i41CX Frequently Asked Questions

GENERAL

  • G0. How can I restore the application to a fresh initial state?

  • G1. How do I access the i41CX settings, such as the skin preference?

  • G2. There are many i41CX settings that appear to have no effect. Why is that?

  • G3. How do I access the back view of the calculator?

  • G4. What is the "Sleep Enable" option?

  • G5. Is there a user manual that describes the operation details and available functions?

  • G6. The key click sounds are audible even when the calculator is powered off. Is this a bug?

  • G7. How do I access the Flags, Registers, Usage & Examples, and Quick Reference Guide?

  • G8. Scrolling the Flags, Registers, Usage & Examples, and Quick Reference Guide tables to find the item of interest can be cumbersome. Is there a more efficient way to navigate those tables?

  • G9. The display color control sliders are disabled, the display colors changed, and the LCD font changed to "Bauhaus Smooth" when I selected an LED skin. Is this a bug?

  • G10. Changing the "Stack Display" global setting on the iPad has no effect. Is this a bug?

CALCULATOR

  • C0. What is RPN?

  • C1. Is there a user manual that describes the operation details and available functions?

  • C2. How do I execute functions that are not on the keyboard?

  • C3. How do I display the calculator's time module clock?

  • C4. What is the image on the back view of the calculator?

  • C5. I want to enter a large program into the calculator. It would be easier to do this using a text editor on my computer than on my iOS device. Is there a way to create a program file on the computer and transfer it to the calculator?

  • C6. Is there a way to view the status of all flags and registers?

  • C7. The values in the Flags and Registers tables are not updated in real time. Is this a bug?

  • C8. Attempting to execute the I41CX commands introduced in version 2.0 results in NONEXISTENT. Is this a bug?

  • C9. Can I operate the calculator using a Bluetooth keyboard?

FEATURE UPGRADES

  • FU0. What features are enabled by the available upgrades?

  • FU1. Is the "i41CX+ Features Upgrade" simply the combination of the "Overlays Upgrade", "Printer Upgrade", and the "CAS Upgrade"?

  • FU2. Is there any difference between the CAS functionality in the "CAS Upgrade" and the "i41CX+ Features Upgrade"?

  • FU3. Is there any difference between the overlays functionality in the "Overlays Upgrade" and the "i41CX+ Features Upgrade"?

  • FU4. Is there any difference between the printer functionality in the "Printer Upgrade" and the "i41CX+ Features Upgrade"?

  • FU5. I purchased an upgrade and now there are more functions available in the I41CX module but attempting to execute many of them results in NONEXISTENT. Is this a bug?

  • FU6. I loaded an overlay and it appears distorted. Is this a bug?

  • FU7. I purchased the "i41CX+ Features Upgrade" but the application name and launch image are unchanged. Is this a bug?

  • FU8. I purchased an upgrade and after I restored my device, I lost the upgrade features. How can I get them back?

  • FU9. I purchased an upgrade and would like to use it on my other devices. Do I need to purchase the upgrade again on each device?

GENERAL

G0. How can I restore the application to a fresh initial state?

Because i41CX has a persistent state, simply clearing the memory does not restore the application to the initial installation state. Moreover, because this state and other information is backed up by iTunes, deleting the application from your device touch also does not completely restore the application to a completely fresh initial state. If you ever run into a problem that cannot be resolved by quitting and restarting the app and/or clearing its memory, please follow the below procedure.

  • Delete i41CX from your device.
  • Delete i41CX from the Applications section of iTunes.
  • Re-download i41CX from the iTunes App Store on your computer (not on your device). Note that so long as you use the same account that you used to purchase it, you won't be charged for downloading it again.
  • Sync with iTunes to re-install i41CX.

This procedure will restore i41CX to a fresh initial state and hence will resolve any issues that may arise from application update problems, use of incompatible modules (if you purchased the i41CX+ Features Upgrade), etc.

Note that if you had previously purchased the i41CX+ Features Upgrade, you will need to go through the features upgrade process again by tapping the "Upgrades" button on the back view of i41CX. However, you won't be charged so long as you use the same iTunes account that you used to originally purchase the upgrade.  During the upgrade purchase process, the iTunes App Store will recognize that you've already purchased the upgrade and ask you whether you want to download it again.

