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From: John Savard <quadibloc@servername.invalid>
Newsgroups: comp.arch
Subject: Re: PDP-6/10 text, Byte Addressability And Beyond
Date: Tue, 07 May 2024 19:31:10 -0600
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On Wed, 1 May 2024 19:33:54 -0000 (UTC), "Stephen Fuld"
<SFuld@alumni.cmu.edu.invalid> wrote:

>I don't know about the PDP 10, but you are right that Univac 1108 had
>both a six bit (technically a sixth of a word), and nine bit (quarter
>word) operations.  The 6 bit was Fieldata and used for most older
>softwaare.  The quarter words held an 8 bit ASCII character with one
>"wasted" bit per byte.  This became the dominent usage for
>applications, but the Exec itself still uses a lot of Fieldata.

The PDP-10 used ASCII, and not other codes.

The six-bit code of the Univac was derived from FIELDATA, but the
actual FIELDATA code, developed by the military, was a 7-bit code
which included lower-case.

In my cryptography pages, on the page

http://www.quadibloc.com/crypto/mi060103.htm

there's a diagram comparing Univac's Fieldata code with the actual
FIELDATA code.

John Savard