They were valid column binary.

--
Shmuel (Seymour J.) Metz
http://mason.gmu.edu/~smetz3

________________________________________
From: IBM Mainframe Discussion List [IBM-MAIN@LISTSERV.UA.EDU] on behalf of 
Steve Smith [sasd...@gmail.com]
Sent: Tuesday, June 2, 2020 5:06 PM
To: IBM-MAIN@LISTSERV.UA.EDU
Subject: Re: Punched cards and character set

That's plausible, I think.  While there are plenty of adjacent punches in
the full 256-characters, I'm sure most cards were mostly alphanumeric only,
and it might pay to make them as strong as possible.  I remember seeing
some cards that were punched in every position; those were very delicate,
and definitely couldn't survive a pass through a card reader, regardless of
the fact they had no validity at all.

sas

On Tue, Jun 2, 2020 at 4:55 PM Jesse 1 Robinson <jesse1.robin...@sce.com>
wrote:

> I haven't seen this mentioned. The punch card codes for letters went like
> this:
>
> A - I rows 1 - 9
> J - R rows 1 - 9
> S - Z rows 2 - 9
>
> So why was S assigned to row 2 instead of row 1? The answer I was taught
> was that row 1 was  too close to an adjacent location. The punching/reading
> devices and card stock of the day could not reliably handle punches that
> close together, so row 1 was skipped for the third alphabetic sequence.
>
> What's amusing is that this pattern was carried over to EBCDIC. The code
> for S likewise skips a possible combination: D9 to E2; 'E1' is not assigned
> to an alphabetic character.
>
>

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