Terminated: unknown
This series of programmable calculators (TI SR-52, TI SR-56, TI 57, TI 58, TI 58 C, TI 59) really set the tone of most programmable scientific calculators to follow. But they also clearly borrow from the fabulous HP calculators that came before them.
The TI 59 has volatile memory, but memory strips can be used to store user programs and to load user programs or commercially available programs.
There’s an excellent web page on the TI 59 which does however claim the TI 59 is the first "real" programmable calculator in the world, which obviously isn’t true. The first "real" programmable calculator in the world is pre 70s, and the very first hand-held programmable calculator was made by Hewlett Packard, that being the HP 65.
Still, take a look at the TI 59 site by going to http://www.ti59.com (link validated 2024-01-13).
The programming instructions of this calculator include flags (which could be used for a number of hidden functions as well), indirect addressing, subroutines,
Thanks for this rather nice addition to my collection, Alexander Veenstra!