Page 261 - ARM 64 Bit Assembly Language

250 Chapter 8

The value of this number in base 10 can be computed by taking the two’s complement, sum-
ming the values of the non-zero bits, and adding a negative sign to the result. The two’s com-
plement of 1011010101111010 is 0100101010000101 + 1 = 0100101010000110. The value
of this number is:

− 2 14−7 + 2 11−7 + 2 9−7 + 2 7−7 + 2 2−7 + 2 1−7

7
2
0
4
=− 2 + 2 + 2 + 2 + 2 −5 + 2 −6

1 1
=− 128 + 16 + 4 + 1 + +
32 64
=−149.046875 10
For a final example we will interpret this bit pattern as an S(−5,16). In that format, the layout
is:

The value of this number in base ten can be computed by taking the two’s complement, sum-
ming the values of the non-zero bits, and adding a negative sign to the result. The two’s com-
plement is:

The value of this number interpreted as an S(−5,16) is:

− 2 −6 + 2 −9 + 2 −11 + 2 −13 + 2 −18 + 2 −19 =−0.0181941986083984375