RPN-38 CX is a photo-realistic simulation of Hewlett-Packard's third-generation programmable financial calculator HP-38C.

Released in 1978/79, the HP-38C and HP-38E were the high-end business members of the so-called "Spice" series. The HP-38E was introduced first, followed a year later by the HP-38C which added continuous memory. They were discontinued in 1981 and 1983, respectively.


Features

• Photo-realistic look-and-feel


• Full compatibility with HP-38C


• Much easier to use than the original calculator


• Key-click and key-glow, both optional


• Optional single-tap shortcut keys


• Unrestricted STO and RCL register arithmetic
  (including "double register" ∑+)


• Indirect register addressing


• Swipe left across display to correct wrong number entries


• Cut/copy/paste display values and program steps


• Display stack registers and all memory registers (tap display once)


• Display and annotate programs


• Program looping


• Save, Print, Share programs


• Print program listing and description, or mail them as PDF documents


• Battery indicator lights up when battery charge drops below 10%


• Odd periods and compound interest (like HP-12)


• Nominal and effective interest rate conversion (NOM and EFF)

• Decimal Point: select how the decimal should be represented. Also defines the look of the 1000's separator.


• Top Bar: Shortcuts for frequently used keys are available in the area above the display, eliminating the need to tap the g prefix key for GTO, DEL etc.
  Also shows a number of extra functions. Tap Operations for details.
  Shows the stack after swiping the display right. Swipe the display left, or tap the stack, to hide it again.


• Haptics: Set the desired level of haptic feedback on pressing any key.


• Key Glow Effect: If enabled, tapped keys are shortly highlighted. Useful if key-click sound is off.


• Show Key Fronts: if enabled, tapping the g prefix key will reveal the hard-to-read functions printed on the key fronts.


• Show Prefix Indicators: if enabled, prefix keys like f, g, STO will be marked with a white outline as long as they are active. A prefix key may be tapped again to deactivate it.


• Use Odd Periods: if enabled, non-integer periods enable odd-periods calculations. See section "Advanced".


• Auto-Select Step 00: changing from program mode to run mode will reset the step counter to 00. This is standard HP-38 behavior. If it gets in the way of your work-flow, turn the switch off.

• • Added warning when attempting to replace a Sample Program.
• • Visual adjustments to iPhone 16 Pro and Pro Max.

• • Internal optimizations and cleanups
    New sample programs are now automatically loaded when opening the list of programs.
    Changed the default font for program listings from Courier New to Menlo.


• • Modified the info screen to avoid clipping by the Dynamic Island.
  

• New:
• • Runs on Apple Silicon Macs (Notes)

• Bug Fix:
• • Exporting a program would cause a crash

• New:
• • Set the haptics feedback level in the Settings
• • Key Glow: enable or disable flashing of tapped keys

• New:
• • Change the program listing font with a simple tap on the button F
• • Sample Programs may be hidden in the list of programs
• • Apply a filter to quickly find any program

• Bug Fix:
• • IRR and NPV cash flow calculations produced incorrect results if the group count of the initial investment CF₀ was larger than 1

• New:
• • Improved Solve for Interest function handles extreme cases.
• • Address LASTx indirectly via RCi and Sti by treating it as register 20.
• • When executed interactively, ISG and DSE do not change the program counter.
• • CLEAR FIN clears the Compound Interest indicator only when "Use Odd Periods" is off.

• Bug Fixes:
• • ISG/DSE commands were susceptible to internal rounding effects
• • Deleting a block of program steps could result in wrongly adjusted branch targets in some cases

• New:
• • Print (or mail as PDF) the program or its description.
• • A program running longer than 1 minute will emit a sound when finished (by GTO 00).
• • 12- or 24-hr clock (by tapping f or g, followed by P/R)
• • Improved accuracy in extreme cases of y^x with positive, integer x.
• • Call up "What's New" anytime from Info screen

• Bug Fixes:
• • Display issues when operating the iPhone in "Zoomed" mode
• • RND didn't work correctly in regions using comma as decimal point
• • Double- or triple-tapping the empty program listing area caused a crash

• New:
• • Replaced function π with NOP in top function bar
• • π is now located on the "+" key
• • NOP instructions show as LBL if targeted by GTO or GSB
• • Key flashing may be turned off and on:
    – Store 19390101 in R1 to turn off
    – Recall 19390101 from R1 to turn on
      (Hewlett-Packard Company was founded on Jan 1, 1939)
• • Haptic feedback may be turned off and on:
    – Store 1939010X in R0 to set amount of feedback
      (where X = 0: no feedback, X = 3: maximum feedback)
Storing other values in these registers doesn't change the settings.

• New:
• • Register view shows localized formatted value while number is being entered

• Bug Fix:
• • Using scientific notation could crash the app in some regions, i.e. Australia, Sweden, Slovenia

• New:
• • Support for iOS 13: Dark Mode, file sharing
• • Email programs directly from the program list
• • Replacing registers by pasting a program into the display is now optional
• • Many under-the-hood optimizations
• • iOS 11 or later

• Bug Fixes:
• • Executing the summation command ∑ with a very large argument would cause a crash

• New:
• • New editing commands in programming mode:
    – DELx,y (= f DEL) deletes range of program steps
    – DELEnd (= g DEL) deletes all steps from current position to end of program
• • New program added: "Multiple Linear Regressions"
• • Updated program: "Solve f(x) = 0"
• • Improved accuracy when solving for interest
• • Renamed "x=0", "x=y", etc. to "x=0?", "x=y?" in listings
• • Added error 9 ("Iteration Error")

• Bug Fixes:
• • The instruction GSB 90 could not be entered
• • In some situations, "Error 5" could only be cleared by executing CLR FIN

• New:
• • Added full register arithmetic support for ∑+ (acting on registers R2,R4 and X,Y)
• • Long-press program listing to change font of description from proportional to non-proportional and vice versa.
• • More detailed descriptions and additional examples in the built-in sample programs.

