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Evaluating the Bits of the Status Word with Floating- Point Instructions


Floating-point instructions affect the following bits in the status word: CC 1 and

CC 0, OV and OS.



The following tables show the signal state of the bits in the status word for the results of instructions with floating-point numbers (32 bits):





Valid Range for the Result
CC 1
CC 0
OV
OS
+0, -0 (zero)
0
0
0
*
-3.402823E+38 < result < -1.175494E-38 (negative number)
0
1
0
*
+1.175494E-38 < result < 3.402824E+38 (positive number)
1
0
0
*



*    The OS bit is not affected by the result of the instruction.





Invalid Range for the Result
CC 1
CC 0
OV
OS
Underflow
-1.175494E-38 < result < - 1.401298E-45 (negative number)
0
0
1
1
Underflow
+1.401298E-45 < result < +1.175494E-38 (positive number)
0
0
1
1
Overflow
Result < -3.402823E+38 (negative number)
0
1
1
1
Overflow
Result > 3.402823E+38 (positive number)
1
0
1
1
Not a valid floating-point number or illegal instruction
(input value outside the valid range)
1
1
1
1


1 comments:

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