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: Over Flag. The most recent operation caused a two‘s-complement overflow----either negative or positive
For example, suppose we used one of the ADD instructions to perform the equivalent of the C assignment t = a+b, where variables a, b and t are integers. Then the condition codes would be set according to the following C expressions:
CF: (unsigned) t < (unsigned) a Unsigned overflow
ZF: (t == 0) Zero
SF: (t < 0) Negative
OF: (a < 0 == b < 0) && (t < 0 != a < 0) Signed overflow
「操作系统」：The most useful condition codes
原文：http://www.cnblogs.com/sangoly/p/3566539.html