G1. How do I access the i41CX settings, such as the skin preference?

The i41CX settings are available in the built-in iOS Settings application that is on your home screen by default.  If you tap it and scroll toward the bottom you'll see an entry called "i41CX" that when tapped will reveal the i41CX settings.

Note that some frequently used settings can be accessed on the back view of the calculator and the skin/LCD settings can also be accessed via the overlay picker if you purchased the "Overlays Upgrade" or the "i41CX+ Features Upgrade".

G2. There are many i41CX settings that appear to have no effect. Why is that?

Because of iOS limitations, third-party applications cannot modify the global settings. Therefore, i41CX comes with the complete set of settings available in i41CX+ such that those options become available to users that purchase the "i41CX+ Features Upgrade".

G3. How do I access the back view of the calculator?

To access the back view of the calculator, tap the center of the LCD display area. Alternatively, you can also perform a vertical swipe gesture in the LCD display area to flip the calcualtor over to the back view.

G4. What is the "Sleep Enable" setting?

This option controls whether all operations are suspended while the calculator is the running application and the device is inactive/asleep (i.e. screen locked) to minimize battery drain. Note that time will still be maintained with no power consumption impact because the app will determine the time interval that it was inactive and adjust the time accordingly when it resumes operation.  This is useful for users that leave i41CX running in the foreground for prolonged periods of time.  Conversely, disabling this option allows programs to run, alarms to go off, etc. even after the device/screen becomes inactive at the expense of reduced battery life. Note that this setting has no effect when i41CX is in the background on devices running iOS 4 or later. All operations are suspended in iOS 4 or later when the app is in the background.

G5. Is there a user manual that describes the operation details and available functions?

i41CX is functionally equivalent to the classic HP-41CX calculator. Warren Furlow's The HP-41 Archive Website is a comprehensive archive of all things related to the HP-41, including internal documentation that was donated by HP. You'll find the operating manuals of the HP-41 in the Owner's Manuals section. PDF versions of the manuals can also be downloaded from here.

G6. The key click sounds are audible even when the calculator is powered off. Is this a bug?

No, this is actually a feature. The key click sounds are meant to emulate the tactile feedback of physical keys. As such, they are always present regardless of the powered state of the calculator. If desired, the key click sounds can be disabled either by turning the calculator sounds volume all the way down using the "Sounds Volume" slider that can be accessed on the back view of the calculator (see G3 for how to access the back view) or by selecting "None" for the "Key Click Sound Type" option in the global settings (see G1 for how to access the global settings).

G7. How do I access the Flags, Registers, Usage & Examples, and Quick Reference Guide panels?

The Flags, Registers, Usage & Examples. and Quick Reference Guide panels are accessed by horizontally swiping inside the orange frame on the back view of the calculator. The views are organized as follows, where "<-" denotes a right-to-left finger swipe inside the orange border area: ED Keyboard <- Flags <- Registers <- Usage & Examples <- Quick Reference Guide.

G8. Scrolling the Flags, Registers, Usage & Examples, and Quick Reference Guide tables to find the item of interest can be cumbersome. Is there a more efficient way to navigate those tables?

Yes. Tapping the right edge of these tables will jump to the proportionate location in the table (e.g. tapping the middle of the right edge will jump to the middle, tapping the bottom of the right edge will jump to the bottom, etc.), similar to the way that tapping a letter in the built-in address book works. Furthermore, tapping the title area of these tables will jump back to the top of the table, similar to the way that tapping the status bar in Safari jumps back to the top of the web page.

In addition, the Usage & Examples and Quick Reference Guide tables can be searched by tapping the "magnifying glass" icon at the top left of each table.

G9. The display color control sliders are disabled, the display colors changed, and the LCD font changed to "Bauhaus Smooth" when I selected an LED skin. Is this a bug?

No, this is not a bug. To honor the skin designer's wishes, the display color scheme and LCD font are fixed and cannot be changed while using an LED skin. The control sliders and LCD font selection will become available if a non-LED skin is selected.

