[TUHS] origin of null-terminated strings

[Tom Lyon]

Re: getting a 360 - IBM and AT&T really hated each other, so 360s were
avoided for strategic reasons. That said, they could not be practically
avoided; Holmdel had a large installation:
https://www.youtube.com/watch?v=HMYiktO0D64&ab_channel=AT%26TTechChannel

When Amdahl and UTS/UNIX came along, the Bell System was by far the biggest
customer.

On Fri, Dec 16, 2022 at 8:12 AM Dan Cross <crossd at gmail.com> wrote:

> On Fri, Dec 16, 2022 at 8:42 AM Dan Halbert <halbert at halwitz.org> wrote:
> > ASCIZ was an assembler directive used for a number of different DEC
> computers, and also the name for null-terminated strings. I learned it for
> the PDP-10, but I'm sure it existed on other machines. It is in some PDP-10
> documentation I am looking at right now. Anyone who used DEC and did
> assembly programming would have known about it. Various system calls took
> ASCIZ strings.
>
> This raises something I've always been curious about. To what extent were
> the Unix folks at Bell Labs already familiar with DEC systems before the
> PDP-7?
>
> It strikes me that much of the published work was centered around IBM and
> GE
> systems (e.g., Ken's wonderful paper on regular expressions, and of course
> the
> Multics work). Were there other Digital machines floating around? I know a
> proposal was written to get a PDP-10 for operating systems research, but it
> wasn't approved.
>
> Relatedly, was any thought given to trying to get a 360 system?
>
> On 12/16/22 04:13, Dr Iain Maoileoin wrote:
> > ASCIZ
> > Lost in the mists of time in my mind.
>
> Origin, perhaps, but it exists in contemporary assemblers. Like most
> sane people I try to avoid being in assembler for too long, when you're
> first turning on a machine it is useful to be able to squirt a message
> out of the UART if something goes dramatically wrong, and the directive
> is handy for that.
>
> It seems to have made its way into Research assembler via BSD; it's in
> locore.s in 8th Edition, for instance, but doesn't appear before that.  The
> "UNIX Assembler Manual" describes "String Statements" for the 7th
> Edition assembler; strings are sequences of ASCII characters between
> '<' and '>'.  But it doesn't say that they're NUL terminated, and they are
> not: adding the terminator was manual via the familiar, `\0` escape
> sequence.
>
>         - Dan C.
>
>
> > 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.
> >
> > I
> >
> > Yes, it put a null byte at the end of a string.
> >
> > On 16 Dec 2022, at 03:14, Ken Thompson <kenbob at gmail.com> wrote:
> >
> > asciz -- this is the first time i heard of it.
> > doug -- yes.
> >
> >
> > On Thu, Dec 15, 2022 at 7:04 PM Douglas McIlroy <
> douglas.mcilroy at dartmouth.edu> wrote:
> >>
> >> I think this cited quote from
> >> https://www.joelonsoftware.com/2001/12/11/ is urban legend.
> >>
> >>     Why do C strings [have a terminating NUl]? It’s because the PDP-7
> >> microprocessor, on which UNIX and the C programming language were
> >> invented, had an ASCIZ string type. ASCIZ meant “ASCII with a Z (zero)
> >> at the end.”
> >>
> >> This assertion seems unlikely since neither C nor the library string
> >> functions existed on the PDP-7. In fact the "terminating character" of
> >> a string in the PDP-7 language B was the pair '*e'. A string was a
> >> sequence of words, packed two characters per word. For odd-length
> >> strings half of the final one-character word was effectively
> >> NUL-padded as described below.
> >>
> >> One might trace null termination to the original (1965) proposal for
> >> ASCII,  https://dl.acm.org/doi/10.1145/363831.363839. There the only
> >> role specifically suggested for NUL is to "serve to accomplish time
> >> fill or media fill." With character-addressable hardware (not the
> >> PDP-7), it is only a small step from using NUL as terminal padding to
> >> the convention of null termination in all cases.
> >>
> >> Ken would probably know for sure whether there's any  truth in the
> >> attribution to ASCIZ.
> >>
> >> Doug
> >
> >
> >
>
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