Texas Instruments TI‑25


Brand: Texas Instruments
Model: TI-25
Type: Scientific calculator
Picture: TI-25
Batteries: LR 44 x 2
Lifetime: Introduced: 1978
Terminated: unknown
Notes: Black is beautiful, or at least someone at Texas Instruments must have thought. A very dark design, hard to read when lighting is poor. Called the "Slimline™ 25" in the calculator's manual.

This is a standard school calculator with all the required functions, including statistical functions.

This calculator has some peculiar quirks. For instance, when you press π and then the "EE"-key to add an exponent, it will. No problem. I'm not sure however when you would need π multiplied by a factor of ten.

So to enter π⋅1042 simply type "π", "EE", "4", "2".

Another funny thing is the way it handles the "!" operator. As with all calculators with two-digit exponents it will calculate up to and including x! for any natural x in the range 0 ≤ x ≤ 69. For any natural x > 69 it will produce an error. However, for any natural x in the range 70 ≤ x ≤ 99 it will still try to calculate x! up to the moment it will encounter an internal error. For any natural x > 99 it will immediately give an error without trying to calculate x!. Maybe this way of handling x! has a smaller memory footprint or something.

Thanks for this nice addition to the collection, Michel "Mikki" Waucomont!