> On Jun 23, 2016, at 12:11 PM, Paul Koning <paulkon...@comcast.net> wrote:
>
>
>> On Jun 23, 2016, at 12:07 PM, Al Kossow <a...@bitsavers.org> 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.
>
> That's true. It certainly can be done and has been. But since one's
> complement arithmetic uses end around carry, when you have multiple word you
> have to defeat the word carry and instead do the carry around the whole
> number.
Something to look into.... in the Electrologica machines (Dutch computers from
the late 1950s to mid 1960s), double-length values are encoded with the sign
bit replicated in each word. I wonder if that makes this problem go away
(entirely or mostly).
paul
