Question

知X=27/32和Y=31/32,用变形补码计算X+Y和X–Y,同时指出运算结果是否溢出?

Answer 1

变形补码就是双符号位补码

(1)取补：[x]补=00.11011 [y]补=00.00011 [-y]补=[[y]补]变补=11.11101

[x+y]补=[x]补+[y]补=00.11110 x+y=[[x+y]补]补=0.11110

[x-y]补=[x]补+[-y]补=00.11000 x-y=[[x-y]补]补=0.11000

(2)取补：[x]补=00.11011 [y]补=11.01011 [-y]补=[[y]补]变补=00.10101

[x+y]补=[x]补+[y]补=00.00110 x+y=[[x+y]补]补=0.00110

[x-y]补=[x]补+[-y]补=01.10000 符号位为01,结果正溢