Sign magnitude, one's complement, two's complement

Toby Thain toby at
Sat Aug 22 16:32:40 CDT 2015

On 2015-08-22 5:23 PM, Sean Conner wrote:
>    For my own morbid curiosity, and because it came up on another mailing
> list I'm on [1], what machines commercially avaialble were sign magnitude
> and one's complement?  Every machine I've encountered was two's complement
> (okay, IEEE 754 [2] is a sign magnitude format but I'm talking about integer
> implementations here, not floating point).  I've only found reference to one
> sign magnitude computer (the IBM 7090, release in 1959) and a few one's
> complement machines (mostly the PDP series from DEC).
>    Where there others?  And honestly, are there any machines that use
> anything other than two's complement today?

CDC 6000 series are significant one's-complement machines.


>    -spc
> [1]
> [2]	AKA floating point.

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