The primary advantage of two’s complement over one’s complement is that two’s complement only has one value for zero. One’s complement has a “positive” zero and a “negative” zero.
Next, to add numbers using one’s complement you have to first do binary addition, then add in an end-around carry value.
Two’s complement has only one value for zero, and doesn’t require carry values.
You also asked how the range of values stored are affected. Consider an eight-bit integer value, the following are your minimum and maximum values:
Notation Min Max
========== ==== ====
Unsigned: 0 255
One's Comp: -127 +127
Two's Comp: -128 +127
References:
- http://en.wikipedia.org/wiki/Signed_number_representations
- http://en.wikipedia.org/wiki/Ones%27_complement
- http://en.wikipedia.org/wiki/Two%27s_complement