One’s complement
1’s±1
640
321
160
80
41
20
11
stored 10100101
MSB = 1 → negative · flip all bits
1280
641
320
161
81
40
21
10
10100101 → flip → 01011010 = 90 → −90
How it works
1/3- 1. Positive values look like ordinary binary.
- 2. Negatives: invert every bit of the positive pattern.
- 3. To read a negative: MSB = 1 means −; flip all bits, then read as unsigned magnitude.