I have photographed here the HP programmable calculators that I have kept since I bought them in the 70s.
They are still complete with accessories and all the many manuals whose contents is perfect even today for their accuracy and usefulness.
The HP41c is programmable through its keys or via the optical barcode reader or by inserting a magnetic card on the card reader. Moreover a series of ROMs modules allow the customization of the calculator and overlay masks configure the keyboard.
HP41c and its following versions remain an unsurpassed masterpiece produced by the company that has practically founded Silicon Valley and which has constituted an example ,unique in the world, for innovations and cultural approach that has pervaded Silicon Valley for decades and until today.