This calculator was programmable using a magnetic card reader/writer. Users were able to write and save programs of up to 100 lines. Pre-programmed cards were available with magnetic media on one side and a writable surface on the other. The card was pased through the calculator and then slid into a slot above the top row of keys, enabling the writable side to be used as the key labels. The HP 65 was also used by the Apollo astronauts in space in the 1970s.
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