FTST
Usage: FTST Modifies flags: See below.
Compares the value in the ST(0) register with 0.0 and sets the condition code flags C0, C2, and C3 in the FPU status word according to the results.
Test ST0 Against Zero
FTST ; D9 E4 [8086,FPU]
FTST compares ST0 with zero and sets the FPU flags accordingly. ST0 is treated as the left-hand side of the comparison, so that a 'less-than' result is generated if ST0 is negative.
FTST Results
Condition C3 C2 C0
ST(0) >0.0 0 0 0
ST(0) <0.0 0 0 1
ST(0) =0.0 1 0 0
Unordered 1 1 1
EXAMPLE:
ftst