Why NULL is 0
Stan Switzer
sjs at spectral.ctt.bellcore.com
Thu Apr 7 22:52:43 AEST 1988
In reference to:
> > People (usually ;>) have no problem with the idea the while assigning a
> > zero to a float gives it the vaule 0.0, in most implementations the
> > float value does not have all bits set to zero.
And:
> I do believe IEEE and Vax's version of float is a bit pattern
> consisting of all zeros. So what are these implementations that don't
> use zero bit pattern?
The Honeywell 6000 Series and GE 625/635 machines represented NORMALIZED
float zero as o400000000000 (36 bits, msb ON). This may date back to its
grand-uncle the 709.
BTW, all 0 bits WAS a float zero, but it wasn't normalized. The results of
most float operations on unnormalized values was undefined. I suspect that
additions and subtractions would lose precision in the process
of alligning the points.
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