This is a simple RPN Calculator which can use on macOS.
How to use
> Green up-arrow is ENTER button
> Stack size can be changed at Preferences.
> You can use multi calculators at same time. Please create new calculator from File Menu.
> Programs trace key operations registered in Preferences.
> You can type numbers and operators with keyboard and numeric pad.
> To use programs and scientific operators, please change to scientific mode from View Menu.