Re: Is ProDOS supported in OSX?

[mjmahon@aol.com (Michael J. Mahon)]

M. Pender wrote:

>Scott Alfter <salfter@salfter.dyndns.org> wrote in message
>news:2%nKa.169806$eJ2.157081@fed1read07...
>...snip...
>
>> With a scanner with an ADF, I'd think that you could automate most of the
>> process of reading in punched cards.  It won't be as fast as a card
>reader,
>> but it'd be faster than anything that would involve manual intervention.
>> (Maybe it'd even do a better job with lace cards than a card reader. :-) )
>
>I think you're underestimating the whole "hanging chads" incident...

I don't think so.

First, hanging chads are made by people, not by properly operating
machines.  In over ten years of working with punched cards, I can't
remember a single incident of data error caused by a partially
punched hole.

Second, most card readers work by either electrical sensing (making
a contact through the hole) or photo sensing (shining a light through
the hole).  All readers pass the card through a "throat" which is
narrow enough to admit only one card.  If a partially punched chad
swung away from the hole, it would be "stripped" by this throat,
and if it swung toward the hole, it would be folded into it and
appear to be a non-punched hole.  In the latter case, of course,
data error would result.

Examination of the throat areas of fast card readers never turned
up any chads that had been stripped in the reading process, so
this confirms that partial punching must be extremely rare.

In dealing with tens of thousands of punched cards that were
punched on keypunches, I never found a non-systematic error
caused by the punch.  (There was a case of a plugged punch
die hole, so that all punches in that row were missing, but
such an error is pretty evident both in physical examination
and in reading the mis-punched data).

In the particular case being discussed, we are probably dealing
with cards that have already been correctly read, and were
stored, and now need to be re-read for archiving.  In this case
I would expect that photo-scanning would be quite accurate
in capturing the data.  If anything, I would be more worried
about mis-feeds and double-picks by the document feeder.

-michael

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