decimal
Converts the lower digits of a 64-bit decimal floating-point value to a Signed Packed Format (packed decimal).
unsigned long long __d64_to_signed_BCD (_Decimal64, _Bool value);
Produces 15 decimal digits followed by a decimal sign in a 64-bit result. The leftmost digit is ignored.
Positive values are given the sign 0xF if value is true and 0xC if value is false.
Negative values are given the sign 0xD.
You can use the __d64_shift_right function to access the leftmost digit.