This repository contains a set of programs written in Prime Programming Language (PPL) for the HP Prime calculator to turn it into a reliable, low-cost celestial navigation computer that can live in a chart table and requires no updates until the year 2200. It can also be used on any PC or Mac running the HP Prime Virtual Calculator program.
The following functionality is provided:
-
Astronomical
- Ephemerides of the Sun, Moon, Mars, Venus, Jupiter, Saturn, and the usual 58 stars used in celestial navigation including GHA, declination, azimuth, altitude, semi-diameter, and rise and set times
- Delta T, equation of time, obliquity of the ecliptic, etc.
- Rise and set times of the Sun and all other celestial bodies, civil and nautical twilight times
- Semi-diameter of the planets and the Moon
- Moon phase
- Centroid corrections for the partial illumination of Venus and Mars
- Interactive stereographic projection of the sky (aka star finder plot) at a given location and time
-
Navigation
- Observation planning by listing all observable bodies (i.e. meeting user-specified altitude and azimuth constraints) during morning and evening nautical twilight and at any time of the day with their respective GHA, declination, azimuth, true altitude, apparent altitude, and semi-diameter
- Sight reduction of sextant observations of any of those celestial bodies to Lines of Position (LOPs)
- Running fix calculations through translation of lines of position by a certain distance on a given bearing
- Plotting of LOPs on a Cartesian plot from which a fix can easily be deduced
- Automatic computation of fixes based on the intersection of 2 LOPs, symmedian center of 3 LOPs, and minimization of the least squares of the distance to 4 or more LOPs
- Determination of the index correction of a sextant from two simple observations of the Sun
The astronomical calculations are derived from the incredible work of Henning Umland. The ephemerides are generally accurate to 0.1' from the 19th to 22nd centuries inclusively (1800-2200) (see Future Improvements section).
The sight reduction formulas used in this program were derived from many sources that are usually provided in the comments within the source code.
For an excellent textbook on celestial navigation and the process of sight reduction, refer to Celestial Navigation: A Complete Home Study Course by David Burch and Tobias Burch. The calculations in this program follow the sight reduction process described in the book.
The program can be installed on an HP Prime calculator or on a PC or Mac running the HP Prime Virtual Calculator from the source files in the /src folder of this repository or from the binary files in the /bin folder. To prevent issues during the installation, such as memory limitations, variable or program name clashes, etc., it is STRONGLY recommended to perform the installation on a fresh calculator that just had a soft reset done. To reset your calculator, first save all your important programs using the Connectivity Kit described below and press the On-Apps-ESC keys simultaneously.
In order to use and install this program, you need to download this repository to your computer and you need to have the HP Connectivity Kit running on your computer and working with either an HP Prime V2 or G2 calculator (has not been tested on a V1) connected to your computer with a USB cable or with the HP Prime Virtual Calculator program running on the same computer as the HP Connectivity Kit.
You can download a ZIP archive containing all the files in this repository from this link. Extract it to some folder on your computer. Alternatively, if you are familiar with git, you can clone the repository into your current folder in a command shell window with git clone https://github.com/placidanomaly/HPPrimeSightReduction.git, which will make getting updates easier (using git pull from the main folder of the repository).
Follow these steps to download and install the HP Connectivity Kit and the HP Prime Virtual Calculator programs:
- Download and install the HP Connectivity Kit program from this link
- If desired, download and install the HP Prime Virtual Calculator program from this link
- Launch the HP Connectivity Kit program
- Connect an HP Prime Calculator to the computer with a USB cable, or launch the HP Prime Virtual Calculator program, and confirm that the calculator appears in the Calculators window of the Connectivity Kit.
NOTE: endpoint protection software like Windows Defender can interfere with the HP Connectivity Kit program. Try disabling any such software if you're having trouble connecting to the HP Prime Virtual Calculator.
