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

Paul Koning paulkoning at
Sat Aug 22 20:26:36 CDT 2015

> On Aug 22, 2015, at 9:15 PM, Chuck Guzis <cclist at> wrote:
> On 08/22/2015 04:40 PM, Paul Koning wrote:
>>> On Aug 22, 2015, at 6:27 PM, Chuck Guzis <cclist at> wrote:
>>> ...FLoating point can engender some interesting representations.
>>> Consider the exponent field on the aforementioned CDC 6000 series.
>>> It's a "biased by 2000 octal) system--and the assumed binary point
>>> of the mantissa is to the right of the LSB.  So, 2000 0000 0000
>>> 0000 0001 octal = 1 exactly.
>> EL-X8 doesn't use the bias, so the floating point representation of
>> an integer under 2^39 is the same as the integer representation.  And
>> the rule for normalizing float values preserves that (normalization
>> makes the exponent as close to zero as possible -- rather different
>> than the usual rule).
> I recall the "integer multiply" feature (i.e. optional) available on the 6000.  IXi  Xj*Xk, but it didn't provide any more precision than the usual unnormalized double-precision multiply  DXi  Xj*Xk, but saved some time spent fiddling with exponent fields. 

???  Never heard of any such thing.  IXi Xj*Xk is a defined opcode, but it's simply a synonym for Dxi Xj*Xk.


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