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TCP-group 1994


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Re: smashing down callsigns into 32 bits



>It turns out to be easy to map 6-character identifiers (including callsigns)
>into 32 bits uniquely.
>
>Those of us who are "old timers" can remember a DEC funny format called
>"Radix 40".  It coded 3 characters into 16 bits. (You see, 40^3 = 64,000)
>
>The character set had, as you might suspect, 40 charcters:  0-9, A-Z, space
>and 3 punctuation marks.  Have you ever wondered why on those old DEC minis
>you had filenames like FOOBAR.BAZ?  Now you know: filenames fit into 3
>16-bit words!

Actually, it was "Radix-50", not -40.  I think it's documented in
the RT-11 manual set.  It's probaby deep in my attic.

The original poster's fallacy, of course, was in forgetting how to
determine permutations.  The proper value of a field AA9AAA is
26^5 * 10, noting of course other formats too so more likley 27^5
and when you add non-US signs like C21 and 4N7 it gets a bit bigger...
   fred k1io
--------
Fred R. Goldstein   fgoldstein@bbn.com  
Bolt Beranek & Newman Inc.  Cambridge MA USA  +1 617 873 3850




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