[Simh] Announcement: back10

[Johnny Billquist]

On 2017-02-19 10:23, Lars Brinkhoff wrote:
> Johnny Billquist wrote:
>>> If we're casting votes, I'd put mine on ASCII-ANSI.  Because:
>>>
>>> - PDP-10 7-bit ASCII files are transformed into 8-bit ASCII files.
>>> - It's simple.
>>> - Words are always encoded into 5 octets.
>>
>> With one bit lost... (7*5 == 35)
>> Maybe I'm missing the point here, but if you want to handle anything
>> except 7bit text, then I think this format would fail...
>
> The format I've seen called ANSI-ASCII does handle the last bit.  It
> puts it at the top of the last octet.
>
> So one 36-bit word AAAAAAABBBBBBBCCCCCCCDDDDDDDEEEEEEEF becomes the five
> octets 0AAAAAAA 0BBBBBBB CCCCCCC 0DDDDDDD FEEEEEEE.

I think you forgot one 0 before the Cs. :-)

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.

But I don't know how important you think the property of retaining text 
file "compatibility" is.

	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