To install from the binaries, the .hpprgm files must be loaded into the Connectivity kit:
- Launch the HP Connectivity Kit program and ensure the Content window is displayed. If not, use the Window->Content menu to display it
- Drag all the
.hpprgmfiles in the/binfolder of the repository into the Content window of the HP Connectivity Kit program - Drag all the files in the Content window of the HP Connectivity Kit program onto the calculator icon in the Calculators window
- Leave the calculator alone for about 2 minutes while programs are being loaded
- Skip the next section and go to Confirming that Everything Works
- Expand the calculator and the Programs section of the calculator in the HP Connectivity Kit program
- Right-click on Program and select New
- Enter the name Earth and press Enter. An empty editor window will open
- Open the
src/earth.txtfile from this repository in a text editor on your computer - Select all the text (Ctrl-A), copy it to the clipboard (Ctrl-C), and paste it into the editor window in the HP Connectivity Kit program (Ctrl-V)
- Save the file (Ctrl-S) and close the editor window
- Repeat steps 5-8 above for each text file in the repository
- On the calculator, go to the Programs page with
-
and confirm that all the programs are loaded - Open each program and hit
to confirm that there are no syntax errors
When the installation is completed, whether from binaries or from source, confirm that all the programs appear under the Programs section of the calculator in the HP Connectivity Kit. If the programs are not all present, re-do the installation procedure.
If all programs are listed, confirm that the installation was successful by performing the following verification:
- On the calculator, open the Programs page using the - keys. Select the Sight Reduction program using the arrows, press the
soft key, select RESET_SIGHTS using the arrows and press 
. This will initialize all the necessary variables for the program to work. - Select the Sight Reduction program using the arrows (the big round button) on the calculator (see note below), press the soft key on the screen, select EPHEMERIDES using the arrows and press . Fill out the form with a date, time, and location following the conventions in the next section and press . If everything was installed properly, the calculator will process the requested ephemerides for about 16 seconds (on a V2 calculator) and display them in the Spreadsheet app. You can scroll through them using the touchscreen to check some of the values against an Almanac for accuracy.
- If anything fails, double-check that all the programs are installed. Open each one of them using the key. Validate that the file is not empty and push the soft key per Step 12 in the Installing from Source section. If the file is empty, try reinstalling the binary file. If that fails, install it from source following the instructions in the previous section. If you're stuck here, contact the author at the address at the bottom of this document.
IMPORTANT: if you inadvertently click on a program name on the touchscreen or press
All the functionality is accessed through the Sight Reduction program. The other programs support astronomical calculations that are too voluminous to fit within a single program. Those programs need to be present for Sight Reduction to work, but they should not be invoked by the user under normal usage scenarios.
The program relies on dates, times, positions, and other information to perform the calculations. Whenever a field is highlighted for input, the line at the bottom of the screen will provide hints as to which unit and format should be used for that field. Keep in mind that the units are not consistent, they follow the conventions of celestial navigation. For example positions, hour angles, and declinations are expressed in degrees, corrections are in arc minutes, and the semi-diameter of celestial bodies is expressed in arc seconds, so pay attention to the input hints.
Negative numbers must be prefixed by a - symbol entered using the 
key, and NOT with the subtraction key, which will cause an error. If the calculator is in Reverse Polish Notation (RPN) mode, all characters in an input field must be cleared before a negative value can be entered. This is why we recommend setting the calculator in Textbook mode (the default value) using the SHIFT-Home key combination prior to using this program. An alternative to avoid having to enter negative numbers is to enter western longitudes as their corresponding eastern equivalent, e.g. instead of entering 45W, which must be entered as -45 as will be explained later, you can enter 315E, which is entered as 315.
Positions are represented in degrees of latitude and longitude which can be entered either as DD°MM'SS" using the 
-
key combination or in decimal degrees DD.ddddddd. Northern latitudes are positive, so 14°45'21"N is entered as 14°45'21", while southern latitudes are negative, so 20.2321S is entered as -20.2321. Same with declination: N45.2345 is represented as 45.2345 while S12°51'03" is represented as -12°51'03". Positive values of longitude greater than 180° will be converted to a negative value corresponding to the western longitude, e.g. 220 will be converted to -140.
Celestial navigation positions, declinations, corrections, hour angles, etc., are traditionally represented using degrees and decimal minutes to one decimal place, e.g. DD°MM.m', but the calculator does not natively support that format. Decimal minutes must be converted to arc seconds which are equal to the decimal part of minutes multiplied by 6. For example, S24°8.4' must be entered as -24°8'24". That being said, the program usually outputs values using decimal minutes.
Date values are represented using the native calculator format which is YYYY.MMDD. For example, April 23, 2026 must be entered as 2026.0423.
Time values are represented in 24-hour format using the same format as angle degrees, i.e. HH°MM'SS", using the - keys. For example 11:43:12pm is entered as 23°43'12".
