🚀 go-pugleaf

	I claimed that 200 bits is a good upper limit on address size
because there are 2^200 electrons in the universe.  I was taken to task on
this and it was suggested that I meant 10^200.  I reiterated that I meant
2^200, which is what other people would call about 10^40th.

	In article <668@hropus.UUCP> jin@hropus.UUCP (Jerry Natowitz)
pointed out that 10^40 is off by rather a lot.  My apologies.  I used a
calculator program on Unix to calculate 2^200 and came up with 1.7e38.
Stupid me, by now I should recognize that number as something magic -- the
largest number you can represent in floating point on a Vax.  It seems that
2^200 produces floating point overflow and the calculator program I used
doesn't catch overflows.  And yes, I did think 1.7e38 was a bit low (I was
expecting more like 1e60, or about 3.something bits per decimal digit).
There is a discussion going on in RISKS-DIGEST (aka mod.risks) about people
trusting computers too much.  Now I find myself just as guilty.  Mea Culpa.

	Anyway, I stand by my assertion that there are 2^200th electrons in
the universe.  If you prefer to work in decimal, work out the conversion
yourself.  For the purposes of this discussion, I consider any arithmetic
error in that conversion (even a factor of 10^20!) to be trivial.

	A reasonable argument that 200 bits is not a good upper bound has
been made by various other people, however.  There are often times when a
sparse address space is useful.  If you take my home address as a number,
RoySmith222UnionStreetBrooklynNY11231, you need more than 200 bits (7-bit
ASCII).  For a world data base, it might be convienent to use this directly
as an index into a table, and the hell with hashing.
-- 
Roy Smith, {allegra,philabs}!phri!roy
System Administrator, Public Health Research Institute
455 First Avenue, New York, NY 10016