One's Complement Method

Notes about the $1$'s complement method:

• Adding numbers became much simpler: regardless of whether you have positive or negative numbers that you need to add, you always do addition!
  • In case you get a carry bit of $1$ beyond the leftmost bit, you don't discard it: just add this $1$ back to the rightmost (smallest) bit. This is called "end-around carry".
• Unfortunately, we still have two representations of zero: positive zero ($00000000$) and negative zero ($11111111$). [We'll soon see another complement method that solves this problem!]

Fun Activity: Represent the following in $8$-bit, $1$'s complement format: (1) $9_{10}$ (2) $-9_{10}$ (3) $-17_{10}$.

Next, we'll check out some examples of (easily!) adding numbers in $1$'s complement format.