My original HP 28S from 1988 died a couple of years ago. I've been trying to get by with an HP 48GX simulation app on my phone but I missed the tactile feel of the keys and the muscle memory of almost 30 years using the 28S. When I found a used 28S in good condition (the battery covers are susceptible to breaking) I jumped on it. I just wish that I would've bought a replacement sooner.
Verified purchase: Yes
This calculator is the beginning of a brave new world for Hewlett Packard scientific ones. New way of programming, viewing the "infinite" stack, graphing capability and much more. This calculator took HP to a new level beating all others. You must get one HP 28s if you can.
Verified purchase: Yes | Condition: Pre-owned
My 30-year old HP28C died recently, the best calculator ever, except for the 28S upgrade, which has more RAM, so I was happy to find the 28S online used, and seems in great condition, manuals as well. I can't possibly list a fraction of the features of the calculator, but having a full alphabet keyboard is great even if you have to get used to it being in alphabetical order. A friend said no one needs calculators since phone apps can do it all, but that's simply not true, and having a dedicated calculator is simply more convenient than finding apps, and friendlier than touch screen buttons.
Verified purchase: Yes
The 28s dates to about 1990. This is my third or fourth one of these. Bottom row of keys quit on the last one. I just buy another one when this happens. This particular one was hardly used.
Verified purchase: Yes
This is a great calculator. It takes the RPN concepts and brings them forward into a Forth-like programming experience. It is also more compact than the newer HP48 type calculators and has a dedicated alpha keyboards.
Verified purchase: Yes | Condition: Pre-owned