[TUHS] [TUHS} PDP-11, Unix, octal?

Charles Anthony charles.unix.pro at gmail.com
Thu Jan 19 04:58:40 AEST 2017

On Wed, Jan 18, 2017 at 10:47 AM, Peter Jeremy <peter at rulingia.com> wrote:

> On 2017-Jan-18 07:04:31 +0100, Lars Brinkhoff <lars at nocrew.org> wrote:
> >The PDP-10 did not have a fixed byte size.  Were there any 9-bit
> >machines?
> The Honeywell 6000 series (aka 66/DPS, a rebadged GE 6xx series) was
> 36-bit and supported either 6-bit or 9-bit characters.  I don't recall
> how you selected which you were using but I recall both Pascal and APL
> used the 9-bit byte.
The [EIS] instruction set supported 4, 6 and 9 bit operands; it was a
matter of which instructions you used.

For pl1, the instructions generated were driven by the DCLs; for Pascal and
APL, [I would guess] that the compiler/interpreter writers defined
character size to be 9 bits and generated the 9 bit variants of the

Move 9 6-bit bytes starting at the 3rd byte in the word, convert to 4 bit
bytes in some signed manner, and store as 10 4-bit bytes starting at offset

MLR ,,400        move with sign captured
ADSC6 FLD1,3,9   sending descriptor
ADSC4 FLD2,6,10  receiving descriptor

-- Charles
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