[TUHS] Re: origin of null-terminated strings

[Phil Budne <phil@ultimate.com>]

> From: Bob Supnik
> Tim can comment on the PDP10.

MACRO10 (the DEC PDP-10 assembler) had the ASCIZ directive,

I don't see it in the May 1964 MACRO6 (PDP-6 assembler) document at:

http://bitsavers.trailing-edge.com/pdf/dec/pdp6/F-64MAS_MACRO6_Assembly_Program_May64.pdf

Nor the February 1965 version:
http://bitsavers.trailing-edge.com/pdf/dec/pdp6/DEC-6-0-TP-MAC-LM-FP-ACT01_MACRO-6_Assembly_Language_Feb65.pdf

But it does appear in the May 1965 MACRO-6 manual:

http://bitsavers.trailing-edge.com/pdf/dec/pdp6/DEC-6-0-TP-MAC-LM-FP_ACT02_MACRO-6_Assembly_Language_May65.pdf

Which has the fullly trifuricated character packings:

ASCII/ASCIZ:	7 bit bytes, with the low order bit left over
		(set at the start of lines in files to indicate a Line
		Sequence Number metadata for line number based editors)
SIXBIT		"6-bit ASCII" -- ASCII characters 040 thru 0137
		stored as 00 thru 077 in six six bit bytes
RADIX50		6 characters from a 40 (050) character character set
		(plus four flag bits) used to store symbol tables
		https://en.wikipedia.org/wiki/DEC_RADIX_50#36-bit_systems

And ASCIZ is used in listings of the PDP-6 "T.S. Executive" version
1.4 dated 8-18-65:

http://bitsavers.trailing-edge.com/pdf/dec/pdp6/tsExec1.4/COMCON.pdf

COMCON is "COMmand CONtrol" -- the top level command interpreter built
into the monitor (the file name was retained into the later days of
TOPS-10), and messages output to the user use ASCIZ directives.

And to tie the thread back (closer) to the list subject, the "sub
title" headers in the above assembler listing file are "T. HASTINGS
8-2-65" (who I believe is Tom Hastings), which also appears in many
other files, including the job scheduler:

http://bitsavers.trailing-edge.com/pdf/dec/pdp6/tsExec1.4/CLKCSS.pdf

*AND* T. Hastings also appears as an author of the CTSS scheduler:

https://softwarehistory.csse.rose-hulman.edu/index.php/ctss-scheduler/
(in the "Full Code" section):

          :R******TIME SHARING SCHEDULING ALGORITHM***********
          :R    T. Hastings and R. Daley
          :R    Minor Modifications by G. Schroeder when NEW
          :R    I/O Package Installed....Summer, 1965