guys please help me in this Logic gates problem?

Which of the following expressions obtains -n for an 8-digit binary number n when a negative number is expressed as the two's complement? Here, + indicates addition,while OR and XOR indicate,respectively , the logical sum and exclusive logical sum of the bits

a) (n OR 10000000) + 00000001

b) (n OR 11111110) + 11111111

c) (n XOR 10000000) + 11111111

d) (n XOR 11111111) + 00000001

ans_________

guys can you pls also explain... i really having a hard time in this problem... i just need your help... thnx

1 Answer

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  • Anonymous
    1 decade ago

    converting to negative in 2's complement:

    flip all the bits, then add 1. looks like D. although i haven't thought that hard about it, because this is the algorithm for turning a positive into a negative so i dunno if it works in reverse.

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