G10. Changing the "Stack Display" global setting on the iPad has no effect. Is this a bug?

No, this is not a bug. The stack display is always enabled on the iPad and cannot be disabled. The "Stack Display" global setting is only applicable for the iPhone and iPod touch where, due to the limited screen real estate, the user must choose between displaying the stack display or the system status bar. Now, because i41CX is a universal iPhone/iPad application, the global settings are common as iOS currently does not support separate global settings based on device types.

CALCULATOR

C0. What is RPN?

Mathematical operations are generally taught in infix notation, with the mathematical operators placed between the data that they operate on. For example, in the expression 2 + 3 = 5, the "+" operator is placed between the 2 and the 3. RPN (Reverse Polish Notation), formalized by the Polish Mathematician Jan Lukasiewicz in 1920, is a way of expressing mathematical operations in postfix notation. Using the previous example, 2 + 3 = 5 would be expressed as 2E 3+ 5, where E denotes the Enter operator. Thus, in RPN all operators follow each data item and hence the term postfix.

In the above example, the number of keystrokes is the same in both cases, four to obtain the answer 5. However, this is not always true. RPN makes it possible to enter data and operations without having to write down the intermediate answers or use parentheses. For example, the infix notation expression (3 + 4) * 6 = 42 requires 8 keystrokes to obtain the answer. In RPN, this would be 3E 4+ 6*. That is a saving of 2 keystrokes for this very simple calculation. For more complex calculations, RPN can save a considerable number of keystrokes. In fact, RPN is never less efficient than infix notation so, in general, it can be said that RPN is more efficient.

C1. Is there a user manual that describes the operation details and available functions?

Please see G5.

C2. How do I execute functions that are not on the keyboard?

There are two ways to execute functions that are not on the keyboard. The first is to use the "execute" (XEQ) function. For example, to obtain the absolute value of the number being displayed, press the following sequence of keys:

The other option is to use the "assign" (ASN) funtion to assign the desired function to a key in USER mode. For example, to assign the absolute value function to the Sigma+ key press the following sequence of keys:

Thereafter, in USER mode (toggled using the USER key) the Sigma+ key will execute the ABS function. To clear a key assignment, simply do an empty key assignment to that key. The function assigned to a given key can be determined by tapping and holding down the key. If the key is held down long enough, NULL is displayed and the key press is effectively cancelled.

C3. How do I display the calculator's time module clock?

Press SHIFT and then the ON key to display the calculator's clock.

C4. What is the image on the back view?

The image on the back view of the calculator shows the functions of the keys in the calculator's built-in text editor (ED) mode. For example, in the text editor, the USER button acts as a left arrow key to move the cursor one character position to the left and SHIFT followed by USER acts as a page left key to move the cursor 12 character positions to the left. For more details about the built-in editor, please refer to the HP-41CX owner's manual (see G5).

C5. I want to enter a large program into the calculator. It would be easier to do this using a text editor on my computer than on my device. Is there a way to create a RAW file on the computer and transfer it to the calculator?

i41CX does not support this capability. If you would like this capability, please consider getting i41CX+ instead which allows for this and much more.

C6. Is there a way to view the status of all flags and registers?

Yes, the state of all flags and registers can be viewed in the tables that can be accessed by swiping inside the orange frame on the back view of the calculator (see G7)

C7. The values in the Flags and Registers tables are not updated in real time. Is this a bug?

No, this is not a bug. In order to avoid "flickering" of the values (e.g. when a program is running), the values are updated only when they are out of view (i.e. outside the visible bounds of the table) and remain static while they are visible. The values are updated if/when the items go out of sight and become visible again (i.e. by scrolling the table contents).

C8. Attempting to execute the I41CX commands results in NONEXISTENT. Is this a bug?

No, this is not a bug. The commands are arguments to the I41CX function.  The I41CX function must be executed to run the commands. For example, to execute the ACCXYZ command, you would need to do the following.
  • Enter ACCXYZ into the Alpha register
  • Execute I41CX

Note these commands and more can be directly executed (e.g. XEQ ACCXYZ) if you purchased the "i41CX+ Features Upgrade".

