After searching some topics w.r.t. Mainframes, YouTube suggested a video about Punchcards to me (that suggestion in and of itself is quite devastating for mainframes, isn’t it?). It was informative, but left me wondering about the encoding of the punchcards: which combination of holes in a column encodes which character?
Luckily, the video mentioned that the system was invented by Herman Hollerith. This supplied a very good search-term to find out more. I quickly found the virtual keypunch, where you can create images of punchcards. This page also contains a detailed description of the encoding.
I also found a few videos of the described devices in action: a keypunch, a collating machine and an IBM 604 with an IBM 521 punchcard reader. I considered aquiring a punchcard reader – They might be useful (or at least decorative) – and since they were so common and are so out of fashion, I assumed they should be affordable, but they can seemingly only be found in museums.
I came across a hobbyist project where they read punchcards visually from pictures. For a while, I thought about building such a machine (or an electronic one like this) myself, but found that it would be much simpler to just use a scanner with a paper-feeder.
I did implement our own version of the image recognition software, so we can now offer our clients to digitize their punchcards.