The color theme used by the calculator can be set to Light or Dark mode on page 2 of the Settings menu. The program will adjust its display based on the theme set. When making observations during twilight hours, it is preferable to set the calculator to a Dark theme to preserve night vision. The screens below illustrate the display in dark mode.
The program keeps data about sights and lines of position in the calculator's memory, and that data is preserved when the calculator is turned off. Generally, you should clear the program's memory prior to any new fix. If you ever get an Invalid Input error, you likely inadvertently opened the Sight Reduction program for editing and need to clear the memory (see the NOTE in the Confirming that Everything Works section). To clear all program variables:
- Highlight the Sight Reduction program and press the soft key
- From the list of options, pick RESET_SIGHTS on the touchscreen or with the arrows and the key. Click any key to dismiss the confirmation message.
The calculator has a pretty accurate internal clock that can be used to automatically record the time of observations. It should be set to a reliable external time source from time to time to ensure it is accurate. To set the calculator's internal clock and timezone:
-
Run the Sight Reduction program and pick the SET_TIME function and set the calculator's local time clock and timezone:
- Local time: the local time to which to set the calculator's internal clock. Enter a time a few seconds in the future and click the
soft key when your time source reads the time entered - UTC Offset: the number of hours the local time is ahead of or behind UTC. Use a positive value for locations East of Greenwhich and negative for West (e.g. -5 for New York standard time). Keep in mind that this offset changes with Daylight Savings Time (DST). Fractional offset values like the one used in Newfoundland (-3.5 in standard time) are supported.
- Local time: the local time to which to set the calculator's internal clock. Enter a time a few seconds in the future and click the
It can be helpful to know which celestial bodies will be visible and where ahead of an observation session with the sextant so that the bodies to be observed can be selected ahead of time based on whether they meet certain a criteria for visibility based on their altitude and azimuth. The program shows, for a given date, all the bodies that meet the visibility criteria at morning and evening nautical twilight, as well as at a specified time during that day. Here's how it works:
- From the programs screen of the calculator, select the Sight Reduction program and click the soft key and click on the SIGHT_PLANNING function. An input screen will appear:
-
Fill out the observation parameters and visibility criteria:
- Date: the date on which the observations will be made in YYYY.MMDD format
- Time: an arbitrary time at which to show the visible bodies, in HH°MM'SS" format
- Latitude: the latitude in degrees where the observations will be made. This will typically be your DR position at the time of the observations.
- Longitude: the longitude in degrees where the observations will be made
- Altitude: the minimum altitude in degrees of the celestial bodies to be included in the list. This can be useful to hide bodies that would be obscured by a ship's superstructure, trees on a shoreline, etc.
- Azimuth from: the true heading in degrees of the beginning of a clockwise arc within which the azimuth of bodies must lie in order to be included in the list. Same as for Altitude, this can be used to suppress bodies that would be obscured by a ship's superstructure or the land side of a shoreline
- Clockwise to: the true heading in degrees of the end of a clockwise arc within which the azimuth of bodies must lie in order to be included in the list
-
It will take about 50 seconds to compute all the ephemerides. You will be prompted to press a key to show the results at the end of the calculation. The output will be shown in the Spreadsheet app with all times in local time (assuming SET_TIME was run to specify the time zone). It will include, in clockwise order of azimuth within the prescribed arc:
- Sunrise, sunset, civil twilight, and nautical twilight times
- Local time of Meridian passage at the specified longitude
- List of observable bodies (i.e. meeting azimuth and altitude constraints entered on the first screen) with, for each, the azimuth, true altitude (Hc), apparent altitude (Ha) (i.e. the one that a sextant with no index error and no dip would read), Greenwhich Hour Angle (GHA), declination (dec), semi-diameter in arc seconds of the body (if applicable), and rise and set times (if applicable), at 3 different times:
- Morning nautical twilight: from morning Nautical Twilight Time to Civil Twilight Time (if there is a sunrise at that location), with body positions calculated at the midpoint of the twilight period, shown in parentheses
- Evening nautical twilight: from evening Civil Twilight Time to Nautical Twilight Time (if there is a sunset at that location), with body positions calculated at the midpoint of the twilight period, shown in parentheses
- The time specified in the input form
Performing a sight reduction is a straightforward process:
-
Go to the Programs screen, highlight the Sight Reduction program and press the
soft key. -
Reset all previous observations and calculations by running RESET_SIGHTS in the Sight Reduction program.
