6 Oct
2007
6 Oct
'07
7:33 p.m.
On 6 Oct 2007 at 21:52, William Donzelli wrote:
Back to 6 bits. For the type of stuff that the BDP community did, 6
bits per character was plenty.
In that sense, using an 8 bit character was a real waste. Two 6-bit
characters can pack 3 BCD digits--exactly the same efficiency as
S/360 packed decimal--and packing/unpacking is not much different
Six bits also is VERY inefficient for numeric data -
all that stuff
the bank uses. In the 1960s, IBM found this was a HUGE percentage of
what was stored on disk. Yes, you could pack 1.5 BCD digits into six
bits, but then there is a overhead dealing with the translation. The
overhead may be tiny on a per digit basis, but when you need to crunch
zillions of digits per nightly run of the batch...
If efficiency was the primary goal, hollerith cards could have been
punched in column- or row-binary; packing 3 digits per colum, with
leftover codes for sign and point. Think of the trees saved! Yet I
never saw a BDP application do that. Would have been hell on the
punches in any case.
In retrospect,
a 12-bit character would have made a huge amount of
sense--12 rows on a punch card, so nn need for translation hardware
to somehow turn legal and illegal punch combinations into characters.
Once again, very inefficient for character data - at least character
data back then. Too many wasted bits. from converting from packed to zoned decimal.
Cheers,
Chuck