Model: HP 28S
Type: Scientific programmable calculator
Picture: HP 28s
Batteries: Type N x 4
Lifetime: Introduced: 1988
Terminated: 1992
Notes: This is one of those calculators that has so many options and functions that I never really got to know it well. The design of this calculator is beautiful. It folds open and has all common functions on the right, and the less-often-used on the left keyboard. The left keyboard also shows the known object types and examples thereof.

The left keyboard folds back under the right keyboard to leave a handy calculator for every-day usage.

I remember the row there was at the university when this calculator was introduced. For one it does symbolic calculations and has graphical capabilities! But the calculator was too expensive for most students (including myself).

The Hewlett-Packard Company Archives site also has some information on this calculator, see The HP 28C: HP's First Graphing Calculator (link valid 2023-01-07).


This calculator can communicate with peripherals (unidirectional) using its IR output port. I do not own any of them unfortunately.