-
Enter a new observation: select SIGHT and press the
soft key. -
The program can store up to 10 different observations, each resulting in a line of position, and they are accessed by an LOP register number from 1 to 10. Select an empty LOP register for this observation (they should all be empty if you ran RESET_SIGHTS), let's say 1 for this first one, and hit the
soft key. LOP registers containing a translated LOP cannot be edited and, if selected for editing, will be treated as an empty sight that will overwrite the translated LOP. The source of a translated LOP can be edited but its corresponding translated LOP will not be updated so the SHIFT_LOP program should be run against the updated values using the same destination register as before. See Running Fixes.
The Show Progress checkbox simply causes additional computing messages to be displayed during the calculation processes and changes nothing to the results.
- The next screen captures the parameters of the observation:
- UTC Date: the UTC date of the observation in HP Prime date format (YYYY.MMDD). The hint at the bottom of the window displays the current UTC time to help determine if the UTC date is different from the local date. The default value is the current UTC date.
- DR Lat: the latitude of the dead-reckoning (DR) position in degrees at the time of the observation
- DR Lon: the longitude of the DR position in degrees at the time of the observation
- Body: a drop-down to select the celestial body being observed among a list of the Sun, Moon, 4 planets and 58 stars. For certain celestial bodies, the observed limb must also be selected. The Pre-calculated sights option allows entering the Zn (azimut) and a (distance) of the line of position directly instead of letting the calculator perform the sight reduction calculations (this is useful to plot lines of position that have been calculated some other way). The Moon with tables and Sun with tables options allow entering the values for declination and Greenwich Hour Angle manually based on the Almanac tables instead of using the built-in ephemerides.
- Artificial: check this box if the observation is made on an artificial horizon. If that's the case, the sextant altitude values entered must be the actual reading on the sextant, i.e. double the actual body altitude. When this box is checked, the index correction will be applied before dividing the reading by half and no dip correction will be applied regardless of the eye height or dip short values entered
- Average: check this box to perform the observation averaging process described in the next step. Note: this checkbox is unchecked by default if the LOP register contains a previously entered sextant altitude. Checking it will overwrite the previously entered sextant altitude. If no previous value was entered, the checkbox is checked by default.
- On the next screen, enter the observation conditions which will be used to compute sextant altitude corrections:
- IC: the index correction of the sextant in arc minutes, negative values for "on-scale" correction and positive for "off-scale"
- HE: eye height from the horizon in feet (for dip correction)
- Dip short: distance in nautical miles (nm) from the observer where the horizon ends (e.g. the other side of a large lake), or zero if an infinite horizon is used as reference for the observation
- Temp: the air temperature in degrees C (for refraction correction)
- Pressure: the atmospheric pressure at sea level in millibars (for refraction correction)
- If the Average option was selected, the program will prompt the user to enter sextant observations as they are made. It will show a screen displaying the time and asking to press any key when an observation is made. (It might be useful to extend the Auto-OFF delay of the calculator by setting the value of the TOff system variable to a longer delay. See this link):
- As soon as you've aligned the observed body with the horizon, hit any key or touch the touchscreen. This will note the time of the observation (hence why it is important to run SET_TIME regularly) and a screen prompting to enter the sextant reading will appear. IMPORTANT: do not halve observations made on an artificial horizon and do not apply any dip or index corrections to the sextant reading, these corrections will be calculated based on the data input in step 6.
-
The program will return to step 8 and allows entering as many observations of the same body as desired. When no more observations are needed, hit Cancel or enter
0in the HS field and click Ok. If only one observation was entered, the program will skip to step 11 and use the time and sextant altitude values entered in Observation #1 -
If more than one observation was entered, the observations will be plotted on a Cartesian graph with time as the horizontal axis and sextant altitude as the vertical axis. The plot allows choosing among various best-fit curves using the soft keys at the bottom of the screen to pick the one most closely approximating the path of the celestial body in the sky: linear and quadratic regressions are available if 3 or fewer observations were made, and cubic and trigonometric regressions are added if 4 or more observations were entered. A red marker indicates a chosen value on the interpolated curve, which is at the midpoint of time range on the regression curve, unless an extremum exists within the time range, in which case that extremum is chosen (useful for Local Apparent Noon observations). When done, hit the
soft key to confirm the selected interpolated point.
