# 2's complement

1. Oct 14, 2007

### fsm

1. The problem statement, all variables and given/known data
Covert the following numbers to 12-bit binary numbers using two's complement representation.

234
-234
2. Relevant equations
None I know of.

3. The attempt at a solution
I think I'm making this more complicated than it really is. For 234 I can just convert right to binary or do I have to convert 234 to binary, complement, add 1, complement, and then add 1?

For -234:
000011101010
111100010101
111100010110

On a side note converting a negative number to octal or hex say -234. You convert it like any other binary number? When converting back how do you know you have a negative number or positive number? By the MSB?

2. Oct 14, 2007

### huckmank

You did the conversion correctly. The way you can check is to add 234 with -234. The result should be 0 (within the 12 bits).

For positive numbers, you need do nothing. 234 is the same in two's complement, the same in one's complement, the same in unsigned. The conversion method is used to convert positive to negative and negative back to positive.

If the MSB is 1, then yes, that number is negative in two's or one's complement.

3. Oct 14, 2007

Thanks!