Re: Implementation dependent behaviour (WAS: Re: Programming language and IDE design)

On 1/10/2014 3:08 PM, glen herrmannsfeldt wrote:
> Kaz Kylheku <kaz@kylheku.com> wrote:
>> On 2014-01-08, Ivan Godard <ivan@ootbcomp.com> wrote:
>
> (snip)
>>> I am such a CPU designer. We faced the "undefined" issue in our Mill
>>> family of general-purpose CPUs (ootbcomp.com). Not only are languages
>>> under-constraining, they are also sometimes over-constraining: signed
>>> integer overflow is undefined in C but required to wrap in Java.
>
>> It's only undefined on paper. In reality, if you don't make it
>> wrap in C like in Java, unknown numbers of C programs will break,
>> and not all of them doing it by accident.
>
> Well, C has unsigned with defined wrap on overflow. C still allows for
> ones complement or sign magnitude along with the more usual twos
> complement. As I understand it, Unisys still sells some ones
> complement machines. I am still waiting for a C compiler for the 7090
> to test out sign magnitude in C.


Unisys sells *both* one's complement (Univac 1100 descendants) and
sign-magnitude (Burroughs B6500 descendants).
[Wow. Is it custom hardware, or really funky simulators on normal chips? -John]

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