Path: utzoo!attcan!uunet!jarthur!elroy.jpl.nasa.gov!ncar!ico!ism780c!news
From: news@ism780c.isc.com (News system)
Newsgroups: comp.misc
Subject: Re: Punched Cards
Message-ID: <43610@ism780c.isc.com>
Date: 7 Jun 90 20:30:24 GMT
References: <12546@netcom.UUCP> <220@taumet.COM> <12573@netcom.UUCP> <1208@mplvax.EDU> <2219@l.cc.purdue.edu> <7619@tekgvs.LABS.TEK.COM>
Reply-To: marv@ism780.UUCP (Marvin Rubenstein)
Organization: Interactive Systems Corp., Santa Monica CA
Lines: 40

In article <7619@tekgvs.LABS.TEK.COM> toma@tekgvs.LABS.TEK.COM (Tom Almy) writes:
>The IBM 407 Accounting Machine (essentually a printing adding machine for
>punched cards :-) read in the 12 side first.

Actually the cards were read 9 edge first.  On most (if not all) IBM
machines that read cards, the cards were intered 9 edge first.  Card punches
on the other hand processed cards 12 edge first.  An exception was made for
the case of the card punch on the 704 and 709* computer.  On these machines
the punches were also 9 edge first.  This was so a read into a buffer
followed by a write of the same buffer would duplicate the card.

>                                               The accumulators were wheel
>like devices, that worked like odometers.  If you were adding a field to
>this to be a digit parallel design where the digit value is encoded by 
>pulse length. You could also consider the 407 to be a multiprocessing system!

Indeed!  The accumulator wheels could be connected together by wiring a
carry proprgate from one wheel to the next.  Thus the number of accumulators
and their precision was under patch panel control.  RPG was originally
devised as a sort of simulator of the 407.

The encoding was not by pulse length.  Each pulse lasted for exactly the
same time (called a digit pulse time).   It was the time required for the
punched hole to pass a read brush.  The card passed between a copper drum
and a set of 80 side by side brushes. If there was a hole in the card,
current flowed between the brush and the drum.  So the value of a digit
depended on when it occured.  The timing chart in front of me shows the the
digit time for the card reader is about 6 miliseconds.  For the 407
printer, the digit time was about 9.75 miliseconds.

An interesting feature of the 407 was that supplied what was called "print
echos".  A print echo was the 9's complement of the digit printed.  The
computer had an instruction, read printer.  This could be used to read the
print echos for a redundency check of the printer.  However, it most frequent
use was to read time of day.  A digital clock was available that delivered
time in Holerith code.  It was connected to the computer through the printer
via the printers patch panel.  I actually had to simulate the printer clock
for the 7094 immulator that I implemented.

     Marv Rubinstein  -- I really programmed these gadgets