[Simh] Announcement: back10

[Johnny Billquist]

On 2017-02-19 10:40, Lars Brinkhoff wrote:
> Johnny Billquist wrote:
>>> So one 36-bit word AAAAAAABBBBBBBCCCCCCCDDDDDDDEEEEEEEF becomes the five
>>> octets 0AAAAAAA 0BBBBBBB CCCCCCC 0DDDDDDD FEEEEEEE.
>>
>> I think you forgot one 0 before the Cs. :-)
>
> Oh, yes.
>
>> But ok, such an encoding would work. But then your PDP-10 7-bit ASCII
>> files might not truly convert into 8-bit ASCII files... That final bit
>> can be a zero or a one... Some code on a PDP-10 did use that last bit
>> as well, when playing with 7-bit text, if I remember right.
>
> That's right.  I understand some programs encoded a line number in a
> word with the final bit set.  But I would not call those pure text
> files.
>
> I never heard of any other kind of text files with the final bit set.
> But there could be.

I'm trying to remember if there were some who, for example, indicated 
that this was the final word by setting the high bit. I'm sure someone 
like Rich can chime in and tell if he know of any examples.

>> But I don't know how important you think the property of retaining
>> text file "compatibility" is.
>
> If you were to display those converted files with line numbers, I guess
> you would see five strange characters at the beginning of every text
> line.

Yes.

> I propse that handling this would be done outside of a 36-bit <-> octet
> transformation.  Same as line ending conversion between CRLF and
> newline.

By "newline", I assume you mean LF. :-)
After all, there is actually no character named newline.
Although you might also be meaning whatever newline convention used on 
whatever system you might be running on, in which case it might 
sometimes be left as CR+LF, sometimes converted into just an CR or an 
LF, and for some systems might be something completely different.

But if we're getting back into that you need a tool to convert the text 
for local usability, then you loose that whole point about the suggested 
format as transparently giving you the text again, and you might as well 
go with another format that is a bit more compact?

	Johnny

-- 
Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: bqt at softjar.se             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol