GATE | GATE-CS-2002 | Question 21

In 2′ s complement addition, overflow
(A) is flagged whenever there is carry from sign bit addition
(B) cannot occur when a positive value is added to a negative value
(C) is flagged when the carries from sign bit and previous bit match
(D) none of the above

Answer: (B)
Explanation: is flagged when the carries from sign bit and previous bit DO NOT match. Refer http://en.wikipedia.org/wiki/Two%27s_complement#Addition
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