[TUHS] v7 K&R C

Dave Horsfall dave at horsfall.org
Tue May 19 17:41:31 AEST 2020

On Mon, 18 May 2020, Peter Jeremy wrote:

> 8-bit bytes, 32/64-bit "words" and 2's complement arithmetic have been 
> "standard" for so long that I suspect there are a significant number of 
> computing professionals who have never considered that there is any 
> alternative.

You haven't lived until you've dealt with a 1's-complement machine i.e. -0 
!= 0 ...  To be fair, it was *mostly* normalised.

>> Yep, I think that is the real crux of the issue.  If you grew up with 
>> systems that used a 5, 6, or even a 7-bit byte; you have an 
>> appreciation of the difference.
> I've used a 36-bit system that supported 6 or 9-bit bytes.  IBM Stretch 
> even supported programmable character sizes.

Ever tried a Univac or a Honeywell?  I don't remember the exact details, 
and I prefer to keep it that way...

> The Alpha was byte addressed, it just didn't support byte operations on 
> memory (at least originally).  That's different to word-oriented 
> machines that only supported word addresses.  Supporting byte-wide 
> writes at arbitrary addresses adds a chunk of complexity to the 
> CPU/cache interface and most RISC architectures only supported word 
> load/store operations.

I had to support an old Alpha once; that was one of the reasons why I was 
happy to leave the joint.  We had just one customer who used an Alpha, and 
thus we/I had to maintain the thing.

And don't even ask me about HP-UX (just as well that they weren't called 
Packard-Hewlett), nor Xenix, nor early Slowaris, nor National Cash 
Registers, nor...

Excuse me, I now have to take my sleepy pills :-)

-- Dave

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