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binarysubtraction

Subtraction of 2, 2s complent numbers

I have a problem with the subtraction of 2s complement.

I tried subtracting (-22) - 12 = (-22) + (-12) this is what I get:

-22 = 1110 1010
-12 = 1111 0100

1110 1010
+   1111 0100
= (1)1101 1110

If I understand it correctly, the overflow indicates that it's a negative number but 1101 1110 isn't 34 ?

I don't see where I'm wrong ...

Thanks !

Solution

  • Your answer is:

     111011110 = -(2^8-(2^7+2^6+2^4+2^3+2^2+2))=-34

    you can calculate it another way

      111011110  = -(000100001 +1)= -(000100010)=-34