[TUHS] Re: origin of null-terminated strings

[Dan Halbert <halbert@halwitz.org>]

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On 12/16/22 16:02, Warner Losh wrote:
> On Fri, Dec 16, 2022, 1:12 PM Dave Horsfall <dave@horsfall.org> wrote:
>
>     On Fri, 16 Dec 2022, Dr Iain Maoileoin wrote:
>
>     > I remember running into a .asciz directive n the 70s
>     “somewhere”. It was
>     > an assembler directive in one of the RT11 systems??? or perhaps
>     the unix
>     > bootstrap and/or “.s” files - when I get some time I will go
>     read some
>     > old code/manuals.
>
>     MACRO-11 on RSX-11D seems to ring a bell...
>
>
> I first encountered it on RSTS/E 6C in the MACRO-11 it had... But the 
> v6 macro assembler from DEC via Harvard that eventually wound up in 
> 2BSD is older and dates to 1977 or so.
>
> Warner

The PDP-10 manual I spoke of is from 1971, and there were older 
editions. For the PDP-7, this manual from 1965, 
http://www.bitsavers.org/pdf/dec/pdp7/PDP-7_AsmMan.pdf, printed pages 
38-40, does not mention "ASCIZ" specifically, but talks about assembler 
directives "TELETYPE" and "ANALEX" that add a "termination code" of 00 
octal, for characters.

DEC also used SIXBIT, a truncated ASCII code that had printing 
characters but no control characters, so no newline, etc. In that 
scheme, 00 octal was SPACE. Table here: 
https://en.wikipedia.org/wiki/Six-bit_character_code#Examples_of_six-bit_ASCII_variants.

Dan H

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