- The next input screen captures the time of the observation and the actual sextant altitude for the sight. If the observation averaging process was used, the fields will be pre-populated with the averaged values for time and angle and you can just click to confirm it. Otherwise, enter the values for observation time and sextant altitude (and remember NOT to halve the sextant altitude if an artificial horizon was used).
- The calculator will display the values for observed height Ho, Greenwhich Hour Angle GHA, declination dec, Local Hour Angle LHA, and the calculated height Hc of the body. Review them and click OK.
- The calculator will then display the LOP register used and the usual 4 parameters of the line of position: distance a from the LOP either TOWARD or AWAY from the body, azimuth Zn to the body, and the DR position latitude and longitude as entered (no correction of DR position to an assumed position is necessary here because the calculator naturally handles fractional values of LHA and Zn). These parameters enable plotting of the line of position.
- Lastly, the calculator displays the equation for the line of position in a longitude (x) and latitude (y) Cartesian plane which can be used to plot it in a program. That equation is stored in the
Fregister of the Function app of the calculator corresponding to the LOP register selected, e.g. LOP 1 will be stored inF1, which means they can be plotted using the calculator's Function app.
In order to make a fix using two or more lines of position from observations taking at a different DR position, for example to make a fix based on a morning and an afternoon Sun sight while navigating, the earlier fixes need to be translated by the DR delta between those two positions. This is easily accomplished by running the SHIFT_LOP program. The first screen will prompt for the LOP that needs to be translated:
The next screen prompts to enter by what distance and bearing to shift the LOP. Enter the bearing in true degrees and the distance in nautical miles:
The next screen prompts for the LOP register in which to store the resulting translated LOP. You can select the same LOP as the source LOP, in which case it will be overwritten with the translated LOP and the original observation will be lost (which is usually fine), or another LOP register:
The calculator will output the magnitude of the translation in degrees of latitude and longitude.
Once 2 or more LOPs have been defined (i.e. 2 or more sights have been entered in separate LOP registers), a fix can be made either manually by visualizing the LOP plot or automatically by computing a center of LOP intersections.
A manual fix is made by visualizing the LOPs on a Cartesian plane with longitude as the horizontal axis and latitude the vertical axis. To do that, run the Sight Reduction program and select PLOT LOPs. This will open the calculator's Function app and a line of position will be plotted for each LOP defined in the SIGHT program. The calculator functions accessible through the soft keys can then be used to calculate the intersection of LOPs, etc., and the cursor can be used to manually find the centroid or some other position inside the "cocked hat" to make a fix. In order to determine which line color corresponds to which LOP, use the Symb key to view the color coding and the corresponding LOP equations, and use the Plot key to go back to the graph.
Alternatively, the calculator can compute a fix based on LOPs. The computation varies depending on how many LOPs are defined:
- 2 LOPs: the intersection of the 2 LOPs is the fix
- 3 LOPs: the symmedian center, or Lemoine point, of the triangle formed by the 3 LOPs
- 4 or more LOPs: the coordinate that minimizes the square of the error with each LOP based on the distance between the calculated coordinate and the shortest path to each LOP. This is achieved using derivatives of a function which is the sum of the squares of the distance of the coordinate to each LOP.
LOPs that were translated to a different LOP register are omitted from the calculation, but their translated destination registers are included.
