[Simh] Question about card readers.

[Rich Alderson]

> Date: Wed, 25 May 2016 19:54:22 -0400
> From: Richard Cornwell <skyvis at sky-visions.com>

>>> Date: Wed, 25 May 2016 18:07:15 -0400
>>> From: Richard Cornwell <skyvis at sky-visions.com>

>>> I am asking for feedback on how to handle Punched card input. I am
>>> wondering about how to handle the case of reading a greater then 80
>>> character record on a 80 character punch card. Should characters beyond
>>> the end of the card be truncated, or should they continue on the next
>>> card.

>>>    Any ideas? 

   [I wrote:]

>> Would you mind expanding on the query a bit?  Since an 80-column card
>> can't store more than 80 characters' worth of data, how can there be
>> anything to be truncated or continued in a read?

>   Sometimes there is extra stuff in a line, or sometimes records come
>   from other sources. For example the IBM 7090 used 84 character
>   records on tape. But the native reader could only read in 72 columns.
>   Sometimes when editing a file, you end up putting blanks at the end
>   of the line, that you might miss. 

>   One use for producing longer then 80 character records at a punch
>   would be to include the stacker information at the end of the record.
>   The deck could then be read directly back in without manual editing. 

>   I am going to be adding card reader/card punch support to my KA10
>   simulator soon now and wanted to get some feedback on how to handle
>   this.

"Extra stuff in a line"?  "Records on tape"?  Color me confused.

I began my programming career on an IBM 1401 using 80-column Hollerith
cards and a 132-column 1403 printer, so I have some experience with fixed-
width devices.

A card is 80 columns wide.[1]  (OK, there were special purpose 51-, 60-, and
66-column cards, but the data on them would fit into 80 columns.)  There is
no way to put more than 80 columns of data onto a Hollerith card.

Tape is a different medium, and has nothing to say about how cards behave.
(By the way, I had a look at the IOCS manual for the 7090, and the only
reference I see to "84 character records" on tape refers specifically to
tape labels, which are metadata on the tape, and not even required.)  The
fact that the card reader only passed 72 columns' worth of data to the
processor again has nothing to do with how many columns of data are present.

I agree with Bob about adding metadata to the card image, so nothing's
needed for that.  Recording "column binary" data in 160 characters is an
implementation decision, but it does not mean that there are more than 80
columns on the physical card which is represented.

So what do you mean by "extra stuff on a line"?  There are no lines, only
80-column cards.  What are you trying to represent here?

                                                                Rich

[1] OK, there are the Univac "90-column" cards, which are the same
    dimensions as the IBM Hollerith card.  They record 90 6-bit characters
    across 45 columns, upper and lower halves of the card.  The holes are
    circular and larger than the rectangular IBM holes.  They would have to
    be special-cased in SimH.