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From: Douglas McIlroy <>
To: TUHS main list <>
Subject: [TUHS] Re: Does anybody know the etymology of the term "word" as in collection of bits?
Date: Fri, 9 Sep 2022 13:26:31 -0400	[thread overview]
Message-ID: <> (raw)

> Doug or anyone, why do bit pointers make sense?  Why?

Bit-addressing is very helpful for manipulating characters
in a word-organized memory. The central idea of my ancient
(patented!) string macros that underlay SNOBOL was that it's
more efficient to refer to 6-bit characters as living at
bits 0,6,12,... of a 36-bit word than as being characters
0,1,2,... of the word. I've heard that this convention was
supported in hardware on the PDP-10.

In the IBM 7020 floats and ints were word-addressed. But
those addresses could be extended past the "decimal point"
to refer to bits. Bits were important. The computer was designed
in parallel with the Harvest streaming "attachment" for
NSA. Harvest was basically intended to gather statistics useful
in code-breaking, such as frequency counts and autocorrelations,
for data typically encoded in packed 5- to 8-bit characters. It
was controlled by a 20-word "setup" that specified operations on
rectangular and triangular indexing patterns in multidimensional
arrays. Going beyond statistics, one of the operations was SQML
(sequential multiple lookup) where each character was looked
up in a table that specified a replacement and a next table--a
spec for an arbitrary Turing machine that moved its tape at
byte-streaming speed!


             reply	other threads:[~2022-09-09 17:27 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-09-09 17:26 Douglas McIlroy [this message]
  -- strict thread matches above, loose matches on Subject: below --
2022-09-11 13:30 Douglas McIlroy
2022-09-11 15:08 ` John Cowan
2022-09-11 15:30 ` Bakul Shah
2022-09-11 15:45   ` Paul Winalski
2022-09-11 16:20     ` Steve Nickolas
2022-09-09 19:39 Nelson H. F. Beebe
2022-09-09 20:27 ` Bakul Shah
2022-09-09 21:12   ` Henry Bent
2022-09-09 21:44   ` Dave Horsfall
2022-09-09 18:46 Norman Wilson
2022-09-10  1:35 ` Paul Winalski
2022-09-09  1:33 Douglas McIlroy
2022-09-09  2:12 ` Larry McVoy
2022-09-13 14:23   ` John Foust via TUHS
2022-09-09  2:45 ` George Michaelson
2022-09-16  5:55 ` Marc Donner
2022-09-08 21:16 Noel Chiappa
2022-09-08 21:24 ` Dan Halbert
2022-09-08 18:20 Noel Chiappa
2022-09-08 19:28 ` Jim Capp
2022-09-08 16:51 [TUHS] " Jon Steinhart
2022-09-08 16:56 ` [TUHS] " Andrew Hume
2022-09-08 17:28 ` Dan Halbert
2022-09-09  0:00   ` Greg 'groggy' Lehey
2022-09-09 15:49     ` Paul Winalski
2022-09-09 18:44       ` Bakul Shah

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