On Tue, Jun 27, 2017 at 4:02 PM, Keith Medcalf <kmedc...@dessus.com> wrote:
>
> > If an implementation "uses" 8 bits for ASCII text (as opposed to
> > hardware storage which is never less than 8 bits for a single C char,
> > AFAIK), then it is not a valid ASCII implementation, i.e. does not
> > interpret ASCII according to its definition. The whole point of
> > specifying a format as 7 bits is that the 8th bit is ignored, or
> > perhaps used in an implementation-defined manner, regardless of whether
> > the 8th bit in a char is available or not.
>
> ASCII was designed back in the days of low reliability serial
> communications -- you know, back when data was sent using 7 bit data + 1
> parity bits + 2 stop bits -- to increase the reliability of the
> communications. A "byte" was also 9 bits. 8 bits of data and a parity bit.
>
> Nowadays we use 8 bits for data with no parity, no error correction, and
> no timing bits. Cuz when things screw up we want them to REALLY screw up
> ... and remain undetectable.
>
Actually, most _enterprise_ level storage & transmission facilities have
error detection and correction codes which are "transparent" to the
programmer. Almost everybody knows about RAID arrays which (other than
JBOD) have either "parity" (RAID5 is an example) or is "mirrored" (RAID1).
Most have also heard of ECC RAM memory. But I'll bet that few have heard
of RAIM memory, which is used on the IBM z series of computers. Redundant
Array of Independent Memory. This is basically "RAID 5" memory. In addition
to the RAID-ness, it still uses ECC as well. Also, unlike with an Intel
machine, if an IBM z suffers a "memory failure", there is usually the
ability for the _hardware_ to recover all the data in the memory module
("block") and transparently copy it to a "phantom" block of memory, which
then takes the place of the block which contains the error. All without
host software intervention.
https://www.ibm.com/developerworks/community/blogs/e0c474f8-3aad-4f01-8bca-f2c12b576ac9/entry/IBM_zEnterprise_redundant_array_of_independent_memory_subsystem
?
--
Veni, Vidi, VISA: I came, I saw, I did a little shopping.
Maranatha! <><
John McKown
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