困扰我一晚上关于补码的一个问题 - V2EX
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Hsinyao

困扰我一晚上关于补码的一个问题

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  •   Hsinyao Mar 3, 2019 via iPad 2782 views
    This topic created in 2620 days ago, the information mentioned may be changed or developed.

    为什么-1 的补码是 1.0000 ?还有为什么说纯小数下补码能比原码多表示一个-1 ?

    7 replies    2019-03-03 13:55:07 +08:00
    sulinehk
        1
    sulinehk  
       Mar 3, 2019 via Android
    -1 的补码在 4 位下应该是 1111
    小数或者说浮点数应该是按照 IEEF 754 标准
    midasplus
        2
    midasplus  
       Mar 3, 2019 via Android
    ???
    clker
        3
    clker  
       Mar 3, 2019 via Android
    补码只是针对整数而言。小数完全是另外一套表示法,IEEE754。
    Hsinyao
        4
    Hsinyao  
    OP
       Mar 3, 2019 via iPhone
    @sulinehk
    @clker 我指的是定点小数的补码表示法,即纯小数,小数点前面是符号位,小数点后是数字位那种。ieee754 是浮点小数的
    Hsinyao
        5
    Hsinyao  
    OP
       Mar 3, 2019 via iPhone
    @111qqz ???
    rammiah
        6
    rammiah  
       Mar 3, 2019
    因为原码的 x.xxxx 是表示不到-1 的,1.0000 在原码中是-0,0.0000 是+0,补码将最高位不再看作符号位,而是赋予一个负权值,1.0000=-1*2^0 + 0=-1,负 0 消失,变成-1,而在源码中+0 和-0 是被看成相等的,变成补码后自然多了一个-1。
    midasplus
        7
    midasplus  
       Mar 3, 2019
    @Hsinyao 不好意思,一开始没看懂你的问题
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