FXTRACT
Usage: FXTRACT Modifies flags: See below.
Separates the 'src' value in the ST(0) register into its exponent and significand, stores the exponent in ST(0), and pushes the significand onto the register stack. Following this operation, the new top-of-stack register ST(0) contains the value of the original significand expressed as a floating-point value.
Extract Exponent and Significand
FXTRACT ; D9 F4 [8086,FPU]
FXTRACT separates the number in ST0 into its exponent and significand (mantissa), stores the exponent back into ST0, and then pushes the significand on the register stack (so that the significand ends up in ST0, and the exponent in ST1).
The sign and significand of this value are the same as those found in the source operand, and the exponent is 3FFFH (biased value for a true exponent of zero). The ST(1) register contains the value of the original operand's true (unbiased) exponent expressed as a floating-point value. (The operation performed by this instruction is a superset of the IEEE-recommended logb(x) function.) This instruction and the F2XM1 instruction are useful for performing power and range scaling.
FPU Flags Affected C1 Set to 0 if stack underflow occurred; set to 1 if stack overflow occurred. C0, C2, C3 Undefined.
EXAMPLE:
fxtract