Why NULL is 0

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In article <6594 at bellcore.bellcore.com> sjs at spectral.UUCP (Stan Switzer) writes:
>In reference to:
>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.

Are you sure?  on the 709 all zero bits is the NORMALIZED zero.  quoting from
the 709 reference manual on page 8 (I still have one) "A normal zero has no
bits in both the charactersic and the fraction."  The form o400000000000  is
the unnormalized form and using this one is the way to get "funny" results.
My recloction is that the GE 635 (I no longer have that manual) did indeed
copy the 709.

     Marv Rubinstein -- Computer historian