Experiments with Punch Cards

September 12, 2016

In our ongoing efforts to explore and replicate historical humanities computing (where we take replicate to be about interpreting rather than reproducing), Geoffrey Rockwell and I have been experimenting with punch cards; how they worked and how they were used. We’ve created a very simple emulator below. Punch cards were used for data storage and processing until the mid 1980s, they’re essentially stiff paper with holes. Punch cards actually date back to the 19th Century and were used for the 1890′s US, so they predate digital computers by at least a half century. In fact, one thing that intrigued us as we were playing with this interface was the tension between a more decimal-based system (0 to 9 with a couple of extra control rows) and the more binary-based digital processing (0 or 1). A typical punch card had 12 rows to represent any one character, which in fact is potentially very high resolution (12-bit = 212 or 4096 possibilities), whereas the first character sets for computers were at most 4, 5 or 6-bit (64 possibilities).

There were many variants of character sets and punch card systems, but the one below is meant to be closest to correspond to the IBM’s 026 punch card system that used Binary Coded Decimal Interchange Code (BCDIC) to represent 48 characters. This is because we’re especially interested in early uses by Father Roberto Busa.

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