Question

Convert -18 to 8-bit sign magnitude, 1's complement and 2's complement.

Answer 1

-18
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This is negative. so, follow these steps to convert this to various binary formats.
Divide 18 successively by 2 until the quotient is 0
18/2 = 9, remainder is 0
9/2 = 4, remainder is 1
4/2 = 2, remainder is 0
2/2 = 1, remainder is 0
1/2 = 0, remainder is 1
Read remainders from the bottom to top as 10010
Adding 3 zeros on left hand side of this number to make this of length 8
So, 18 in normal binary format is 00010010
sign-magnitude:
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set 1 as left most bit, since this number is negative.
so, 00010010 becomes 10010010
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||    sign-magnitude: 10010010    ||
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1's complement:
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flip all the bits. Flip all 0's to 1 and all 1's to 0.
   00010010 is flipped to 11101101
=====================================
||    1's complement: 11101101    ||
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2's complement:
-----------------
Add 1 to above result
11101101 + 1 = 11101110
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||    2's complement: 11101110    ||
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