Hp-21 a constant companion !
I bought my HP-21 shortly after i saw it in Machine Design magazine in 1976. From then on it became my constant companion until appx 1995 or so when it gave up the ghost and would no longer illuminate. Much later on I was overjoyed to find an e-version replica of my faithful pocket resource, though he was no longer needed after I retired from field work. Today I have switched to Android apps and regret that I cannot find a replica of this trusty device,,,,, and would like to ask IF THERE IS ONE (?) or one under development? All iOS products havre become too expensive and unreliable !
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50 years later - Thank you
Many thanks for giving me the opportunity to use this RPN calculator. I bought my very first HP 21 C in 1972 when studying at Polytechnic School of Cameroon. 50 years later, I am still very happy and proud using RPN devices and programming Common LISP.
Hate that high visibility setting
To me, the value of this app (and all the other RPN apps that I have) is the authenticity of them. Otherwise, there are a gazillion calculators with different sized displays out there with RPN.
Instead of making the X view high visibility, why not enlarge the calculator itself to be full screen (even getting rid of the stack view optionally)
Then Iβll go back to 5 stars again which otherwise this app absolutely deserves.
Instead of making the X view high visibility, why not enlarge the calculator itself to be full screen (even getting rid of the stack view optionally)
Then Iβll go back to 5 stars again which otherwise this app absolutely deserves.
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Response from developer
For some thoughts on sizing, see: https://www.bigcatos.com/BigCatOs/go-2x-scirpn/go-21sizehistory.html The App seems to be sized as authentically as possible. The stack view is and always has been optional, simply hide it forever, as described in the documentation. The High Visibility Display setting is optional and disabled by default so you never have to see it, thus the calculator remains in its pristine state. This option has been requested by two groups of users: as an Accessibility assist for those with diminished vision, and folks who use the App outdoors as part of their work.
Works fine
Wonderfull app that I use daily... A recent display bug was corrected and now everything is OK. Just one regret : why the go-29 doesnβt exist !!!
Response from developer
I am starting on HP-29c, but it will be a while before completion!
Lean & Mean
Iβve been using this app for a number of years and have been very satisfied and figured it was time I gave it a review. As an engineer, I loved my HP-21 and was sad when it finally died many moons ago. I searched and searched for a simple reverse Polish calculator app, but could never find a good one. This is a good one. A clean but elegant emulation of a classic design. Highly recommended.
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My thoughts on the HP 21 app
I have an hp 21 that we purchased new and I've always loved it, not only for the RPN feature but for the simplicity. This is such a nice app for anyone familiar with the HP line plus it shows the stack. Highly recommend.
Return with us now to the days of yesteryear
I bought an HP-21 during my third semester of college in 1976. At that time they were still teaching students how to use a slide rule.
The app is a very good reproduction of the HP-21's look and functions/functionality. I has the functions I want and doesn't have a lot of functions that I don't use. It has a useful Help file.
The app is a very good reproduction of the HP-21's look and functions/functionality. I has the functions I want and doesn't have a lot of functions that I don't use. It has a useful Help file.
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HP 21 workhorse of the 70's
This calculator was the best around in 1975 and saw me through college in electronic engineering. It is a RPN (reverse polar notation) unit that's is a powerful method of doing calculations without the need for brackets and "equal" buttons. Once one get used to entering the numbers on a stack and then choosing an operation, it makes for fast and logical processing.
In 1992 I up graded to a HP 48S which can do much more mathematics than I am able to understand. A truly wonderful machine, but with this comes complexity and is not as easy to use as the 21 which does almost everything I need. I love the HP 21 and glad I can enjoy it on my IPad.
In 1992 I up graded to a HP 48S which can do much more mathematics than I am able to understand. A truly wonderful machine, but with this comes complexity and is not as easy to use as the 21 which does almost everything I need. I love the HP 21 and glad I can enjoy it on my IPad.
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Δ°t's like the good old days
Great calculator, I use it everyday in my engineering office work. Money well spent.
Nice
Loved my 21; spent many hours with it in college. Doesn't charge anymore, but I still keep it around. This is an excellent reproduction. And then some.
BRILLIANT!!!!!!!
I've been after a 21 for decades. This is probably the closest I'll ever get to owning an original. Love this calculator for many sentimental reasons.......would be great if there was a way to include the full user manual as well. Great job!!!
Great Improvement on a Classic Calculator
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.
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5 star emulation of the HP21
I still have a working HP21 and use it almost daily - this app puts it on all my iHandhelddevices. It is just like the real thing - except with visible memory and stack (that you can hide under the calculator if you want to). I have bought several RPN calculators for iPhone - this is the first to not dissapoint.
Side note... The Hewlett Packard 20 series calculators (Woodstock) were released in the mid 70's, at the time they were state of the art technically and in terms of industrial design. HP developed far more powerful calculators, but the HP21 & 25 remain as a benchmark for pocket scientific calculators - it's worth getting a real one as well.
Side note... The Hewlett Packard 20 series calculators (Woodstock) were released in the mid 70's, at the time they were state of the art technically and in terms of industrial design. HP developed far more powerful calculators, but the HP21 & 25 remain as a benchmark for pocket scientific calculators - it's worth getting a real one as well.
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HP 21 vintage
Very good ergonomics and in m'y opinion one of the very best HP virtual calculator for iPhone . Highly recommanded for RPN addicts for every day use!
Delightful
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.
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Best RPN calculator ever!
This RPN calculator is so realistic that it's like using the 1975 HP-21. Having the stack registers and memory displayed at all times is a bonus. The ability to move the calculator around on the desk top makes it suitable for left and right-hand use. How great it would be to have the HP-25 (same form factor) with its 49 programming steps visible, too. Hope the author considers it,
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Great implimentation!
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.
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Great RPN 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!
Reverse Polish Notaion rises again!
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!
