Complex sentence: For example, in the 1960s, they used an IBM Card on which a few lines could be written which would be transcribed into another card which looked the same but which had holes in it which a computer or "unit record" machine could read.
Split into simpler sentences: For example, in the 1960s, they used an IBM Card on which a few lines could be written which would then be transcribed onto another card. The other card looked the same but had holes in it which a computer or "unit record" machine could read.