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The first desktop programmable calculators were produced in the mid-1960s by Mathatronics and Casio ( AL-1000 ).

These machines were, however, very heavy and expensive.

The first programmable pocket calculator was the HP-65, in 1974 ; it had a capacity of 100 instructions, and could store and retrieve programs with a built-in magnetic card reader.

Two years later the HP-25C introduced continuous memory, i. e. programs and data were retained in CMOS memory during power-off.

In 1979, HP released the first alphanumeric, programmable, expandable calculator, the HP-41C.

It could be expanded with RAM ( memory ) and ROM ( software ) modules, as well as peripherals like bar code readers, microcassette and floppy disk drives, paper-roll thermal printers, and miscellaneous communication interfaces ( RS-232, HP-IL, HP-IB ).