C9. Can I operate the calculator using a Bluetooth keyboard?

Yes, i41CX automatically detects the presence of a Bluetooth keyboard and with the exceptions listed below, the hardware keyboard keys are mapped according to the ALPHA mode labels shown on the calculator keypad. For example, 'K' is mapped to XEQ and shifted 'K' is mapped to SHIFT XEQ (ASN). Numerical and arithmetic operator keys are mapped directly. For example, the hardware keyboard sequence "6 return 7 *" calculates the product of 6 and 7. The exceptions to these rules are listed below. 

  !       		ON
  @       		USER
  #       		toggle overlay/skin/display control panel
  $       		PRGM
  %       		ALPHA
  `       		SHIFT
  tab     		R/S
  '       		VIEW/AVIEW
  return  		ENTER in normal mode, exit ALPHA in ALPHA mode
  >       		SST
  <       		BST
  {       		CLX/A
  shift N 		CAT
  shift K 		ASN in normal mode, append in ALPHA mode
  shift L 		LBL in normal mode, ASTO in ALPHA mode
  shift M 		GTO in normal mode, ARCL in ALPHA mode
  Q~Z, =, ?,
  :, space,		the SHIFT'ed functions on the labelled keys
  and comma 			

  (       		switch between printer and calculator views
  )       		switch between calculator and back views
  &       		toggle printer on/off
  [, ]    		switch printer mode left, right
  |       		print
  ;       		paper advance
  _       		tear paper roll
  }       		new paper roll

NOTE: Printer related actions have no effect without either the "Printer Upgrade" or i41CX+ Features Upgrade".

FEATURE UPGRADES

FU0. What features are enabled by the available upgrades?

The available upgrades provide access to the following features.

  • CAS Upgrade
    • Access to a workstation-class CAS comparable in capabilities to Mathematica or the computational engine of Wolfram Alpha and, best of all, it runs natively so no internet connection is required (the CAS engine is based on REDUCE, a time proven CAS in use at many research institutions)
    • Fully programmable CAS with the ability to reuse previous results in computations
    • The CAS environment has full access to the calculator registers, making it possible to combine RPN programs with CAS programs
    • CAS supports symbolic, arbitrary precision, scalar, vector and matrix algebra calculations, 2D and 3D plotting, and much more
    • Full-screen text editor (I41CXED) for extended memory text files and CAS output and plot viewer with configurable font style, font size, and color scheme
    • I41CXED Macro keyboard with 15 user configurable macros
    • I41CXED provides the ability to render LaTeX documents
    • 600 Extended Memory registers
  • Overlays Upgrade
    • Support for custom keyboard overlays
    • Support for downloading overlays from a URL or importing from the clipboard (i.e. copy email attachment)
    • Use the standard overlays as templates or use the blank overlay templates available from the i41CX+ home page
    • Support for optional use of system keyboard for alphanumeric entry, greatly enhancing function name and program entry
    • Configurable calculator speed, allowing for up to 4 times faster normal operation and up to 40 times faster execution of programs
  • Printer Upgrade
    • Support for character based printing, plotting, graphics, and special characters
    • User configurable and programmable print color
    • Support for emailing printer output in text format
    • Ability to save a JPEG snapshot of the virtual paper roll to the Photos album where they can then be emailed or transferred to the computer and printed out on a real printer
  • i41CX+ Features Upgrade
    • All of the features of the "CAS Upgrade"
    • All of the features of the "Overlays Upgrade"
    • All of the features of the "Printer Upgrade"
    • Expansion: four module ports provide access to HP-41 expansion pacs, including the HEPAX module
    • Virtually unlimited data, program, and text file storage capacity using the device's flash memory for local storage
    • Import/export data, programs, text files, overlays, modules, etc. via iCloud, the web, email, and iTunes file sharing

FU1. Is the "i41CX+ Features Upgrade" simply the combination of the "Overlays Upgrade", "Printer Upgrade", and the "CAS Upgrade"?

