The MACRO-10 assembler used a keyword ASCIIZ to store that 7-bit/1-bit-wasted ASCII format.

MOVEI 0,[ASCIIZ /Hello there
/]

for example. It was the defacto standard for null-terminated ASCII strings.

When I later moved to C on 8/16-bit computers, I remember thinking "what's with this signed 8-bit char thing?" ;)

There was also SIXBIT - almost everything ASCII had, but only upper case. The filesystem used that for filenames and extensions, and it was used in a few other areas. So any library calls like open() would have had to convert the ASCII filename to SIXBIT before doing any monitor calls.

On 9/18/2017 9:50 AM, Clem Cole wrote:


On Sun, Sep 17, 2017 at 11:22 AM, Arthur Krewat <krewat@kilonet.net> wrote:
I have a C compiler for TOPS-10 that I got off the Internet back in 1988. Still haven't messed around with it enough to get it to run, but ...

​There was a PDP-10 C compiler in the late 1970s, that was kicking around CMU, MIT and Stanford which we used to write backup10 and ​and an implementation of tar.   IIRC, it was based on the the Ritchie front end and was V6 in syntax (i.e. pre-V7 or typesetter C - aka 'White Book).   I've forgotten the rules of chars, but I remember you had to be careful.   I think it was 4 9-bit chars to transfer things (4*9=36 bits), but I think I remember there were cases on output that it wanted to wash it through a 7-bit PDP-10 char (5*7+1 =36bits) which was the 'norm' for most languages like SAIL, BLISS et al.

I did not mess with much, but that time, I was transitioning from the 10's to UNIX by that time.   I added support for the -20's dumper tapes to backup10 which were almost but not quite the same.  But that was the last I messed with it.   Mike Accetta and Fil Aliva (of CMU Mach fame) I remember had their had in that subsystem, at one point.  And of course Danny Klein is always a good one from those days to ask too. I'll see if I can dig them up and ask.