Classification tree for calculator logic

With this tree you can classify electronic calculators by logic. It works with all calculators with "=" key, with scientific calculators and even with simple 4-function calculators (not with RPN-calculators).

There are 81 (!) classes discovered.

Check it out. Type in the "input" and serch for the "result". Clear the calculator. Do it again until you find the result "class"

If the calculator has not a "=" key, please use the "+=" key. Calculators with a "K" switch for constant-function are working in two classes (with constant and without constant function).

Download the tree

Almost all modern 4-function calculators have class "FA". Many old calculators are in classes "BA", "EBB" and "GBBB". Many Soviet calculatos have class "EBB".

Please help me to enlarge the tree. If you have suggestions or new classes please send me an email:

Thank you for your assistance