Condition Codes

CF:Carry Flag.The most recent operation generated a carry out of the most significant bit.Used to detect overflow for unsigned operations.

ZF:Zero Flag.The most recent operation yielded zero.

SF:Sign Flag.The most recent operation yielded a negative value.

OF:Overflow Flag.The most recent operation caused a two‘s-complement overflow-either negative or positive.

Suppose we used ADD instructons to perform the equivalent of the C assignment t=a+b,where variables a,b,and t are integers.

CF:(unsigned)t<(unsigned)a

ZF:(t==0)

SF:(t<0)

OF:(a<0==b<0)&&(t<0!=a<0)

时间： 2024-11-02 21:56:32

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