To compute a fix, run the Sight Reduction program and select COMPUTE_FIX. The output will indicate which method was used to compute the fix and the longitude and latitude of the fix. In the screen shots below, we computed a fix after two sights, then entered a third sight and computed the fix again, and entered a fourth sight and computed the fix again:
If you have access to your actual position using a GPS or some other means to make a fix, you can compare the computed fix with your actual position. To do this, click the Check soft key at the bottom of the fix screen. You will be prompted to enter your actual position:
Once your actual position is entered, the calculator will display the distance between the computed fix and the actual position:
The program can show the Greenwich Hour Angle (GHA) and declination of the Sun, Moon, Mars, Venus, Jupiter, Saturn, and the 58 celestial navigation stars for any point in time between 1800 and 2200, as well as the corresponding azimuth and altitude from a specified geographical location. The semi-diameter of certain bodies will also be shown. A graphical representation of the ephemerides is available through the Star Finder function which is covered in the next section. To use this feature:
- From the programs screen of the calculator, select the Sight Reduction program and click the soft key and click on the EPHEMERIDES function. An input screen will appear:
-
Fill in the required information:
- Date: the date of the ephemerides in YYYY.MMDD format
- Time: the UTC time of the ephemerides in HH°MM'SS" format
- Latitude: the latitude in degrees to calculate azimuth and altitude
- Longitude: the longitude in degrees to calculate azimuth and altitude
-
The calculator will display several astronomical calculations such as Delta T, mean and true obliquity of the ecliptic, true GHA Aries, Moon phase (illumination %), UTC time of Meridian passage at the specified longitude, etc. along with the GHA, declination, azimuth, altitude, semi-diameter, rise and set times of all the celestial bodies:
A plot of the sky with the 58 celestial bodies based on their ephemerides can be displayed by using the STARFINDER function of the Sight Reduction program. The input screen is the same as for the ephemerides function, with additional fields to specify the observer's gaze: initial center of the star finder view in terms of azimuth and altitude, and the initial field of view (which is the inverse of a zoom level):
Upon submitting the form, the calculator will perform the ephemerides calculation for the selected date and time. At the end of the calculation, a graphical representation of the sky will be displayed. The view is a stereographic projection of the sky which preserves the angles between the celestial bodies and the shapes of constellations. The stars and planets are shown as blue dots if above the horizon or red dots if below the horizon. The center of the screen corresponds to the azimuth and altitude of the viewer and is displayed at the bottom of the screen. The following keys can be used to navigate the plot:
- Up/Down Arrows: tilt view up/down
- Left/Right Arrows: pan view left/right
- Touchscreen drag: you can drag the view using the touchscreen drag gesture
- ESC or On: exit the program
While dragging or holding a key down, only the stars and planets will be redrawn. The grid lines will be redrawn when the keys and the touchscreen are released.
Whenever a new sight is entered, a value for the index correction of the sextant must be specified. A default value for the index correction can be defined using the INDEX_CORRECTION program. The value of the default index correction can either be entered directly or it can be calculated based on a measurement of the diameter of the Sun.
Start by launching the INDEX_CORRECTION program and choose either the Direct or the Solar method using the soft keys. At the end of the procedure, the value of the index correction for all sights that have no sextant angle entered will be set to the new default index correction value (i.e. the index correction of existing sights will not be changed).
When selecting the Direct soft key, the following input screen appears. Enter the default index correction in the field in decimal minutes (MM.m), with a negative value for an on-scale correction and a positive value for an off-scale correction.
Calculating the index correction from a measurement of the diameter of the Sun is accomplished by following the procedure described in this document. The procedure assumes that the index correction is small enough such that the top measurement is on-scale and the bottom measurement is off-scale. The program briefly describes the measurements that need to be taken:
Values for the Below and Above observations as read on the sextant, in decimal arc minutes (MM.m), can be entered in the input form. Do NOT correct the off scale Below reading by subtracting it from 60, the program will do that for you. Use the value directly read on the instrument.
The program will display the calculated index correction result as well as the implied semi-diameter of the sun, which is then compared with the actual semi-diameter of the sun at the current time. This allows validating the inputs used before applying the calculated index correction to future sights.
If the observed diameter of the Sun is close to the actual value, press the Accept soft key to apply the calculated index correction, or Cancel otherwise. It is recommended to run the procedure a few times to confirm the validity of the index correction. The mean value of several calculations can be entered using the Direct Entry method.
The ephemeris calculations are usually accurate to within less than 0.1' of the values in the Almanac for the period 1800-2200 (subject to Delta T adjustments), but errors of up to 0.3' are sometimes seen. This is sufficient for most practical cases of celestial navigation but perfect precision would be better. The differences are still being investigated because the same program in Javascript from Henning Umland's web site seems to always output the exact same numbers as the Almanac. The possibility of a discrepancy in the code is one theory but a more likely one is that the lower number of significant digits in the calculator vs. a regular computer introduces rounding errors that add up in the lengthy calculations, but that has yet to be proven.
Instead of storing all sights as local data in the Sight Reduction program, we are considering making them global which would prevent their erasure when the program is open for editing. But that would mean that dozens of variables would pollute the global scope of the calculator. Comments on this would be welcome.
This program was developed by Charles Vaillancourt. I welcome comments and suggestions for improvement and will gladly review pull requests for inclusion into the program. And if you do try it, drop me a note to let me know how the installation and use of the program worked out for you, and if you were able to make a fix!