Calculators that allow direct operations on data stored on persistent storage?

[Garth Wilson]

The HP-71 does what I think you're looking for. Files reside in RAM (not flash or EEPROM), and can be expanded or contracted easily, and it's pretty transparent from the user's perspective. I have an extra 160KB of RAM in mine, 96KB in a card-reader-port module, and 64KB in a front module. (I would like to have gotten the full 160K in the card-reader-port module, the maximum available at the time, but it was outside my budget.) Each module goes in 32KB "ports," however many it takes to fill up the capacity of the module. Any memory port that is "claimported," ie, made part of the basic RAM, can be used directly for variables too, not just files. Claimported memory is not divided into 32K sections. They're just all run together.

Since I use my 71 so little now (as I mostly just use my 41cx), the 71's batteries last many years with all this additional RAM in it. CMOS RAM's power-supply current when it's in standby mode is only the leakage current, meaning probably picoamps or femptoamps. In my work in about 1986, I noticed an 8KB SRAM IC holding its data from one day to the next with only a 10uF capacitor for a power supply. If the current were even 1uA, a 10uF capacitor would go dead in ten seconds. I did not stretch it out to see how long it would go though, like a week, month, or whatever.