Terminated: unknown
The TI 58, TI 58 C
and the TI 59 are
programmable calculators that can be extended using Solid State Software
Libraries. There is a small slider at the back where these Solid State Software
modules can be inserted. The module shown here is the default MASTER LIBRARY MODULE.
The TI 58 has volatile memory. In other words, all programming is lost when the calculator is switched off.
This series of programmable calculators (SR-52, 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 programming instructions of this calculator include flags (which could be used for a number of hidden functions as well), indirect addressing, subroutines, ...
I actually used this calculator for quite a while, until its battery pack finally gave up.