Punch cards were used as early as the 1700s to program textile looms or player pianos.  By the early 1900s, they were used to store and process data in the precursors to modern computers. In fact, IBM was originally called the Computing Tabulating Recording Corporation and produced machines for creating and manipulating punch cards well into the 1970s.

Programmers using punch cards either used a keypunch to enter their programs one line at a time or would send handwritten sheets to an operator for entry.  The stack of cards they received after this painstaking process was completely untested.  The programmer would then have to give their deck to another operator and wait until computer time was available for the program to be run.  Once it did run, they got a paper print out of any output, often an error.

How different punch card codes work.

Check out a cultural history of the punch card.

Write out your own cards using different codes.

There’s even art made of punch cards.