3 ms·

Blurb on punch cards, they are not binary! https://retrocomputing.stackexchange.com/questions/16112/what-did-code-on-punch-cards-do-with-the-other-six-bits-per

• masswerk 5y ago
  Fun fact, there were binary punch cards, both row binary and column binary. These were used prominently for system software (startup, diagnostics, etc). The problem with punch cards is that they lose integrity, if there are too many punches (holes). So the usual variants of Hollerith code and EBCD worked around this by applying never more than 3 punches per column. Mind that punch cards were a major storage format even in the interwar years, long before computers, when they were filling entire warehouses with accounting data, etc. And you wanted these to be somewhat robust as they were subject to rather rough treatment by purely electro-mechanical appliances. E.g., WWII was mostly payed for by punch card accounting on the US side. (Later formats on the IBM S/360 and S/370 used much larger sets and therefor more fragile encodings, including the full ASCII set.) Punch cards were actually legacy technology in the computer age, right from the beginning. E.g., the Univac I, the first computer commercially available in the US, used high-speed steel tape. IBM, on the other hand, favored punch cards and built their growing imperium on the compatibility with existing storage formats (which was a strong argument), while other vendors eventually gave in, more or less reluctantly.