23 Jun
2016
23 Jun
'16
9:07 a.m.
On 6/23/16 8:17 AM, Chuck Guzis wrote:
On 06/23/2016 07:31 AM, Paul Koning wrote:
I have also heard that 2s compliment was popular in shorter word length
machines because 1s compliment multiple precision arithmetic is a PITA
to implement.
I have a copy of 1948 (!) lecture notes on
computer design. It
discusses one's complement and two's complement. It points out the
advantage of two's complement (no two zeroes) but also the
disadvantage that negating is harder (requiring two steps). In early
computers that was significant, which explains why you see one's
complement there.
There are also a few obscure bit-twiddling tricks that work in ones
complement, but not in two's.