
Repairing a 1960s-era IBM keypunch: controlled by mechanical tabs and bars - sohkamyung
http://www.righto.com/2017/12/repairing-1960s-era-ibm-keypunch.html
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userbinator
It's interesting to see that the number keys are almost exactly in the same
spot as they are in the integrated numpads of modern laptops' keyboards,
although the layout is "telephone style" with 123 at the top.

 _Since each character can have punches in any of 12 rows, you can think of
cards as using a (mostly-sparse) 12-bit encoding._

The sparseness of early punched-card formats has always seemed a little odd to
me --- instead of storing up to 960 bits per card, this encoding only holds
480 bits (80 columns * 6 bits/63 characters each.) Perhaps people just didn't
understand binary very well at the time?

The way that the mechanism works also reminds me of early teletypes --- they
encoded and decoded characters using a similar system, essentially doing
serial/parallel conversion entirely mechanically. Here's one example:

[https://kb8ojh.net/station/teletype/](https://kb8ojh.net/station/teletype/)

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jordanb
People understood binary perfectly! This was only about 50 years ago!

It's a function of the electromechanical technology: It's a lot easier and
more reliable to have a wheel with ten index positions on it than to have four
wheels with two index positions.

Many early electronic computers used binary coded decimal as a bridge between
the electromechanical and the purely electronic worlds.

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nerdponx
Those keycaps are gorgeous.

What does it feel like to type on?

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ams6110
Slow. You can only press one key at a time. Like an old manual typewriter.