No. The "i41CX+ Features Upgrade" provides access to exclusive features that are not available in any of the other upgrades. Namely, support for expansion modules, file I/O and import/export, and iCloud support are only available in the "i41CX+ Features Upgrade". Therefore, if you plan to purchase all three individual upgrades, the "i41CX+ Features Upgrade" is the best option.

FU2. Is there any difference between the CAS functionality in the "CAS Upgrade" and the "i41CX+ Features Upgrade"?

Yes. File I/O capabilities are only available in the "i41CX+ Features Upgrade". Therefore, the CAS function in the "CAS Upgrade" can only operate on files in the calculator's extended memory. To alleviate this limitation, the "CAS Upgrade" includes the largest possible extended memory configuration (600 vs. 124 extended memory registers). The CAS function in the "i41CX+ Features Upgrade", on the other hand, can operate on files in the device's flash memory and hence has virtually no limitations on the CAS input and output file sizes. The CAS functionality is otherwise identical in both upgrades.

FU3. Is there any difference between the overlays functionality in the "Overlays Upgrade" and the "i41CX+ Features Upgrade"?

No. The overlays, system keyboard, and calculator speed features in the "Overlays Upgrade" and the "i41CX+ Features Upgrade" are identical.

FU4. Is there any difference between the printer functionality in the "Printer Upgrade" and the "i41CX+ Features Upgrade"?

No. The printer features in the "Printer Upgrade" and the "i41CX+ Features Upgrade" are identical.

FU5. I purchased an upgrade and now there are more functions available in the I41CX module but attempting to execute many of them results in NONEXISTENT. Is this a bug?

No, this is not a bug. When an upgrade is purchased, the I41CX module is replaced with the same module used in i41CX+ to provide access to the functions that are enabled by the purchased upgrade(s). Therefore, only those functions associated with the upgrade are activated and the remaining functions are inactive. All I41CX module functions become available if the "i41CX+ Features Upgrade" is purchased.

FU6. I loaded an overlay and it appears distorted. Is this a bug?

No, this is not a bug. Overlays are optimized for specific skins and devices. You probably have an overlay that is not optimized for your selected skin. Currently, there are overlays available for the "classic" skins (Bauhaus, Classic, Gris, Noir, Skinny, and Vintage) and their variants and for the "Genuine" skin. These are all available for non-Retina (iPhone 3GS and earlier), Retina (e.g. iPhone 4 and later), and iPad devices. Overlays for the various skins and devices can be downloaded from the i41CX+ Home Page. Please see entry C8 of the i41CX+ FAQ for details on how to import overlays into i41CX+.

FU7. I purchased the "i41CX+ Features Upgrade" but the application name and launch image are unchanged. Is this a bug?

No, this is not a bug. Because of App Store technical limitations, the application icon name and launch image cannot be changed by in-app purchases.  In fact, strictly speaking, even after purchasing the "i41CX+ Features Upgrade", the application remains i41CX but it is feature equivalent to i41CX+ in every regard except for the icon name and launch image.  That is why the upgrade is called "i41CX+ Features Upgrade" rather than "i41CX+ Upgrade".

FU8. I purchased an upgrade and after I restored my device, I lost the upgrade features. How can I get them back?

In order to get the upgrade features back you will need to go through the upgrade process again by tapping the "Upgrades" button on the back view of i41CX and selecting the upgrade that you wish to restore. Note that you won't be charged so long as you use the same iTunes account that you used to originally purchase the upgrade. During the upgrade purchase process, the iTunes App Store will recognize that you've already purchased the upgrade and ask you whether you want to download it again.

FU9. I purchased an upgrade and would like to use it on my other devices. Do I need to purchase the upgrade again on each device?

No. A purchased upgrade can be applied to all iOS devices that you own without paying again. In order to install the upgrade on other devices, please go through the upgrade process on each device by tapping the "Upgrades" button on the back view of i41CX and selecting the upgrade that you already purchased on your other device. You won't be charged for the upgrade so long as you use the same iTunes account that you used to originally purchase the upgrade. During the upgrade purchase process, the iTunes App Store will recognize that you've already purchased the upgrade and ask you whether you want to download it again.