• New:
• • Added instructions STO I and RCL I with full register arithmetic support

• Bug Fix:
• • Crash on double-tapping GTO nn in program listing when step nn didn't exist

• New:
• • The I-register can now be observed in Register View, formatted for easy interpreting in ISG/DSE commands

• Bug Fixes:
• • DSE command didn't skip on negative counter values
• • Storing a value in a regular register, then pressing a financial key would not store the value but execute the function instead

• New:
• • Optional stack display (swipe display right/left)
• • Indirect addressing of all 20 registers via the I register (on f and g keys)
• • Improved NOM/EFF operations use number of periods currently stored in n
• • Set flags are shown as highlighted register numbers in Register View
• • Flags are now saved and loaded along with programs
• • Warning dialog on deleting program memory or program files
• • On-screen error descriptions
• • Improved reliability of comparisons
• • New programs: LogFactorial, Interest/Discount Conversions

• Bug Fixes:
• • Viewing a program containing any of the commands x̅w, s, or ∑- would crash the app
• • Errors didn't always report the correct error number

• New:
• • Improved Program Listing (tap "?" in listing screen)
• • New buttons at top to select TOP, MID or END of program
• • Built-in descriptions of extra functions (see Settings)
• • Pressing R/S shows next command to be executed; releasing R/S starts running program
• • Cancel R/S by dragging finger off the key
• • Renamed button "Load" to "Save"
• • Changed "Undo digit" sound to same as found on other CuVee calculators
• • Support for late 2018 iPhones

• Bug Fixes:
• • Layout issue when showing g-shifted keys
• • Digit separators were not cleared when starting number entry with EEX

• Bug Fix:
• • Result of DATE operation was not correctly displayed

• New:
• • Improved compatibility with iPhone X

• Bug Fixes:
• • Incorrect app icon shown when installed on iPad
• • Number format issues and possible crash when using the EEX key
• • Top GTO button could not be toggled on and off

• New:
• • Improved trig functions for extremely small angles
• • Support for iOS 11 and iPhone X

• Bug Fix:
• • Separators didn't always disappear when changing display mode to SCI or ENG

• New:
• • Sample program "Prime Factors" added

• Bug Fix:
• • Examples "Odd Period Example" did not work as shown in description

• Bug Fix:
• • RAND could not be programmed

• Bug Fixes:
• • Pi didn't auto-lift the stack
• • RND didn't work correctly on certain values
• • Deleting steps caused wrong address corrections in some cases

• New:
• • New commands:
    Real subroutines with 4 levels of nesting
    Loop control
    10 flags
  
• • 10 comparison commands added
• • New operations: x², LOG, π, RAND (random number)
• • CLEAR ALL is now programmable

• New:
• • Better FRAC results for large arguments
• • Program added: "Easter Date"

• Bug Fix:
• • RND is now ignored if SCI display format is active

• New:
• • Easter date for 1583 thru 4099: set y = 0, x = year, execute DATE
• • New command "D.MY/BEGIN?" to read mode switch. Tap "f", then mode switch to program.
• • Calculator sounds mix with background audio and have their own volume control

• New:
• • Pause activity is shown in main and register view
• • Decimal addition/subtraction for higher precision

• New:
• • Register view gets updated while a program is running
• • Run/stop and single-step program without leaving register view
• • Added copy of actual display to register view
• • LastX may be used in register arithmetic operations, e.g. RCL + ENTER
• • Tapping any key stops program execution
• • SST and BST may be cancelled by dragging finger off key
• • Shared programs include calculator settings and registers
• • Improved handling of values pasted as text
• • Improved address correction when deleting program steps
• • Support for uncommon number groupings (e.g. India)

• Bug Fixes:
• • Fixed x ≤ y function involving very large numbers
• • Fixed automatic target correction of GTO command at end of program memory
• • Fixed an issue where RCL g R/S in some cases would not find a solution
• • Fixed wrong key codes for g-shifted functions in bottom row
• • Statistical functions didn't lift the stack correctly
• • Text correction in sample program "Trigonometric Functions"
• • Entering too many digits was not properly handled
• • Self-check doesn't clear LASTx value anymore

• New:
• • Support for odd-period calculations using simple or compound interest (like HP-12C)
• • Guesses for IRR solutions may now be entered using RCL g R/S (see HP-38 manual)
• • Registers, display format, mode switch setting, and odd-period flag are saved with programs
• • Program loading sets display format, mode switch, and odd-period flag
• • The setting of the mode switch is programmable
• • Registers may be preset by pasting multi-line text into the display
• • Current program step is shown below display. Tap to show or hide.
• • In program mode, progress bar shows fill status of program memory
• • User programs are listed separatedly from sample programs

• Bug Fixes:
• • GTO statements pasted into the display as text are handled correctly
• • f 9 (to set 9 decimal digits) is now programmable
• • GTO 25 was not programmable
• • Fixed ∑- function producing error message
• • Fixed sign conventions of simple interest function
• • Fixed a number of stack-lift issues
• • FV doesn't show as PV anymore
• • Fixed crash on storing illegal counter value or using illegal register
• • Fixed a possible crash on NPV and IRR calculations

• First public version.

RPN-38 CX

The Spice Pac