4 Feb
2021
4 Feb
'21
5:46 a.m.
System/360s, or at least 370s, could do ASCII perfectly well.
When we started UNIX on VM/370, it was clear to us that we wanted to run
with ASCII. But some otherwise intelligent people told us that it *just
couldn't be done* - the instructions depended on EBCDIC.
But I think there was only 1 machine instruction with any hint of EBCDIC -
and it was an instruction that no-one could imagine being used by a
compiler,
Of course, plenty of EBCDIC/ASCII conversions went on in drivers, etc, but
that was easy.
On Wed, Feb 3, 2021 at 12:09 PM Dave Horsfall <dave(a)horsfall.org> wrote:
On Wed, 3 Feb 2021, Peter Jeremy wrote:
--
- Tom
I'm not sure that 16 (or any other 2^n) bits
is that obvious up front.
Does anyone know why the computer industry wound up standardising on
8-bit bytes?
Best reason I can think of is System/360 with 8-bit EBCDIC (Ugh! Who said
that "J" should follow "I"?). I'm told that you could coerce it
into
using ASCII, although I've never seen it.
Scientific computers were word-based and the
number of bits in a word is
more driven by the desired float range/precision. Commercial computers
needed to support BCD numbers and typically 6-bit characters. ASCII
(when it turned up) was 7 bits and so 8-bit characters wasted ⅛ of the
storage. Minis tended to have shorter word sizes to minimise the amount
of hardware.
Why would you want to have a 7-bit symbol? Powers of two seem to be
natural on a binary machine (although there is a running joke that CDC
boxes has 7-1/2 bit bytes...
I guess the real question is why did we move to binary machines at all;
were there ever any ternary machines?
-- Dave