GO-21 SciRPN

Any 50 something-year-old should appreciate the nostalgia of this beautiful application. Brings back memories of my school daze..... Makes me want to find my old Jethro Tull albums.... Excellent job on a classic calculator!

Perfect implementation. It is fabulous to have access to the RPN calculator I used most of my career (and still have and use) and not have to learn another model!

A Classic! Just like my old HP-21 -- even to the realistic LED display. I have at least a dozen RPN calculators (both real and as iPhone Apps). Many are much more complex with lots of advanced features. But, if you are a RPN user, this HP-21 App is just perfect for going to for quick straight forward calculations. It has become my most used calculator.

I was 18 when the HP-21 was released but did not buy one until years later when I was in College (I was in the US Army until age 21). This iPhone version is delightful to use and it works very well on my iTouch with the latest OS and indeed fast app switching works well. The display and buttons are easy to see and use. Swiping to see the entire stack is useful. Thanks for writing this app.

I used an HP-21 calculator in college back in the late 70's and early 80's. The rectangular-to-polar and polar-to-rectangular conversions were a lifesaver for an engineering student back then. This app is a great update to the original. The built-in help is excellent too. The ability to "commify" numbers is my favorite added feature. The developer is also very responsive.