Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!iuvax!cica!ctrsol!sdsu!usc!ucla-cs!uci-ics!zardoz!tgate!ka3ovk!drilex!axiom!linus!alliant!werme
From: werme@Alliant.COM (Ric Werme)
Newsgroups: comp.arch
Subject: Re: Flash! 16 not power of 2!
Message-ID: <3316@alliant.Alliant.COM>
Date: 7 Aug 89 02:24:07 GMT
References: <38139@stellar.UUCP>
Reply-To: werme@alliant.Alliant.COM (Ric Werme)
Distribution: usa
Organization: Alliant Computer Systems, Littleton, MA
Lines: 48

In article <38139@stellar.UUCP> wright@sol.UUCP () writes:
>In article <3050@blake.acs.washington.edu>, mrc@Tomobiki-Cho.CAC.Washington.EDU
>(Mark Crispin) writes:
>
>>Back in days long by, people would actually *do work* in a power-of-2-based
>>number counting system.  You would not believe how much easier it is to do
>>arithmetic in octal instead of hex -- not to mention translating between
>>octal and the values displayed in the lights or that you key in the switches!
>
>This is either missing a smiley or is the dumbest thing I have ever read
>on comp.arch.  Listen carefully, bucko:  hexadecimal is base 16.  Last
>time I looked into the matter, 16 was a power of two, and I have not had
>much trouble translating it into binary, if you know what I mean and I
>doubt you do.
>
>(*flame off*)

No, he's right, and you're missing the point.  By the time I left PDP-10s and
-11s, I had learned the octal addition table and most of the multiplication
table.  (I rarely had to multiply octal numbers, otherwise I would have learned
that too.)  When you have to use the console panel to debug a broken system
(or broken debugger...) it's very handy to be able to figure out where to
look if you know a control block is at 46342 and you need to look at the
word 42 words into it (i.e. look at 46404).  I've been working on hex machines
sine 1978 and I still can't figure out 48a9c+44 without including something
like 9+4 = 13(base 10) = b(base16).  The problem is that the hexadecimal
addition table is 4 times bigger than octal's.  Even worse when you consider
that half the octal table is filled with the easy +0, +1, and +7 rows and
columns.

Sigh.  That was another nice thing about the first PDP-10.  The console
switches were contoured nicely to make binary addition easy.  I would set the
address switches to the start of the control block and add in the offset
like a binary abacus.  Those PDP-11 switches with their sharp edges - ugh.

:-) on
Listen carefully, bucko: I'm pleased that you can convert hex to binary and
back again.  But I'm not impressed.  If you can multiply 3 digit hex numbers
in you head, then I'll be impressed.  Me?  I gave up and bought a HP16.
:-) half off
BTW, haven't you learned not to followup to us comp.archaic folks?  It just
prods us into still more reminiscing about the good ol' days.
:-) off
-- 

| A pride of lions              | Eric J Werme                |
| A gaggle of geese             | uucp: decvax!linus!alliant  |
| An odd lot of programmers     | Phone: 603-673-3993         |