Comparison

RPN vs O'der stack

Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.

Head to head
About

RPN

This app simulates a legendary vintage scientific calculator, offering a "live" display of its internal states and a virtual paper tape printer. It allows loading and running original sample programs, with advanced features that can be switched off for an authentic experience.

Highlights
  • Live display of stack and registers
  • Virtual paper tape printer
  • Email or print paper tape
  • Cut/copy/paste display value
  • 30 selectable background images
  • Non-volatile memory
Features
Read full description

RPN-67 NP is the non-programmable version of RPN-67 Pro, the first complete simulation of Hewlett-Packard's HP-67 legendary programmable calculator for iOS. Produced from 1976 to 1982, the HP-67's capability to store programs on magnetic cards, wide array of functions, merged keycodes, indirect addressing and other enhancements made it a huge success among scientists, engineers and other professionals. Thousands of programs were written for it. RPN-67 NP allows you to load and run 25 original HP sample program cards. It lacks the program creation and card management features of the Pro version, as well as its massively expanded array of functions and operations. Apart from these restrictions, RPN-67 NP is a very capable vintage scientific calculator. Features: • "Live" display of stack, memory registers, program counter, flags • Virtual paper tape printer • E-mail or print the paper tape • Cut/copy/paste display value • 30 selectable background images, even add your own. More features the HP-67 never offered: • Non-volatile memory - stack, registers, program • Status indicators for prefix keys (f, g, h, STO, RCL, GTO, DSP) • Keycode-to-command translation while single-stepping a program • Cancel SST or BST operation by sliding your finger off the depressed key All advanced features may switched off with a single setting, allowing you to experience a real HP-67 as closely as possible. For more information visit the RPN-67 website: cuveesoft.ch/rpn67

About

O'der stack

Features
Read full description

O'der stack is a scientific calculator that is precise for up to 38 digits and is highly flexible. It can be used for various purposes, from learning to professional use, and has many functions that are convenient when mastered. The formulas described can be saved together with the results of the calculations and easily shared among members. Also, labels and memos can be set for formulas as well as each item that makes up the formulas. For example, by adding the label "radius" to "50" in 2 x 50 x π, it is possible to make the meaning of the formula even clearer. It is also perfect for entering explanations of formulas as memos and using them as tools to assist in learning. O'der stack offers two plans, the Pro plan which offers unlimited use of all functions, as well as the Free plan which makes it usable as an easy-to-use scientific calculator. —Functions— 1. A powerful editing function that allows partial overwriting of values without erasing the formula 2. Label and memo functions to support the understanding of formulas 3. A clipboard function that allows formulas to be pasted in notebooks, etc. 4. Setting the precision of calculations from 0 digits to 38 digits 5. Setting units (degrees/radians) for trigonometric functions 6. Setting the format of displaying results of calculations (normal notation, scientific notation, and percentage notation) 7. Basic functions (exponentiation and nth root) 8. Undo function —Pro plan— Please download O'der stack and try out the Pro plan for free for seven days. In addition to all the functions in the Free plan, the Pro plan allows for the activation of even more convenient functions. 1. Functions to save and load formulas and calculation histories 2. Function to share formulas and calculation histories 3. A sub-formula function that allows for the breakdown into several formulas and simple entry 4. 18 types of versatile and widely-used functions 5. 652 highly precise numerical and physical constants and observed values 6. Setting the format of displaying results of calculations (binary, octal, hexadecimal)        - Each item can be selected from 8bit, 16bit, 24bit, 32bit, 64bit and 128bit.        - Supports negative values and decimal points.        - Negative values are displayed in complement. After the free trial has ended, if you would like to continue to use the Pro plan, a purchase of a non-autorenew-subscriptionis required. For a subscription, you can choose either a monthly purchase or yearly purchase, and the yearly purchase allows you to enjoy a discount worth two months of monthly purchases. Payment will be charged to your Apple ID account at the confirmation of purchase. If you purchase a plan during the effective period, it will be extended by the number of days of the purchased plan from the end date. The plan is effective on all devices linked to the purchased Apple ID account. Privacy policy https://ictfractal.github.io/official/PrivacyPolicy.html Terms of service https://ictfractal.github.io/official/AppTerms.pdf Disclaimer ICT Fractal Inc. does not guarantee the accuracy, credibility, and compatibility of the results of calculations and information provided through this app. Furthermore, it does not bear the responsibility for direct or indirect damages that might occur through this app.

Screenshots

O'der stack4 screens

Verdict

The call

The clearest difference is in-app purchases: RPN at none against O'der stack's 3. RPN also leads on iOS requirement (12.0 vs 15.6). O'der stack's advantage is device support (3 vs 1). On price, update cadence and ads there is nothing between them.

Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS

CostPrice · In-app purchases · Ads · Monetization

Both are free to download. O'der stack sells 3 one-off in-app purchases. RPN asks for nothing beyond the download.

UpkeepUpdate frequency

RPN ships an update every 5 months, O'der stack every 3 months. The most recent releases landed on November 1, 2026 and October 25, 2026 respectively.

Scorecard3 real differences · 7 level
RPN versus O'der stack: the parameters behind the verdict, then further details
ParameterRPNO'der stack
PriceFreeFree
Rating4.0 (4 ratings) — better—
Positive reviews83.3% of reviews—
Number of ratings4 — better—
Update frequencyEvery 5 monthsEvery 3 months — better
AdsNoNo
In-app purchasesNo — betterYes
MonetizationFree—
DevicesiPadiPhone, iPad, iPod — better
Requires iOS12.0 — better15.6
Further details — not scored
Size38 MB59 MB
Age rating4+4+
DeveloperCuVee SoftwareICT Fractal Inc.

In-app purchases

None

RPN

No in-app purchases

3 purchases

O'der stack

One-time3
  • Free trial for 7 days.Free
  • Activate for 1 month.$0.99
  • Activate for year.$9.99

Questions

Is RPN free?
RPN is free to download, with no in-app purchases.
Is O'der stack free?
O'der stack is free to download, with in-app purchases available.
Do RPN or O'der stack have ads?
Neither RPN nor O'der stack shows ads.
Which is updated more often, RPN or O'der stack?
RPN ships an update every 5 months, and O'der stack every 3 months. Most recently, RPN was updated on November 1, 2026 and O'der stack on October 25, 2026.

Other comparisons