[Info-vax] C limitations, was: Re: VMS process communication

[Johnny Billquist]

On 2023-04-13 21:20, bill wrote:
> On 4/13/2023 5:12 AM, Jan-Erik Söderholm wrote:
>> Den 2023-04-12 kl. 18:26, skrev bill:
>>
>>> But that is only during communications.  I am not aware of any program
>>> that computed the value of a character in transit and cared what that
>>> value was.  Pr1me set the values in their firmware forcing all programs
>>> in any language to deal with an ASCII set that had values from 128 to
>>> 255.
>>
>>
>> Now, if the highest bit really was a parity bit, you would end up with
>> values in the whole range 0-255, depending on the number of 1's in the
>> lower 7 bits.
>>
>> But maybe that wasn't a real parity bit...
>>
> 
> They always referred to it as "Mark Memory Parity".  Knowing the
> function of parity I never understood just what they thought it did.

The "memory" part here, makes no sense. This is communication we're 
talking about (see your own quote).

But with that said, mark parity do not make much sense, I agree. It 
ensures that at least one bit is set in any transmitted byte, and it 
helps confirming that you are indeed running at the correct speed, but 
that's about all the value it adds.

   Johnny